: Why does painting with 1% opacity not always do something? I tried this with Adobe Photoshop Elements 9. When I have a black background, and a white brush with an opacity of 1%, the color

@Sims5801359

The ceiling is indeed a rounding issue -- it's a limitation of storing pixel values as 8-bit integers.

In Photoshop CS2, using decimal values rather than hex and looking at one channel for simplicity:

The value of the pixel appears to be given by:

NewValue = RoundToInteger(
(CurrentValue * (1 - InkOpacity)) + (InkValue * InkOpacity)
)


When InkOpacity = 1%, InkValue = 255,

NewValue = RoundToInteger(
(CurrentValue * 0.99) + 2.55
)



For CurrentValue < 44, this gives you an increment of 3 per click
For CurrentValue >= 45 and < 129 this gives you an increment of 2 per click
For CurrentValue >= 129 and < 213 this gives you an increment of 1 per click
For CurrentValue >= 213, there is no increment at all.


Note that with higher bit depths, InkValue would be greater. The effect of each click still diminishes, but the ceiling would be closer to pure white.

Assuming the same formula (I haven't tested in Photoshop yet), 16 bit channel values (for which InkValue = 65535) should eventually get you to 65486/65535 which is greater than 99.9% pure white. It'll take you 703 clicks though!

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@Margaret771

It's intended and more of a math concept than anything else. Think about when you multiply 1% x 1% x 1% etc., you will always get a number that is infinitely smaller. The same concept can be applied to colors / opacity. Meaning there will be a limit, which, in "color" or "hex", is your #d5d5d5

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