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Meters (was Day one camera evaluations)

 

As a matter of interest does anyone use a Lumi with an iPhone?

I have a Sekonic meter but the idea of a meter that does CT for only £200ish is very appealing.

Michael

Michael Sanders
London Based DP.

+ 44 (0) 7976 269818




On 9 Jul 2018, at 20:34, Art Adams <art.cml.only@...> wrote:

The sensors in exposure meters have spectral shaping filters so they only read the visible spectrum and not UV or IR. They peak around 525 ("green") and sensitivity tends to roll off toward the upper and lower ends of the visible spectrum.

Leonard Levy
 

On Jul 10, 2018, at 12:21 AM, Michael Sanders via Cml.News <glowstars=me.com@...> wrote:
As a matter of interest does anyone use a Lumi with an iPhone?

I use Adam Wilt’s Cine Meter II for IOS and find it quite accurate even for color. Its astounding IMHO.
The Foot candle readings  jump around so its hard to get a precise number but I’m used to analogue meters  like my old spectra combo 500 that don’t give digital read outs anyway. It seems to be as accurate as that was. 
Its certainly not perfect, but I’ve compared it to expensive  color meters and  its seems to be within the same lousy tolerances those are. 

You can use it with a LUMI but frankly I just carry a little paper hood in my wallet thats calibrated for the meter so I always have it with me. 
So its more like a disk than a ball but who cares.    Well worth the $25 or whatever it costs these days. Very useful on a scout. 

Leonard Levy, DP
San Rafael, CA 





Adam Wilt
 

It’s not uncommon for exposure meters to differ under different light sources, and to differ from camera metering. Most exposure-only meters (as opposed to color meters) use a single sensor chosen for photometric sensitivity but not filtered to precisely match the spectral sensitivity of a digital camera. Under typical full-spectrum lighting these spectral sensitivity differences are usually negligible, but with spiky spectra from fluorescents and LEDs — or with strongly colored lighting — the differences can be more noticeable.

My Gossen Starlite and Spectra Pro IV A meters agree under tungsten, but the Gossen reads 1/10 stop lower under daylight, and 3/10 lower under a cheap household LED “tungsten balanced” bulb (EcoSmart 6.5w).

The Cine Meter II app uses the iPhone’s camera as its sensor (full disclosure: Cine Meter II is my app). As it has a Rec.709-ish spectral sensitivity based on its own RGB Bayer pattern filter array, it tracks the spectral sensitivities of other digital cameras fairly closely. I expect it would be less divergent from other cameras under wonky LEDs than an unfiltered “analog” light metering sensor might be. 

FWIW Cine Meter II agrees with the Spectra under that EcoSmart LED, as do my still cameras’ meters when shooting a gray card. I haven’t been able to test exposure metering divergence beyond that as my other available sources don’t show more than a 1/10 stop difference between Cine Meter II, the Gossen, and the Spectra, and my cameras only report exposure with 1/3 stop resolution. I don’t have SkyPanels handy, alas.

I know Geoff is stuck in the Android ghetto (grin) but if anyone on his test crew wants to throw Cine Meter II into the mix please write me off-list and I'll send a download code. For straight-on incident/color readings a scrap of Lee 216 over the lens works as well as the $30 Luxi photosphere, and is probably more immediately available. Note that you will need to calibrate Cine Meter II before use, but as you have (a) other meters available and (b) proper tungsten lighting, that shouldn’t take more than a minute or two.

I’ve also tested the Lumu Power (plug-in incident / color meter) and found it’s pretty much spot-on for exposure, at least under tungsten and daylight.

Lumu Power’s color temperature readings track those of my other color meters most of the time. Lumu’s green/magenta tint readings are unusually low for fluorescent sources, but the various meters I have generally lack agreement about tint, so I can’t cast too many aspersions. Cine Meter II seems to predict my cameras’ tint sensitivities fairly consistently; your mileage may vary. (Detailed color test results are available if anyone’s interested and/or extremely bored.)

Adam Wilt
technical services: consulting / coding / camerawork
Vancouver WA USA (no, not that Vancouver, the other one)


Leonard Levy
 

On Jul 10, 2018, at 12:55 PM, Adam Wilt <adam@...> wrote:
 For straight-on incident/color readings a scrap of Lee 216 over the lens works as well as the $30 Luxi photosphere, and is probably more immediately available. Note that you will need to calibrate Cine Meter II before use, but as you have (a) other meters available and (b) proper tungsten lighting, that shouldn’t take more than a minute or two.

And for those on a serious budget i can testify that “Staples - 92 bright, 20 lb, ink jet printer paper also makes a perfect diffuser screen for the Cine Meter II giving accurate foot-candle readings and color readings after calibration. Testing with a few random Chinese  LED’s it was spot on with the results from my Sony FS7. At NAB I compared it to a Sekonic C700 under  room fluorescents and an under the counter floro. In one case it was a perfect match and in another only differed a bit. 

BTW - Geoff your rant was the chuckle highlight of my day and spot on!

Leonard Levy, DP
San Rafael, CA 






Leonard Levy
 

On Jul 10, 2018, at 12:55 PM, Adam Wilt <adam@...> wrote:
 For straight-on incident/color readings a scrap of Lee 216 over the lens works as well as the $30 Luxi photosphere, and is probably more immediately available. Note that you will need to calibrate Cine Meter II before use, but as you have (a) other meters available and (b) proper tungsten lighting, that shouldn’t take more than a minute or two.

And for those on a serious budget i can testify that “Staples - 92 bright, 20 lb, ink jet printer paper also makes a perfect diffuser screen for the Cine Meter II giving accurate foot-candle readings and color readings after calibration. Testing with a few random Chinese  LED’s it was spot on with the results from my Sony FS7. At NAB I compared it to a Sekonic C700 under  room fluorescents and an under the counter floro. In one case it was a perfect match and in another only differed a bit. 

BTW - Geoff your rant was the chuckle highlight of my day and spot on!

(Sorry about an empty post)

Leonard Levy, DP
San Rafael, CA