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September 7th, 2011, 10:53 PM | #1 |
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Dynamic Range
Sorry for this geeky thread, but I had an idea that seemed somewhat interesting, to me at least.
It seems clear that the future of digital video is going to be in maximizing dynamic range. The 5dmk2 is a great camera because it gets around 10 stops of range compared to the 6 or 7 stops most digital video had just a few years ago. The dream, that seems not to distant is when we can buy a consumer camera that tops the 14 or so stops of range that a 35mm film camera has. If you go on to imagine more sensitive chips going way past 14 stops, to 20 or 30 stops (I know, but maybe in 20 years) then there would never be a scenario where you didn't get the shot because of exposure. You could choose a just a part of the range or apply a curve and cram it all within the range of whatever you are outputting to. You could shoot against a window with no lights and decide later how much fill to dial in. You could go from candlelight inside to a sunny day outside. Here is the especially geeky part: Because of one of the quirks in the 5Dmk2 design, not all of the lines of resolution are used. The chip is capable of a 21 megapixel image but has to throw out lines of data in order to make a 1080 image. It seems that if one line was used for an over exposure then the next line could have a slight nd and the next line a little more, and you would have several exposures within the same frame. The several exposures captured could be used to create a high dynamic range photo just like in still photography. And the fact that it all happens at the same moment and through the same lens, the subject wouldn't need to keep still. ...so, someone at Canon get to work on this right away. |
September 8th, 2011, 02:09 PM | #2 | |
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Re: Dynamic Range
Quote:
Having chips that are "more sensitive" doesn't necessarily improve dynamic range. What is really needed to do that is to increase the effective full well capacity. |
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September 9th, 2011, 08:57 AM | #3 |
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Re: Dynamic Range
Dynamic range is not limited to shadows. The 5Dmk2 shines in the upper area / highlights. That's why it's called dynamic range. Dakest to lightest. 6stops? You must be using a custom profile or have a bad 5D to achieve that result.
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September 9th, 2011, 09:52 AM | #4 |
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Re: Dynamic Range
Hardly. It's only 3 stops of headroom over middle gray. That's no great feat. If you enable HTP, you can bring that up to 4, but only by taking away one stop of shadows due to pattern noise.The only way to get more than 4 is to underexpose and boost exposure in post, but that's also limited by pattern noise.
In my experience, most people greatly overestimate the number of stops they think they are using until they actually measure it. |
September 9th, 2011, 10:39 PM | #5 |
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Re: Dynamic Range
I never checked it myself but I saw the figure of 10+ stops on the Zacuto shootout, also Robert Primes ASC did an evaluation.
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September 9th, 2011, 11:53 PM | #6 | |
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Re: Dynamic Range
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So then they do a realistic comparison to see how the shadow noise actually looks, where the deepest shadows are 4.5 stops under middle gray. No pattern noise, so we're OK. Then they use the same settings on a highlight test where the highlights are 5.5 stops over middle gray and the 5D2 just falls flat on its face. If the 5D2 would have held the highlights in that shot, Zacuto would have proven it capable of 10 stops (4.5+5.5). But since it failed miserably, how much range was actually shown? This is actually easy to calculate since the 5D2 only has two levels of highlight headroom: HTP is about 4 stops and normal is exactly one less (~3 stops). (You can get more by underexposing and increasing brightness in post, but it's pretty clear they didn't do that from the test.) Since the Window looks a lot more blown out than just 1 stop, I would guess they didn't use HTP, which means about 3 stops. Add that to the 4.5 and you get 7.5. |
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September 12th, 2011, 05:27 AM | #7 |
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Re: Dynamic Range
Interesting. I wonder how all of this is affected (if at all) by the picture profile used? In particular, if one was using Technicolor's Picture Profile for the 5D, would that enable a greater apparent range to be captured to which one would apply the appropriate LUT later? Or is this just not the case (ie. hardware capacity limited versus software algorithms?).
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September 12th, 2011, 10:11 AM | #8 | |
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Re: Dynamic Range
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Yes. |
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