Under Exposure Over Exposure w/Digital
I realize that by asking this question I will be perceived as a rank amateur, and maybe I am, but I'm going to ask it anyway because I would rather embarras myself and improve my photography!:confused:
With digital when do you over expose an image and when do you under expose one? Thanks for your help.:)
It would be good to clarify what you mean by "over expose" and "under expose". Are you talking about intentionally overexposing or underexposing an image relative to the correct exposure or are you asking about when to use positive vs. negative exposure compensation?
Kinda of a tough question.
You need to at times overexpose or underexpose the overall scene in order to correctly expose for you subject...especially if the subject is back lit or it's a dramatically different tonal value than the background.
You might also want to intentionally over or under expose for effect as with a silhouette at times.
Is the real question which you're trying to get across how to properly expose for your subject or do you already have an understanding of that?
Hi James There are no bad questions !!! Glad you decided to post it !!
Agree with above, good advices.
I think confusion seems to be with the terms, generally you don't want to over exposed an image ... meaning having pixels running up the right side of the histogram or blinking on your LCD. On very few instance we might push a few pixels over the edge and try to recover during the conversion for difficult subjects.
Exposure wise you want to have data on the fifth box of the histogram as close as you can to the right without going over !!! .... lots of times when you hear under expose or over expose it is referring to compensating for a particular subject to fit the tonal range but not to over expose the image on the histogram ... compensation would be a better term.
Here is an explanation of the Expose Right theory. As has been stated it is not really an over exposure.
http://www.luminous-landscape.com/tu...se-right.shtml
Bill
In certain situations, using the "Expose to the Right" method does result in an over exposure at time of image capture. For example, let's say that you have a case where the lightest tone in a scene is a middle tone. Using the expose to the right approach would lead you to choose an exposure that will render that middle tone (and everything else in the scene) about 2 stops brighter than it appeared in nature. If the subject was a Black Bear, it will become more of a gray bear. That is the correct thing to do with digital in order to minimize noise at time of capture but you would need to bring the exposure back down during RAW conversion to have the scene appear natural. So you are overexposing at time of capture for reasons dealing with digital technology but then correcting for it during RAW conversion.Originally Posted by William Malacarne
I look at my Histogram in camera in RGB, with blinking highlights, and it show if something is clipped. If so I back off a little.
Bill
Mike, Positive Vs Negative Exposure Compensation. Thanks, Jim
Jim, I already have an understanding of that but I see when someone posts an image that they say +/- exposure compensation and other than over exposing 1 1/2 to 2 stops in snow I'm really not sure. I was talking to a fellow about hummingbird photog. and he said about under exposing a stop and a half (I think) and I thought the picture should have been over exposed.
Just two different ways of saying the same thing. To " - compensate" (if I can say it that way :)) is to under-expose the whole image, meaning to expose it less than what your camera meter is suggesting (you knew that already).
Last edited by Desmond Chan; 01-06-2010 at 12:57 AM.
If you rely on your camera's histogram to show you what's overexposed, you need to make sure your camera's image settings setup properly. If not you could be underexposing your "overexposed" images. I've had cases ware there were blinkies on the camera but when loaded in Lightroom, not only was there no clipped highlights, there wasn't even data in the right-most block of the histogram.I look at my Histogram in camera in RGB, with blinking highlights, and it show if something is clipped. If so I back off a little.
The recommended settings, AFAIK, for Canon at least, are to set the picture style to Neutral, color space to AdobeRGB, sharpening to 0 and contrast to -4.
Alternatively if you can monkey with the contrast to add some buffer between clipping on the camera and clipping in the RAW file. On my Mk3 changing the contrast form -4 to +4 nets about a 1 histogram block increase in data. At +4 the camera shows a "proper" exposure, with data all the way to the right edge but not clipping, for an image that's 1.5 stops underexposed in Lightroom. -4 on the camera seems pretty close to what I'm seeing in Lightroom.
Sharpening doesn't seem to make an appreciable difference at all.
If there were two features I'd like to see on SLRs, they are a RAW histogram and a focus/sharpness map (think something like the focus mask in Capture One 5). I want to see if the RAW file is clipping and what is/isn't sharp, quickly and without guessing or having to messing around with the camera.
Hi James,
Sugest you take a look at the Education Resources section - in particular take a look at the entry "Why Your Camera's Meter Does Not Matter... Lots on Exposure". Artie gives a very good explanation of why and how to add compensation - also he suggests taking a look at ABP II section on Exposure theory.
Good advice, actually!
G.
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