Print to File: Removing white border

Question

I have a lot of issues going on here.  I'm sure that a lot of my problems are a result of my lack of understanding of file size and print resolution.  I'm a newbie to printing with Lightroom, and, to be frank, a newbie to printing in general because I've never understood the terminology and technical aspects.  (Reading articles about dpi, ppi, image size, and resolution is a VERY difficult undertaking.  There is conflicting information, and it's hard to find someone who can explain it in easy to understand terms.)
I print at Costco, and I use their printer settings.  As far as I can tell, the only way to embed the printer profile in an image is to print to file.  What I would prefer is to save my image as a .jpg and upload it to Costco.
When I set up a photo for print to file, Lightroom places a white border around it because it's trying to arrange my photo on the printer paper.  Even when I change the Print Job to print to .jpg, it does this.  The only way to get around this is to check "custom file dimension" under print job, and then select a size.  Then, under layout, I'm able to set the margins to zero and the cell sizes to the dimensions of the photo I'm going to print.
I notice that when I use a custom file dimenstion, the size of the image changes.  If I choose 8 x 10, it chooses a file size about the same as the original image (8mb).  If I'm printing a poster, 20 x 30, it creates a huge 27mb file.  At first, I thought I could just use ratios, such as 2 x 3, but it seems like that would shrink the photo down to such a small extent that it would be pixelly.
And how is all this affected by resolution?  If I choose 300 ppi how is that affected by whether an image is printed 5 x 7, 8 x 10, or 20 x 30.
Before using lighroom, I simply croppoed a photo, added the printer profile, saved it, and uploaded it.  I do not understand why Lightroom is making me choose the paper size.

Answer 1

[email protected] wrote:
I have a lot of issues going on here.  I'm sure that a lot of my problems are a result of my lack of understanding of file size and print resolution.  I'm a newbie to printing with Lightroom, and, to be frank, a newbie to printing in general because I've never understood the terminology and technical aspects.  (Reading articles about dpi, ppi, image size, and resolution is a VERY difficult undertaking.  There is conflicting information, and it's hard to find someone who can explain it in easy to understand terms.)
I print at Costco, and I use their printer settings.  As far as I can tell, the only way to embed the printer profile in an image is to print to file.  What I would prefer is to save my image as a .jpg and upload it to Costco.
When I set up a photo for print to file, Lightroom places a white border around it because it's trying to arrange my photo on the printer paper.  Even when I change the Print Job to print to .jpg, it does this.  The only way to get around this is to check "custom file dimension" under print job, and then select a size.  Then, under layout, I'm able to set the margins to zero and the cell sizes to the dimensions of the photo I'm going to print.
I notice that when I use a custom file dimenstion, the size of the image changes.  If I choose 8 x 10, it chooses a file size about the same as the original image (8mb).  If I'm printing a poster, 20 x 30, it creates a huge 27mb file.  At first, I thought I could just use ratios, such as 2 x 3, but it seems like that would shrink the photo down to such a small extent that it would be pixelly.
And how is all this affected by resolution?  If I choose 300 ppi how is that affected by whether an image is printed 5 x 7, 8 x 10, or 20 x 30.
Before using lighroom, I simply croppoed a photo, added the printer profile, saved it, and uploaded it.  I do not understand why Lightroom is making me choose the paper size.
How you are getting rid of the border is pretty much the way to do it -- you can save this layout as a preset for next time.  However, as far as printing to JPEG for printing at a service, I just use the regular export dialogue.  Unless you are printing 8x10s with some custom layout of multiple files (e.g., you could print a number of little wallet-size photos, and then cut them out yourself) and don't need the features the print module gives you, this is just easier. But exporting a JPEG from the regular export makes borderless print-ready images if you select the right options.
DPI/PPI can be a confusing subject, but there are tools on the internet that allow you to calculate the number of pixels you need to clearly print at certain sizes.  Honestly, for most of us not doing fine prints (and given you are sending these to Costco, I'm assuming this is not the case) just do 240 or 300 for 4x6s and 5x7s, increase this to 600 for 8x10 and similar sizes, and go to 1200 or 2400 when you step up to the really large sizes. Remember, the larger the print, the further back you stand to get the whole thing, so at some point resolution becomes less important.
You can probably export at less than 100% quality and get very good results.  There is an article out there that discusses JPEG quality and file size in Lr, which is different than Photoshop. The upshot is that you get very good results at around the 85-90% range.  This, of course, depends on the information in the image.  You also want to strip most of the metadata from the file. This can account for a large amount of room in the file.
Find out if your service expects sRGB or can accept AdobeRGB (surprisingly, a lot of photo kiosk prefer AdobeRGB) and then you can get your colours closer to what you expect.
Ideally, you want to export at the size you expect to print at. Lr will optimize the sharpening and so on based on the target file dimensions along with the resolution, and you will just get better, sharper results. You will want to crop to the right ratios, too, so that the target dimension makes sense. Lr will never try to distort your image to fit certain dimensions, so some creative sampling will occur, otherwise.
Lr is actually one of the easiest apps I've ever used for getting images print-ready.  Between the sharpening, the white and black points (because blow-outs in print look terrible) and so on, it is easy to get pretty good results as amateur.  You do have to decide the dimensions and resolution, though, in order for Lr to make the right choices when rendering the final JPEG.