# Illustrator

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## Why don't 10 stacked objects at 10% opacity equal 100% black?

### Jun 16, 2012 2:54 PM

A friend asked, and I had no answer - what am I missing here? .ai file

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Jun 16, 2012 3:17 PM   in reply to felixthehat-ffs

Felix,

Because 0.9x0.9x0.9x0.9x0.9x0.9x0.9x0.9x0.9x0.9 ~ 0.349 > 0.

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Jun 16, 2012 3:18 PM   in reply to felixthehat-ffs

Roughly speaking:

What's 10% plus 90% of 10%?

.1 + (.9*.1)=

.1 + .09=

.19 (19%)

What's 10% plus 90% of 19%?

.1 + (.9*.19)=

.1 + .171=

.271 (27.1%)

...and so on.

JET

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Jun 16, 2012 11:28 PM   in reply to felixthehat-ffs

So if you want it black you can set it to multply and use opaque shades instead of black.

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Jun 17, 2012 1:43 AM   in reply to felixthehat-ffs

Felix,

To elaborate on the answer in the first post, you may create an object with an opacity of 100 - 34.9 = 65.1% for comparison.

Similarly, with two overlapping 50% opacity objects, you may create an object with 75% opacity (0.5x0.5 = 0.25).

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Jun 17, 2012 9:49 AM   in reply to felixthehat-ffs

For my part you are welcome, Felix.

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