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Author Topic: Aperture is color shifting my exports  (Read 3784 times)
peteforde
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« on: November 30, 2010, 02:47:46 AM »
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I work with 48 bit TIFF images (color & b+w) imported from SilverFast 64 bit HDR images that were processed down to 48 bit. Tonight I became aware of a disturbing color cast which I initially assumed was a color space profile issue with Photoshop CS5. However, I realized that the case is visible in the copy that is made even before Photoshop loads.

The cast is best described as selectively taking some of the brightest areas and ratcheting up the gamma, giving the shadows an implausible (gross) sheen. I have Aperture configured to export 16 bit TIFF files with no embedded profile. Meanwhile, b+w images seem to get darker. I'll reiterate that this happens on both TIFF and JPG exports.

The weird thing is that if I make a duplicate of the image from the master image and export that (whether to Photoshop 5 or as a JPG) then the file seems to come out fine. It's only images with modifications that seem to be affected.

What is messing with my photos?
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digitaldog
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« Reply #1 on: November 30, 2010, 10:50:42 AM »
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I have Aperture configured to export 16 bit TIFF files with no embedded profile.

That be the first place I would examine, there’s zero reason to create untagged documents.
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Andrew Rodney
Author “Color Management for Photographers”
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peteforde
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« Reply #2 on: November 30, 2010, 07:11:32 PM »
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Just to update on my findings today (after setting my Aperture export color space to Adobe RGB (1998)), I've tested all of the combinations and concluded some disturbing things about the way Aperture previews files.

Essentially, my mistake when I posted was that I assumed the issue was with the file that was being generated when I shuttled an image to Photoshop for cleaning. As it turns out, the new image is faithfully accurate to how my photo *really* appears. I realized this when I was in zoom mode and jumped between the two copies of the file.

Zoomed in, the images are identical. The original image has the same harsh tones as the copy (which makes sense). Zoomed out to fit the whole image on my screen, the preview on the original is different. I've replicated this phenomena for about a dozen photos, both color and greyscale.

The weird part is that it only seems to happen if I have changed the levels of the photo (histogram) or enabled edge sharpening. It's like those two functions are not properly rendered by the preview you see when zoomed out.

To be clear, I've regenerated the previews and even tested with my preview quality set to 0 (terrible) to verify.

If you're zoomed to fit on the screen and you've changed your curves or used edge sharpening, the image you see is NOT the image that you'll end up with.

I'm perturbed and a little heartbroken thinking about the hundreds of hours that I've spent preparing my work and then always quietly being disappointed with the digital output. I chalked it up to JPG rendering. Now I'm faced with either finding a workaround (likely doubling the effort required by my workflow) or just live with it.

Anyone?
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digitaldog
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« Reply #3 on: November 30, 2010, 07:28:50 PM »
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Zoomed out to fit the whole image on my screen, the preview on the original is different.
Anyone?

That is not uncommon to find some applications do not produce totally accurate previews when not zoomed to 1:1 (100%).
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Andrew Rodney
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peteforde
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« Reply #4 on: November 30, 2010, 07:36:49 PM »
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Okay, I guess... understand that my frustration is not targeted at you when I say: how is this acceptable?

If we weren't discussing a pro-level photo management application, I'd give Apple a pass. This seems like one of those "get it right" moments. After all, Aperture spins up threads to generate previews precisely so that the CPU burden of applying all of the effects in the chain isn't imposed upon the user in real-time.

I think it's the inconsistency (only certain functions/manipulations will result in unpredictable effects) that really irks me, and I say that as a career software developer.

I'm going to go take an Advil.
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