Applying import rules to images based on file size

This reply is sort of off to the side and it’s going to sound nerdy, but it doesn’t seem like a file size filter is the best solution. Because it sounds like you actually want to be concerned with pixel dimensions (width x height in pixels), and not ppi/dpi or file size without context.

What you are trying to filter for is if an image has enough pixels to reach a given enlargement. Only pixel dimensions tell you that.

PPI alone doesn’t tell you enough, unless you also state how many inches you want to print it at 300 ppi. But most people leave out that part. A filter for “300 ppi” can return a 300 x 240 image that just happens to have “300 ppi” in the metadata, which on the surface, sounds like what you want. Except that if you look closer, that “300 ppi” image is only good for one inch wide at 300 ppi, because it only has 300 pixels on the long side. So a ppi-based filter can mislead you by only telling you pixel density without the physical dimension. Again, you need to know how many pixels long, much more than you need to know the ppi alone.

File size alone doesn’t tell you enough. If you require it to make a 10 x 8 inch print at 300 ppi (3000 x 2400 pixels), the file size of those pixel dimensions could be anywhere from 0.3MB to 44MB depending on the combination of file format, compression method, color mode, and bit depth you used to save the scan. This could be a problem if you scanned part of your collection at different specs, causing a file size based filter to return inconsistent results. Again, it’s about the number of pixels much more than the highly variable file size.

By now you’ve gotten a good answer that you can use a Smart Collection to filter for the images you want. But because of the above, the least ambiguous way for you to filter for the images that meet your enlargement size is to base the filter on the long dimension in pixels. If you want images to be able to print 10 inches wide at 300 ppi, then the long dimension must be equal to or greater than (10 inches * 300 ppi) or 3000 pixels.

LrC doesn't have a 'Sort' function for Filesize in the Import dialog, but after importing (all) photo files you could use Smart Collections to find images using 'size' as a criteria.

There is no way to apply this sort of rule at import. You can filter after import by image size (not file size) using Smart Collections, and then assign other metadata as you see fit after you create the Smart Collection. Image size is a better indication of the size of the photo than file size is.

I do not understand your discussion of DPI in this context. Digital photos do not have a DPI.