When should feather tool be used?

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Posted By
exingo
Sep 24, 2003
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1897
Replies
20
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Closed
When making a selection around part of an image to move to a new location, when should the feather tool be used? Should it always be used?

Thanks.

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YrbkMgr
Sep 24, 2003
Always. AND Never. I’m kidding.

Do this and you’ll answer your own question, because we cannot.

Open an image – preferably a photo, not a drawing, for the sake of illustration. Now, draw a rectangular marquee somewhere in the image. Now copy it to clipboard. Don’t Deselect it.

Create a new image and accept the defaults (for this exercise, make sure the background is white). Now Paste your selection into this new image.

Go back to the original image and do Select|Feather Selection… and enter like, oh, 25 pixels. Now Copy that to clipboard. Do the same thing you did before, create a new image and paste this into the image.

Do you see? One has a hard edge, one has a soft edge. You get to pick when you need them – exact v. transitioning.

You might use feather when putting your girlfriends head on Heather Locklear’s body, and you might use the hard edge when you want to perform a task on a well defined area of an image.

So, <shrug> it depends.

Peace,
Tony
MC
Martin Coleman
Sep 24, 2003
I’m also interested in the Feather question. Can someone explain exactly what it does? My understanding is that it kind of fuzzies up the edges to help the selection blend with something else. So, if PS chooses to omit some pixels around the edge how does it decide which pixels it doesn’t want? Does it discard some? If so, are they outside the line or in? If you select a feather of say, 6 pixels is that 3 inner and 3 outer or 6 inner?

I been PSing for about a year now and this is something that I still can’t get right. Does it improve with experience? I only use PS for editing digitally captured images, selecting for adjustments, changing a sky, etc. Usually, I try 3 or 4 times with selections and still don’t seem to get it perfect.

Sad tale I know!

Martin
Y
YrbkMgr
Sep 24, 2003
Martin,

Go through the same exercise I posted in number one. Then study the images.

If you want a better visual representation, then save each selection from that exercise with Select|Save Selection. Then look at the channels palette, and click on the selection you saved. Black is selected, white is not selected. Pay attention to the borders….
JM
John Mensinger
Sep 24, 2003
Martin, you make a selection, say, with the Marquee Tool. All the pixels within your marquee selection are fully selected. Choose Select > Feather, and enter a value…yes, entering a value of 6 affects an area 3 pixels deep inside your original marquee, and 3 pixels outside. These pixels are "partially selected," in an even gradation across the 6-pixel distance, from 100%, (4 pixels inside your marquee), to 0%, (4 pixels oustide your marquee). Though it’s not so mathematically sound, higher Feather values also tend to round off the corners of a rectangular or polygonal selection.

You can "witness" the effect of Feather by saving a feathered selection, (Select > Save Selection), as an Alpha Channel, then go to the Channels Palette and view the grayscale equivalent of your saved selection. Every selection is nothing more than a grayscale image, and Feather creates a grayscale gradient, over the distance you specify, along your selection edge.

I hope that helps.
P
Phosphor
Sep 25, 2003
"…I’m also interested in the Feather question. Can someone explain exactly what it does?…"

OK, Martin, here’s "Exactly" what feathering does:

When feathering a selection, the selection "edge" (where the marching ants appear) becomes the 50% opacity locus. All pixels on that edge have an opacity of 50%. Since opacity and transparency are inverses of each other, you might prefer to think of the edge as the 50% transparency locus.

From the edge inward, the opacity increases toward 100% (transparency decreases toward zero). From the edge outward, the opacity decreases toward zero (transparency increases toward 100%).

The gradation of opacity at the edge is exponential (not linear). The feather radius which you set allows you to control the gradation. At a distance inward from the edge of one feather radius, the opacity has changed 63% of the way toward 100%, becoming 82% there. The opacity gets to 100% at 2.7 feather radii inward.

Outwardly, likewise, the opacity drops to 18% at one feather radius and to zero at 2.7 radii.

When there is no feathering (radius = 0), there is a discontinuous change in opacity from 100% to zero at the selection edge.

Since you’re working with digitized rather than analogue variables, the opacity changes with distance are stepped rather than continuous and the opacities you read are not going to be precise—but they will be close enough for all reasonable intents.

Feathering does not "drop" any pixels. It keeps all of them. But it does change the opacity attribute of some of them, as detailed above

George
BL
Bill Lamp
Sep 25, 2003
George,

Is there a way to feather in just one direction from the "marching ants"?

IE: Marching ants=100% opaque
250 pixels out would be down to 0% (with a feather of 250 pixels)

Thanks,
Bill, who HAS needed to do this (a slow gentle saturation fade NOT a piece of an image)
CW
Colin Walls
Sep 25, 2003
Bill,

Seems to me that, as soon as you want to do anything beyond the simple, symmetrical selection fade of a feather, you should be using masks. With a mask, you can do anything [well, almost].
P
Phosphor
Sep 25, 2003
Bill,

To start with 100% opacity at the edge with 100% opacity imward from there and tapering off to zero outwardly, you could fool the system by expanding the selection 2.7 feather radii. That is, shift the feather profile outward enough to avoid inside effects.

The opacity would grade off in a flattened S-shape spread over 5.4 feather radii. The 50% point would be reached at the half-way point, i.e., at the expanded selection location (2.4 feather radii from the original selection site. You would use a feather radius of 46 pixels to get to zero opacity at 250 pixels.

Keep in mind that the opacity change starts out and ends up very gradual. For easily definable shapes such as rectangles and circles, you might better use the gradient tool or the Filter Factory. The "feather" algorithm is hard-wired and you can’t linearze it, but you probably wouldn’t want to anyway. It gives you a "soft" take-off and landing.

George
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Phosphor
Sep 25, 2003
Typo in response #8: In second paragraph, change 2.4 feather radii to 2.7 feather radii.

George
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Phosphor
Sep 26, 2003
Bill,

I should also have suggested that, if you don’t want to pick up any feathering outside the selection boundary, you could shrink the selection by 2.7 feather radii. That way the opacity is 0 at the original selection boundary and outwardly from it and, inwardly, it grades from 0 to 50% at 2.7 feather radii and to 100% at 5.4 radii. The gradation, again, is not linear, tapering smoothly at the beginning and end.

George
L
LenHewitt
Sep 26, 2003
Bill,

I agree with Colin.

If you paint directly into an Alpha channel, or use Quick Mask Mode you can create a selection with exactly the properties you require, soft edges where YOU want them and hard edges where YOU want them
BL
Bill Lamp
Sep 26, 2003
I will be printing this thread!

I may have things confused/difference in terminology (I am 95% self taught & 5% book taught with Photoshop).

In the case in question:

1.) I made a selection around part of the center of a picture.

2.) I checked it with red overlay and switched back to the ants.

3.) I went to modify and ran feather to the maximum.

4.) I went back to the red to make sure I had the feather going the right way as "stuff" indeed does happen. <grin>

The final product for this negative scan is 12" x 18" at 360 DPI on an Epson 2200.

So at this point I’m beginning to think that there may be a feather tool/paint brush in addition to the feather of a selection/mask.

Please don’t get too upset over my slowness in this. It took me way too long to be able to do much of anything with CURVES.
P
Phosphor
Sep 26, 2003
Bill,

To see the quantitative opacity profile created across a selection edge, drag the feathered selection to a blank document having a transparent background. Scroll the cursor back and forth across the edge while reading from the Info palette the opacity at varying distances from the edge.

It is good for the soul to verify for one’s self that the opacity is indeed 50% at the edge and—depending on whether the scroll direction is inward or outward—reaches either zero or 100% at a distance 2.7 times the feather radius.

Still not convinced? Try different feather radii. And remember, you are working with digitized, not analogue, quantities so the values you read will be stepped, not continuous. If you read, say 48% where you expect 50%, don’t sweat it—that’s quantification in action.

George
JR
John R Nielsen
Sep 26, 2003
To get the feather to go inward only, how about this:

Start with the hard-edged selection, and enter Quick Mask mode (Q). Gaussian blur the Quick Mask; this is the same as feathering. Now, with the Quick mask still active, Image > Adjust > Levels (Ctrl+L), and enter 127 in the left-most Input box, and press Enter. You could also play around with the Gamma slider here, to control the "hardness" of the feather. Finally, go back to standard mode (Q again).

– John
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Phosphor
Sep 27, 2003
John,

"…Gaussian blur the Quick Mask; this is the same as feathering…"

Your procedure may or may not be preferable depending on the user’s intent. In any case, although similar in some respects, Gaussian blur has a distinctly different effect across an interface bretween two colors.

Gaussian blur mixes pixels from both sides with each other. The intrusion from one side to the other shows up as a halving of the color value right at the interface tapering to zero at (like feathering) 2.7 radii. At the same time the "home team" color also halves in value at the interface but increases from there and is restored to ambient value at 2.7 radii. Ditto on the opposite side of the selection.

Feathering involves no mixing across the interface. It works exclusively on the opacity profile.

This is not to say that one is more appropriate than the other. Your method has definite merit and is certainly one to consider, but it does not appear to be equivalent. When should you use one or the other? I haven’t thought about it so would not venture to say.

George
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Phosphor
Sep 27, 2003
John,

On second glance, by golly, I see that you are right about the equivalence because you are applying the blur to a MASK, rather than the image, and the mask presents a black/white interface across which the Gaussian Blur interchange of colors occurs—in this case, black with white on one side and white with black on the other.

This produces 50% gray at the interface and shades of gray on up and on down in the two directions from there. With the rates of change being the same as in feathering and the mask colors getting converted to opacity when you return to standard mode from Quick Mask, you’ve got yourself a literal feather—an exponential opacity gradient from 50% at the interface tapering up in one direction and down in the other and with the same radius parameter in the blur operation as in the feather.

I’ll be darned. Nice going, John! I thought I had put this aside, but my subconcious kept working and just woke me right now (5 am) with this clear as crystal insight. I feel guilty because my conscious self had nothing to do with it, to say nothing of being perverse. Am I getting schzoid? Good thing I’m outa here for the weekend!{-:

George
CW
Colin Walls
Sep 27, 2003
George, John

Isn’t this just what I was saying – I just didn’t spell it out. Doesn’t actually matter whether it’s QuickMask, a layer mask or an alpha channel. You always have this fine control. Who needs selections? [Don’t answer that – it’s a rhetorical question 🙂 ]
Y
YrbkMgr
Sep 27, 2003
Yeah Colin, you’re right. In fact, it’s a sentence or two short of where I was pointing in post #3.
JR
John R Nielsen
Sep 27, 2003
Regardless of whether one uses the Feather command, or blurs a mask, one thing I hadn’t thought of before was using the Gamma slider in Levels on the selection to change its ‘profile’? ‘hardness’? (can’t think what the propper term would be), without changing the distance of the feather.

That’s one of the great things about this forum – someone puts forth a problem, and in the process of playing around trying to solve it, you discover two or three things you never thought of doing before.

So at this point I’m beginning to think that there may be a feather tool/paint brush in addition to the feather of a selection/mask.

You could paint on the edge of the mask with the Blur tool.

– John
MC
Martin Coleman
Sep 28, 2003
Wow!

I wanna marry you guys!

Martin

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