 Petra Hultqvist |
Understanding resizing images Hi, I have to admit I dont really fully understand about 'resizing' images, which I probably should... (have had a lesson about it). Anyway, for example, I have a RAW img, open it up in PSE and pixel dim is 5100x3400, document size 21x14 inch and resolution 240. I then crop my image and all the numbers change, which I understand. New numbers are: pixel dim 4400x2900, document size 6x4 inch and resolution 735. But it is here it all becomes confusing for me what I should do to keep best quality for printing. I was told that resolution 300 is the way for printing, so shall I change it from 735 to 300, is that ok? and if so, should I untick 'resample' or not so the number of pixels are unchanged? (and then I see the document size increases...) If anyone can shed some more light over this topic it would be highly appreciated. Thanks Petra
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
300 is a generally accepted minimum for resolution. You shouldn't go below that because it's said that you'll start to see things become not so good looking, and going above that you probably wouldn't be able to tell the difference in things looking better. Remember it's generally accepted that way. Using your example with what you start out with, the picture that is 5100x3400 and 21 inches, when you resize down to 4x6, the best result would be to resize without throwing away pixels. The 4x6 should still have the same 5100x3400. But the resolution should be 850. It's ok to make the resolution 300 because you may not be able to tell. But why not keep all the pixels that you naturally start out with. It's resizing up is where people are more concerned about keeping the resolution around 300. That's when, depending how many pixels you start out with, you may have to use resample to get a decent resolution.
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chrisbudny.com - Chris Budny Contact Chris Budny Chris Budny's Gallery |
Another take on this... when your original said 5100x3400 and 240 resolution, the math was simply: 5100 / 240 = 21.25" and 3400 / 240 = 14.17". Meaning if you were to take the 5100x3400 file to a printer that used 240 dpi resolution, your natural print size (and the "ruler dimensions" PSE is currently showing you) would be 21.25" x 14.17". Then you cropped out some of the image, and ended up with 4400x2900 pixels. Using the same printer in the example above, your natural print size would be 18.3 x 12. However, if you were sending the file to a printer that printed at 735 dpi, yes, the resulting print would only be 6x4. If you think of "300 resolution" as being the printer resolution you're aiming for in your prints, then doing the math (300 divided into your Length and Width pixels) gives you a good indicator of the print size you can expect from a given file... that doesn't mean you can't print substantially bigger, sometimes... your 4400x2900 could perhaps just as easily make a usable print 2 feet wide... Much of it depends on the printer, the paper, the inks and of course, the subject matter... you could find that the 4400 image prints quite successfully as a big enlargement, on a printer using just 180 dpi, if the subject matter doesn't need pin-point sharp tiny details visible in the print... Generally, unless you're upsizing a file, you may not need or want to Resample... just keep your 4400x file, with all your final editing in place, as your print file... depending on where you send out the printing (and their printer resolution offerings) will govern how big a print you can realistically obtain.
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doug Nelson |
Handle Resample with the same care you would a chainsaw. Resampling down means throwing away pixels you earned using decent optics, good equipment and competent technique. You can resample down for purposes of emailing an attached image, as long as you do this as a SAVE AS, preserving your original. Resampling UP means allowing PSE to generate pixels based on surrounding pixels. I've UPsampled only about twice, when my nitwit bro-in-law shot an otherwise excellent wedding photo (mine) at screen resolution. I had to upsample to get a mediocre 4 x 6.
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
"...when my nitwit bro-in-law..." Hope it doesn't run in the family. 
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