Trying to understand print resolution.

[n1as]

My printer (MPix) says to use 250 PPI for the image resolution. If I adjust my file to that resolution, it becomes very small, maybe 80 KB, compared to the original which is over 1 MB.

If I were to sent them both files, one 1MB with lots of pixels, the other 80KB with just enough pixels to do the print, would the print look the same?

If the print would be different, would it be only due to the difference in the way my SW converts to 250 PPI compared to the way their system does the same task?

Am I even close to being on track with this?

[Damo77]

Hi Keith, yes, you're on the right track.

Essentially, the prints from the two files would look the same - to all but the most careful examination, that is. There are two main reasons to resize before sending:

1) The obvious one - file size. They won't thank you for sending dozens of 1MB files, where 80KB files will suffice. Quicker for you to send, and them to receive.

2) Sharpening. It's best to sharpen at the correct output size. If you sharpen the big file, and it's halved in size when printed, the sharpness is effectively halved as well. If you're as geeky about sharpening as I am, that's a problem.

As always, I'll point you to this thread - http://photography-on-the.net/forum/showthread.php?t=363868&highlight=FAQ+printing - it's full of essential info about this stuff.

Another thing occurs to me - 80KB is quite a small file size for a print file. I assume you're saving as a jpeg, but perhaps your quality setting is quite low? What software are you using?

[n1as]

I went and looked at my files. They are 280 KB, not 80. Memory isn't serving well today I guess. Those files were resized to be 4x6" at 250 PPI, giving dimensions of 1500 x 1000.

I'm using Lightroom for this sort of thing these days. If not that, then Elements 5.0

[Damo77]

Ok, that's cool. As long as you're happy that you're not compressing your files too much.

[tim]

280kb is pretty tiny, even for 6x4" at 250ppi. Can you put one on a web server for us to take a look at?