You got to realize that that 600 DPI is vue is FAKE. it just instructs the printer to print it on the fly to 600 DPI. you loose a lot of tone doing it that way and your image ends up being slightly blurry. You got no control over the process.. Look at it this way.. You got a picture that's 1 pixel red one pixel green and one pixel blue. you tell it to print 600 dPI from it's present 72DPI. You get 8.3 pixels red 8.3 pixels green and 8.3 pixels blue. There is no magic. A better way is to resample it in Photoshop say but now that it's faked to 600 DPI you got to copy and paste it to a new image that's 72 DPI then make it bigger in steps the more the better cause then you will get a whole range of blended colors more closly to what it would look like if you had rendered it bigger in the first place. But it gets blurry also but you can fix it in Photoshop by changing it to lab color and using Unsharpen mask on the lightness channel and then change it back to RGB before printing it. You got total control this way and it's the best way other than actually rendering it 600 DPI. Meaning for every inch of picture your going to render 600 pixels. Your image is only 2.3 inches by 1.6 inches... Everything else is fake, does not exist and will just be resampled on the fly. Every pixel will be made 8.3 times bigger. That's too much, the print will suffer.