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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Dynamic Range

S

Stephen Webb

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In the interests of being the first to post in this forum, I thought I'd ask cinematographers out there who've actually tested the camera what they think the dynamic range actually is.

I've yet to see a full and controlled exposure and latitude test, but what I've been hearing recently hasn't sounded too good. In fact one guy whose been testing recently has insisted that there's only 6 stops, something I find hard to believe (that'd be worse than DigiBeta) - but then I'm not a cinematographer.

Has anyone done any thorough tests?
 
See my earlier posts on Dynamic Range..... I posted grabs of a stouffer test wedge chart that allowed you to see the distinction between ~34 wedges. Each wedge is 1/3 stop. There's more detail in my post, but I'll leave the simple math above to the reader....

Graeme
 
Don't give the game away. That's top secret :-)
 
Hi,

I think the reason people are seeing less than the 11.3 stops is that many people overexpose by ETTR. There is nothing left for highlight sparkles.

I am sure using a spot meter at 320 asa one would be able to work +/- 5 stops from there.

Stephen
 
ETTR would assume you're exposing to keep sparkles in range though. I think what you're saying people do is ETFTTR, or expose too far to the right?

What ETTR means to me is put the brightest significant data as far right as you can without clipping it. The creative expertise comes in the word "significant".

Graeme
 
Hi Graeme,

On a still frame it's easy to see where the highlights are, as somebody moves a highlight off their watch (for example) may be +3 stops higher than anything else for a few frames leading to clipping.

Stephen
 
Absolutely - that's where the "art" comes in.

Graeme
 
It's not a silly concept. But neither is ETTR - they all act as means to inform you of what is the "best" exposure. All tools, all good tools, but the only exposure tool that really matters is the brain.

Graeme
 
Also, there is the philosophical question of whether you want exposure decisions to be based on a momentary amount of clipping, like when a car drives by and the sun glints off of the surface. General practices is to give all the shots in a sequence the same density on the negative (with film), or same scene level exposure, so that shot-by-shot adjustments in overall brightness are kept to a minimum, lest more extreme corrections cause variations in grain / noise levels. This is the one problem with thinking of exposure in still photography terms. A sequence in a movie traditionally has to have a continuous textural feeling shot-to-shot.
 
Graeme,

I'd already seen your DR test and very useful it was too.

The problem is that I've recently heard from someone who has tested one of the first 100 cameras and they've insisted that (in their tests) the camera consistently shows 6 stops. Personally I don't believe that 'cause, even though I'm not a DP, I can see that in comparison to other cameras in the 8+ stops league it clearly has more range.

Thing is, this guy is a pro, and a well respected one and (importantly) independent. What I was looking for was anyone such as Mr. Mullen here, or maybe Mr. Mathers, who have actually had opportunity to do professional, independent latitude tests that tell me something different. The nearest I've seen are Mr. Wilt's tests (with Mr. Mathers I believe) that were apparently not in ideal circumstances (and which from memory show about 8 stops).

It's difficult to argue with someone when they appear to have done the only controlled independent tests and I've nothing really to set against that.
 
Measuring dynamic range is tricky. Measuring high dynamic range accurately is trickier still.

1) you need a target that has greater DR than you're measuring. A backlit Stouffer with care to avoid ambient or reflected light has a 13 stop range. We can confirm that with a spot meter.

2) you need to know how to process the image. RAW conversion is new to a lot of video people.

3) you must define what DR is. If you have a different definition, you'll get a different result.

If someone says it gets 6 stops, then they're doing something seriously wrong.

The good thing with science, is you don't have to be independent - you just have to document your experiment.

As you point out, if a less than idea test in less than ideal circumstances (ie light contamination of the target) can gather 8 stops, then 6 is bogus beyond belief.

Graeme
 
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