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Old Feb 21, 2016, 3:48 PM   #1
conor
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Default Problems with colours / image formats

Pardon my ignorance... here goes...

Attachment 205876

This is a slice cropped from two different copies of an image.
Allow me to explain.

I fired up PS-CS5 and loaded in a RAW image.
I made the tweaks I wanted and opened the file in PS.
I did my editing, layers, colours, etc and saved as PSD.
I then flattened the image and saved as PNG.

I opened the PNG and the PSD side by side in Photoshop and did a screengrab of a section of both images. On the left is the PNG, on the right is the PSD.

Why are the colours different?

If you can't see the difference, use a different monitor:
The right-hand image appears slightly more red.
The left-hand image appears slightly more green.

Last edited by conor; May 3, 2016 at 2:13 PM.
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Old Feb 21, 2016, 5:27 PM   #2
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As a guess, you were working in 16bit format and saved the PSD that way. Did you have your settings at 'lossless' for the PNG? Also, was the PNG saved in 8bit or 16bit color?
Compression/decompression, and the interpolation of colors from 8/16bit to your display can result in minor differences. If your PSD editing was done in 16bits, you would also need a monitor capable of display of the full 16bits for the colors to be accurate.
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Old Feb 21, 2016, 10:08 PM   #3
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I'll run through this work flow and see what I did.
I'm guessing that you're right about my mistake, this is something I would never have considered myself.
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Old Feb 22, 2016, 6:58 AM   #4
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PNG uses 8 bits per color (R, G, and B) plus 8 bits for Alpha (transparency), whereas PSD uses either 16 or 32 bits per color.

When you convert a PSD image to PNG, you're limiting the color palette, so subtle changes are likely to occur.
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Old Feb 22, 2016, 9:49 AM   #5
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I wouldn't call it a 'mistake' at all. It is just part of the learning curve.
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Old Feb 22, 2016, 11:53 AM   #6
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Ok, so the *only* file type that keeps colours as expected is PSD.
TIFF, JPEG, PNG all result in an image that looks like:
- has lower contrast
- has higher brightness
- has lower saturation

I think I can come up with a way to tweak the resulting images back to what was expected...
Is there a way to work in the same colour space as the output will be to avoid this issue?
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Old Feb 22, 2016, 1:34 PM   #7
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Oops, on my part. I hadn't considered color space. If you are editing in Adobe RGB, the conversion to sRGB will certainly result in color shifts.
I don't know enough about PS to tell you how, but I believe you may be able to use sRGB as your working space, or emulate it on the monitor. Another option might be to create an action to adjust the photo after you finish editing.

I used to try all the recommended tricks for getting the best out of my 5 and 6 megapixel cameras, and obsessed about color accuracy. Finally realized that, except for things I printed myself, colors depend too much on factory monitor settings, which most people don't change, for colors to be accurate. Best you can do is relatively close.
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Old Feb 22, 2016, 4:57 PM   #8
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Quote:
Originally Posted by VTphotog View Post
I used to try all the recommended tricks for getting the best out of my 5 and 6 megapixel cameras, and obsessed about color accuracy. Finally realized that, except for things I printed myself, colors depend too much on factory monitor settings, which most people don't change, for colors to be accurate. Best you can do is relatively close.
My book is an actual, physical book. My workflow is as follows:

1. Shoot
2. Use raw plugin to open the NEF in PS
3. Edit, save as PSD.
4. Flatten, Save as PNG/JPEG
... repeat steps 3-4 for additional versions of the edit
5. Flatten, Resize, Sharpen, Save as PNG/JPEG
... repeat steps 3/5 for additional versions of the edit for web

Full sized PNGs are what get shipped out for printing if the printer supports the format, otherwise I ship JPEG files. (I'd use TIFF, but printers don't tend to accept TIFF)

So, it's one thing that my edit looks different from the print. That's an issue with my monitor that I can account for / calibrate for. The major issue here is that my image changes after editing.
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Old Feb 22, 2016, 6:12 PM   #9
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Quote:
Originally Posted by conor View Post
Ok, so the *only* file type that keeps colours as expected is PSD.
TIFF, JPEG, PNG all result in an image that looks like ...
Actually, TIFF preserves color depth as well as PSD, DNG and RAW (NEF). In fact, most (if not all) RAW formats are based on TIFF.

Quote:
Originally Posted by conor View Post
Full sized PNGs are what get shipped out for printing if the printer supports the format, otherwise I ship JPEG files. (I'd use TIFF, but printers don't tend to accept TIFF)
I'm surprised by that. TIFF is widely used as the direct output from image scanners, which many printers use to create their own originals.

PNG is better than JPEG, but either will constrict the color palette, which will result in what you're seeing, and there's no way back from that.

I think I'd look for other printers.
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Old Feb 22, 2016, 9:18 PM   #10
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Is the difficulty in the prints? If so, it may be the printer is not (or cannot) print in the Adobe RGB color space, so the pictures are being forced into the sRGB color space, which will certainly give different results. Your printer needs to know which color space you are using. (this would be embedded in the Exif from the camera, but may be getting lost somewhere in your workflow)
If complete accuracy is necessary, go with a calibrator which can standardize your monitor and be used to check your prints.
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