Changing the resolution when saving.

[michaelk15108978]

I just bought a new Mac and have Lightroom 2.3 (May 3, 2019). With my old computer, I had Lightroom classic and when I would export, I was able to change the DPI. I want to print, but the resolution that it is saving to is not print quality. How can I change the resolution when I save so that it can be of print quality?

[JP Hess]

If you are using the cloud-based version of Lightroom then your best option is to save a full-sized JPEG image. The DPI setting is pointless anyway because regardless of what that setting is you still have the same number of pixels. Changing the DPI (or PPI) setting isn't going to change the quality of the image in any way. That number is only something to calculate how large the image would be at any given setting. I know you won't believe that, but it's true.

[JohanElzenga]

Correct. Just 'Save as maximum size' and print it or get it printed. You will find it will print just fine. Pixels per inch (PPI) is just an instruction for printing. It specifies how many pixels should fit into one inch of paper. Most printers ignore this. They simply take the number of pixels available and print, so they effectively use a variable ppi setting.

[99jon]

When I check a saved image in Photoshop the default is usually 240 ppi which produces high quality prints

[JohanElzenga]

99jon  wrote

When I check a saved image in Photoshop the default is usually 240 ppi which produces high quality prints

The point is that in practice, ppi has little or nothing to do with the quality of the print.  Modern printers disregard the ppi setting, so only the total number of pixels has an effect on the print quality. Say you have a 3000 pixels wide image and you want to print that at 10 inch width. Then your print resolution becomes 3000 pixels / 10 inch = 300 ppi, regardless of what the ppi value of the file says. This is always the case when you order prints online, and also when you print yourself from an app like Photoshop.

[JP Hess]

A full-sized image has the same number of pixels at 72 PPI as it does at 300 PPI. Changing that setting isn't going to affect the quality of the print at all. If you compare saving the image at the two different resolutions you will discover that there will be no difference in the size of the file. And if you print the image the same size on any printer you will discover there will be no difference in the quality of the print.

[99jon]

I’m simply confirming the default in Lightroom Export (save to) 

[JohanElzenga]

99jon  wrote

I’m simply confirming the default in Lightroom Export (save to) 

Yes, but by doing so and saying "240 ppi which produces high quality prints" you probably confuse the OP, because at the same time we tell him that PPI is irrelevant.

[99jon]

It’s even more confusing to say it’s irrelevant. Most book software will flag up warnings if ppi is insufficient.

[JohanElzenga]

99jon  wrote

It’s even more confusing to say it’s irrelevant. Most book software will flag up warnings if ppi is insufficient.

No, most book software will flag a warning if the image size is insufficient. I have never seen such warning if I add a large enough image that just happens to have a 72 ppi setting. That would be very poorly written software indeed!

[99jon]

Image size is irrelevant. A large advertising poster can be printed at 20ppi because it’s expected to be viewed at a great distance.

[JohanElzenga]

99jon  wrote

Image size is irrelevant. A large advertising poster can be printed at 20ppi because it’s expected to be viewed at a great distance.

Image size is all that is relevant. Let's say that the poster is 200 x 300 inch. Then you need an image that is 4000 x 6000 pixels. It does not matter whether that image is saved as 4000 x 6000 pixels @ 20 ppi or as 4000 x 6000 pixels @ 5 ppi. All that matters is that it is 4000 x 6000 pixels (or larger).

If on the other hand, you only have an image of say 1000 x 1500 pixels, then that will be insufficient for your poster, no matter what ppi you set it to.

[99jon]

It certainly does matter.

Print size and ppi are most definitely related. It’s simple math!

But lets end this since the OP knows he can get a good print at the default 240ppi.

[JohanElzenga]

99jon  wrote

It certainly does matter.

Print size and ppi are most definitely related. It’s simple math!

It is indeed very simple math. A x B/A = B. Inches x pixels/inch = pixels. The only thing that matters is pixels.

99jon  wrote

But lets end this since the OP knows he can get a good print at the default 240ppi.

No, no, no no, no! The default 240 ppi says nothing about the quality of his prints. Only the size in pixels does, and as long as he exports in full size that should be fine (assuming he did not make a ridiculous crop).

Here's is a 20 x 30 pixels image @ 240 ppi.

Could you make me a good quality 20 x 30 inch print? Thanks in advance.

[JP Hess]

Very few people really understand the concept, and it's pointless to try to explain it.