Jpeg Quality Settings and Noise

Friday, January 30, 2009 ·

In an effort to keep file sizes down, I use Photoshop's "save for web" setting. It makes a good job of crunching images down to a reasonable size but I have to say that it can sometimes have a disastrous impact on noise.

I was a bit shocked when I saved the two pics above. They were shot at ISO 2,500 and were slightly under-exposed. Pulling out the shadow detail - and there was plenty there - has understandably increased noise considerably, as it usually does. The top shot was helped a bit by the fact that I'd directed my car's headlights at the boats in the foreground for a bit of fill-in.

But using the medium "save for web" setting made the noise "look like golf balls" as we used to say back in film grain days. I used the next quality setting up but the noise is still far more apparent than it is in the original, uncompressed file.

If you're impressed by the lack of noise in small, on-line images from the D700 it might be worth bearing in mind that the original will probably look even better!