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Photography Question 
Karen Schreiber
 

over/under expose when shooting digital


I have heard one professionals say it is better to overexpose a bit when shooting digital and one said that it is better to underexpose a bit (they mean from correct exposure).

Is there a correct way to under/over expose for digital and if so what is the reasoning behind the theory?

Thanks


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8/21/2007 11:09:35 AM

 
Gregory LaGrange
BetterPhoto Member Since: 11/11/2003
gregorylagrange.org
  I don't know if they were talking about what's best or if you're off which direction is better to be off. From what I've heard and from what I've felt is that it's better to be a little over if you're not on the correct exposure.
The reasoning is the presence of noise in dark areas and in under exposure. To be a little over you can darken a little without quality of the image suffering, or very little. And when it comes to printing, it's better for the darker colors to keep even tones.
Digital doesn't have much room to be off on exposure. So you can easily go too far over and make the whites excessively white to point there is no detail(blown out). And you can cause a color shift. You'll start to get yellowish borders around the blown out areas.
If someone feels it's better to underexpose, perhaps it's because with underexposed digital you can bring out some detail in dark areas, however you'll also have greater noise. But if you go too far with overexposure, once you loose detail you can't darken to bring it out.
So if you loose detail in the whites at two stops over, you won't be able to get it to show. If you loose detail in the blacks at two stops under, you can lighten to get some of it to show, but the quality of the image still suffers greatly. And to me, that doesn't make it something better.


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8/21/2007 12:17:03 PM

 
Jon Close
BetterPhoto Member Since: 5/18/2000
  Generally, when people say "over (or under) expose" a bit from the "correct" exposure, what they really mean is to apply exposure compensation to the metered exposure. The point is fine-tune the shutter/aperture combination to get a good or correct exposure, not to literally over (or under) expose.

Digital cameras are very similar to slide film. As Gregory pointed out, detail can be retained in shadow areas, but there is no salvaging bright highlights that "blow out" to white. So many digital cameras (especially DSLRs) meter conservatively to save the highlights. If you're not doing post-processing of your images, the resulting jpg from the camera can look a bit dull. To get a brighter image straight from the camera, many advise "expose to the right", which means to add + 1/3, +2/3 or +1 stop of exposure compensation to the exposure the camera meters. "Expose to the right" is a reference to the histogram, which is a graph that displays the relative number of pixels that are exposed from very dark (on the left) to very bright (on the right).


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8/21/2007 1:44:17 PM

 
Oliver Anderson
BetterPhoto Member Since: 11/16/2004
  I agree with both Greg and John on this. With Digital you don't want to blow out the highlights on whites. My father a gifted film photographer said this was one of the main differences between film and digital. Karen if youre gonna be doing any post production on your photo just try to nail it in the beginning. The only time I really make adjustments are when I shooting with my flash.


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8/21/2007 7:24:51 PM

 
Karen Schreiber   Thanks to each of you for helping me out with this one.


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8/22/2007 6:21:17 AM

 
Jerry Frazier   I try to expose perfectly. But, if I am shooting people in bright sunlight, I'll dial it way down in order to ensure that I don't overexpose the skin. Blown highlights is worse than blocked up shadows.


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8/22/2007 10:17:49 AM

 
David A. Bliss   Everything everyone said is correct, but I have a couple more points.

When shooting slides, it was best... well, generally considered better, by some ;-) ... to underexpose, because that saturated the colors more and added better contrast. Of course, like Jon said, underexpose meant by a very small degree, to the point it wouldn't necessarily even be visible at first glance. During the printing process, the image could be lightened a touch, if necessary.

With digital, it goes both ways. If you shoot jpeg, you need to be careful of overexposure, because, like it was said above, this can cause blown highlights which are unrecoverable. In this way, shooting jpeg is more like shooting slide. If you shoot raw, it is better to err on the side of overexposure, since highlights can be more easily recoverable, and there is less noise created in digital when an image is darkened than there is when it is lightened.

Of course, again, this doesn't mean to OVER or UNDER expose, it means to err just slightly one way or the other.

The hardest part for me when switching from slide was to stop slightly underexposing the images. Old habits die hard! ;-)


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8/22/2007 2:49:48 PM

 
Gregory LaGrange
BetterPhoto Member Since: 11/11/2003
gregorylagrange.org
  The original idea wasn't to go way anywhere. But I keep my apertures set to go 1/3 stops so if the actual exposure is at a 1/2 somewhere, I'll shoot at a 1/3 over instead of a 1/3 under.


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8/22/2007 2:56:54 PM

 
Diane Dupuis-Kallos
BetterPhoto Member Since: 12/27/2003
  I've heard that if you're exposure is off - it's better to be under exposed. Once you blow out your highlights, you can't get the details back.


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8/25/2007 6:16:12 AM

 
David A. Bliss  
 
  Showing the clipping
Showing the clipping
© David A. Bliss
Canon EOS 10D Digi...
 
  Showing the blown highlights
Showing the blown highlights
© David A. Bliss
Canon EOS 10D Digi...
 
  Showing what can be recovered
Showing what can be recovered
© David A. Bliss
Canon EOS 10D Digi...
 
 
I spent some time this morning creating some examples to show how it differs when shooting jpeg or raw.

The first image shows the clipping of the highlighted areas in the raw file "as shot". The area in red will be imported at pure white. If I had shot this in jpeg, this entire area would be saved as white, and would be unrecoverable.

The second image is imported as shot, to show the white area. If you use the eyedropper, it indeed shows that any area in red on the first image imports as white.

The third image shows an exagerated decrease in exposure when importing. This shows how much latitude there is with raw, and how much detail can be brought back from overexposed areas.

I am in now way using this as a raw is better than jpeg example. It is simply to show that when shooting jpeg, err on the side of underexposure, when shooting raw, err on the side of overexposure.


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8/25/2007 8:09:16 AM

 
David A. Bliss   An addendum... First, the lighting setup for this shot was purposely designed to blow out the backdrop. If I were to finish processing the photo, the entire backdrop would be white. It just seemed like a good picture to use as an example.

Second, I realize this isn't a good shot, it just happened to be the one I used, because it had so much area of blown highlights. ;-)


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8/25/2007 8:15:08 AM

 
Richard Lynch
BetterPhoto Member Since: 6/12/2005
  Either way I would not want to go so far over or under as to lose detail, as it is a bear to replace and makes for a lot of unnecessary post-processing. I do personally underexpose a bit in low light because I feel I get more noise with longer exposures, but prefer correct exposure in any case -- so long as it does not lead to blowout in highlights.

As far as RAW, David is showing the right stuff. If you feel the need to go over or under, expose with RAW if you can to get high-bit captures and more potential detail to minimize issues with adjustments.


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8/25/2007 1:56:45 PM

 
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