… a quick test of the Guetzli JPEG encoder published some weeks ago by Google. To my big surprise, you cannot encode TIFF or another lossless image format into JPEG. You need to export your RAW camera file first to JPEG @ 100% quality. Then you encode that file with Guetzli. Seems a tad odd to me, as you have a lossless compression two times. The speed of Guetzli is furthermore quite disappointing. I didn't time the encoding, but about one minute for just one 1000x666px 714k JPEG? No idea if that is worth the hassle… Here some pics for comparison:
Lightroom Export from a RAW camera image @ 100%: 714K - the starting point for Guetzli
Guetzli converted, 100% quality: 570K - no difference to the original JPEG
Lightroom Export @ 75%: 294K - still no difference to the original JPEG
Lightroom Export @ 50%: 204K - I have the feeling that some detail is lost in the mountain
Guetzli converted, 90% quality: 182K - at least as good as the pic above
Guetzli converted, 84% quality (Guetzli does not allow quality below 84%)): 144K - the blue gradient of the sky is not so nice anymore
Lightroom Export @ 25%: 143K - the blue gradient of the sky is not nice anymore