I understand that when you crop an image you throw away pixels. Are the pixels uniformly thrown away from all areas of the image? Also, if I start with a RAW file size that is 4992 X 3328 or 16.6 MP and I custom crop it, at what point do I actually see a decrease in IQ? ( either size of image crop or a percentage).
Are the pixels uniformly thrown away from all areas of the image?
Jim, imagine a magazine picture - you've pulled out a page yeah ? Take a pair of scissors and trim an inch off all round. Thats what cropping a shot is like.
The second part of your question directly relates as to how big you wanna print that crop and how far away you'l be viewing it from.
Bigger print from a small crop will need massive interpolation of pixels that aren't there in the first place so a decrease in IQ is gonna take place by the software to "up" the content of the shot so to speak and give it the size you want to print at.
reggie747 wrote:
Jim, imagine a magazine picture - you've pulled out a page yeah ? Take a pair of scissors and trim an inch off all round. Thats what cropping a shot is like.
Not in Adobe Camera Raw: The image data outside the crop bounding box is not lost. It can be retrieved anytime.
And not in Photoshop. If you use the crop tool and click on "Hide" (rather than "Delete") in the toolbar, cropping doesn't destroy data outside the cropping frame.
Thanks for responding. As for the magazine example I understand the first part. But now I have a smaller dimension image because I cut the border around the original photo or picture in the magazine to frame it better. If I want to get the newly framed image back to it's original size, or any size larger then what happens? I assume I lose IQ and that the software has to fill in pixels, or make up material that was not there in the first place. Is this correct?
Thanks for responding. As for the magazine example I understand the first part. But now I have a smaller dimension image because I cut the border around the original photo or picture in the magazine to frame it better. If I want to get the newly framed image back to it's original size, or any size larger then what happens? I assume I lose IQ and that the software has to fill in pixels, or make up material that was not there in the first place. Is this correct?
In many applications you may be able to simply use a lower ppi resolution instead of actually interpolating, though... But if you want to get your cropped image back to the size it started at, you're stretching what you've got left in some way (whether it's spreading the pixels out with a lower ppi or inventing new ones with interpolation).
Thanks for the response. I did not realize that this information could be retrieved at a later time or that it does not necessarily have to be destroyed. So, if I have an image that has a RAW file size of 4992 X 3328 and I custom crop it, what is the minimum amount of crop I can do without significant IQ loss? If I want to have at least 300 ppi, can I reduce the long side of an 8.5 X 11 inch to 3300 ppi? (11 inches X 300).
The reason I ask is because I have had images on my monitor look pretty good and have only minimally cropped them only to have the print come out average at best. However, when I print the image without cropping at all, it is much improved. So, I am assuming that I cropped it too much in the first place.
Thanks for the response. I did not realize that this information could be retrieved at a later time or that it does not necessarily have to be destroyed. So, if I have an image that has a RAW file size of 4992 X 3328 and I custom crop it, what is the minimum amount of crop I can do without significant IQ loss?
Cropping doesn't affect image quality; it simply gives you less of whatever image you started with. Resampling does affect image quality. But note that you can crop and resample at the same time. If you want to crop but not resample, make sure the resolution window in the crop toolbar is blank: http://img514.imageshack.us/img514/481/cropxw1.jpg
If you have to downsample an image for a small print size, keep a copy of the image in its original resolution. Once you downsample, those pixels are gone.
I noticed that you put the height and width dimensions in the crop tool bar windows. I do not do anything there. After custom cropping, I have been putting the dimensions in on the print page only. Eg. Plug in 11 inches for width for a 8.5 X 11 inch paper size in the landscape orientation. Where ever the height falls I use if acceptable. Is this wrong? Should I be doing it differently? Obviously I have a gap in my understanding here.
I noticed that you put the height and width dimensions in the crop tool bar windows. I do not do anything there. After custom cropping, I have been putting the dimensions in on the print page only. Eg. Plug in 11 inches for width for a 8.5 X 11 inch paper size in the landscape orientation. Where ever the height falls I use if acceptable. Is this wrong? Should I be doing it differently? Obviously I have a gap in my understanding here.
When I'm going to send an image to a print lab, I will crop it to size (5x7, 8x10, whatever) and make sure the resolution is what the print lab wants.
Although I don't print at home, if I did, I would crop first to make sure the image contained all and only what I wanted in it. It would also be a good idea to know your printer's optimum resolution and size your images accordingly. Otherwise, the printer may be downsampling your images.
