Full Res or Downsize for 4"x6" prints

Say I'm getting a bunch of photos printed (either online or at a store)...
I only want 4"x6" prints.

Say all my pics are full res (15 MP) images/jpegs.

Image quality-wise, is it advantageous to downsize the pics to 1200x1800 (300dpi) and then have them printed - assuming the printer they use recommends 300dpi?

Obviously there's an advantage for size of the files and therefore upload time.

But strictly image-quality???

If I'm taking them on a USB stick to the store to print, then the speed issue is insignficant... So basically, is there a reason to go through the hassle of making another copy of everything at 1200x1800?

(Of course, this then applies to resizing to 1500x2100 for 5"x7" prints... etc.)

Would my downsizing via Photoshop CS3/CS4 or Lightroom be "better" then them (the store) doing it however they do it to get it to the printer?

Thanks in advance!

Call them and request details on their printing process? Odds are that it's a lot higher than 300dpi.

Assuming identical proportions between your original file and the output size, I see no reason other than speed, unless you want to apply specific sharpening to the resized file (which you can't control when you drop images off for printing). However, cropping could be an issue as the proportions of a 5x7, 8x10, and 4x6 are all different - so something has to change there...

I would do the resizing before sending. Rather me than someone else.

It's extremely unlikely that they are using anything higher than 300 but call them and find out. If you can get the printer profile they are using, all the better. Whatever the answer, I would do it, rather than leave it up to their automated software.

I have in the past printed 12mp photo's on 4x6 with loss of quality, it was dissapointing now I resize them, otherwise they look pixelated which is dissapointing.

Whenever I send anything for print, I do the resize before it goes. I like to control the quality and not leave it up to a machine operator.

bohdank wrote in post #6570738
I would do the resizing before sending. Rather me than someone else.

ssim wrote in post #6570898
Whenever I send anything for print, I do the resize before it goes. I like to control the quality and not leave it up to a machine operator.

Agree 100% with these comments. Plus, internet speeds are awful here in Australia (powered by hamsters on wheels, I think) so I need my file sizes to be no bigger than necessary.

Thanks for the feedback guys. So far it seems like downsizing them myself is majority recommendation...

And yes, Klynam, I realize if I need other sizes (5x7, 8x10, 8x12, etc.) I would need to crop & downsize to the different, corresponding sizes...

Resize, sharpen, send is my workflow.

BigDaveE wrote in post #6571332
And yes, Klynam, I realize if I need other sizes (5x7, 8x10, 8x12, etc.) I would need to crop & downsize to the different, corresponding sizes...

I know, kind'a goes without saying...but you never know...

tim wrote in post #6571893
Resize, sharpen, send is my workflow.

same here.

White House Cutom Color gives guidance which says that they expect images croped to the size requested at 300 dpi and saved as a levle 10 jpeg. They claim there is no visible improvment for higher DPI or greator then level 10. The problem I have with local sources is to stop them from making adjustments to the images. Even if you tell them its not well controlled.

Easy and cheap enough to test. I recently uploaded some picture to Walgreens and they have a 5 times faster upload. So I tried it and then uploaded a full size. Big difference in quality.

If you are saying the full res was much better....that makes no sense unless they are processing all images through some, unknown, software.

Me, too. Remember that you should sharpen for that final size if you want the best quality print. I never let the lab do anything but print with their "Auto-corrections" turned off.

I ran some tests with them & found a big difference in quality in the same print only an hour later!