Quick dpi question

What is the best dpi to use when cropping? 300dpi,320dpi, 400, 700dpi? If I crop a pic to be made into a 4x6" if you up the dpi from 300 to 320, is there a difference, or does it come down to the printer?

Another example....making a 20x30" does uping the dpi crop make a better poster or could it possibly make it worse?

consider destination of your photo when deciding on dpi. web/screen display = 72 dpi, print = 200-300 dpi depending on printer. larger prints may require up scaling of your image: consider using a stepped approach by up size only, say, 10% each time until reaching the size you desire.

personally i never use dpi crop. when cropping an image i'm only concerned with two things: the area that i want and the proper aspect ratio. i size my image and set the dpi at the very end, after all the editing is done.

-alex

In theory, could a person just make every pic 400dpi, or could it possibly effect the final print for the worse? Just wondering....for a long time, I forgot to set my dpi back to the "standard" and it was at 320 and 350.

as long as you don't alter the physical dimension (pixel count width and height) of an image, setting the dpi alone won't alter the quality of the image. it only affects the final print size.

in another word, an image of 600x400 at 100dpi is identical, quality wise, to the same image at 200 dpi. only the first will print out at 6x4, the second, 3x2.

-alex