If you're using Lightroom's print module to export JPGs, there are limits on minimum and maximum dimensions. Here are some partial workarounds.
A reader recently asked this question. He wanted to use Lightroom’s Print Module to export a JPG image that measured less than 4 inches, but Lightroom wouldn’t let him.
The short answer is that you can’t. If you try to put a value of less than 4 in the Custom File Dimensions entry box, you’ll get an error like this.
With the default PPI setting of 300, the smallest JPG that will create is 1200 by 1200 pixels.
The reasoning behind these limits is sensible enough. The Print module is designed for making physical prints of your images. That you can output a JPG file instead of sending it to the printer can come in very handy for other uses that take advantage of the module’s layout functionality (or prepping files to upload to a print lab), but the primary focus is squarely on physical prints.
But what if you’re using it for one of those other uses and need to create something under 4 inches? Here are two workarounds.
Each accomplishes the same thing in a different way. Both will reduce the minimum file dimensions you can use down to 288 by 288 pixels.
The first way is to change the PPI setting in the File Resolution option from the default 300 to 72.
The 4 inch limit will remain in place, but 4 inches at 72 PPI results in a JPG that’s 288 x 288 pixels when you hit the Print to File button.
The second way to do it is to change the Ruler Units to points. For this purpose, points are functionally the same as pixels.
You’ll find the option to change the Ruler Units further up the right side under the Layout panel.
And you’ll then up with this:
While we’re at it, here are the lower and upper limits for each of the different ruler units in case you’re using metric or one of the others.