Noob question about large prints

240 will print just fine... it gives you a little wiggle room for sharpness and clarity if you are pushing the limits on the file size.... My labs require 300dpi, but I regularly print 240 with no issues at all.

It sounds like yoou maybe don't comprehend the "asect ratio" problem -- the fact that a 10x15 image can't produce a 12x12 print! You have to crop it!

Some printers insist upon 300 pixels per inch in the print size...you would need to provide a file which is 3600x3600 pixels, which would entail resizing the image in post processing by 4% larger (104% of original image size).

Some printers do not insist upon a source file which permits 300 pixels per inch in the print size requested, but merely print the supplied image to fit whatever paper size is requested. In that case your original file will result in 264 pixels per inch, as previously posted by others, but that would not reduce your print quality noticeably!

Be sure to inquire to the lab about how to submit the image, given that you want a SQUARE print but their standard print sizes are 3:2 format...you might simply ask for a 12x18" print using a 3600x5400 file, and cut the print to the 12" square yourself!

i noticed on the lab info supplied by OP that they did provide a 12x12 size

tonylong wrote in post #14519118
It sounds like yoou maybe don't comprehend the "asect ratio" problem -- the fact that a 10x15 image can't produce a 12x12 print! You have to crop it!

I think you're right, Tony. If I have a 10x15, then in my mind, the one side is 10, so how the hell am I supposed to "crop" 12in out of 10in? I've always thought of "crop" as cutting a smaller section of an image out of a larger image. I've never thought of "crop" as upscaling to a larger size, i.e., taking something that's 10in out of the camera to 12in.

Wilt wrote in post #14520757
Some printers insist upon 300 pixels per inch in the print size...you would need to provide a file which is 3600x3600 pixels, which would entail resizing the image in post processing by 4% larger (104% of original image size).

Some printers do not insist upon a source file which permits 300 pixels per inch in the print size requested, but merely print the supplied image to fit whatever paper size is requested. In that case your original file will result in 264 pixels per inch, as previously posted by others, but that would not reduce your print quality noticeably!

Be sure to inquire to the lab about how to submit the image, given that you want a SQUARE print but their standard print sizes are 3:2 format...you might simply ask for a 12x18" print using a 3600x5400 file, and cut the print to the 12" square yourself!

Thank you. MPix replied and just said I should send them the image in the size that I want printed, or in my case crop to 12x12.

Mpix requires a minimum DPI of 100.

deronsizemore wrote in post #14534278
I think you're right, Tony. If I have a 10x15, then in my mind, the one side is 10, so how the hell am I supposed to "crop" 12in out of 10in? I've always thought of "crop" as cutting a smaller section of an image out of a larger image. I've never thought of "crop" as upscaling to a larger size, i.e., taking something that's 10in out of the camera to 12in.

Your image in the computer doesn't have a "size" in inches, it has dimensions in pixels with an "aspect ratio", so for a DSLR camera it has a ratio of 2:3, so the widest dimension is 1.5x the shortest dimension.

To get a "square" print out of that you need to crop the image to be a square, so yeah, you crop the longer sides off to make it "smaller" in that sense, but then you print the result to whatever you need, and a 12x12 print can be done fine from a T1i photo!

If you upload the file to Mpix, they will tell you the maximum size you can blow it up to that will still be presentable. I uploaded a 10mp shot and had it printed at 16x20 and I still could have gone higher.

I would crop it to your desired composition first, however. Don't even fiddle with the DPI. Just get the LxW scale right.

There was a thread on here a few months ago with some test shots by a professional printer. Most everybody was pretty amazed at how quality was retained in large prints. You might be able to find it in a search.

The thing about large prints is that they are viewed from large distances. The controlling factor should be human visual acuity, not DPI. Walk up to a highway billboard some time. Up close, it looks horrible. But that's not the intent. I have an 8 mp shot that was blown up to 3x5 feet and on display in the Long Island Aquarium. Up close it's soft, but again, the idea is that it will be viewed from across the room. Your 12x12 will be fine.

Skipping all the above discussion about aspect ratio and dpi and ppi, here are the steps you need to produce the required output from Lightroom:

1. Make it into a square: In Lightroom's Develop module, use the Crop tool to crop the image to a have a square (1x1) aspect ratio. Feel free to rotate a bit if you need to straighten the horizon. Yes, you'll be hiding part of the image (it's not permanently gone; it's just not going to be in the print).

2. Export the photo to send to the printer: In Lightroom's Export module, in the "Image Sizing" pane, use the following options:
- Check box for "Resize to Fit"
- UN-CHECK the box for "Don't Enlarge" (Since Lightroom will be scaling it up very slightly on export)
- Choose "Long Edge" *
- Enter 3600 Pixels
- Resolution of 300 pixels per inch **


When you export, Lightroom will scale up the image to 3600x3600, which is 12"x12" at 300 DPI, which will fit the printer's requirements and make your daughter happy.

Depending on the medium upon which the image will be printed, you probably should also check the box for Output Sharpening, Matte or Glossy Paper, and Standard amount.


* You could probably also do Short Edge of 3600 pixels, or H and W of 3600 and 3600 pixels. There are a couple of ways to accomplish the same thing.
** Or, you could do a pixel dimension of 2880x2880 at 240 pixels per inch. That would be just fine too, unless the print service DEMANDS a resolution of 300 pixels per inch.

It's important to note that in this case, cropping is related strongly to the aspect ratio of the file (square, 2x3, 16x9, whatever) but only indirectly related to the SIZE of the image. The size of the image (the pixel dimensions) is determined during the EXPORT dialog of Lightroom.

just for kicks, check out meridian labs. they make getting the size print you want really eazy. prices are also great. ihave had prints to 14x16 with my t1i and they were great.

tonylong wrote in post #14534418
Your image in the computer doesn't have a "size" in inches, it has dimensions in pixels with an "aspect ratio", so for a DSLR camera it has a ratio of 2:3, so the widest dimension is 1.5x the shortest dimension.

But a lot of commercial shop's printers DO see that 'size' as defined by Photoshop (or whatever is in the image file). If you get is wrong, you're screwed. For instance, just making the image square may not be enough (depends on the shop and exactly what dpi you have and the pixel dimensions - yes it can become a quagmire if you don't get it right).

Unfortunately I don't have Photoshop and had to learn the hard (and expensive) way - finally figured it out in gimp. To add to my confusion the place I got mine sent to (via Wolf camera) would upsize the photo to fit the frame, cropping anything that goes over on one side, but they would not downsize to fit. So if you gave then a 3000x3000 pixel image at 300 dpi it would print OK onto a 10x10 or any larger square, but you'd get only the center if you tried printing on anything smaller (or accidentally set at 75 dpi - Doh!)


Anyway, looks like the OP should be set. I would also recommend up scaling yourself to 300 dpi and doing a final sharpening, but you should also be just fine at 240 dpi. I printed a shot at 175 dpi and (IMO) it looked 'OK' and fine from a reasonable viewing distance - definitely still worth printing and hanging.