I tend to gravitate to exposure times of more than 8 seconds and less than 20 seconds and avoid the lowest f stop and f stops over (focal length/4). The first is for control. Timer error and time for manipulation are factors for very short exposure times. Very long times seem less effective as well. As far as f-stop - It is my understanding that the threshold for diffraction in the iris of a lens is about (focal length/4). That would be a good max of f22 for my 150mm lens and f16 for my 50mm lens. I have read posts here that indicate some of you are using very short times. Is there a benefit? Are you just using the "sweet spot" on your lens? What about times over 30 sec. I hate these long ones. My old timer really starts to stick over 30 seconds. What have you observed??
I use f8 with my 80/4 Schneider Componon S (f11 for postcards), and either f5.6 or f8 with my 50mm lenses (EL-Nikkor 50/4 and Schneider Componar 50/3.5) I only justification for this is viewing the grain though the focus thingy (Peak Microsight) where it looks best, and the regular bleatings of people who say "stop down 2 stops from wide open". My exposure times for a 10x8 generally are about 8-10secs which I'm comfortable with in regard to burning and dodging (hardly ever dodge).
f8 on an EL-Nikkor 50mm, but for no terribly scientific reason! It gives me useful exposures of between 10 and 20 seconds for most straight 10x8's on Ilford MG WT RC and I have no gripes about sharpness or distortion.
Allow me to tempt you spend money, however:
I bought one of these late last year after humming and hawing about it for a longish time because of the undeniably steep price (about 2/3rds what I paid for the rest of my darkroom!). Best money I ever spent. My only regret is that I waited so long.
I printed a B&W calendar for family and friends last year made up of, 12 5x7's mounted on a pre-printed calendar. I did 9 of the *%$&**$% things and if it hadn't been for this timer I'd be printing them yet!
Sorry to wax lyrical but really good kit brings out the evangelist in me! ;-)
My exposure time (when using the Opemus 6a) is 10 seconds. I use an Ilford print exposure meter, and adjust filtration for contrast, then set aperture and ND filtration to give an exposure of 10 seconds. If the contrast isn't right, I then decide whether to change the filtration or try burning first.
I have ended up never dodging, but I might well burn in everything but one tiny spot...
My timer is a metronome - if it was good enough for Saint Ansel in the Dark, it's good enough for me!
Interesting comment about never dodging but burning everything but one spot. I find myself doing that too from time to time and always laughed at myself...saying "why not just dodge that spot?".
What is the Ilford exposure meter you mentioned?
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (OleTj @ May 15 2003, 06:15 AM)</td></tr><tr><td id='QUOTE'> I have ended up never dodging, but I might well burn in everything but one tiny spot...
hehe! I've never thought of it like that but I tend to do the same in that situation.
I'm guessing Ole is talking about a Ilford EM10?
Ilford EM10 it is - I didn't know what type it is since it's only ever used in the dark. It's sensitive to safelight, too...
I've had it for yeard, but nver figured out a good way to use it. Then I got bored one dy, and ran a whole series of tests: One negative, one paper, all grades. I measured key values (black, almost black, midtone, almost white, white) at constant 10 seconds exposure, hten plotted the readings on graph paper. Suddenly it all became clear, so I can now produce a test print right away - and know what I'll get with 10 seconds base exposure.
I've got an EM 10 also, I used to use it like that too. Now I use a beseler pm2 analyzer pretty much the same way for B&W printing. I can get twice the range on it as I do the EM 10. Stll takes a while to get things zeroed. Usually when I get a good tonality print I'll do some readings on selected areas and jot down the results along with the time and filtration. Pretty soon I have a list of values for each time and contrast filter setting I use the most and saves time and paper. So if I make a big print and my aperture is nowhere big enough for a 20 second reading I can shift to a 60 second reading for similar tones and get on with business.
As and alternative you can do your setups for a standard aperture setting and read your values to find differing times for each tonal value. I think this takes longer to establish but can be worthwhile.