Computer Graphics with Photoshop - PS6: Feather puzzle

Author

PS6: Feather puzzle

Don

2004-06-02, 7:14 pm

Version 6.

I ran some tests by creating two images: one white and one black.
Next, I selected a small area of one and copied it to the other.

Now then, without Feather the border between the copied and underlying
color was solid, as expected, i.e. instant transition from white to
black.

However, once I applied Feather the number of affected pixels for the
transition was not what I expected! For example:

Feather: 1 - took 6 pixels to go from pure black to pure white
Feather: 2 - resulted in transition needing 10 pixels
Feather: 3 - took 14, and so on...

I would've expected a feather of 1 to take, well... 1 pixel. I could
also understand if Feather of 1 resulted in a 2-pixel transition: 1 on
the white side and 1 on the black. But 6!?

What's going on here?

Don.

Warren Sarle

2004-06-03, 7:14 pm

In article <40be0760.11616559@news.individual.net>,
phoney.email@yahoo.com (Don) writes:
> Version 6.
>
> I ran some tests by creating two images: one white and one black.
> Next, I selected a small area of one and copied it to the other.
>
> Now then, without Feather the border between the copied and underlying
> color was solid, as expected, i.e. instant transition from white to
> black.
>
> However, once I applied Feather the number of affected pixels for the
> transition was not what I expected! For example:
>
> Feather: 1 - took 6 pixels to go from pure black to pure white
> Feather: 2 - resulted in transition needing 10 pixels
> Feather: 3 - took 14, and so on...

Hmm. I thought Photoshop used Gaussian blur to do feathering, but
those numbers are way off for 8-bit mode. They're closer for 16-bit
mode, but if you're pasting in PS6, you can't be 16-bit mode, can you?

--

Warren S. Sarle SAS Institute Inc. The opinions expressed here
saswss@unx.sas.com SAS Campus Drive are mine and not necessarily
(919) 677-8000 Cary, NC 27513, USA those of SAS Institute.

Don

2004-06-04, 12:14 pm

On 3 Jun 2004 19:23:49 GMT, saswss@unx.sas.com (Warren Sarle) wrote:

>
>Hmm. I thought Photoshop used Gaussian blur to do feathering, but
>those numbers are way off for 8-bit mode. They're closer for 16-bit
>mode, but if you're pasting in PS6, you can't be 16-bit mode, can you?

Yes, this was in 8-bit mode (although, I have figured out a -
convoluted - way to copy in 16-bit as well using my lowly PS6...).

So what does this pixel value mean in the context of Feather?

It's clearly not the number of pixels used for the transition which,
sort of, makes it a meaningless number.

Don.

Don

2004-06-04, 12:14 pm

P.S.

I just tested Gaussian Blur and, you're right, the values are about
the same.

But I figured out the Feather mystery. Nothing is as simple as it
seems...

There are *two* Feathers. One is in the tool bar when Selection Tool
is active and the other is in the Select menu. To a casual observer
(read, yours truly) this would appear to be the same thing. It is
not!!!

For one, it's possible to enter 0 pixels in the tool bar but not in
Select/Feather - where 0 is converted to a "minimal" value of 0.2.

Long story short (too late...) it's the conspiracy of these two
settings which produced the weird results.

Don.