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Re: notches on the L*axis
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Re: notches on the L*axis


  • Subject: Re: notches on the L*axis
  • From: Rick Gordon <email@hidden>
  • Date: Thu, 13 Dec 2007 17:46:33 -0800

I think that if there were a variance, that testing could amplify into visibility by repeated iterations or whatever. I think it's much more likely that the reason it's moot is that 15-bit math is operating under the surface. I DO think that it would be a problem if a 50% gray level could affect a luminosity change in an overlay blending situation, because the whole technology of overlay is based on the fact that it won't.

Rick Gordon

------------------

On 12/13/07 at 9:55 AM -0800, Marco Ugolini wrote in a message entitled
"Re: notches on the L*axis":

>Rick Gordon wrote:
>
>>The overlay modes (Overlay, Soft Light, Hard Light, Vivid Light, and Linear Light) are the various blending modes in which the following occurs:
>>
>>1) A value lighter than 50% gray blended into the source layer or channel will cause lightening to occur
>>
>>2) A value darker the 50% gray blended into the source layer or channel will cause darkening to occur.
>>
>>3) A 50% gray will exhibit no change.
>
>If you are saying that the imprecision inherent in rounding up the numbers would show as a visible difference in lightness, I doubt that, mainly because the imprecision is so small that the effect would likely not be readily visible, or would not make a difference in practical terms.
>
>Also, since there is no way either to input or view decimal values in 8 bits in Photoshop, how would you exactly know whether the rounded-up number is 50.2 or 49.8?
>
>Marco Ugolini


--

___________________________________________________

RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________________

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