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is there a way for PS to calculate the average...

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  #1  
Old 06-26-2010, 11:56 PM
kkamin kkamin is offline
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is there a way for PS to calculate the average...

Is there some way to have PS calculate what the average gray scale value of the image is? For instance, if I were photographing a "normal" scene with a nice even distribution of tones, I would get a calculation value close to 128 on an 8-bit image (mid point of 256).

So essentially I want PS to average out the gray scale value of each pixel.
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Old 06-27-2010, 01:39 AM
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Doug Nelson Doug Nelson is offline
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Re: is there a way for PS to calculate the average

Do you mean like Filter>Blur>Average ?
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Old 06-27-2010, 02:00 AM
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Re: is there a way for PS to calculate the average

If I understand you right then Doug Nelson's suggestion sounds like what your looking for. If your trying to just find the pixels in the image that are at 128 you can do it by filling a layer with 50% gray setting it to difference blend mode and using threshold to identify the 50% gray pixels in your image.
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Old 06-27-2010, 04:41 AM
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gene_spark gene_spark is offline
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Re: is there a way for PS to calculate the average

Ok, if you want the exact Gray value..you have to duplicate the Background layer..and then als Doug wrote Filter> Blur>Average...these is the Average color of the Picture if you want the Gray values you have to convert to Lab..don`t flatten ,select the a and b Chanel fill it with a middel grey edit> fill> 50% Gray...convert back to RGB.

To get the middel Gray its not so easy as it looks on first sight....the Gray values of a gray Card is a 50 % gray in Lab and to what it converts depends on your RGB space or exact on the Gamma settings of your RGB Space..in a 2.2 Gamma like Adobe or SRGB it is 118 and on a 1.8 Gamma like Profoto or Color match its 100 and not 128.

lg.
Gene

Last edited by gene_spark; 06-27-2010 at 04:55 AM.
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Old 06-28-2010, 07:58 AM
kkamin kkamin is offline
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Re: is there a way for PS to calculate the average

Thanks everyone! Awesome techniques. I know it doesn't mean much what the average pixel value of an image is, but I am using it along with the histogram to explain to a client that their video footage (I'm exporting frames for analysis) is underexposed and needs levels and shadow/highlight adjustments in post.
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