Photoshop: problem with "legacy" Brightness/Contrast in 16-bit images of a specific size (512x512).

  • 1
  • Problem
  • Updated 6 years ago
  • Acknowledged
  • (Edited)
1. Create a new 16-bit color RGB file with the exact size of 512px * 512px.
2. Fill the background layer with color 313131.
3. Open Image > Adjustments > Brightness / Contrast.
4. Check "Use Legacy."
5. Instant solid black/white instead of brightness/contrast.

If you can't reproduce this, reply here and ask for a file.
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Stan V.

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  • frustrated

Posted 6 years ago

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Chris Cox

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Which version of Photoshop are you using?
Which OS version?
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Stan V.

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Hi, Chris.

I've reproduced this on multiple OS.

Reproduced with Photoshop CS6 Extended for Windows, under Windows XP 32-bit.
Reproduced with Photoshop CS6 Extended for OS X, under Mac OS X 10.6 Snow Leopard.

---

I wanted to clarify step 5 if I was unclear:

Basically the background turns solid white the moment I check Use Legacy. If I play with the sliders, it will turn solid black or solid white, but I can't adjust the shade of my color as Brightness/Contrast is supposed to.

Interestingly, you need those exact steps listed above to reproduce it, because otherwise:

1) Change to 8-bit image, you won't reproduce it.
2) Use a Brightness/Contrast *adjustment layer* instead of effect, you won't reproduce it.
3) Resize to, say, 513*513 px, you won't reproduce it.
4) Change the color (!!!), to say, 313132 instead of 313131, you won't reproduce it (notice all grayscale values reproduce it, but even the slightest saturation won't reproduce it).

So it must be some very interesting edge case. Unfortunately I have a ton of images at 512x512 with grayscale graphics, so it's annoying to me.
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Stan V.

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New: just updated to 13.0.1, I still reproduce the bug under both OS X and Windows.

New detail: the image color mode must be RGB (Grayscale color mode won't reproduce it, haven't tested the rest).
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Chris Cox

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OK, you found a real bug. The 16 bit code for Brightness & Contrast hasn't been quite right for many years. But it takes specific sizes and values to make it show behavior that bad (usually it wasn't quite right, but wasn't obviously wrong).

QE says "Wow, that's pretty cool"

I'm fixing it now.
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Stan V.

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Thanks!

Please note that the other topic I've posted was interpreted incorrectly, it's not "not a problem", it's an actual Photoshop bug. The title was changed incorrectly. I have no problem with strokes being rendered on open paths. I have a problem with them being rendered incorrectly in a specific way I've described.
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Chris Cox

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Then you need to clarify your post in that topic.