The 5D should have plenty of resolution for a very nice 20 x 30 print. I don't photograph or print for a living, but...
I would do whatever processing (color, WB, levels, etc), you're going to do at the native size (the size it opens as)... this would include some mild sharpening. (Most would say edit the image as 16 bits, and only reduce to 8 bits when your're ready to save as a jpeg for output.)
Then, using Image, and then the Image Size menu... Up-size it to the output size (20 x 30), using the Bicubic Smoother choice, and apply any final sharpening before its ready for printing (whether that's Costco, or some other lab).
I don't know what editing software you're using, so these suggestions are from CS3:
I'm sure others will have other suggestions. this is what my limited knowledge would tell me to do.
A 20 X 30 print should print very nicely from a Canon 5D. I personally do all of my printing out of Adobe Lightroom. However which program you print out of you need to make sure that you do that following steps
1. Make sure your monitor is correctly calibrated.
2. Make sure you that the correct paper profile selected.
3. Output sharpening. In lightroom I usually select around 50 point of sharpening for output.
Over the past year I have had five 20X30 prints made of pics from my 5D. I use MPix and I have never changed the file size (enlarge, up-res, or whatever). I just do my thing in Photoshop at native size till I'm happy, then send the file to them. To quote from their site:
"Our printing equipment will resize the files as needed when they are printed. Like sharpening an image, re-sampling and interpolation is very much dependent upon the particular printer being used and the print size being created. Interpolating an image without knowing the specific characteristics of a printer can be counterproductive. Re-sampling and interpolating images take time, time that is better spent on the creative aspects of your photography. It is not an effective use of your time to resample images to higher resolutions than the original camera files. This interpolation will take place on our end, at a higher quality and much quicker than it will on your end using your computer."
I have always been happy with their resizing and with the sharpness of the picture. However, even though I routinely profile my monitor, I find their colors a bit off from mine and I take that into account in processing my files for print, and I also get a smaller print made to check the colors before I order the 20X30. I have learned to adjust my monitor to account for their printers and the last couple of sample prints were right on. Their prints are a bit darker than my monitor profile, a good bit stronger in red, a tad stronger in green and a bit weaker in blue. But, unless you have very precise colors (with lots of red hues) and luminance values you are trying to get, like in a sunset, you probably won't notice the difference. But a cheap 4X6 is well worth the price to insure a good result.
Oh! A quick addition to avoid confusion. I check the box during check-out "Do Not Color Correct" because I generally am looking for precise colors in unusual lighting situations. If you don't check that box they will color correct and I expect they will do a good job of it for normal daylight pictures.
I've been having 20x30 prints made from a number of different labs and as far back as when I had a 10d body and not once have I done anything to up-res/enlarge an image before sending it to the lab.
Steven Young wrote:
interesting, thanks guys. I exported the raw file from Lightroom as a 20 x 30, made photoshop changes and now gonna send it over to WHCC.
A note for the records: WHCC prefers that you do the upsizing yourself like you did here rather than letting their software do it. I asked.
Interpolating an image without knowing the specific characteristics of a printer can be counterproductive. Re-sampling and interpolating images take time, time that is better spent on the creative aspects of your photography. It is not an effective use of your time to resample images to higher resolutions than the original camera files. This interpolation will take place on our end, at a higher quality and much quicker than it will on your end using your computer
Working professionally, I believe in running my own tests to make sure I agree with such statements.
A note for the records: WHCC prefers that you do the upsizing yourself like you did here rather than letting their software do it. I asked.
I agree with that, although WHCC's documenation advises to let them do the upsampling.
It was pretty much true in the past that it was always better to let the lab's Raster Image Processor do the work. However, today's CS is not your grandfather's Photoshop.
Moreover, nobody really knows how you like your images sharpened at the final size better than you do. Using WHCC, I've found that I prefer to tweak sharpness at the actual final image size myself and send it to them at the size to be printed, than to depend on their RIP.
The bottom line is that you have to do some testing both ways with your chosen lab.
