Cine gamma settings in the EX1

[Alister Chapman]

Thanks for completing the plots Serena. It confirms what we are all seeing with the CG's, lifted blacks, linear mid section and compressed highlights.

[Simon Denny]

Hi Serena,
Could you plot the chart for Cine gammas 2 and 3 if you have time.

Cheers

[Gavin Rawlings]

Originally Posted by Alister Chapman

The EX has around 11 stops of latitude when using CG1, CG3, CG4 or with Std gamma plus correctly set knee.

Thanks Alister. Thats more then I thought. I was expecting around 10 or so...

[Serena Steuart]

Originally Posted by Bill Ravens

Serena...
Can you share with us how you abtained this data? Is it empirical or predicted? The knee of the S1 curve shows a bit of overshoot, which I would guess is data scatter? If it's real, there will be some serious distortions(non linearities) in high-lites of the image. Plotting this with a log scale on the abscissa makes the data look less serious than it may be.

Empirical data only and a different technique to that used previously to try to keep things simple.
That overshoot on S1 is an error (a small but important slip in transferring data) and thanks for raising the question. I might have queried that myself had I not been required to do other neglected things. I've replotted the corrected results in the attached (and checked I hadn't done the same elsewhere). Also repeated S1 to provide an indication of error magnitude, and added S1 with default auto-knee "on" (unintentionally).

The methodology is simple, repeatable and I think useful. Employs only data on the LCD. Requires a uniform constant light source large enough to fill the FOV, with the camera locked down. I used the lens wide to ensure max effective aperture, but the f/stops are relative anyway. The camera gives you a %brightness reading and the f/stop, so starting with the f/stop giving 109% I close down in half stops recording brightness at each change in f/stop reading. The change in f/stop reading is finely repeatable and I took that point (closing) as being the actual aperture value. The process is equivalent to decreasing the test subject's brightness in half stop increments, and because it is all relative it is unimportant whether the f/number is the true value, provided the increments are accurate (which they might not be towards the high f/stop end). I used ND filters to work aperture over a limited range.
In plotting the results the geometric value of the f/number was used in place of the rounded figure which is displayed.
The usefullness of the plots is in understanding the gamma options. There are aspects of the method which I'm still evaluating and I'm sure there will be discussion about its validity.

EDIT: A slight problem with my plots attached to this post. They are all normalised for subject brightness, so making the standard gammas very similar to the cine gammas (in terms of sensitivity), a matter which I'm sure Piotr doesn't believe! Rightly so. However I won't delete this plot, since people have already considered it and once the normalisation is known it still contains useful information. A new post below shows all cine gammas compared to STD 1 gamma, and this time not normalised!

[Robert Young]

Originally Posted by Vincent Oliver

Bill, without your and others knowledge we would be totally stuck, or at worst not get the best results from our gear.

So very true.
This is the first camera I have owned that provides for this level of profile adjustment. Virtually all of the little bit I know about this subject comes from trolling thru posts by the generous experts on this forum, cranking in the various settings, looking at the footage, and slowly, slowly finding what I like, and what settings get the job done. I would have not even known where to begin otherwise- certainly not from Sony.

[Bill Ravens]

Serena...

Thanx for having done this. And thanx for providing your test method.

[Dominik Seibold]

I'm using cine2 all the time, because I don't want to have to deal with above 100IRE information. Also cine1/2 looks most linear/neutral.
Cine4 has heavy highlights-compression (too much in most situations). Cine3 also has a lot of highlights-compression, but additionally the darks get pushed down a bit relatively to cine1/2 leading to contrasty low-mids. Therefore cine3 actually is the most complex curve.

Btw, I guess that the dynamic range/latitude gets maximized with cine1/2, because the noise of the ex1 is too much that black-stretching could actually retrieve extra-information in the darks which else would get lost because of 8bit-quantization. But heavy highlights-compression of cine4 together with 8bit quantization will definitely crush highlight-information.

[Barry J. Anwender]

Thank you Serena, Bill, Alister and all who have shed more light on the Cine Gamma settings.

[Michael B. McGee]

Thankfully we have this forum to express the need for this thread, as well as the good folks who are willing to generously give of their time-talent-experience for the benefit of all. Cheers!

i second that. i wouldn't be where i'm at today without the contributions from all of you. i've learned more in the last year since i bought my EX1 then just about all the previous years combined. I don't really consider myself a Newbie anymore. maybe a veteran Newbie.

[Simon Denny]

This is the Alan Roberts review of the Cines in the EX1.
I have copied and pasted this so I hope that this is ok?

Cine2 is the only curve suited to production without grading, since it clips at 100%.
Cine1 is similar but copes with overexposure by extending beyond 100% video level.
Cine3 and 4 differently share the contrast range, use these to taste.

If using Cine1, 3 or 4, make sure that video will not be clipped in post-production. Or that grading can cope with the over-voltages.

[Serena Steuart]

Here is a plot of the four cine gammas plus standard 1 gamma. Given in two forms: the usual log of subject brightness, plus with a linear subject brightness which is the form in Sony's sketches.
The data was taken with the following conditions:
subject surface brightness: 16000 lux; 5600K; white; broad; diffuse.
Effective subject brightness at 1.0 on curves 900 lux approx.
WB: 5600K
camera gain: 0dB
shutter speed:1/50
HQ mode, 25fps
PP properties: default with knee "off" and changing only the gamma selected.
When iris was closed the brightness reading was 3%. This could have been adjusted using black level, but I left defaults as is.

The LCD shows image % brightness to a whole number, so accuracy decreases with decreasing reading. The readings are repeatable within 1 digit (generally get the same reading).

[Simon Denny]

Thanks serena.
Looking at the graph's I really like the curve of Cine 2.
I'm really suprised that Cine 1 peaks at 110 as I thought the top end droped off a bit in brightness.

Thanks agina for your effort.

[Christopher Brown]

Originally Posted by Serena Steuart

Here is a plot of the four cine gammas plus standard 1 gamma. Given in two forms: the usual log of subject brightness, plus with a linear subject brightness which is the form in Sony's sketches.

Fantastic info, Serena. Thank you very much.

[Bill Ravens]

I'm happy to see that Cine2 uses a knee rather than a hard clip to be asymptotic to 100%. The drawback is the "somewhat" flattening of the midrange(contrast reducing), relative to C1, to get the knee that I wonder about.

[Serena Steuart]

Sometime back when I first tried to evaluate the gamma curves the SAW curve generation facility made me suspect that the EX camera is natively balanced to 3200K. Still I don't know the answer to that, but the SAW facility did suggest that the gamma curves vary with WB. Out of curiosity, using my more direct method, I've looked again at the effect of changing WB and the results are attached.
I used the same subject source and added a full orange gel, which cut the source by a stop. The camera white balanced at 2800K, so I accepted that.
The effects are greater than I expected. The camera showed greater sensitivity and the results are plotted to retain relative subject brightness of 1.0 matching the previous plots. STND 1 gamma exhibits a steeper roll off (or knee) prior to clipping.

In the 5600K plots the plotted dynamic range is 10 stops, with some unreliable data going down another half stop with black half a stop further down. So you could say 11 stops, with a bit of a stretch. However at 2800K the range (with the same considerations) is 12 stops, so the BBC statement of 11 stops dynamic range certainly holds under tungsten.

I'm interested in any comments on these observations.