Topics

Depth of Field question

Argyris_Theos_cml
 

A question addressing lens experts:
 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?
 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Mike Nagel
 

if my math doesn’t betray me…

 

~ T10.5 on S35

~ T15 on FF

 

 

 

- Mike Nagel

Director/Producer

L.A.

_._,_._,_

Argyris_Theos_cml
 

Mike,
What are the circles of confusion you are using ?
How did you choose them?
A. 

Argyris Theos, gsc 
DoP, Athens Greece,
+306944725315
Skype Argyris.Theos
via iPhone

31 Μαρ 2018, 12:41 μ.μ., ο/η "Michael Nagel via Cml.News" <michanagel=yahoo.com@...> έγραψε:

if my math doesn’t betray me…

 

~ T10.5 on S35

~ T15 on FF

 

 

 

- Mike Nagel

Director/Producer

L.A.

Mike Nagel
 

0.03 mm for both

 

What CoC are you using ?

 

 

- Mike Nagel

Director/Producer

L.A.

Geoff Boyle
 

In the lens comparisons I used 2 stop's between FF & S35
Whilst not exactly right it works well with the built-in ND's
Oh and posting which lens you prefer here will have no effect on the outcome which has been gradually changing.
Still need more votes otherwise the only way to find out which is which is to ask Carey at NAB as he's the only other person who knows.

Cheers
Geoff Boyle NSC
Cinematographer
EU based
+31 (0)637155076

Argyris_Theos_cml
 

The point is that you need different CoC because you have a different native resolution. 

Argyris Theos, gsc 
DoP, Athens Greece,
+306944725315
Skype Argyris.Theos
via iPhone

31 Μαρ 2018, 1:16 μ.μ., ο/η "Michael Nagel via Cml.News" <michanagel=yahoo.com@...> έγραψε:

0.03 mm for both

 

What CoC are you using ?

 

 

- Mike Nagel

Director/Producer

L.A.

Keith Putnam
 

Steve Yedlin, ASC addresses the issue of matching FOV and DOF (more precisely, "blur circles") on different format sizes in this document: http://www.yedlin.net/170504.html
It's very straightforward and a fascinating read. There's a lengthy intro which may feel redundant to you; he gets into the meat of the issue about halfway through.

Keith Putnam
Local 600 DIT
New York City

Mike Nagel
 

CoC calculation, AFAIK, has to do with size of image plane diagonal, not with resolution. For example, film has no “resolution”.

 

In any case, I was unclear before:

 

The different image plane is accommodated via crop factor. The 35mm FF reference CoC I used was 0.03.

 

I used a 1.6 crop factor for S35. You did not specify whether it’s S35 3 perf or 4perf target area.

 

Another slight deviation: DOF plane is 2.42m – 3.93m – close to what u wanted.

 

I did this quickly on the fly, u can adjust as needed... or maybe my math was off... what is your result ?

 

 

Thanks.

 

 - Mike Nagel

Director/Producer

L.A.

Argyris_Theos_cml
 

Excuse but you are totally wrong in saying :
"CoC calculation, AFAIK, has to do with size of image plane diagonal, not with resolution."

CoC is defined by magnification.
That's why I specified Screen Size
The CoC is the smallest projected circle that cannot distinguished (by naked eye) from a single point.
So we begin with a single recorded point (and this is not synonymous to a single pixel) but on the smaller sensor, in my hypothesis, we get 4 times the pixel count of the bigger sensor. That is per dimension, aka 16 times in total.
In such a case I would think that the CoC for this case's S35 sensor might be significantly smaller than this case's FF35 sensor.
Allow me to repeat that the S35 sensor would be 8K and FF would be HD only.
When starting this thread I asked this question to optics experts. The reason was that the answer is really complicated.
Thank our colleague for referring us through a link, I will study the document later.
Best regards

Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

31 Μαρ 2018, 3:18 μ.μ., ο/η "Michael Nagel via Cml.News" <michanagel=yahoo.com@...> έγραψε:

CoC calculation, AFAIK, has to do with size of image plane diagonal, not with resolution.

Thomas Gleeson
 

Argyris,

I must admit I don’t fully understand the nature of your question but when calculating the stop difference to match DOF on different size sensors assuming the same aspect ratio you can use a simple formula. In our tests we used the 8k setting on the Monstro at 40.96mm and the 4.5K setting which is 23.04mm. Divide 40.96 by 23.04 and you get 1.78 stops. You could also use the diagonal measurement.

Back to your question I imagine you are doing a thought experiment but in the real world nobody will ever build a HD or  1920x1080 FF35 sensor. This would be a pretty abysmal imager. Even back in the Dark Ages ten years ago did anybody ever build a 1920x1080 single chip camera? I know I am going off on a tangent but even the cheapest S35 cameras have relatively high resolution chips. These machines may have limited processing and recording so you cannot access the full resolution but only the downsampled version at 1920x1080.   

I can recommend this rather long video https://vimeo.com/248235757 from Panavision that discusses many of these topics including the value of capture resolution even over presentation resolution.

Tom Gleeson
Sydney DOP






On 31 Mar 2018, at 8:28 pm, Argyris_Theos_cml <cml@...> wrote:

A question addressing lens experts:
 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?
 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Mike Nagel
 

mine was based on the Zeiss formula, which relates to DOF calculations - which is what you asked about, see here: https://en.wikipedia.org/wiki/Zeiss_formula

again, CoC cannot be based on resolution (as you stated), as film has no resolution - but based on size (as you now seem to state yourself in your last post).

Am I understanding you correctly that you assume the CoC changes based on the final display format ? Or why do you keep mentioning "screen size" ?

Only the capture medium is important here... FF vs. S35

In any case, please keep us updated on your findings, interesting stuff  ;-)

- Mike Nagel
Director/Producer
L.A.

Florian Stadler
 

I used P-Cam and using an Epic Weapon in S35-8K HD (16:9) it prescribes a CoC of 0.00075

To get the Depth of field required you would need an 11 (slightly under)

For the FF HD I used a Canon 5D Mark II cropped to 1.78. P-Cam uses 0.00114 as CoC, needing a 16 stop to get your depth of field.

Florian Stadler
323-377 2242 

On Mar 31, 2018, at 4:04 AM, Geoff Boyle <geoff.cml@...> wrote:

In the lens comparisons I used 2 stop's between FF & S35
Whilst not exactly right it works well with the built-in ND's
Oh and posting which lens you prefer here will have no effect on the outcome which has been gradually changing.
Still need more votes otherwise the only way to find out which is which is to ask Carey at NAB as he's the only other person who knows.

Cheers
Geoff Boyle NSC
Cinematographer
EU based
+31 (0)637155076

Florian Stadler
 

I used P-Cam and using an Epic Weapon in S35-8K HD (16:9) it prescribes a CoC of 0.00075

To get the Depth of field required you would need an 11 (slightly under)

For the FF HD I used a Canon 5D Mark II cropped to 1.78. P-Cam uses 0.00114 as CoC, needing a 16 stop to get your depth of field.

Florian Stadler, DP, LA
www.florianstadler.com

Mark H. Weingartner
 


 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?


As an aesthetic exercise this would depend a little on the two cameras but  as a technical exercise, i worked this through comparing 
a RED Weapon with Helium 8k sensor  compared to Monstro 8kVV sensor … all other things are not equal of course, but
as a starting point:

Horizontal angle of view match to a 50 on the S35(ish) sensor is 68.5 on the Weapon 8k VistaVision (which is not really VistaVision)
Using pCAM 

Using pCAM I worked the focus split for the two sensor/lens combinations.  I somewhat arbitrarily set the circle of confusion to the same 0.00049”…  to see what an “apples to apples” comparison would be based on the projector resolution( magnification) as being the limiting factor.

This gave me f/16 for the  S35 and f/32 1/2 for the VV sensor…
Now , going back to an F35 which has a default setting of .00067  pCAM suggests f/16 1/4  …

Obviously all other things are never equal - I would argue that the differences in acuity from different debayer choices and different manufacturers and different lens series makes this a “guestimate” at best… because perceived depth of field in an image is dependent on so many factors… but that is how I would go about the exercise.

We’ve been using circle of confusion as our “fudge factor” much more (i think) in the digital world than when we were looking at film stocks of  a consistent grain size (ish)  projected on a screen of a standard size (sort of)   so that circle of confusion was really varying more with regard to degree of magnification on projection than any other single factor

Weingartner
LA


 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Pierre Hugues Routhier
 

I think it should be mentioned that closing the iris that much will lead to diffraction -
depending on the lens, you may actually lose what you gained in DoF and end up
with a very soft image.

Pete Routhier, Eng., M.Eng.
Advanced imaging specialist
L.A. and Montreal


On Mar 31, 2018, at 12:11 PM, Mark H. Weingartner <vfxmark@...> wrote:


 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?


As an aesthetic exercise this would depend a little on the two cameras but  as a technical exercise, i worked this through comparing 
a RED Weapon with Helium 8k sensor  compared to Monstro 8kVV sensor … all other things are not equal of course, but
as a starting point:

Horizontal angle of view match to a 50 on the S35(ish) sensor is 68.5 on the Weapon 8k VistaVision (which is not really VistaVision)
Using pCAM 

Using pCAM I worked the focus split for the two sensor/lens combinations.  I somewhat arbitrarily set the circle of confusion to the same 0.00049”…  to see what an “apples to apples” comparison would be based on the projector resolution( magnification) as being the limiting factor.

This gave me f/16 for the  S35 and f/32 1/2 for the VV sensor…
Now , going back to an F35 which has a default setting of .00067  pCAM suggests f/16 1/4  …

Obviously all other things are never equal - I would argue that the differences in acuity from different debayer choices and different manufacturers and different lens series makes this a “guestimate” at best… because perceived depth of field in an image is dependent on so many factors… but that is how I would go about the exercise.

We’ve been using circle of confusion as our “fudge factor” much more (i think) in the digital world than when we were looking at film stocks of  a consistent grain size (ish)  projected on a screen of a standard size (sort of)   so that circle of confusion was really varying more with regard to degree of magnification on projection than any other single factor

Weingartner
LA


 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Mark H. Weingartner
 

True - depending on the lens design of course… but I didn’t set the exercise

I also did not go through the process I should do to adjust the circles of confusion properly - 

This is actually a much more complicated exercise because of the “all other things being equal” issue…

Since our perception of focus is tied to contrast  we really have to consider the mtf of two entire systems…

one from lens to sensor to image processing to projection for the S35 1920x1080 example, and
one from lens to sensor to image processing to projection for the VV 8k example

So many variables in the real world.

Steve Yedlin’s piece probably gives the most concise way of getting from A to B as a practical exercise… it’s pretty close to what I do when shooting, but I have to tweak things frequently when shooting vfx elements because I am rarely shooting an entire frame - more likely an element that does not encompass the entire depth of the scene.
Weingartner
LA

On 31Mar, 2018, at 10:12 49, Pierre Hugues Routhier <pierre.routhier@...> wrote:

I think it should be mentioned that closing the iris that much will lead to diffraction -
depending on the lens, you may actually lose what you gained in DoF and end up
with a very soft image.

Pete Routhier, Eng., M.Eng.
Advanced imaging specialist
L.A. and Montreal


On Mar 31, 2018, at 12:11 PM, Mark H. Weingartner <vfxmark@...> wrote:


 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?


As an aesthetic exercise this would depend a little on the two cameras but  as a technical exercise, i worked this through comparing 
a RED Weapon with Helium 8k sensor  compared to Monstro 8kVV sensor … all other things are not equal of course, but
as a starting point:

Horizontal angle of view match to a 50 on the S35(ish) sensor is 68.5 on the Weapon 8k VistaVision (which is not really VistaVision)
Using pCAM 

Using pCAM I worked the focus split for the two sensor/lens combinations.  I somewhat arbitrarily set the circle of confusion to the same 0.00049”…  to see what an “apples to apples” comparison would be based on the projector resolution( magnification) as being the limiting factor.

This gave me f/16 for the  S35 and f/32 1/2 for the VV sensor…
Now , going back to an F35 which has a default setting of .00067  pCAM suggests f/16 1/4  …

Obviously all other things are never equal - I would argue that the differences in acuity from different debayer choices and different manufacturers and different lens series makes this a “guestimate” at best… because perceived depth of field in an image is dependent on so many factors… but that is how I would go about the exercise.

We’ve been using circle of confusion as our “fudge factor” much more (i think) in the digital world than when we were looking at film stocks of  a consistent grain size (ish)  projected on a screen of a standard size (sort of)   so that circle of confusion was really varying more with regard to degree of magnification on projection than any other single factor

Weingartner
LA


 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos


Gavin Greenwalt
 

“I want my Depth of Field to match“ \ “The point is that you need different CoC because you have a different native resolution.” - Argyris

This really emphasizes the need to understand a question fully to provide the ‘right’ answer.  In this case the word “match” is ambiguous and needs a little more clarification before you can get the answer you’re looking for.

From an aesthetic perspective what’s most important in matching two plates (say a VV green screen shot and a location s35 shot) is the overall image and you shouldn’t be taking resolution, only the sensor size, into account to match by eye.  If you are compositing multiple plates one would want the foreground  and background defocused areas to look equally out of focus (proportional to the frame) in both shots, otherwise one actor will be incredibly out of focus while the person they’re talking to is perceptually much more in focus.  You want the circl/bokeh to “match” in frame for two things at the same distance. But you also asked for the effective focus region to match.  That’s a different “match” entirely and with the specs you listed would be mutually incompatible with the first form of “matching”.

Without knowing what “matching DOF” means to you in the context of this question you’re going to get two very different answers.  You’ll need to scale the CoC by gate\sensor size alone to match visually.  You’ll need to scale the CoC by resolution and sensor size to match effective focus range (but accept that your images with any subject matter outside of the effective focus region will look very different).  

I can recommend this rather long video https://vimeo.com/248235757 from Panavision” – Tom Gleeson

I would not recommend that video without a list of caveats.   For instance they used sensor plane position instead of Entrance Pupil position when comparing perspective and as a result ended up with differing perspectives which they incorrectly attributed to the format change.   It perpetuates the stubborn myth that faces look inherently different on different sensor sizes (which if true would have meant that decades of Vistavision VFX plates shouldn’t have matched.)  It should be watched with the full knowledge that’s it’s more of a marketing than educational video.

Gavin Greenwalt
VFX Supervisor
Seattle, WA

Leonard Levy
 

First I want to say that I would like to thank the OP for posting a very interesting question that raises a host of issues that don’t seem to have been resolved to me in the many worthy responses I’ve seen so far.
I have recently been wondering just what CoC I should be using to calculate depth of field in video and it seems there are at least 3 variables.

1- The final screen display size - 
I’m guessing this is the most important as I imagine ( though I could be wrong) that classic 35mm DOF tables were based on typical cinematic projection. 
If I am shooting on a Monster but releasing on a web page ( as is more often the case than any of us want to admit) I should have a hell of a lot more perceived  DOF than if its going to end up on an IMAX screen.
So just calculating a DOF without knowing the screen size seems  pointless. 

2- The size of the sensor - 
This would classically have been the critical factor since say in 16mm we needed a much wider lens than in 35 for the same DOF but frankly I can’t recall if there was much difference between DOF in 16mm or 35 with the same lens and F stop,.
In my distant memory through I seem to recall that even here screen size was important and that 16 was assumed to be projected on smaller screens (that’s just a guess though)

3- Pixel density - well that’s a new one isn’t it. Does that affect anything?

I would love to see a clear discussion of how these  parameters ( or any others) weigh against each other.

Leonard Levy, DP
San Rafael, CA




Mitch Gross
 

Screen size used to be the shorthand measure as there was an assumed resolving power & magnification of film projection and another much lower resolving power & magnification for what was then broadcast SD TV. This has changed now, as people can watch a curved 40” 4K computer monitor at home from a distance of less than two feet. This will show higher acuity than a decent movie projection from the front row. 

An from the original question, the idea that a FF-captured HD image will be uprezzed somehow to 8K projection really throws everything out the window. Uprezzed how? Will there be some dithering and smoothing or will pixels simply be repeated to fill out the resolution? The moment this was introduced to the mix it pretty much tossed the comparison out on its ear. 

As to one person’s question if any company had ever actually bothered making a Full Frame 35mm chip that’s only HD resolution, the answer is yes. Vision Research had some super high speed industrial cameras with enormous photosites and that oddball low light Canon is FFHD. 


Mitch Gross
Cinema Product Manager 
Panasonic Media Entertainment Company
New York

On Mar 31, 2018, at 4:22 PM, Leonard Levy <nsll@...> wrote:

First I want to say that I would like to thank the OP for posting a very interesting question that raises a host of issues that don’t seem to have been resolved to me in the many worthy responses I’ve seen so far.
I have recently been wondering just what CoC I should be using to calculate depth of field in video and it seems there are at least 3 variables.

1- The final screen display size - 
I’m guessing this is the most important as I imagine ( though I could be wrong) that classic 35mm DOF tables were based on typical cinematic projection. 
If I am shooting on a Monster but releasing on a web page ( as is more often the case than any of us want to admit) I should have a hell of a lot more perceived  DOF than if its going to end up on an IMAX screen.
So just calculating a DOF without knowing the screen size seems  pointless. 

2- The size of the sensor - 
This would classically have been the critical factor since say in 16mm we needed a much wider lens than in 35 for the same DOF but frankly I can’t recall if there was much difference between DOF in 16mm or 35 with the same lens and F stop,.
In my distant memory through I seem to recall that even here screen size was important and that 16 was assumed to be projected on smaller screens (that’s just a guess though)

3- Pixel density - well that’s a new one isn’t it. Does that affect anything?

I would love to see a clear discussion of how these  parameters ( or any others) weigh against each other.

Leonard Levy, DP
San Rafael, CA




Mike Nagel
 

On Sat, Mar 31, 2018 at 01:22 pm, Leonard Levy wrote:
If I am shooting on a Monster but releasing on a web page ( as is more often the case than any of us want to admit) I should have a hell of a lot more perceived  DOF than if its going to end up on an IMAX screen.
Nobody knows the final delivery "screen size", since there are too many and you cannot control how the audience watches your content. In addition, IF (!) - and that is a BIG IF - there would be a drastic shift/change in perceived DOF based on the viewing medium, then that would not only encompass screen size but also screen technology, as Mitch already partially mentioned. And there are plenty of different screen technologies, and then manufacturer deviations., etc etc etc... And then there is viewing environment, which obviously also has an impact.

I would like to see the equation for all of that.

Gavin Greenwalt
 

Once you start going down that rabbit hole, there is literally no end.  Sure your circle of confusion diameter might be smaller than a pixel on your capture medium, but what if it’s half in one pixel and half in the other? You’ll no longer have a perfectly sharp pixel.   And even if you did focus down to critical focus… you would end up with unwanted moire and aliasing, so camera manufacturers will throw on a low pass filter to soften the image anyway.

And then you have to account for the contrast of the point, there’s always a couple pixels of glare.  So even at critical focus with a theoretical 0.0000000001 micron CoC, the image on your sensor with enough contrast will still have some amount of halation and flaring, there will be some diffraction in the system.

Ultimately all of these formulas and charts will narrow your focus on how to conduct the test, but nothing can substitute a good representative test. (If “representative” is even possible with the myriad of delivery formats available today). 

Gavin Greenwalt
VFX
Seattle, WA

Argyris_Theos_cml
 

Mitch has a valid point here and I apologize for the insufficient explanation.
In my imaginary situation (and I see now that I should have specified 2K instead of HD) the data are rewrapped so that each pixel is repeated four times to form an 8K image.
The idea is that no resizing takes place inside the imaginary 8K projector, so that it delivers its native resolution.
I am talking about theatrical screening, not monitoring of course.
I imagine a spectator seating in a distance that will maximize perceived resolution. I have not calculated this, sorry.

For all who simply divide the acquisition sensor diagonal by a number (eg 1500), I would say that this is irrational. If spatial resolution was the only form available we would probably have been forced to use a CoC almost four times larger for the FF 2K image.
But temporal resolution leans in also.

And Ceteris Paribus is not valid anymore.

Best

Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

31 Μαρ 2018, 11:57 μ.μ., ο/η "Mitch Gross" <mitchgrosscml@...> έγραψε:

uprezzed

Mike Nagel
 

@ Gavin: couldn't agree more

One can control acquisition, and the DOF calculations for that work. Everything afterwards is not in our hands.

curious to see what Argyris finds out, since he said he has a white paper from some optical experts.

Mike Nagel
 

On Sat, Mar 31, 2018 at 02:55 pm, Argyris_Theos_cml wrote:
For all who simply divide the acquisition sensor diagonal by a number (eg 1500), I would say that this is irrational.
All DOF calculators use that formula. You can change adjust the number that you divide the image plane diag accordingly, if you feel you have "better working" value.

But - clearly - CoC is one of a few parameters in the DOF equation, not the only one. Worthwhile to investigate which parameters have the highest impact...

clearly the DOF equations work, as they've been used for ~ 100 years and are being used every day.

so what did the white paper state in regards to DOF impact of the viewing format ?

- Mike Nagel
Director/Producer
L.A.

Mark H. Weingartner
 


On 31Mar, 2018, at 15:10 28, Mike Nagel via Cml.News <michanagel=yahoo.com@...> wrote:

clearly the DOF equations work, as they've been used for ~ 100 years and are being used every day.

If you talk to some older, multi-format experienced focus pullers you will find that they (and by extension we)  adjust COC #s until the tables, Kelly wheels, or calculators give us numbers that work for us in the real world for a given project.

They are a starting point, but they are the easiest single variable to change in order to adjust our DOF calculations without having to create offsets.

When we moved from film-to-telecine to digital HD camera-final color  a number of focus pullers commented that the numbers weren’t working as strictly calculated, and there are a couple of different mechanisms likely in play to account for that.

one of them is that there is a difference between sharpness (or acuity) and spatial resolution.  When we were moving from photochemical to digital cameras for tiled HDR backgrounds, our tests of the early DSLRs showed that while they had a lower spatial resolution, the images looked sharper… a function of higher contrast at edges among other things.

eg. The focus fall-off on a really high contrast lens looks steeper than with a slightly less contrasty lens.



Add some smoke or diffusion between the lens and the scene and your DOF goes up… when the sharpest thing is a bit softer then you get a wider range of things that are "acceptably sharp”

So while this is to some degree quantifiable - at least enough to be able to make comparative judgements,  the gradient of the fall-off and the acuity of the result of the entire image chain vary within the bracket of “same imager size, same display size, same viewing distance, same brightness range, same, display gamma etc etc etc

At some point you have to just look at the damned pictures and decide what is sharp enough and what isn’t and make a note on your 3x5 card and move on:-)

The right CoC to use is the one that gives you acceptable results based on viewing the images…  


FYI regarding viewing distance, it is generally considered that  1/60th of a degree of arc (one arc minute) is the finest level of detail that the human vision system can discern…    so when figuring out 
minimum viewing distances for jumbotrons, projected systems etc  the display pixel pitch has to be below one arc minute to avoid detection… so you can work out minimum viewing distance to avoid seeing the standing pattern of the display pixels to get your closest viewing distance… not necessarily your most pleasing viewing distance, but that’s another story.

Another discussion revolves around the difference between standing pattern and random pattern receptors…I won’t even go there right now.

Mark Weingartner, ASC
LA




Mike Nagel
 

On Sat, Mar 31, 2018 at 03:54 pm, Mark H. Weingartner wrote:
If you talk to some older, multi-format experienced focus pullers you will find that they (and by extension we)  adjust COC #s until the tables, Kelly wheels, or calculators give us numbers that work for us in the real world for a given project.
yes, absolutely. You adjust as needed. CoC is not hammered in stone, it is an adjustable parameter in the equation (and so are other things).

but since CoC is a "moving target" (based on many factors, such as the ones you mentioned yourself) while the other parameters in the equation are not, it is IMO advisable to adjust what you know you have control over in order to get the DOF that you need - IF your shot setup allows that, obviously.

- Mike Nagel
Director/Producer
L.A.

Manousiakis Dimitris
 

Good evening. 
Two months ago i had a similar problem, how to calculate easily DOF for different cameras, lenses, f,T/stops and print them.
With a friend of mine created an excel file that did  the job.

DOF CULCULATOR,

1. Culculate CoC diameter on specific distances, depending of focus distance.
2. DoF culculator (near, far, total)
3. Compare the DoF of two lenses side by side. (e.g. 50mm f/2 [DoF]  =  100mm f/8 [DoF] on same size sensor)
4. Hyperfocal distances for one camera at the time (table & chart)
5. Included a list with 33 cameras and modes. At least but not last is always possible to add new Cameras, CoC and lenses.
>> Edit only GREEN cells.

Argyris the CoC limit is by (Pocket AC). Screen dimension between 10-20m.

Check out here...
* there is also some ,pdf examples.

Dimitris Manousiakis
Camera Assistant, Colorist
Thessaloniki, Greece
0030 698 929 3017
skype: manousiakisd

Δημήτρης

On 31 March 2018 at 12:28, Argyris_Theos_cml <cml@...> wrote:
A question addressing lens experts:
 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?
 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Argyris_Theos_cml
 

Dimitris
this a great tool you created, but I do not understand your first tab
(CoC calculator)
How do you calculate CoC, that is the main question
What am I missing?

Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Geoff Boyle
 

And that is why I’ve been staying out of this 😊

 

Theory and real world clash once again.

 

These angels on the head of a pin theory discussions are interesting but in terms of getting out there and shooting something…

 

Cheers

 

Geoff Boyle NSC FBKS

Cinematographer

Zoetermeer

www.gboyle.co.uk

+31 (0) 637 155 076

 

From: cml-glass@... <cml-glass@...> On Behalf Of Mark H. Weingartner

If you talk to some older, multi-format experienced focus pullers you will find that they (and by extension we)  adjust COC #s until the tables, Kelly wheels, or calculators give us numbers that work for us in the real world for a given project.

 

,_

Manousiakis Dimitris
 

Argyris, to calculate the CoC we inverse the fomulas of Near focus and Far focus and then we solve for CoC'.
Please take a look at "formulas" tab.

On the first tab, select camera, FOCUS DISTANCE, lens, f-T/stop, and all the distances you want to check CoC on the left column. 

I've just updated the "DOF - TWO LENSES CHECK" tab. Check out the Folder "_Argyris CML" on my link below.
FF35 50mm T2  == S35 75mm T6.7 [DOF]   .... Always exactly 2+1/2, T/stops and DOF maches.


Have a nice day,

Δημήτρης

On 31 March 2018 at 12:28, Argyris_Theos_cml <cml@...> wrote:
A question addressing lens experts:
 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?
 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Manousiakis Dimitris
 

Argyris, to calculate the CoC we inverse the fomulas of Near focus and Far focus and then we solve for CoC'.
Please take a look at "formulas" tab.

On the first tab, select camera, FOCUS DISTANCE, lens, f-T/stop, and all the distances you want to check CoC on the left column. 

I've just updated the "DOF - TWO LENSES CHECK" tab. Check out the Folder "_Argyris CML" on my link below.
FF35 75mm T2.8  == S35 50mm T2 [DOF]   .... Always exactly 1, T/stop and DOF maches.


Have a nice day,

Δημήτρης



Δημήτρης

On 31 March 2018 at 12:28, Argyris_Theos_cml <cml@...> wrote:
A question addressing lens experts:
 
Suppose we have two cameras: one carrying S35 8K sensor, the other is FF35 with an HD sensor
I  employ a ~50mm lens on the first, a ~75 on the other. (I choose the exact focal lengths to match field of view)
I place my object at 3 meters and want my Depth of Field to match in both cameras, holding focus from 2.5 to 4 meters. 
The shot wiill be screened in a 10 meter wide screen, via a digital 8K projector. 
The only  post production work allowed is minimal color correction and uprezing of the HD image to 8k at the final stage, in order to avoid using the scaling machine of the projector server. 
Question:
At what f stop do I need to shoot on each camera to match DoF ?
 
Best Regards

Argyris Theos, gsc
DoP Athens Greece
cml@...
skype Argyris Theos

Argyris_Theos_cml
 

OK it appears my mind game confused things.
Allow me to simplify it.
Suppose we have two cameras (let's say S35) with equal sensor size but one is 2K resolution, the other is 8K.
Suppose we use the same lens on both, and the lens' performance is ideal.
Suppose we shoot the same shot with both

Suppose we project via two projectors that are equal on the exception that one is natively 2K the other is natively 8K
Screen size is 10 meters
Spectator has excellent vision and is seated at a distance that will allow him to fully resolve the 8K footage.

So Ceteris Paribus the only difference is in sensor resolution.

My guess is that the higher resolution camera will exhibit shallower depth of field.
The question is how much?
And
How does CoC change according to that?

Best Regards


Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

1 Απρ 2018, 12:13 μ.μ., ο/η "Manousiakis Dimitris" <manousiakis.dimitris@...> έγραψε:

On

Christos Oscar Kambiselis
 

Now why do you believe the resolution would have to do anything with the depth of field, if it is based on sensor/film size, focus length, focal length and f-stop, upscalling it also has nothing to do with it.

Christos Oscar Kambiselis 
Lynx Pictures 
Finland 

On Sun, Apr 1, 2018, 16:26 Argyris_Theos_cml <cml@...> wrote:
OK it appears my mind game confused things.
Allow me to simplify it.
Suppose we have two cameras (let's say S35) with equal sensor size but one is 2K resolution, the other is 8K.
Suppose we use the same lens on both, and the lens' performance is ideal.
Suppose we shoot the same shot with both

Suppose we project via two projectors that are equal on the exception that one is natively 2K the other is natively 8K
Screen size is 10 meters
Spectator has excellent vision and is seated at a distance that will allow him to fully resolve the 8K footage.

So Ceteris Paribus the only difference is in sensor resolution.

My guess is that the higher resolution camera will exhibit shallower depth of field.
The question is how much?
And
How does CoC change according to that?

Best Regards


Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

1 Απρ 2018, 12:13 μ.μ., ο/η "Manousiakis Dimitris" <manousiakis.dimitris@...> έγραψε:

On

Gavin Greenwalt
 

Depth of field as defined as ‘acceptable focus area’ will be larger with the lower resolution sensor but aesthetically, as a whole image, the depth of field characteristics will match. Your terms are ambiguous so the answer is too. The 2k will match(ish) a down sampled 8k image’s DOF. The background bokeh will be the same. You will see the image get softer than 8k on the 8k pipeline sooner and therefore define the acceptable focus region as smaller.

Gavin Greenwalt
VFX Supervisor
Seattle, WA

Mitch Gross
 

It is not just sensor resolution but also projector resolution. You posit one complete system that is 2K and one complete system that is 8K. 

Assuming ALL other aspects are equal (a huge assumption), that OLPFs, signal compression, lens diffraction and EVERYTHING else do not contribute, then the 8K system will have a shallower Depth of Field as  a smaller CoC is required. 

Mitch Gross
Cinema Product Manager 
Panasonic Media Entertainment Company
New York

On Apr 1, 2018, at 9:26 AM, Argyris_Theos_cml <cml@...> wrote:

OK it appears my mind game confused things.
Allow me to simplify it.
Suppose we have two cameras (let's say S35) with equal sensor size but one is 2K resolution, the other is 8K.
Suppose we use the same lens on both, and the lens' performance is ideal.
Suppose we shoot the same shot with both

Suppose we project via two projectors that are equal on the exception that one is natively 2K the other is natively 8K
Screen size is 10 meters
Spectator has excellent vision and is seated at a distance that will allow him to fully resolve the 8K footage.

So Ceteris Paribus the only difference is in sensor resolution.

My guess is that the higher resolution camera will exhibit shallower depth of field.
The question is how much?
And
How does CoC change according to that?

Best Regards


Argyris Theos, gsc
DoP, Athens Greece,
theos@...
+306944725315
Skype Argyris.Theos
www.vimeo.com/argyristheos
via iPhone

1 Απρ 2018, 12:13 μ.μ., ο/η "Manousiakis Dimitris" <manousiakis.dimitris@...> έγραψε:

On

Gavin Greenwalt
 

“Assuming ALL other aspects are equal (a huge assumption), that OLPFs, signal compression, lens diffraction and EVERYTHING else do not contribute, then the 8K system will have a shallower Depth of Field as  a smaller CoC is required. “ 
Mitch Gross

Also assuming that you need a full 8k detail within the entire acceptable focus range and that anything between 8k - 2k detail isn’t “acceptable” enough for some of the “acceptable focus range”. 

Considering 2k has been acceptable for cinema up to this point I think that’s also a huge assumption. 

Gavin Greenwalt 
VFX
Seattle, WA

Brian Heller
 

The primary determinants of DOF are f:stop and subject size on the image plane.
By subject size, is meant the literal actual size of the subject on the imager.

For instance, if the subject is 8mm in height on a 35mm sensor and 8mm in height on a 65mm sensor, the the DOF will be identical provided the f:stop is the same and nothing else is changed.

However, if you are positing that the subject on each sensor occupies the same percentage of the frame, say 50%, then there will be less DOF with the larger sensor. That is not a function of DOF, but image magnification.

Sensors do not have Depth of Field,
neither do lenses. A WA lens “appears” to have more DOF than a long lens simply because the subject is smaller. When the subject size is compensated for by moving the camera to match the subject size the the DOF will be identical, assuming the f:stop is the same, etc.

Brian Heller
IA 600 DP

Mitch Gross
 

Brian is of course correct, but in the given question of identical lenses in front of identical-sized sensors to identical-sized screens with the only difference being one is an end to end 2K and the other is end to end 8K, then resolving power comes into play as what we are really talking about is PERCEIVED resolution. 

This is all a question of when you can tell when something falls out of focus, meaning the point you can perceive the CoC of a point. A tighter grouping of pixels will allow for a tighter perception point, therefore a smaller CoC. 

Depth of Field is an illusion, and all imagery a fantasy concocted by our brains. In practice these differences are so minute as to be pointless. Contrasty lighting will affect perception of focus and Depth of Field more. Dancing on the head of a pin indeed. 


Mitch Gross
Cinema Product Manager 
Panasonic Media Entertainment Company
New York

On Apr 1, 2018, at 4:11 PM, Brian Heller <brianheller1@...> wrote:

The primary determinants of DOF are f:stop and subject size on the image plane.
By subject size, is meant the literal actual size of the subject on the imager.

For instance, if the subject is 8mm in height on a 35mm sensor and 8mm in height on a 65mm sensor, the the DOF will be identical provided the f:stop is the same and nothing else is changed.

However, if you are positing that the subject on each sensor occupies the same percentage of the frame, say 50%, then there will be less DOF with the larger sensor. That is not a function of DOF, but image magnification.

Sensors do not have Depth of Field,
neither do lenses. A WA lens “appears” to have more DOF than a long lens simply because the subject is smaller. When the subject size is compensated for by moving the camera to match the subject size the the DOF will be identical, assuming the f:stop is the same, etc.

Brian Heller
IA 600 DP

Michael Brennan
 

On 2 Apr 2018, at 5:11 am, Brian Heller <brianheller1@...> wrote:

A WA lens “appears” to have more DOF than a long lens simply because the subject is smaller.
Associated with this, the higher displayed resolution of the image the more apparent is the depth of field.


Be it IMAX viewed from 60ft, a 70 inch screen in your living room or the use of virtual reality glasses.

I know for head shots, it’s subjective and of course, the industry is naturally behind in conducting audience research.

On a closeup, I think we have gone too far if one eye appears softer than the other.

What does the audience think?


Mike Brennan
DP
Melbourne.

Pawel Achtel ACS
 

Mike Brennan: On a closeup, I think we have gone too far if one eye appears softer than the other.”

 

I don’t think there is one fast rule and the answer is, as usual: “it depends”. You mentioned IMAX. Well, there are (or there shouldn’t be) any close-up shot on IMAX. Otherwise, 1/3 of the audience will be looking at left ear out of focus, the middle third will be looking at hair up the talent’s nose and the remaining third will be looking at right ear that is out of focus. When you shoot for IMAX, or Giant Screen in general, the framing is much, much wider and the deeper the DOF the better. Particularly that almost all IMAX is 3D. Deep DOF and presence of sharp detail are critical to perception of 3D.

 

Conversely, when filming for mainstream cinema or television, there have been many shots that have paper thin DOF or even deliberately out of focus, which just make sense in the story telling.

 

The delivery medium plays critical role to shot composition, framing, DOF, pacing and just about any other aspect of our craft.

 

Kind Regards,

 

Pawel Achtel ACS B.Eng.(Hons) M.Sc.

“Sharp to the Edge”

 

ACHTEL PTY LIMITED, ABN 52 134 895 417

Website: www.achtel.com

Mobile: 040 747 2747 (overseas: +61 4 0747 2747)

Mail: PO BOX 557, Rockdale, NSW 2216, Australia

Address: RA 913 Coles Bay Rd., Coles Bay, TAS 7215, Australia

Location: S 42° 0'14.40"S, E 148°14'47.13"

Email: Pawel.Achtel@...

Facebook: facebook.com/PawelAchtel

Twitter: twitter.com/PawelAchtel

Skype: Pawel.Achtel

 

From: cml-glass@... [mailto:cml-glass@...] On Behalf Of Michael Brennan
Sent: Monday, 2 April 2018 10:46 AM
To: cml-glass@...
Subject: Re: [glass] Depth of Field question

 

On 2 Apr 2018, at 5:11 am, Brian Heller <brianheller1@...> wrote:

A WA lens “appears” to have more DOF than a long lens simply because the subject is smaller.

Associated with this, the higher displayed resolution of the image the more apparent is the depth of field.


Be it IMAX viewed from 60ft, a 70 inch screen in your living room or the use of virtual reality glasses.

I know for head shots, it’s subjective and of course, the industry is naturally behind in conducting audience research.

On a closeup, I think we have gone too far if one eye appears softer than the other.

What does the audience think?


Mike Brennan
DP
Melbourne.

Art Adams
 

I think one eye not appearing softer than the other is nigh impossible on a modern closeup. My concern is more about which eye. The far (usually lit) eye seems to be the proper one, and that's the way I've always done it, but more recently I've seen some TV series go for the close eye and for some reason it's a bit disturbing. I'm not sure why.

--
Art Adams
Director of Photography
San Francisco Bay Area

Jen White
 


On Apr 2, 2018, at 7:05 AM, Art Adams <art.cml.only@...> wrote:

I think one eye not appearing softer than the other is nigh impossible on a modern closeup. My concern is more about which eye. The far (usually lit) eye seems to be the proper one, and that's the way I've always done it, but more recently I've seen some TV series go for the close eye and for some reason it's a bit disturbing. I'm not sure why.


I feel the opposite. When I watch a film where the close-ups are focused on the far eye I find my left hand twitching trying to correct it. I always focus on the closer eye because for me that feels more natural. If a subject/actor is turned enough that their eyes aren’t both in focus, my eye will automatically want to connect with their eye that’s closest to camera. 

I wonder if there’s a psychological explanation for this. 


Jen White
Local 600 DP
Finally back in Los Angeles

Shilpa Mankikar
 

Yes I agree, and it made me unsettled in Call Me By Your Name, for example, when some of those shots were not in focus.   Or I wanted them to pull focus back to the Left/Front of the face.
Shilpa

On Mon, Apr 2, 2018 at 8:58 PM, Jen White <imajen@...> wrote:

On Apr 2, 2018, at 7:05 AM, Art Adams <art.cml.only@...> wrote:

I think one eye not appearing softer than the other is nigh impossible on a modern closeup. My concern is more about which eye. The far (usually lit) eye seems to be the proper one, and that's the way I've always done it, but more recently I've seen some TV series go for the close eye and for some reason it's a bit disturbing. I'm not sure why.


I feel the opposite. When I watch a film where the close-ups are focused on the far eye I find my left hand twitching trying to correct it. I always focus on the closer eye because for me that feels more natural. If a subject/actor is turned enough that their eyes aren’t both in focus, my eye will automatically want to connect with their eye that’s closest to camera. 

I wonder if there’s a psychological explanation for this. 


Jen White
Local 600 DP
Finally back in Los Angeles

Brian Rose
 

I’m going to try to find the original Instruction Manual for David Samuelson’s Depth of Field Test Rig. We built these for David when I was at OpTex.

As David said, the rig was used to ‘explore’ DoF rather than simply to ‘measure’ it. We found that there were many different factors affecting it, some quite surprising.

It’s a shame that the rig went out of use, it was a great tool…

Cheers

Brian

 

Brian Rose
Tel: +44 (0)20 8868 1729
Mob: +44 (0)7768 635 788
email: brianmrose@...

 

Brian Rose
 

There’s an SMPTE article here:

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7308727

 

 

 

Brian Rose
Tel: +44 (0)20 8868 1729
Mob: +44 (0)7768 635 788
email: brianmrose@...

From: cml-glass@... <cml-glass@...> On Behalf Of Brian Rose via Cml.News
Sent: 03 April 2018 09:57
To: cml-glass@...
Subject: Re: [glass] Depth of Field question

 

I’m going to try to find the original Instruction Manual for David Samuelson’s Depth of Field Test Rig. We built these for David when I was at OpTex.

As David said, the rig was used to ‘explore’ DoF rather than simply to ‘measure’ it. We found that there were many different factors affecting it, some quite surprising.

It’s a shame that the rig went out of use, it was a great tool…

Cheers

Brian

 

Brian Rose
Tel: +44 (0)20 8868 1729
Mob: +44 (0)7768 635 788
email: brianmrose@...

 

Brian Heller
 

Brian Rose wrote:

I’m going to try to find the original Instruction Manual for David Samuelson’s Depth of Field Test Rig. We built these for David when I was at OpTex.

As David said, the rig was used to ‘explore’ DoF rather than simply to ‘measure’ it. We found that there were many different factors affecting it, some quite surprising.

It’s a shame that the rig went out of use, it was a great tool…


That would be wonderful to see again.

Brian Heller
IA 600 DP

Richard Bradbury
 

There’s still one of these in available for use at Arri Rental in London, and I’m sure I’ve seen something similar at Panavision. 

Richard Bradbury
Focus Puller
London


On 3 Apr 2018, at 10:59, Brian Rose via Cml.News <brianmrose=virginmedia.com@...> wrote:

As David said, the rig was used to ‘explore’ DoF rather than simply to ‘measure’ it. We found that there were many different factors affecting it, some quite surprising.

It’s a shame that the rig went out of use, it was a great tool…

Cheers

andyrmail@...
 

And speaking of David Samuelson didn't this conversation begin way back here? (I hope the files are visible...)

Andy Romanoff
making pictures one at a time in sunny Los Angeles

Mako Koiwai
 

Andy … just to be clear … we’re talking about this rig:



Last time I saw one was at Clairmont Camera, now Keslow Camera. 

makofoto, s. pasadena, ca

andyrmail@...
 

yes Mako, I remember it well. A useful tool for reality checking against the tables and charts.

I wasn't commenting on the Brian Rose post but rather the thread and how long variations of this discussion have been going on.

Still interesting though:)

Andy Romanoff

Making motorcycle pictures one at a time, some of them here;  http://andyromanoff.zenfolio.com/motorcycles