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Photoshop is full of surprises
Hi Guys,
I've been using Photoshop for a very long while since it ported to win32 platforms in the early 90s. It's a great program but I've always been aware of its limitations when it comes to precisely crop (at the pixel level) and I avoid to do such things.
I've been playing with mosaics a bit lately and I came across an issue that I was able to reproduce and wasn't aware of so I thought I'd post and ask for feedback, see if anyone else noticed it.
The version I was using doing the process is PS CS3. Here's what I did step by step.
1_ I opened a high resolution 16bit RGB tiff. Approx (7000px square).
2_ I selected the crop tool and started adjusting the crop window on the bitmap.
3_ I started rotating the crop window by dragging the handles and resizing it so I could maximize the crop area within the mosaic.
4_ I cropped the picture.
The result was shocking. I looked at the stars and thought wow! I can't remember getting that much drift in my guiding?... Checked the original back quickly and the stars were round.
So what happened? Because the crop area wasn't aligned with the original image some type of skewing occured in the picture. Ever so slightly but noticable. I was able to work around by rotating the whole canvas then crop squarely to the new picture borders.
Looks like the resampling and transformation during oblique cropping is not the same as straight cropping.
Any thoughts?
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