Please Help! Resizing and Printing Questions

[GooniesNeverSayDie11]

If the aspect ratio is right and the cropped photo has sufficient pixel dimensions, the print lab's RIP software will handle the sizing.

Don't crop the original. Crop a duplicate.

What about sharpening? If you send them a sharpened 8x10 and they resize it to 16x20 or sending a 10x15 and having it shrunk to a 4x6,isn't that going to negatively affect your image?

 

[KmH]

"and the photo has sufficient pixel dimensions"

 

[GooniesNeverSayDie11]

"and the photo has sufficient pixel dimensions"

So I am guessing you mean that if the Lab keeps the ppi the same through the resizing ( although it may be interpolating the data ) that the sharpening wouldn't have any change?

Also, just to be clear, I am not trying to argue or contradict what you said, just trying to clarify things for everyones benefit.

 

[KmH]

The print lab can't keep the PPI the same for different sizes.

Many labs have a minimum resolution they will print at. For instance, Mpix has a 100 PPI minimum. If you upload a 1599 x 1999 pixel photo, they won't print it at 16x20, because it would be under 100 PPI.

For the OP, here is some more valuable information: Mpix.com - How to prepare your images

By the way, for those that insist 300 PPI is the way to go? Note:

The Mpix printers output at 250 ppi.

 

[GooniesNeverSayDie11]

I think I confuse myself with thinking of sharpening in the workflow and then resizing (for instance, after applying a high pass sharpening ). Unless you re-adjust that effect
( if the layer is a smart object ) then you may be overdoing the sharpening.

 

[GooniesNeverSayDie11]

By the way, for those that insist 300 PPI is the way to go? Note:

The Mpix printers output at 250 ppi.

If you send an online printer an 8x12 at 300ppi and then crop it to 8x10, my guess is that you would be somewhere around that 250ppi. For instance, on Costco's site, you can upload a picture and then manually crop it yourself if you choose a different aspect ratio.

Also, here is an interesting test: 300 PPI Print Myth
It should be noted though, for submitting photos to be published, the industry standard is 300ppi.

 

[KmH]

By the way, for those that insist 300 PPI is the way to go? Note:

The Mpix printers output at 250 ppi.

If you send an online printer an 8x12 at 300ppi and then crop it to 8x10, my guess is that you would be somewhere around that 250ppi.

No. The 8x10 would still be 300 PPI, but the pixel dimensions of the long side of the photo would be reduced by losing 2 inches worth of pixels, 2" x 300 PPI = 600 pixels..

If you have an 8x12 that is 300 PPI, the pixels dimensions of the photo are 2400 px by 3600 px. Cropping to an 8x10 then leaves pixel dimensions of 2400 px by 3000 px.