Ben Horne wrote:
By shrinking the red channel, now the color channels are all the same size. When aligned properly, the vast majority of the CA will be fixed.


Yes, but how do you do that (shrink only the red channel)?

I can view it, select it, move it around relative to the other channels, but if I try to use Image>Image Size to shrink it (only red channel visible, active and selected), the entire image (G&B in addition to R) is affected. So clearly I'm doing something wrong. What?

monoprint wrote:
Ben Horne wrote:
By shrinking the red channel, now the color channels are all the same size. When aligned properly, the vast majority of the CA will be fixed.


Yes, but how do you do that (shrink only the red channel)?

I can view it, select it, move it around relative to the other channels, but if I try to use Image>Image Size to shrink it (only red channel visible, active and selected), the entire image (G&B in addition to R) is affected. So clearly I'm doing something wrong. What?


Exactly. This doesn't make sense, perhaps because I have never tried to "shrink" a channel. Image resize affects everything, RGB channels combined. I know a lot about using channels, but obviously not this...

Click on the red channel (you should see a black and white image now), then use the keyboard shortcut to select all of the canvas (Control A on PC, or Command A on mac). Copy the image to the clipboard, then paste it into a new document. Resize the image, then copy it, and paste it back into the original red channel. Next, just move the pasted in copy of the red channel so it aligns properly.

Ben Horne wrote:
Click on the red channel (you should see a black and white image now), then use the keyboard shortcut to select all of the canvas (Control A on PC, or Command A on mac). Copy the image to the clipboard, then paste it into a new document. Resize the image, then copy it, and paste it back into the original red channel. Next, just move the pasted in copy of the red channel so it aligns properly.


Thanks. With all the people pretending to know what you meant, I'm relieved to know there is not something that mysteriously got by me regarding PS channel "resizing".

Basically, you can't do it. This is definitely not a straight forward technique and your really creating and combining two images. I'd have to play with it before attempting to do it but perhaps if I review my images shot with the 24, 45, and 90 I'll find something worth "repairing" in this way.

jamesf99 wrote:
Ben Horne wrote:
Click on the red channel (you should see a black and white image now), then use the keyboard shortcut to select all of the canvas (Control A on PC, or Command A on mac). Copy the image to the clipboard, then paste it into a new document. Resize the image, then copy it, and paste it back into the original red channel. Next, just move the pasted in copy of the red channel so it aligns properly.


Thanks. With all the people pretending to know what you meant, I'm relieved to know there is not something that mysteriously got by me regarding PS channel "resizing".

Basically, you can't do it. This is definitely not a straight forward technique and your really creating and combining two images. I'd have to play with it before attempting to do it but perhaps if I review my images shot with the 24, 45, and 90 I'll find something worth "repairing" in this way.

I setup an action to do it. Pretty much everything is automated and it takes a split second.

Ben,
I'm not sure that this is a big shortcut but you could resize a channel without copying. Click on the channel, Select all, Edit->Transform->Scale.

Alex

After finding out how to do the resizing - thanks Ben and Alex - I tried the technique on an extreme Architectural shot taken with the 24 on full shift. I couldn't get the correction quite right, although I did improve the terrible CA quite a bit. The final fix, which leaves the image "perfect", is to convert to Lab, use Dust and Scratches filter on the a channel, and then sensible sharpening on the L channel.

Hope this is useful.

Mark

Mark,

I tried something similar. I converted to LAB mode, then applied a slight blur to the a and b channels, and it seemed to help fix the remaining CA issues. Both of those channels got very pixelated, and softening it seemed to smooth that out.

I tried the PS lens correction, and it did work, but it did not seem to do much different than the technique that I have been using. Also, it was a bit slower.

This is a test shot for the 45mm TS-E that I have just acquired. Tilted 7 degrees to get the plane of focus between the Canon cap and "XP" letters and then used a small aperture to bring in maximum DOF

Ben,

Did you remove the images?

I cleared out my server of old shots, so it looks like it wiped them out as well.