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Input/Output/Workflow Scanning, printing, color management, and discussing best practices for control and repeatability

resizing and cropping

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Old 12-10-2005, 10:59 AM
Albert Albert is offline
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Exclamation resizing and cropping

Hi, I hope this makes sense. I have an image that is 2048 pix x 1536pix which at 300 dpi I print at gives me a photo of 6.827 ins x 5.12 ins. I know that I can resample ticking bicubic and altering the size to 7ins x 5.25ins and then cropping to 7ins x 5ins that I print at. My question is really this, If I use the crop tool on the original image using a preset of 7ins x 5ins @ 300dpi what method is photoshop using and which method is best.

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Old 12-10-2005, 11:41 AM
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mistermonday mistermonday is offline
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Photoshop will use the original available pixels to readjust to the new specified size to the extent that the new size does not require more or less pixel than the original. If that is the case, then Photoshop is forced to manufacture more pixels via extrapolation (according to the algorithm selected) or it the new size calls for fewer pixels, PS throws away pixel data to "downsample". You typically lose more quality and incurr more image blur when you upsize. Regards, MM
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Old 12-10-2005, 12:03 PM
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garazon garazon is offline
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This page from adobe may also help explain it all a little better.

Although I don't have PS, in all the other image editing programs I have, I have noticed that just using a crop tool will actually lower the resolution slightly depending on how much of the original image gets cropped, however if I resize to 7 x 5.25 in this case, then crop, the resolution stays constant. In this particular case the image you have is already close to the 5x7 ratio to begin with so the effects would be neglible with regards to printing either way you chose to do it. It's my understanding that cropping doesn't resample the image at all persay, but merely remove/add data form the original image.

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Old 12-10-2005, 03:55 PM
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byRo byRo is offline
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Replying in reverse order..
- Which type of interpolation will PS use when cropping? I have always believed that is is what you specify in Edit>Preferences>General. This comes pre-defined as Bi-Cubic which is usually the best alternative;

- Resizing then cropping? The PS crop tool also performs the resizing function, so you don't need to resize the image first. Just fill in the size you want and crop away in just one operation;

- Why crop? (My question, now) Your image is very close to the final size. If this is going to be framed and/or matted then is the 0.173" so important? Any resizing of the image will always introduce some "noise". So, if you have an option of not resizing, all the better!

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Old 12-11-2005, 07:04 AM
Albert Albert is offline
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Thanks to all for your quick responses and help. I appreciate that given the example used, matting would be good solution, but sometimes I wish to crop tighter and still print at 7x5. Following the Adobe link from garazon (thanks ) and reading the following, I am still a bit unsure which way is best.


Using the term resamping when you use the Crop tool to resize images is unclear because there is no Resample option to select when you use the Crop tool. When you use the Crop tool to resize an image, the pixel dimensions (and consequently, the file size) can change, even though the image is not being resampled. In these cases, the pixel dimensions and resolution change to incorporate more pixels into each inch of the image based on the number of pixels you select in the crop region, though Photoshop is not specifically adding or removing data from the image. Because of the way the Crop tool handles pixel dimensions, indicating that the amount of data in the image has changed is more useful than indicating whether or not the image has been resampled.
When you crop an image, you are removing data from or adding data to the original image's size to create a new image. Because you are removing or adding data relative to the original image, the concept of resampling loses much of its meaning because the number of pixels per inch can vary based on the number of pixels in the crop selection. When the number of pixels in the crop selection allows, Photoshop will try to keep the same resolution of the original image; this is traditionally considered cropping without resampling. However, when you are not exact about the number of pixels you select, the pixel dimensions and file size changes in the new image.

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Old 01-05-2006, 11:12 AM
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creeduk creeduk is offline
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On this image the crop tool should be fine on larger resizes (correct me if I am wrong) it is preffered to increase the image only 10% at a time, the crop tool will not do this (unless it is really clever) and so then and only then would it an advantage to resample and then crop.
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