I need help with burning in nearly non-existent sky.... I have an image where bottom half is properly printed using 2 1/2 at 18 seconds. When I do this, the sky is nearly a featureless patch of highlight. I tried burning this in quite a bit using the same filter and I got a little. I need more. Question is.... Do I burn this in using less contrasty filter or more contrasty filter? Or - does it make any difference and is this just a function of time I spend burning this portion? My understanding is, higher numbered filter defines darker black and this sky is white, so I should go lower? But this is counter intuitive.... HELP!