This has bugged me for a while in Photoshop (all the versions Ive used) can someone here explain the distortion I get when cropping: If I set the cropping tool option to resample an image to a certain size (say 100 X 245 pixels) I get no distortion on a straight crop, however if I rotate the cropping marquee (45 degrees or so) the cropped image will become distorted. (Even more so when perspective is selected.) I guess it must have to do with pixel interpolation as I dont get the distortion when crop tool parameters are cleared. What is happening? Im sure its a simple answer I just dont see.
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Is this something you are only seeing on the monitor but not on a printout or does it remain distorted on a printout?
What monitor are you using? Are you working in a country that has dependable power supply to your computer?
What version of Photoshop are you now using? What computer model, RAM, other additions/peripherals are you using (give specifics.)
This information will help solve the problem.
Thanks,
Ken
PS: ‘perspective’ is supposed to distort the image – so that part of your statement needs more clarification. Also, after rotation you will need to be more specific on what type of distortion you are getting – please describe. Post links to the images so we can see them in ‘before’ and ‘after.’
Also be aware that if your monitor is not absolutely linear, set for a non-typical aspect ratio, or if you are saving images with non-square pixels, etc., you will see distortion.
Print out the "distorted" page. Is it distorted in print?
I will try to get time to post some examples this weekend. The problem is repeatable on my computers at home and at work (450MHz G4, 2GHz G5 and a Powerbook, OS 9 and X, using both PhotoShop 7 and CS.) And it is real, a printout is distorted. Try this to see: Choose a relatively large image. Set crop option to 100 px wide and 245 px high. (I did not set the ppi as it should not matter). Drag out an area to crop and rotate crop marquee about 45 degrees. (Perspective is deselected). The result is a distorted (skewed) image. Charles
Try this to see: Choose a relatively large image. Set crop option to 100 px wide and 245 px high. (I did not set the ppi as it should not matter). Drag out an area to crop and rotate crop marquee about 45 degrees. (Perspective is deselected).
Why are you doing this? I’m just trying to understand what you are trying to accomplish here.
Ramon, I am trying to rotate an image 45 degrees while cropping to a set size. Of course I know there are ways around this issue. ( Like rotate the canvas first, then crop). My question was more academic: why does rotating a crop marquee with options set to a certain size cause distortion? I believe it has to do with the way PS resamples the image… but I don’t know. As I said earlier, I will try to post some examples tomorrow. Charles
OK. I’ve posted an example of my cropping question: <http://home.earthlink.net/~bbadland/crop.html> You will notice that rotating and cropping the image result in distortion. The cropped image is also way off from what you would expect from the marquee. This only happens when the crop tool is set to resample the image. This is not a new problem, but I hope you all would have some insight to share. cb
This is indeed baffling. I can reproduce your problem, and then some, on a high resolution (2048 x 3072 pixels) TIFF with the resolution set at 96ppi. On a relatively small JPEG (800 x 533 pixels) also at 96ppi, however, the crop and the rotation behave as expected.
Ronald, Strange, yes. I remember wondering about this back to 5.5? (maybe) You should be able to reproduce it as Ramón has done. Start with a large file and set the parameters of the crop tool so it will down-sample. Some of my tests results have been more extreme than the example I posted.
I used a 124MB one layered image and set the crop to 100px x 300px and 96ppi and then cropped a large percentage of the image so I was certain it had to down sample a lot.
Then I rotated the marque to many different degrees but all with the same results…
Every time I got a very different resultant image than what I’d designated.
I guess I’d never had reason to both reduce an image’s size that much while at the same time rotating a crop for me to see this happen before.
Ronald and Ramón- Yes, I think so – a bug. I first noticed this in my job (photographer for the Neuroscience Department at a university) trying to crop photomicrograph images of the axons of neurons to piece together in a figure for publication. They came out distorted with the axonal section sometimes not even in the final crop. Glad to have confirmation from other sources. Earlier posts mentioned this has been discussed before, but no current thread. Thanks much for verifying this. cb
A better way of handling accurate rotation is to use the Measure tool and drag-out its marquee to align with the item in the image that you want to be vertical.
Then go to Image/Rotate Canvas — Arbitrary and choose CW or CCW as appropriate.
Ann, Thanks. Yes, that is the way I end up doing it. I guess my question was: shouldnt I also be able to do this by rotating the crop marquee? It would save a step. I mean PS does allow you to rotate the crop selection a user should expect it to crop and resample predictably.
Though it had never occurred me to try it the way Charles described it, I agree with him that if the tool has the rotation feature, it should work accordingly.
It’s a bug that should be reported. One I could care less about because it doesn’t live in my house: I always do it the way Ann suggests, but Ramón is right.
This is what I said before, but to rephrase it, there seems to be no point in providing a feature in a tool if it doesn’t work. If it’s not recommendable to do something that way, why put the rotation capability in there in the first place?
Ken has an interesting point. (Or attitude?) But this bug does live in my house where I work with images taken by others. In many cases (for publications in scientific journals) I need to crop narrow images of neurons to a set size. The easiest way to do this (if it worked correctly) would be to set the parameters of the crop tool and rotate it to isolate a section of the cell. It saves one step; but in a two-step process, that is big advantage for me. I dont think it falls into the category of extraordinary processes as Ken suggests. If PS lets you rotate the crop marquee, it should be accurate.
I’m only asking for the sake of discussion and consider value to every viewpoint. My viewpoint comes from the print production and web image production standpoint. There are certainly other applications out there: Medical, Engineering, Mechanical Diagnostics, the list goes on. For me, it would be ‘out of line’ to not ‘line up’ the photo for visual objectivity first, and then add cropping parameters second, only because I want to see an image in its best ‘level’ of viewpoint before I go to the next step where I will consider cropping. For this reason, I would have never noticed the problem that has cropped up (pun intended) for other professions that employ Photoshop.
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