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What is the feather when make a new channel?

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  #1  
Old 09-06-2008, 02:27 PM
kevs kevs is offline
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What is the feather when make a new channel?

When I use lasso for a selection, know the feather I'm starting out with.
When I use a duplicate channel and load a selection from that , what is the edge feather I am starting out with? thanks.
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Old 09-06-2008, 03:53 PM
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Markzebra Markzebra is offline
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Re: What is the feather when make a new channel?

zero, none, zilch
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Old 09-06-2008, 05:23 PM
kevs kevs is offline
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Re: What is the feather when make a new channel?

thanks, thats what I would think, but then why does so many of the borders ( make from channels) seem to smooth (ie when viewing in Quickmask) , as opposed to a selection made with the lasso at a zero feather setting, (which looks very hard edged)
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Old 09-07-2008, 04:35 AM
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Re: What is the feather when make a new channel?

Heres some theory: Selections and channels are interchangeable. They are the SAME THING. When you get that flashing dotted line thing that marks a selection its only a crude preview - in an 8 bit image the 256 levels can represent greyscale OR transparency. Each layer has a greyscale transparency mask associated with it anyway - this is viewable by command clicking the layers transparency and then Q entering Quick Mask

Your crude hard edged selections (where the channel equivalent is either black or white) are just that, crude
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Old 09-07-2008, 03:09 PM
kevs kevs is offline
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Re: What is the feather when make a new channel?

Thanks M, I get the gist of that, but what I'm saying is that when you make a mask from a duplicate channel, those edges always seems nice and and smooth out of box without doing anything, am I right about that?
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Old 09-07-2008, 03:28 PM
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Re: What is the feather when make a new channel?

Nope, depends on the channel whether its "smooth" or not. If you mean you duplicated lets say the blue channel from a photographic image and are using THAT as your selection, then yes chances are its "smooth". Your still not being specific enough about what you are doing.
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Old 09-07-2008, 05:17 PM
kevs kevs is offline
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Re: What is the feather when make a new channel?

That's what I'm saying. you admit the blue channel will be smooth. The edges viewing in quickmask.

Sort of like if I draw a lasso with a 2-5 feather.

In others words I have yet to see a channel load up a selection that looks like a hard edged 0 feather from a lasso selection.

I hope that's clear. was it?
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Old 09-07-2008, 06:29 PM
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Re: What is the feather when make a new channel?

Nope not really. is English the first language?

You really want to see a jagged channel? Choose your tragic wand, uncheck anti-alias in the options bar - then after you made your serection hit the new channel icon ( this is at the bottom of yoar chaneels palete). Now look at the channel - see its all jaggedy isnt it? Alternatively take your duplicated blue channel and apply Image/adjustments/threshold - then apply the Stupid Blur filter to whats left of her face.

Sorry its been a bad day
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Old 09-07-2008, 06:51 PM
kevs kevs is offline
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Re: What is the feather when make a new channel?

Sorry, I did not understand that too much. What the point? I am trying to ask if there is something inherently in using channels that make smooth edges. I'm not sure i"m getting anywhere, or that I'm being lucid enough to be understood. I talking soft/hard edges.
(do appreciate you being the only one answering -- and I take responsibility, in that maybe i'm not clear enough in what I'm trying to get answered)
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Old 09-07-2008, 08:40 PM
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Re: What is the feather when make a new channel?

I'll take a stab at this one.

Kevs, Photoshop (PS) has different ways of showing selections. The marching ants only show pixels that are 50% selected or more. However, alpha channels and quick mask can show pixels of any selection % by using a gray-scale representation.

You are correct in that selections from alpha channels may look soft on their selection edges... due to the partial selection capability of using a soft brush, feathering, etc. I attached an example below that shows pixel edges of a lasso w/0% feather within the composite image vs quick mask using a hard edged brush (100% hardness, 100% opacity) on both the RGB channel and the Blue channel. Yes, there is a difference. Quick mask makes a soft edge, but only with the brush. A lasso within quick mask mode produces a hard edge, as expected.

Why ? Everything is working correctly. It is simply due to the fact that the brush tool always creates partial selections of adjacent pixels. Even a brush set to one pixel will partially select adjacent pixels on a straight line. The larger the brush, the more pronounced the effect. Only a tool that allows you to turn off anti-aliasing, i.e. the line tool, will make a clean edge. I have attached a blown-up view of selections made with a brush vs the line tool. You can see why you get soft selections with a brush, and hard edges with a line (at least when it's straight, not when it crosses pixels though).

I hope this simplified explanation helps. It can be explained in more detail, but I thought this was better. If not, let me know.
Attached Images
File Type: jpg Selection Comparison QMvLasso.jpg (103.8 KB, 6 views)
File Type: jpg Selection Comparison BrushvLine.JPG (33.8 KB, 14 views)
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