Help! CS2/Camera Raw and interpolating

Ok, when I shoot I usually crop to 8x10 (3000x2400 @ 300ppi) unless the picture or my composition calls for another crop. My cameras native rez is 3008x2000 @ 240, so Im interpolating a bit. I do this by cropping with a custom crop tool and the ppi set to 300 in CS2's Camera raw. Thats where the problem is coming in. Im getting an almost sharpening halo on edges of subject, most commonly straight or well defines edges. Here are two examples:

(Note: in the comparision pictures, both pictures are the exact same adjustment done to them in Camera Raw, the only difference is picture rez then a normal tight crop done in PS to isolate the area where the Halos appear.)

Comparison 1/1: 3000x2400 @ 300 ppi (look to the edge of the pants)

http://i32.photobucket.com/albums/d2/trogman/Web%20Display/fishingholetest2.jpg

Comparison 1/2: 3008x2000 @ 240 ppi

http://i32.photobucket.com/albums/d2/trogman/Web%20Display/fishingholetest1.jpg

Comparison 2/1: 3000X2400 @ 300 (look to the top of the barn)

http://i32.photobucket.com/albums/d2/trogman/Web%20Display/Farm-untitled-test1.jpg

Comparison 2/2: 3008x2000 @ 240 ppi

http://i32.photobucket.com/albums/d2/trogman/Web%20Display/Farm-untitled-test2.jpg

Any idea what I am doing wrong? Any way of avoiding this?

David, I think you're confusing a couple of things. The camera doesn't have a native ppi setting - that setting is used for printing only. The preferred workflow is to import all image date (uninterpolated), correct color and contrast to your liking, then save a "master" file that you can later use for various purposes.

You should resize/crop the image and set the print resolution (ppi) only when you're ready to print at a given size.

Guy

I was thinking it was the cameras native resolution because out of the box, ACR set the ppi to 240 until I changed it. This also happens in Nikons Capture as well, for some reason every program wants to set the ppi to 240 so I just thought that the RAW file from the camera was native 240, thanks for clearing that up for me Guy

Also thank you for the work flow tip. What I have been doing is cropping and setting ppi in ACR then saving as a .DNG file and using that .DNG file as my master.

Do you think if I do my resizing in PS instead of ACR that will fix my little halo problem?

Your halos look like "chromatic aberration" to me. I see it in both images even before you interpolate. I think up sizing just made it easier to see. Look at the lens tab in ACR. It has sliders that might help you with this issue.

I think your workflow of saving a DNG as your master should work well.

The problem is definatly a form of chromatic aberration. Sometimes the ACR sliders cannot correct for the extreme case of large asymmetrical purple chromatic aberration (my wife and I had a Canon Power Shot used for family snap shots that had that problem). However in this case there is a strong magenta/green symmetry on both sides of the pants legs, so it should be fixable in ACR.

If you are still left with chromatic aberration that is not fixable in ACR (like colored outlines around highlights), I can show you how to correct for this in Photoshop if you are interested.

Another thing to consider when interpolating to a larger file size - the interpolation method. For my images with lots of detail, I use "Bicubic Smoother" If you use regular "Bicubic" or "Bicubic Sharper" you can get halos (especially with "Bicubic Sharper").