Today’s Question: I sometimes send a file from Lightroom Classic to Radiant Photo and the adjusted file is saved as a TIFF. While the raw capture is typically around 40MB in size, the TIFF comes back in the 170MB range. If I convert that TIFF to a DNG in Lightroom Classic and select lossy compression, the file size comes down to the range of 10MB, roughly the size of a JPEG. What am I losing or gaining in this process vs. bringing the file back from Radiant as a JPEG?
Tim’s Quick Answer: In the case of the Radiant Photo plug-in, there’s no issue with converting to DNG or saving as a JPEG, as long as you’re comfortable with the degradation in quality that occurs with converting the TIFF image to a file with lossy compression.
More Detail: If you turn on the “Use Lossy Compression” checkbox when converting an image to the Adobe DNG format in Lightroom Classic, you are getting about the same result in terms of file size and image quality compared to saving the image as a JPEG. That means there will be degradation of image quality due to the lossy compression, which is how the significant reduction in file size is achieved.
This loss of quality isn’t generally a problem for images that will only be shared digitally, such as in a digital slideshow or via online sharing. However, it can be an issue when printing an image, potentially resulting in visible compression artifacts in the print.
It is important to also take into account the software that was used to create the derivative image, and whether there is a benefit to retaining the file created with that software. For example, when editing an image in Photoshop you might create various layers and other elements that are only editable in Photoshop. Converting an image from TIFF (or PSD) to a format that does not support layers, for example, would cause you to lose the editable layer elements from the original image.
Radiant Photo does not use layers in this way, so converting the file created via Radiant Photo won’t cause any issues other than the degradation in quality when lossy compression is used in that conversion.
