To put it in very simple terms, the higher the contrast filter number, the more contrast. The more contrast you have, the whites stay whiter, and the blacks get blacker. Going the other direction, the lower the contrast the more middle tones you get, enabling you to pull more sky tones easier.
Skies are normally low contrast areas, so they are better suited with hard contrast filter (#4, #5). Disadvantage is longer burn in times. Of course this is a personal
preference but I do not like skies that are burned with low contrast filters
I personally do not change aparture in the same picture because the grain pattern can change
It's mostly been covered by succeeding posts, but yes, the issue isn't about how long it takes, but what will look best, and it sounds like this negative needs to be solved from both ends independently, and not just leaning hard on it at 2.5 or white light to beat the sky down.
Originally Posted by tkamiya
You are dealing with the thickest juiciest part of the negative, and just going long at high order of filtration will likely give you way too much contrast in the sky (and in the worst case will begin to show unevenness in development or will multiply flaws in the emulsion). So the best advice is to solve the sky using test strips, starting with filtration as low as you've got and work your way up to maybe a 1 for the most realistic look. People rarely use their 0 or 00 filters but they'd be surprised how useful they are.
And as others have pointed out, opening up the iris on your enlarger lens is the final bit of figuring. In essence, you normally stop down to mid aperture for best resolution, but that also gives you a couple more stops down for leisurely selective dodging and a couple more stops open for timely burns.
Needless to say, an yellow or orange filter over the camera lens can shrink the range you have to deal with.
Hope to hear how it turns out!
I burned the HECK out of my sky last night with #2.5 and the result is.... a sky with too much contrast over thicker part of the cloud on otherwise featureless sky. Looks very fake. I will need to reduce the contrast and do this again. I'll try with MUCH lower contrast filter. Thanks everybody!
Develop, stop, fix.... wait.... where's my film?
Thanks for the thanks. Now that you have discovered for yourself why our help hasn't solved your immediate problem to your satisfaction, you may consider attacking it from a different perspective - the next time you expose your film. The "secret" to good (natural?) skies is to expose for the sky. Given the limitations of B/W film to record naturally occurring light intensity, this may mean sacrificing exposures of the landscape itself. Your choice when making a negative - but then this is where the rubber meets the road, separating the snapshooter from the artist. Of course, some of the compression of light onto film may be mitigated by contracting development, a la the Zone System, but that's another story. And, yes the use of a filter to absorb blue light (i.e., yellow - orange) will do much to clarify (i.e., provide contrast) elements (i.e., clouds) within the sky.
Originally Posted by tkamiya
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You need to expose for a balance of sky and foreground and keep development short enough so it prints without burn/dodge anything.
Meter off a grey card or use an incident meter. Results will be similar. Development time for a condenser enlarger is 80% the time for a diffusion one on which most times are based. An if you use that horrible Massive chart, those times will give the chalk and soot Ansel used to blame condenser enlargers for.
Learn your tools. I rarely burn a sky.
For now, dye dodge the forground and flash the print to threshold so you need not burn it.
Or make a traced cut out from the enlarger light half way between the paper and neg and burn thru it.
Now do some tests and get the process under control so you stop making bad negs. You will be glad you did.
There are but two rules. Exposure controls shadows and development controls highlights. Apply to a standarized test subject with full range of tones from textured blacks to textured whites. You need to be able to print it and show all the tones without burning or dodging. Practice until you can.