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Photo Retouching "Improving" photos, post-production, correction, etc.

Underexposed

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  #1  
Old 06-19-2006, 08:06 PM
tigerphoto tigerphoto is offline
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Underexposed

I took a couple of pics of my friend and all of the pics came out underexposed. How can I fix them? Feel free to give examples.
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Old 06-19-2006, 08:22 PM
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Quote:
Originally Posted by tigerphoto
I took a couple of pics of my friend and all of the pics came out underexposed. How can I fix them? Feel free to give examples.
Depends on your definition of 'fix', tiger. Because you can do all sorts of things to that image, but it'll look 'arty', or 'creative', or 'special'. Maybe even beautiful. Or of course just plain rubbish. But it'll never get the quality of light the photographer seems to have had in mind.

That's why these sessions should be shot 1) in RAW, 2) in bracketed exposure sequences, and 3) checked onsite (on a laptop screen, not a 2 incher). And, obviously, with buckets of light!
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Old 06-19-2006, 08:26 PM
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Underexposed Images

There are many ways to correct underexposed images. In Photoshop CS or CS2, the Image>Adjust>Shadow Highlight works very well for these images. You can also use Image > Adjust> Levels and pull the Highlight slider over. There are also Curves adjustments if you fell comfortable with Curves.
On your orig image all work to produce the same result as shown below. I increased the brightness, raised the saturation a little, and ran a noise filter on the image to reduce the color noise.
Regards, Murray
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Old 06-19-2006, 08:55 PM
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Hi Tiger,
A very quick trick: duplicate the layer, set the blend mode on screen and adjust.
Sylvia
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Old 06-19-2006, 10:41 PM
tigerphoto tigerphoto is offline
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Rokcet: What so hot about RAW and what is a bracketed sequence?

Mr. Monday: What about in PS7

Sylvia: Blend mode?
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Old 06-19-2006, 10:46 PM
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You have to open the layers palette (Window, Layers), click on Normal and scroll down to "screen".
If your photo is overexposed, use the "multiply" mode instead.
Hope this helps!
Sylvia
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Old 06-19-2006, 10:56 PM
tigerphoto tigerphoto is offline
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Thanks sylvia. Second question why does the pic look a little pixelated when I do this?
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Old 06-19-2006, 11:11 PM
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Hi

I know in my underexposed pictures I often have noise in the shadows. It is not always noticeable until the tone is adjusted. Sometimes you will need to run a filter of some kind to reduce the noise.

Or even apply a little gaussian blur followed by a little noise.. say 1.5 pixels . The blur tends to reduce the noise from underexposure and the 1.5 pixels of noise will bring back apparent detail.



Butch
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Old 06-20-2006, 02:31 AM
Tpage Tpage is offline
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If you underexpose like this AND shoot jpeg you are asking for trouble. Jpeg will throw away information that RAW keeps which would allow you to save this image. To see just how much colour information has been lost convert the image to LAB color mode in photoshop and then look at the a and b channels. See how pixellated they are? That's down to the jpeg compression.

With digital it pays to 'expose to the right' and shoot RAW i.e. turn on the histogram in review mode if your camera has one and make sure that the histogram is as far to the right as possible without overexposing.

Most digital sensors use 12 bit colour internally which gives 4096 levels or tonal values for each pixel. You'd think that an underexposure such that only the left 60% of the histogram has any appreciable data would give you 60% of the 4096 values right? (like in your image above)

WRONG. Assume there a 5 stops worth of light in the scene (a reasonable assumption) Every stop of light down means half the amount of light than before ... The above underexposed image is only using about 3 stops worth of light so it is throwing away 2 stops worth of information. Meaning that only 1024 of the 4096 tonal levels are being used.

Because the number of levels being used is reduced, this will introduce colour noise into the image particularly in the darker areas. Trying to bring these levels up will amplify the noise as you have seen when using a duplicate layer set to screen mode as suggested by sylvia.

By shooting in RAW and exposing to the right, you will probably need to darken the image in PS afterwards. You can do this by duplicating the layer and setting the mode to multiply in PS. This has the added benefit of REDUCING colour noise.

The shot supplied will never be as good as a properly exposed image. If you want to do it right you'll have to start again.

Last edited by Tpage; 06-20-2006 at 02:39 AM.
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Old 06-20-2006, 06:43 AM
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Quote:
Originally Posted by tigerphoto
Rokcet: What so hot about RAW and what is a bracketed sequence?
RAW allows you to adjust exposure settings, white balance, etc., after you've pressed the shutter, in the post production/editing phase. Plus what Tpage says.
Bracketed sequence: you depress the shutter once and the camera shoots a sequence of 3, 5, or more frames at, for instance, half f-stop increments (depending on your preset). Many cameras have this feature. Look at your user manual under 'bracket' to see if yours does too.

It still would'nt have been enough with this photo, though. Imo this one needs 3 or 4 times as much light!
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