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Old August 22nd, 2005, 06:35 PM   #1
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Exposing for DV- aggressive is better? (clipping be damned)

The traditional thinking behind exposing for DV is to expose conservatively to avoid clipping important image details. I used to believe that... until I did the following test. What I'm finding is that you can get better-looking results if you expose aggressively for the subject.

http://www.glennchan.info/video/exposure/exposure.htm

I'd be curious to see what you think about this, especially since subjective tastes differ from person to person.
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Old August 22nd, 2005, 06:49 PM   #2
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It depends on how drastic your color correction is. Remember that DV is very deficient in color information, so the less manipulation you do the better. DV simply can't withstand color grading, in my opinion.
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Old August 23rd, 2005, 06:37 AM   #3
 
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Quote:
Originally Posted by Glenn Chan
I'd be curious to see what you think about this, especially since subjective tastes differ from person to person.
As you said, Glen, it's subjective (to a point). But I am more pleased with the results I get from slightly underexposing and adjusting the color curves and any tweeking with color that needs to be done.

Jay
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Old August 23rd, 2005, 09:46 AM   #4
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I have to agree with Glenn, it seems to me that you can mask some of the compression artifacts by decreasing brightness in post, but bear in mind that I shoot mainly in very controlled conditions so I don't have to worry as much about unexpected hot-spots. If I was shooting something "live" I might be more conservative...
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Old August 23rd, 2005, 12:15 PM   #5
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Glenn,

There is a popular theory in digital still photograpy that is often refered to as 'expose to the right'. If a digital sensor has 5 stops of dynamic range and you divide your histogram in 5 equal parts from the darkest to the lightest, each step up on the scale will contain twice as much digital information as the darker step below it. That means that the shadows contain much less info than the lighter areas of the picture. Using this scenerio, the lightest 1/5 of the picture will have 16 times as much information as the darkest. As you manipulate the picture (color, exposure, etc.) the lighter areas will tolerate much more adjustment than the darker areas without looking bad.

For a complete explaination of this, see the following link:

http://www.luminous-landscape.com/tu...se-right.shtml
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Old August 23rd, 2005, 12:46 PM   #6
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Quote:
Originally Posted by Glenn Chan
The traditional thinking behind exposing for DV is to expose conservatively to avoid clipping important image details. I used to believe that... until I did the following test. What I'm finding is that you can get better-looking results if you expose aggressively for the subject.

http://www.glennchan.info/video/exposure/exposure.htm

I'd be curious to see what you think about this, especially since subjective tastes differ from person to person.
Hey Glen,

I think your test shots prove just the opposite.

The clipping was on your shirt, so it isn't that noticeable, but if you were to try and darken that shot, that spot would look oddly gray without detail and some banding. Whereas the shot #5, which was under exposed, looks better than #2 when the levels are brought up... and notice that you didn't loose any detail.

I always under expose if my scene has to much difference between light and dark, or if windows are in the interior scene and I want to keep the detail verses blow out the window for effect. This of course is considering that no lighting controls are available to equalize the set/location.

I just did a fast food restaurant and there wasn't enough room for all of the lighting instruments that I would need to dial in the proper scene contrast, so I under exposed in the field and adjusted in post. I have great window shots and not one piece of stainless steel lost any detail after post :-)

JMHO
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Old August 23rd, 2005, 12:46 PM   #7
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Some of it depends on the camera you are using and your settings while shooting. The DVX and XL2 can both be adjusted to handle highlights and shadows in various ways. The example above is not a great one because you have a guy with a tan complexion and a bright white shirt. You also have uncontrolled light coming from one side only.

The point is not to underexpose the hottest area, it is to underexpose SLIGHTLY the area of FOCUS. I think grab 4 looks best. As far as colors, I would have done a warmer white balance. Nobody thinks overexposing or underexposing is something you SHOULD do, what I am saying is on a scale of 1 - 10 with one being very dark and 10 being blown out,, you should expose to a 4-5, not to a 6-7.





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Old August 23rd, 2005, 12:55 PM   #8
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Quote:
Originally Posted by Ash Greyson
Some of it depends on the camera you are using and your settings while shooting. The DVX and XL2 can both be adjusted to handle highlights and shadows in various ways. The example above is not a great one because you have a guy with a tan complexion and a bright white shirt. You also have uncontrolled light coming from one side only.

The point is not to underexpose the hottest area, it is to underexpose SLIGHTLY the area of FOCUS. I think grab 4 looks best. As far as colors, I would have done a warmer white balance. Nobody thinks overexposing or underexposing is something you SHOULD do, what I am saying is on a scale of 1 - 10 with one being very dark and 10 being blown out,, you should expose to a 4-5, not to a 6-7.

ash =o)
Hey Ash, I agree with you.

I would like to add a point though, it depends on what you consider over/under exposed. In my opinion, unless it is intentional exposing for the highlights (I said under expose before but this is more accurate) in a case where you would loose detail there, is correct exposure, as long as you don't destroy the detail in the shadows.

By keeping information in both extremes, you can have what you want in post. Of course it is always better to light your scene so that you have the exact contrast that you want... without question.
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Old August 23rd, 2005, 01:44 PM   #9
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By keeping information in both extremes, you can have what you want in post.
I don't think that's the case. In shot #5, I used color curves (kind of s-shaped) to raise the brightness and contrast to match. This really brought out the noise in the midtones.

The pictures may make the noise appear better than it is... when you see the video in motion, it may be more apparent.

2- I will try to put up some shots to download, so you can see the images on a broadcast monitor (if you have one).

A lot of computer monitors are messed up, so you can't rely on them. If you have one of those LCDs that have really high gamma, that may skew your opinion towards the darker shots.

Quote:
The example above is not a great one because you have a guy with a tan complexion and a bright white shirt.
In real life, the subject I shot (me) doesn't have a tan.
On camera I guess it looks like that.

Quote:
The clipping was on your shirt, so it isn't that noticeable, but if you were to try and darken that shot, that spot would look oddly gray without detail and some banding.
I don't think so. You should be darkening the shot in a way so that clipped highlights end up at 100% white, which shouldn't appear oddly gray.
Banding shouldn't occur when you're bringing levels down. It could occur when you bring levels up (although noise is usually a bigger problem than banding).
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Old August 23rd, 2005, 02:07 PM   #10
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http://www.lafcpug.org/over_under_expose_video.html
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Old August 23rd, 2005, 03:47 PM   #11
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Hello Glenn,

Semantics may be getting in the way here, but I'll just say that my work in the feld in corporate and film puts me in favor of what I described earlier.

All situations are different and you have to go with what you know :-)
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Old August 23rd, 2005, 05:11 PM   #12
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I uploaded the raw files now (http://www.glennchan.info/video/expo...omparisons.rar), so you can try things like:
A- Try to color grade the raw files yourself, to see the kind of results you'd be getting if you were to do things yourself.

If you have Final Cut, you might really struggle with brightening the darker shots because the 3-way CC will make noise more visible (and the gamma slider causes color shifts). Nattress' filters should be a lot better if using FCP.

B- Look at the graded footage to see the noise in them.

2- In my opinion, DV compression artifacts or 8bit depth or 4:1:1 color sampling aren't a big deal. They certainly aren't in this case.

What does suck about DV is that the cameras pickup noise, so "stretching" exposure in an area will make noise more visible. But then again, all cameras have noise in some form.
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Old August 23rd, 2005, 05:39 PM   #13
 
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Quote:
Originally Posted by Anthony Marotti
Semantics may be getting in the way here, but I'll just say that my work in the feld in corporate and film puts me in favor of what I described earlier.

All situations are different and you have to go with what you know :-)
I can't help but agree with Tony, based on my personal experience. I also agree with what Ash said, "Some of it depends on the camera you are using and your settings while shooting." That is 80% of the battle! Our camera is our instrument! We must learn how to "play" it and play it well.

One thing to keep in mind is that the eye will always go the brightest area in any image (be it painting, photograph, motion image, etc.), and if that's not your design, then you've failed. People are far more accepting of solid blacks in an image than they are of a glaring, bright, white area that has no detail or color whatsoever (yes, there are rare exceptions). So to say "clipping be damned" is a great way to shoot yourself in the foot, visually!

The best example I've ever seen of this was a few years ago. The Discovery Channel aired a beautiful documentary on the geysers of Yellow Stone. It was, without a doubt, one of the most gorgeous programs I've ever seen, on television or elsewhere! What the videographer did was expose for the detail and texture of the white water columns of the geysers. That meant that the shadows, in the trees in the background, for example, fell into black. Had he split the difference, and tried to "save" some of the detail in the shadows, or had he allowed the camera's meter determine the exposure, the geysers would have been nothing more than glaring, blown out white areas that would have been anything but compelling images.

Never be afraid of shadows, even the black ones! Expose for what's important in the frame, as in the case of geysers, it was the white water.

Jay
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