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Old December 12th, 2007, 06:48 PM   #1
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Better to underexpose or overexpose?

Ok, like my subject says.
When it comes to SD video is it better to slightly underexpose footage or slightly overexpose. From what I've seen I've found it better to slightly underexpose and change the levels in post.

My class just went to Nashville today and used a telecine to transfer our 16mm to video. With this it was better to overexpose than underexpose. One group shot at about F2.6 or F2.8 during the day against an almost white background. Using the telecine the operator adjusted it and it looked pretty good, although maybe somewhat grainy. We did a poor job lighting most of our background and the we couldn't get anything out of the background.

So its better to overexpose film, but what about video?
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Old December 12th, 2007, 07:00 PM   #2
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Neither... It's better to expose it properly!
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Old December 12th, 2007, 07:28 PM   #3
 
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Digital is a little different from film. In digital, it's better to overexpose, slightly, then bring the exposure back in post. Overexposed shots will recover blown highlights easier than underexposed shots. Shadows tend to lose the info that was there, while clipped highlights are mildly recoverable. Unfortunately, in order to see all the data that is there, and whether it's truly clipped or not, one needs a histogram. Some video cameras are now putting histograms in the display. Digital still cameras were enlightened a while back and actually show all three color channels in a histogram for each...which is the right way to expose digital properly.
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Old December 12th, 2007, 07:53 PM   #4
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If you're using a decent form of compression like Cineform - i'd say it's better to underexpose...

I've been back and boosted the levels like CRAZY, and you'd be so surprised at the amount of information in those dark shadows... This is again, using uncompressed, or a good compressor like Cineform..

Just my two cents..
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Old December 12th, 2007, 08:45 PM   #5
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From my experience I have better luck if it is under exposed, because if it is over exposed there in no information there.

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Old December 12th, 2007, 09:04 PM   #6
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Over exsposure and clipped highlights are two different things.

For me and my DVX I find it better to overexpose a bit but not blow my highlights. Then I take it down in post and have less noise in the image.

Blown highlights are just that, blown.
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Old December 12th, 2007, 09:14 PM   #7
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ok , im going to really simplifiy it cause it works for me.

have you zebra bars?
if you have keep them off the faces and out of the overall shot as much as possible or you are in trouble.
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Old December 12th, 2007, 10:16 PM   #8
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You can bracket exposures and do a test. An example of my test:

http://glennchan.info/video/exposure/exposure.htm
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Old December 12th, 2007, 10:36 PM   #9
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In the film world...

When shooting old-fashioned FILM, the rule of thumb is:

-- You can OVER expose negatives, since the film has the latitude to record overexposed highlights (you just have to give more exposure to the print, in order to bring out the highlight details).

-- You should NOT over expose reversal film, since the highlight info will be destroyed. But you can slightly UNDER expose reversal film, and get back the highlight details along with most of the shadow details.

I would have thought video was more like reversal film. I see Bill and Bob have differing opinions on this.
Sounds like it's time for you to do some tests! 8-)

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Old December 12th, 2007, 11:08 PM   #10
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On a bright sunny day, I'd go slightly over vs. slightly under. But, it's a fine line. Slightly over, and FCP allows for easy safe filtering, just slap the filter on the clips, and all areas of the image that are over the set limit are clipped. This way, I get to keep more detail in the shadows and more easily stay out of the muddy blacks that lead to bad contrast.

On a uniform cloudy day outdoors, I think it might be better to underexpose slightly, since light is so even across all objects in the frame. Then, bringing levels up across the board to get the most dynamic luminance range possible.

Most of the time indoors, there's really no good excuse for missing the exposure.
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Old December 12th, 2007, 11:20 PM   #11
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As far as zebras go I like to see them only on the brightest highlights and maybe spread over some to the next level up...but it depends on your camera .....

...use your eyes and look and see what you see as the brightest surface that you are shooting....then look back through the camera and check the zebras...

example:
white guy with red guitar/white pick guard outside in sun...pick guard will be totally white and the zebras might not even completely show up in it...his face is darker but lighter than his black leather jacket and jeans....find the medium exposure for the shot and work from there with it...

I would end up with a tad of zebras on the brightest highlight on his face and the pick guard would be possibly full of zebras or even losing them ,because whites are usually 2 stops brighter than 18% gray....

I still keep that rule in my head from film school from 15 years ago.....
but this is how I expose for my shots and then add the fidgeting around a half stop ......it really is a fine line of exposure especially in the sun....

*but first you must know your camera well and how it exposes for latitude.... I go outside and shoot video of different things under different lighting conditions and narrate what I am seeing on the zebras....that has really helped me...also do this for tungsten lights too....and your on-camera light too.

as far as you stopping down your zebras to where they just go off...guess that would put you about a stop under....you should be able to bring the exposure back up in post especially in FCP .....


I would rather underexpose slightly than over .....
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Old December 13th, 2007, 01:02 AM   #12
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There is also a tecnical reason to overexpose digital (both video and stills) rather than underexpose if the subject range fits within the exposure latitude: The tonal gradiation is finer in lighter parts of the image. This means it is possible to darken the image without any quality loss, but as the shadow parts of the image have more coarse gradiation in the file, making the image lighter "rips the tones apart" so to say.

Of course you can over/underexpose only when the total tone scale easily fits withing the available range. If not, the only way is to expose correctly, which sometimes means a compromise between loosing the shadows and/or blowing the highlights.
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Old December 13th, 2007, 01:18 AM   #13
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I always overexposed my color negatives by at least a stop..sure worked out well indeed.
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Old December 13th, 2007, 02:44 AM   #14
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Wow, thank you all for the responses so quickly. From the majority of the responses, when I've been faced with this decision I have been exposing wrong(underexposing) I guess I should do what Glenn Chan suggested and bracket my shots then compare and adjust in post.
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Old December 13th, 2007, 08:07 AM   #15
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If you already know where your optimum level is, why would you choose to shoot over or under it, and then have to adjust it in post?
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