Print Resolution when Exporting


Today’s Question: When exporting from Lightroom Classic, regarding resolution, what is the standard number that should be for the pixels per inch value, and what happens when the number is changed?

Tim’s Quick Answer: The pixels per inch (or pixels per centimeter) resolution value only really applies for images you intend to print. In that case the resolution should be set based on the intended output, which typically means around 360 pixels per inch for photo inkjet prints and generally 300 pixels per inch for other types of printing.

More Detail: For images that will only be presented digitally, such as on a computer monitor or with a digital projector, the pixel per inch value in metadata is not applicable. You simply need to be sure that the image contains enough pixels to be displayed at the intended size.

For printed images a pixel per inch value can be used (though isn’t technically required) to establish the overall pixel dimensions and output size for the image. The basic idea is that it can be easier to describe the pixel dimensions based on the output size rather than the actual number of pixels.

For example, many photographers find it easier to describe (or determine) the overall pixel dimensions by saying “eight inches by ten inches at 360 pixels per inch” rather than as “2,880 pixels by 3,600 pixels”.

Using a specific value for pixels per inch when exporting an image will only have an actual impact on the pixel dimensions of the image if you are not otherwise specifying the image dimensions in pixels. If you specify the output dimensions in pixels rather than inches, for example, the image will have the dimensions that match the pixel value(s) you entered regardless of the pixel per inch resolution value.

If you use inches or centimeters to specify the output dimensions, on the other hand, then the pixel per inch resolution value is used to calculate the pixel dimensions for the image being exported.

If the pixel per inch resolution value is changed in metadata, there isn’t really a significant impact, since changing that value won’t change the number of pixels in the image. You can specify the output size when producing printed output, for example, and the image will be printed at that size. If the overall pixel dimensions aren’t adequate for the actual print size, the image will simply be interpolated as part of the printing process.