Hi Skipper, because I shoot a lot of aircraft, I am many times pointing at the sky and have had this issue 100's of times. You got great advice above and I agree with the use of 16 bit. The other thing you can do is when you start processing, leave the sky alone and only process the lower portion of the image. These artifacts always appear in the sky and sometimes just a small amount of over saturation or other processing as well as compression can make it much worse.
When you say in last line '.... as well as compression...' how am I controlling the compression to worsen this? What should I do differently on the compression front? Or is that something I can't control? Thanks.
So..... photos edited in 16-bit mode can't be saved as jpegs? Just edited a NEF in 16-bit and went to save and jpeg was not option.
"So..... photos edited in 16-bit mode can't be saved as jpegs?"
Correct -- if you want to maintain the 16-bit information. When I want to save a 16-bit file I usually save in Photoshop's .psd file format although, occasionally for specific needs, I will use the TIFF file format. In order to save in the JPEG file format, you must first convert your image to 8 bits and make sure there are no layers. (I think there was, or is, a JPEG2000 standard that may allow more bits and or layers, but I don't know anything specific about it - just that it exists.) If you think you may want to re-visit the file for additional editing in the future, it could be an advantage to save in a 16-bit file format. If you need an 8-bit file for a specific purpose, save it with a new name so that you can retain your original 16-bit file.
If you want to print a 16-bit file at a printing service, make sure you check to see what file formats they can accept. Most "average" printing services accept only 8-bit files, but I'm certain that those who accept 16-bit files will provide full information about the required file format(s).
There are no rules for good photographs, there are only good photographs. -Ansel Adams
Ok, so I re-edited the photo in 16-bit mode. Then when I was done switched back to 8-bit mode and saved as a jpeg. I could not see the debris in the sky anywhere. Sent off to lab for reprinting. Wish me luck! If it comes back bad enough I'm going to tear my hair out. Thanks everyone. Very much appreciated!!!
That appears, to me, to be color noise and often appears when I try to raise (or sometimes lower) the exposure in order to bring the histogram into the "normal" range. I have found that it may help to shoot your images so that the histogram is just to the right of center so that normal exposure adjustments would be to lower the exposure to get it darker. Also remember that exposure adjustments tend to change the histogram on the ends while brightness changes tend to effect the middle section more. Also fill light, used sparingly, will often produce better results in brighting the black areas, for me, than moving the black sliders alone.
Got the new prints back and they look great, no debris in sky. So it must have been the 16-bit editing? Don't think I did anything else differently. I did have to clone (healing brush) one sky spot in that area and maybe I was more 'surgical' this time I don't know. Anyway, all is good now. Thanks again.