Question regarding image size in PS versus output

So I decided on 20x30 inches for a print I sent to the lab; this was set under image size in PS. After uploading to the lab I was presented with the option of having a 1 inch border around the print; I liked this idea and went with it, forgetting about the size I indicated in PS until after the order was placed. The print of course arrived with an image size of 18x28 centered on a 20x30 sheet. Looks great and I'm happy with it but am wondering what just happened there in technical terms, and will there be a visual difference between two prints, one sized 20x30 and printed 18x28 (is this "scaled down?" Help me with the terminology) and one sized and printed at 20x30. I know it's a silly question, I'm just curious and before I do any testing I thought I'd run it by you folks here.. thanks

I think it depends on your printer. The company I use, resizes the full print to fit inside the stated border unless you choose another option. And yes, there will be a difference in prints between full sized and the same size with an indicated front facing border. If I have a large print and want a border, I typically specify the border is to be on the outside of the full sized print, covering visible only in a side view. Fortunately I don't have to spell it out, as my service shows me exactly what the finished product will look like.

So I decided on 20x30 inches for a print I sent to the lab; this was set under image size in PS.

It was how? Size is based on pixels per inch (or otherwise). There is no actual size per se. If you have 1000 pixels, and you specify 1000PPI, it should (repeat should) if that tag is honored, be 1 inch. But that tag by the lab might not be honored. What if the lab simply assumes to divide 1000 pixels up by 300 pixels per inch? You don't get an inch. I'd contact the lab and ask how the specify size from digital images. Did the software front end assume a density per inch from a set of pixels or did it use what you provided? Also, a border in a digital image is of course, pixels (white but pixels none the less).

Thanks SCL. I use Nations Photo Lab. So I think going forward I should size to 18x28 in PS, then go with the 20x30 print with 1 inch border? (I like the border for mounting purposes but that's another discussion lol).

It was how?

Under image size: width 20 inches, height 30 inches, resolution 300 PPI. Aspect ratio OOC was 3:2 so there was no cropping (if that matters).

Under image size: width 20 inches, height 30 inches, resolution 300 PPI. Aspect ratio OOC was 3:2 so there was no cropping (if that matters).

It matters if the lab doesn't divide up those total pixels 6000x9000by 300. Again, you'll have to ask them.

It matters if the lab doesn't divide up those total pixels 6000x9000by 300. Again, you'll have to ask them.

I'll contact them, thanks!

If you set the size in Photoshop, without resampling, the resolution is increased or decreased according to the size, while the number of pixels remains the same. The size is simply a number embedded in the image. Lightroom and most mini-labs tend to ignore the size specification and simply print to fit the paper. With Photoshop and some print drivers, you have a choice to print to an exact size (cropped if it is larger than the paper) or to fit the paper.

 

If you have something printed to fit the paper, the image will always be cropped in some manner. A borderless print will be cropped so that no white edges remain. A print with borders will no longer have a 3:2 aspect ration inside the borders, which will also require cropping. If you want the entire image printed, even if the borders are slightly uneven, use Canvas Size to create a border and ask the shop to print without cropping. You can also crop the image with borders for an exact fit to the paper, with or without resizing it.