Processed a raw file (Nikon NEF) from Lightroom using the “Process with Topaz Photo AI” plugin. The NEF file is about 60 MB, the returned dng file is four times larger, around 250 MB. Why is this?
Steps to reproduce issue:
- Send NEF file to Topaz AI from Lightroom Classic using plug-in
- Edit in Photo Ai using AutoPilot settings
- Save back to Lightroom (as dng)
Topaz Photo AI [v1.5.0] on Mac
The DNG output file size is expected behavior. The original RAW file is likely compressed while our DNG export is full size and uncompressed so the output file is larger. We do not have access to a DNG compression algorithm as that is proprietary to Adobe.
If you need to decrease the DNG file size, use Adobe DNG Converter to compress the DNG file to a smaller size.
Well, I tried using Adobe DNG converter first, on the NEF file. The resulting dng file was 55 MB. I then brought it into Topaz Photo AI, did the AutoPilot adjustments and saved it as a new dng. The file size was over 270 MB! Running this file through the Adobe dng converter again reduced its size to 150 MB, still about three times larger than the original NEF or Adobe dng.
No need to use Adobe DNG converter on the NEF file, you should only use it on the output DNG from Topaz Photo AI.
Adobe DNG Converter has some compression settings that you can use to further decrease the DNG file size
OK, but here is the problem: Adobe DNG converter has two settings for compression: “Do not use lossy compression”, or “Use lossy compression (preserving the pixel count)”.
Not using lossy compression yields a file size of 125 MB, which is 2.5 times larger than the original dng file.
Using lossy compression yields a file of 13 MB, but it significantly degrades image quality, sharpness, and detail. Not acceptable for my needs.
So, best case scenario, with a multistep workflow that adds to the complexity of the job, I end up with a file about 2.5 times larger than my original.
I would recommend using non-lossy compression. The file size is expected to change and at the moment there is not a better alternative for this if you want to stay in the Raw format.
If you do not care about staying in the Raw format, you could use the Photo > Edit in > Topaz Photo AI workflow to edit a TIF or JPG instead. TIF would be a large file comparable to DNG but has some lossless compression options, while JPG is much smaller.