|
I have done a lot of cropping, rotating and twisting in photoshop.
I use a number of different processes to achieve results.
If the picture needs to be rotated I first work out the exact angle of rotation (trial and error) then increase the canvas size (Star fields I use black fill). Then do the rotate
Rectangular cropping after rotation seems to work OK without any distortions.
If I want an intellegent crop then to a specific pixel I usually use a different program "TheGimp" that allows reading pixel coords with the mouse. This works very well.
Another way I crop when making landscapes for stellarium that needs the landscape cut into panels of a given Square size is to use the canvas sizing tool and the pixel count method. This with a sequence of left right crops, save and step back gives me perfect pixel accuracy for the panels.
Another problem I have struck when making these landscapes is that some landscape programs do not accurately match for a spherical join.
This is where file menu automate crop and straighten is useful. I can stetch and slew the two faces to match exactly to pixel level with a bit of patience. Distortion is OK for this use but I would not use it for star fields
In general photo shop is very versatile but there are many functions that are much easier to do in other programs particularly cut and paste.
As for assembling a mosaic. That is something I have never tried but I have cut a few photos of star field into panels for a mosaic to display in stellarium at higher resolution than can be done with a single photo.
Barry
|