Raw footage are underexposed

fryderykp · October 03, 2013, 05:38:11 PM

Hi Everyone!

I've been testing my Canon 5d mark iii out. My problem is, that all raw footage are underexposed.

At first, I was using zebras, later I also switched on the 'false color' function and finally I've taken out the light meter from my cabinet. All the measurements were similar so the raws should be well exposed.

I thought that it is the workflow's fault. I've been working on DaVinci Resolve Lite, but as I've opened the images in PS the results were the same.

Can anybody help me, please?

AnotherDave · October 03, 2013, 05:51:57 PM

There are differences in shooting RAW vs. H.264.

Mainly, the camera actually only exposes in ISO multiples of 2. (IE: ISO 100, 200, 400, 800, 1600, etc) ISO 160 is really ISO 200 with digital correction.

Try using image fine-tuning set to -1 EV and keep in mind that MUCH MORE INFORMATION is stored in the highlights of RAW than in a compressed format. If you over-expose slightly, and adjust in post... you get a much cleaner image out of it.

Don't use zebras, just the RAW histogram with the ETTR hint. As long as you don't underexpose or overexpose too much... you'll be able to recover all the detail in color correction.

dmilligan · October 03, 2013, 05:53:36 PM

ETTR

robert.roth001 · October 03, 2013, 09:43:49 PM

I seem to be having the same problem here. Why shouldn't we use raw zebras?

AnotherDave · October 03, 2013, 10:45:03 PM

Zebras are only telling you that the whites in your shot are blown out based on the display, and your picture profile.

The RAW histogram will show you if that information in those highlights is really completely washed out. Plus ETTR hint will give you an idea of how "overexposed" you can get before blowing out the image.

You want the image to be as exposed-to-the-right (ETTR) as possible to have the highest signal-to-noise ratio.

fryderykp · October 03, 2013, 11:39:20 PM

Thanks for your answer.

So, how should I adjust exposure whit the light meter? Shoud I overexpose by one stop?

robert.roth001 · October 04, 2013, 01:41:42 AM

Hold on I'm confused. I know very well about ETTR. Zebras really is the best way to do that. I'm using the newest complete "alpha" version (I can get the exact build if you want then). Not any of the nightly builds. When I go into the zebras menu I have an option for just regular zebras and then RAW zebras. Are you saying that the RAW zebras is based on the display? From my experiences (I would have to do tests) I would have to say that is not true at all. I have gotten completely different results with both zebras. If someone can confirm that RAW zebras is still just based off of the display that would be very helpful.

Also... if that is the case, labeling it is RAW zebras and basing it off of the display is extremely misleading.

Africashot · October 04, 2013, 05:29:17 AM

Quote from: robert.roth001 on October 04, 2013, 01:41:42 AM
Hold on I'm confused. I know very well about ETTR. Zebras really is the best way to do that. I'm using the newest complete "alpha" version (I can get the exact build if you want then). Not any of the nightly builds. When I go into the zebras menu I have an option for just regular zebras and then RAW zebras. Are you saying that the RAW zebras is based on the display? From my experiences (I would have to do tests) I would have to say that is not true at all. I have gotten completely different results with both zebras. If someone can confirm that RAW zebras is still just based off of the display that would be very helpful.

Also... if that is the case, labeling it is RAW zebras and basing it off of the display is extremely misleading.

I was under the same impression, nevertheless I had started reading this thread because also I realized that I am slightly underexposing more often then not with RAW zebras, although I always try to expose as far as I can to the right... it'd be great to establish the most reliable metering system, I will certainly pay more attention to the histogram from now on!

robert.roth001 · October 04, 2013, 06:33:10 AM

Once I get my 1000x card I'm going to do some tests. Right now I have a 133x so the resolution just isn't high enough to make a good judgment, eventhough it's technically the same. So far though I've had raw zebras work wonderfully for more. We shall see.

a1ex · October 04, 2013, 06:55:53 AM

Auto ETTR with current defaults (any recent nightly, say from last 2 weeks) should be a good starting point. Don't get scared if it chooses a high ISO (if it does, it's because you get less noise with them).

Be careful: it will clip some highlights if the scene has a very high dynamic range (at that point, the overall image would get noisy with pure ETTR). When that happens, you should consider changing the lighting, trying dual ISO, or simply ignoring that highlight detail.

robert.roth001 · October 04, 2013, 08:32:05 AM

Will doing auto ETTR as a starting point still work with a fully manual lens?

a1ex · October 04, 2013, 08:44:51 AM

Why not? ETTR doesn't care about the motors in your lens

robert.roth001 · October 04, 2013, 10:01:09 AM

Well I just figured it would adjust the aperture to dial in the exposure.

timbytheriver · October 04, 2013, 10:23:23 AM

@fryderykp et al

Hi from a first poster,

I too have been keen to develop a reliable exposure strategy for ML-raw. It takes a lot to separate me from my manual spot-meter (Pentax) – but I'm learning to love the (raw) histogram in ML-raw

So, from my 'scratch' tests with 5DMKII on build 10/9 I have observed that shooting with ML-raw can probably capture about 11.9stops of scene dynamic range. It appears to be distributed approx -9 under, +3 over; with a standard grey card setting the 'correct' exposure.

I've observed a bright cloud-filled sky full of zebras; and the three rgb 'dots' of the histogram at about 1,3,1 – and still been able to pull back detail from the highlights in either ACR or Resolve.

For me (so far) I've established that if I want to use my spot-meter, I can meter a grey card in the key light and safely (I would say preferably) overexpose by up to +1 and 2/3stops. This seems to fit in with the old negative-film advice to 'expose for the shadows – and print for the highlights'.

I initially tried shooting at 100ISO in this way and the shadows were pretty noisy, so I've also found that the shadow noise was improved by using a higher ISO (400) when overexposing in this way, and for the scene I described.

These are merely what my eye tells me. I'm not a pixel-peeper or maths man; I'll leave that to the good people here who've made all this exciting magic happen. Thanks developers all!

Tim

5DMkII
build 10/9/13
Komputerbay 64gb 1000x
Stable continuous 1880 x 1058

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Raw footage are underexposed