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HS scope test Results of DMG MIX LED fixture

brad dickson
 

We recently used the HS Scope, part of the 4K scope software, that reads the chroma signal response from a camera, to evaluate the Rosco DMG MIX LED fixture. We used an ARRI and RED camera, preset to 3200K rec 709, for our tests, shooting a DSC chroma dumonde 24 + 4R chart. A Tungsten light source was the target reference for the Rosco DMG MIX to match on camera. This allowed the DMG team to quantify their calibration work on the MIX. The results were encouraging as both on the RED and ARRI the on-camera chroma differences between the actual tungsten source and the MIX were very slight, based on the multiple points of the DSC chart. The HS Scope is a good tool for evaluation and calibration tool for an LED source for on-camera use. Should adjustments to the spectrum be needed they can be adjusted in real time using the HS Scope reference, thus getting camera accurate results.

Brad Dickson
Senior Lighting Designer
Toronto Canada

Mike Nagel
 

can you post the RED cam readout and also which RED cam model it is ?

Thanks.

- Mike Nagel
Director
Los Angeles

brad dickson
 

Hi Mike

The RED was the Epic-W Helium.  I am curious if you find the HS Scope is helpful to immediately quantify a LEDs performance for accurate chroma reproduction on camera? While we have a variety of the standard scopes in the software such as Vectorscopes CIE etc but we created the HS Scope to make it more user-friendly. Unlike the current lighting, metrics used the HS Scope readouts tell you immediately, visually, if a light source such as LED will match the chroma performance of an established target light source such as a tungsten / HMI, etc source on camera. I may do an online webinar on the HS Scope for those interested. We are adding features to it and as an end user myself getting real-time comparative results is my target. While the HS Scope is good on set tool connected to the production camera, we know to make it an easy offset tool for evaluation and calibration of fixtures prior to going in front of the camera is the real goal. However at this point, hopefully, other LED manufacturers, like Rosco are doing, will quantify their LEDs performance and publish results like the HS Scope comparison Rosco has done. 
We use the DSC chart as it meets standards and is used by many camera manufacturers. Plus DSC ChromaDuMonde has a wide chroma range in the 24+4R chart. Using other charts would give too wide of gaps in the chroma signal to give a varied response over a wide range of chroma values. 
Here are the RED results.

Mike Nagel
 

Hi Brad,

are those the exact same two light sources (Tungsten | LED) and the same DSC chart for both the RED and the Arri in your images ?

- Mike Nagel
Director
Los Angeles

brad dickson
 

Hi Mike
Yes the same setup as both cameras were shooting the same chart the same time under the same light. We had both cameras side by side for the tests.

On Sun, Jun 9, 2019 at 05:13 Mike Nagel via Cml.News <michanagel=yahoo.com@...> wrote:
Hi Brad,

are those the exact same two light sources (Tungsten | LED) and the same DSC chart for both the RED and the Arri in your images ?

- Mike Nagel
Director
Los Angeles

--
Thank you 
Brad Dickson
647 784 2350

Lighting Video

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Mike Nagel
 

two things:

(1) so u're mapping spectrum response scaled to SMPTE in a historgram but u're mapping them based on hues 0-359 degrees along the x axis ? is there a view to see the result by nm ?

(2) not sure if I misinterpret this, but Arri separates the color chips and has gaps where there should be, while the Helium seems to smear all chips seamlessly into each other, hence much less color separation...

- Mike Nagel
Director
Los Angeles

brad dickson
 

Hi Mike

Sorry for the late reply.

Since the HS Scope relates to the video chroma signal we use graticules that relate to the vectorscope. We don't show nm but I would like to know how that would be more of a benefit? Since we also have a CIE scope in our software that can be up at the same time as the other scopes in the display that may be helpful. I don't know if nm would make it appear too much like an SPD and the end users would expect the rise to be relative energy instead of the SMPTE values. The goal is to give chroma signal values in a user-friendly easy to read visually when you can see in a spectral form the chroma signal results from a light source. 

Yes, the Red did see the colours differently even shooting the same chart at the same time as the Arri. We plan to look at this again for our reference. 

Brad Dickson
Senior Lighting Designer 
Toronto Canada

Ian Murray
 

Hey guys, 

The HS scope looks a very interesting tool. I've found a lot of inconsistencies with LEDs over the last few years, but have had to introduce them for the efficiency they offer. What I have recently used to help get over this problem is the newer Kino Flo LEDs.  The whites are spot on (best I have used on skin) and they all automatically follow the Planckian curve. The real benefit for me is that in my work I like to play with the whites (Kelvin) and subtle colour, being able to do this on the fly without having to worry about the colour degrading as I shift the whites is a game changer and is evident in the grade! I have just heard they are coming out with a camera LUT version so presumably this will make them produce clean white light to a specific camera response curve – has anyone tried this...this must be the future of digital lighting? 
 
You can see some of my work using these Kinoflo's over on Instagram: @ianmurraydop. I post breakdowns of what I'm doing with lighting in the form of 'set notes'.

Ian Murray
Commercial DOP
London, UK