Today’s Question: Can you please explain how to best use the Quality Slider (under File Settings) when Exporting Images from Lightroom Classic. I am wondering how to best balance the quality with the resulting file size when exporting for online sharing. I assume that for printing I want to keep the quality at 100%.
Tim’s Quick Answer: The Quality slider under File Settings in the Export dialog for Lightroom Classic only applies to JPEG images. I only recommend using JPEG for images that will be shared online, not printed. For those images, I find that a setting of about 80% provides a good compromise between image quality and file size.
More Detail: JPEG images always have “lossy” compression applied to them, which means image quality can be degraded as the image data is compressed. The Quality setting determines how strong the compression is, and therefore the degree to which quality may be degraded.
The actual results will vary based on the contents of the image. For example, images that are very “simple” will compress to a smaller file size with less degradation of image quality. Images that are somewhat “complex” (such as with greater texture and detail) will not compress to as small a file size and will have a greater risk of degradation of quality.
When sharing images online, the JPEG file format provides the ability to balance file size (to reduce download time) with image quality. In my experience a setting of about 80% for image quality provides a very good balance.
Quality settings that are higher than 80% will result in larger file sizes but generally with little to no visible improvement in image quality. If you set the Quality much below 80%, the file sizes won’t be dramatically smaller but the degradation in image quality may become somewhat obvious.
For images that will be printed, I recommend saving as a TIFF image rather than a JPEG, so that you aren’t losing additional print quality by rendering a JPEG image with lossy compression applied to it.