Hi all - first post to this forum and it's really not a question - it's an answer. Yesterday I had a discussion with a colleague of mine about this very issue. A division of our company had asked for high-resolution screen captures of our software product and I responded by saying they should use the 72 dpi images as there was really no way to up the resolution of the image.
This proveked a response from a well-meaning colleague who informed that there was, indeed, a way to up the resolution and they then proceded to tell me about their method. As I read through the solution I recognized immediately that the results they were offering did not improve image quality of the screen grab and it made the screen grab significantly fatter (from 2MB to 50MB) with, again, no added value.
Any time you artificially increase the resolution of any image you run the likelihood of, at worst, degrading the image quality or at best making it a fat file with zero improvement in image quality. Especially with screen grabs.
Simple steps for providing maximum quality on your screen shots in a print environment whithout fattening the file size.
1) open the screen shot in Photoshop
2) select from the menu Image>Image Size
3) turn off 'resample image'
4) resize the image to the size it will be used finally in your layout program (InDesign / Quark)
5) convert to CMYK if necessary
6) save as a TIFF or whatever your favorite print format is
If you are enlarging the image to something greater than it's original size the resolution will get smaller. Your 72 dpi image may drop to 64 dpi. That's ok! If you are resizing the image to something smaller than the original size - with resampling off - the dpi will get larger. If it stops at 221 dpi that's perfectly ok too! The important thing here is that when you're done you will end up with perfectly crisp images that print beautifully even though they are printing at less than ideal resolution.
What about if the file ends up with a resolution above 300 dpi? My advice is don't alter the dpi of the file - you are asking photoshop to interpolate the pixels and you really don't want to do that. In my experience once a screen grab is shrunk below 200 pixes (less than 3" roughly) you will not need more than 300 dpi as the line screen on press will not be crisp enough to maintain the clarity of the image at that level unless you're doing something ungodly like running a job at 600 to 800 linescreen. Then I'd let the res of the image go where it may - even if it's at 700 dpi. lol
Now you might ask - won't the press press shop complain that they're getting lo-res or less than optimal resolution files for printing? Or complain that the file is too high? If they're not used to working with screen grabs it's very likely. But do NOT let them convince you that you need 300 dpi files on screen grabs in your print document. Test it on any printer you like - your b/w laser, your color laser, a di-sub color proofing system - whatever you can afford. But forcing your screen grabs to 300 dpi isn't always the best solution.
That being said there are some exceptions. What if the screen grab is being inserted into a 300 dpi image as part of a design element. Then by all means you will want to fatten that sucker up by using the 'resample image' feature on with 'nearest neighbor' selected in the Image Size dialogue.
Hey - how's that for a first post?
[edited by: Frapster at 4:10 pm (utc) on Feb. 8, 2007]