Channels Help for PhotoShop 7

[subhash_tiwari]

In trying to do 'smart sharpening' by applying the edge filter to a

channel, and then loading that into the image, I seem to miss

something- do I then delete the channel as a last step, or save with

it in ? I am new to PS and am probably confused about some basic

concepts.

Here are the instructions-

http://www.luminous-landscape.com/tutorials/smart_sharp.shtml

Appreciate any help.

Subhash

[robert x]

The channel you create (the aplpha channel) is a mask that only shows up the edges you

wish to sharpen - you apply USM to the image, using this channel as a selection so only

those bits get sharpened.

 

You are supposed to apply "find edges" to a *duplicate* of a channel (lightness in LAB

color he suggests for a color pic) and then "select all" and paste this into a new alpha

channel to create the edge mask. Then you apply the sharpening to only the areas in that

alpha channel, but you must load the selection of that alpha channel onto the image to be

sharpened. (Lightness in LAB color here).

 

There is no need to delete an alpha channel, except to save storage space.

 

I have no idea if this helps at all - I am also learning PS and its helpful to try and explain,

even if just for me.

[subhash_tiwari]

Thanks Robert. Problem is, there is something that I am not quite 'getting". Interestingly, in the link above, if you follow carefully and go to the links at each step, one of them (step 12) is an error. After that, I "dial in" the sharpening. Then the author assumes I know how to save everything, but should one leave the channel in place or delete it? Is the sharpening (at that point) on the channel or the RGB image ? Will try again. If you think of anything I am missing, do let me know...

[robert x]

>>one of them (step 12) is an error.

 

it shouldnt be - you need to make sure you are working on the right layer in your layers

palette tab....

 

 

>>After that, I "dial in" the sharpening. Then the author assumes I know how to save

everything, but should one leave the channel in place or delete it? Is the sharpening (at

that point) on the channel or the RGB image ? Will try again. If you think of anything I am

missing, do let me know...

 

it should be on the image. But you should (according to that tutorial) be not applying it to

the RGB image, but to the "lightness" channel in LAB color. You need to convert the

IMAGE>MODE to LAB color to do this...(still with me?)....so when you make the mask with

the alpha channel you then apply that selection to the lightness channel in LAB color......if

you use USM filter with the alpha channel selection onto the lightness channel, then the

sharpening will only apply to the Lightness channel,. Sharpening on this channel is

supposed to be a good way of doing it. Whether you keep the alpha channel edges mask is

up to you - as I said I think it's really just a question of space you have available. Ideally

you should only sharpen when you are ready to print, so if you are going to print it to

different sizes, and so need different sharpening levels, maybe you should save it. It will

make no difference to the printed image.

 

Personally, its a bit compiclated. I normally sharpen in two goes - once at 250%/0.1/2 and

again at 100%/1/1. If there are lots of empty spaces that suffer from sharpening the edges

is handy, but equally you can set history brush to level before and erase the sharpening in

the unwanted areas.

 

So many different ways to do things in PS, which is what makes ot so great, and also so

hard to learn.

 

Feel free to email me and ask if you are confused, not sure I am much less confused, but

maybe a little ?

 

R