JPEG Export Settings

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Today’s Question: When exporting a raw, TIFF, or PSD file as a JPEG from Lightroom, you may need to reduce the output JPEG file size for sending via e-mail for example. You can reduce the JPEG quality, or you can specify a maximum file size, or you can resize the image and specify the resolution. For the equivalent JPEG file size, which of these approaches give the best quality JPEG image?

Tim’s Quick Answer: When creating a JPEG image, the pixel dimensions primarily determine the potential output size, and the Quality setting determines the amount of quality degradation caused by compression. Both are important, but I would make it a priority to use a relatively high Quality setting (about 80% or above).

More Detail: The pixel dimensions determine how many pixels are included in the JPEG image you’re exporting. That, in turn, determines how large the image can be displayed or printed. When printing the image can certainly be enlarged to a degree, but an extreme enlargement can result in poor print quality.

The Quality setting relates to compression applied to the image in order to reduce file size. Even at a relatively high Quality setting, the file size will be relatively small. But if you use a setting for Quality that is too low, compression artifacts may be visible in the image.

I recommend taking a balanced approach. For printing you’ll need to determine the pixel dimensions required for the intended output. For digital displays, you can set pixel dimensions that will provide an adequate display size based on how the image will be displayed. For a typical monitor display, for example, I’ll generally resize the image to about 2,000 pixels on the long side. I’ll then typically use a Quality setting of 80%. This provides an image of very good quality for a digital display, with a file size that is generally around 1MB or so (with variation based on the actual contents of the image).

Note, by the way, that the pixel per inch setting is not critical and does not impact file size. This is simply a setting that determines the print resolution. It does not affect the image appearance on a digital display.