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S3 - colorspace and file size


sincurves

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Slightly puzzled when I export two versions of the same photo in LR: sRGB (25MB) and AdobeRGB (21MB), both JPGs. All settings are the same except the colorspace. I would have expected the sRGB to have been smaller in size than AdobeRGB - if any difference at all. Any thoughts on what causes this?

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Guessing here...

A smaller color space will have more variation in its numerical color values. A wide gamut color space image looks flat when viewed as pure numbers. Two adjacent pixels with red values of .25 and .75 in an sRGB file might have values 0.3 and 0.7 in AdobeRGB. These look the same on the screen, because the software knows what color these numbers mean in their respective color spaces. But in the file, they are different numbers. Higher variation files (noise, contrast) compress less well than smoother or low contrast files, because the algorithms stop at a level of preserved detail, not at a compression amount. A solid blue rectangle compresses to "Dude, it's a blue rectangle". Pure noise can't be compressed without loss at all.

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16 hours ago, mgrayson3 said:

Guessing here...

A smaller color space will have more variation in its numerical color values. A wide gamut color space image looks flat when viewed as pure numbers. Two adjacent pixels with red values of .25 and .75 in an sRGB file might have values 0.3 and 0.7 in AdobeRGB. These look the same on the screen, because the software knows what color these numbers mean in their respective color spaces. But in the file, they are different numbers. Higher variation files (noise, contrast) compress less well than smoother or low contrast files, because the algorithms stop at a level of preserved detail, not at a compression amount. A solid blue rectangle compresses to "Dude, it's a blue rectangle". Pure noise can't be compressed without loss at all.

That could very well be the case. 

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