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Capture One, Using Curves to correct overexposed Files

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Old 01-17-2006, 12:41 PM
gho64 gho64 is offline
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Capture One, Using Curves to correct overexposed Files

Hi,

I overexposed several EOS Mark II RAW Files. They are more than one stop overexposed. I do not like the results using C1 Level Tool so I want to use C1 Curve Tool to correct them and preserve detail in other parts of the overexposed file.

I have very little experience using The Curve Tool so any suggestions would be greatly appreciated. Thank You.

Hersul
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Old 01-17-2006, 07:49 PM
delic delic is offline
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are the highlights blown out or just overexposed? Blown out is generally a value of 255 is any of the RGB channels..

Generally to lower the exposure try picking the center point in the curves dialog and drag it diagonaly (normal to the original straight line) toward the lower right corner (or upper left depending how you have it setup)..

You might consider posting an image or a portin of one so that other users can point you in the best direction
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Old 01-18-2006, 12:41 PM
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Craig Walters Craig Walters is offline
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gho64,

generally, you want to use curves, levels, contrast/brightness, masks or selections to isolate just the blown out areas, and possibly channels. but, as delic points out, if the area is 'blown out', meaning basically a pure white of 255, especially across a large area, then the only handling is to re-shoot the picture or do some detailed hand editing. curves and those tools can only handle things correctly if there are differences in the whites or hues. if it's all monocolor or all white or all black, then curves cant make any distinctions.

curves is a way of handling different values of color and black and white in ranges of those values. the scale is horizontally you are dealing with the hues or shades, while vertically you are dealing with intensities of those shades. the diagonal dashed line is the medium for all that and that is what you move. if you click on the middle of the diagonal and pull it straight down, you are moving that hue/shade lower in intensity, but since the line is connected always, the rest of the line also dips and thus also lowers all those other values represented by the line. the beauty of this is that you can set more than one point and fix the line so it doesnt move all over. thus, you can set a point on the middle and then move the top quarter of the line and the line will lower all those top values but not the lower values because of the fixed point you set in the middle.

so, in your case, if you have areas that are truly 'blown out' you can move the line down and lower the values of the blown out area, but the whole area is going to move down because the values are all the same, 255. so you could drop all the 255's down to 240, but you cant separate one 255 from another; not with curves, anyways.

hope that made sense

craig
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Old 01-18-2006, 11:21 PM
jfrancisco jfrancisco is offline
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Using the exposure settings

I'm not sure if I got this right so sorry if I'm off base...

I use Capture One (shooting on Phase P25 back) and find setting the exposure in the capture software is a fantastic way to correct over exposure. Far superior to using curves. Set the exposure to -1.0 if it's over exposed 1 stop. Has this not worked for you?
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Old 01-19-2006, 12:24 AM
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Duv Duv is offline
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Quote:
Originally Posted by jfrancisco
I'm not sure if I got this right so sorry if I'm off base...

I use Capture One (shooting on Phase P25 back) and find setting the exposure in the capture software is a fantastic way to correct over exposure. Far superior to using curves. Set the exposure to -1.0 if it's over exposed 1 stop. Has this not worked for you?

I think what he is saying is that "parts" of his image is overexposed by 1. The rest is fine, in which case curves would be appropriate. You will notice that when you move the color picker over the image, there is a light grey dot on your curves line that moves depending on where you are color picking. Determine the lightest part of your image "that you do not want to change". Click on the curves line where the light grey dot is. Add additional points along the line down to the darkest area "lower left". You should now be able to bend your highlites down to reduce exposure. The more points you add along the curves line, the more it is anchored so you can make localized adjustments.

BTW, jfrancisco, welcome aboard. Good to see another Canuck posting. Sorry about the Leafs tonite.

Dave

Last edited by Duv; 01-19-2006 at 12:29 AM.
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