The article is excellent, and it gives a good methodology for doing an approximate calibration. Since enlargers vary and dichro filters age, it may be quite worthwhile if you do much printing. An important part of this calibration is the introduction of neutral density to keep exposure times for the various contrast grades approximately the same. Most people just use the Ilford suggestions and go from there. But the Ilford suggestions do not include neutral density, so you have to adjust the exposure for every change in contrast. There are a set of suggestions from Kodak out there that do include neutral density. Many people like to make small adjustments in filtration (usually by changing the magenta) to get the contrast just right, but these small adjustments (up to a third of a grade) usually don't affect exposure that much. Finally, it should be noted that VC papers vary a lot, and a given filtration will not give the same contrast on two different kinds of paper. The differences can be enormous. The calibration technique assumes you print (at least mostly) on one kind of paper. If you switch papers, you can use the grades established for your favorite paper as a point of departure for the new paper, but it probably will not behave in quite the same way. Finally, nothing has been said about the correspondence between density ranges and paper grades. There are some differences between manufacturers here as well, despite some more or less standards. Here is a table from an old Kodak B/W Photographic Papers pamphlet (G-1, 9-71GX):
Grade Paper Log Exposure Range Negative Density Range
0 1.40 to 1.70 1.40 or higher
1 1.15 to 1.40 1.20 to 1.40
2 0.95 to 1.15 1.00 to 1.20
3 0.80 to 0.95 0.80 to 1.00
4 0.65 to 0.80 0.60 to 0.80
5 0.50 to 0.65 0.60 or lower
yes, worth it, very much so. you will be able to fine-tune contrast like a master printer. i typically adjust contrst to 1/8gradefor a fine-art pint made for sale. try it and enjoy the power!
Perhaps we should just look at the picture to assess it?
Originally Posted by nworth
You got a lot of good advice, I see nothing to contradict...
Your shot of the wheel in the garage, it looks like that might be a flat scene in the first place. If you could have known at the time to develop for approximately 12:30 minutes it would have helped this shot. Other scenes, in full sun, may print at Grade 2 with 9:45 minutes of development.
You develop the print for 1:00 minutes. I used to develop prints for 1:30 minutes, but lately I develop them for 3:00 minutes (Ilford Galerie in Dektol 1:2). Longer print developing will deepen the blacks.
The safelight test, as has been explained, is better if you print a photograph in the test. Then you see how degraded the highlights become if your safelights are not safe. The Kodak test was a still-life Siamese cat sculpture with polished silver pots and pans. When you see the shine next to the dull thud, it is convincing evidence that a little unsafe light is bad for prints.
As far as I am aware and have seen nothing that disproves it, dichroic filters do not fade! According to the latest times for D76 at 1-1 at 68Deg is the times you are using. Is your camera meter accurate? Is the film speed adjusted right?
Originally Posted by bvy
If you are not happy using Ilford Multigrade, change your paper to the Kentmere version. It is made by Ilford after a company buy-out a couple of years ago and it is at least 1 grade harder and at least twice as fast. (Also about 20% cheaper in UK too!) I gave up Ilford MG a long while back because of similar problems to yourself. with no filtration you are supposed to get Grade 2, I estimate comparing it against a non multigrade paper it is about 1 grade softer.
My own experience with this paper/developer combination is one of diminshing returns after the first minute. Still, I might experiment to see how the highlights are affected relative to the shadows after the first minute.
Originally Posted by Bill Burk
You mean the dichroic filters in the color head, I think. I'm talking about the multigrade filters that I'm holding under the lens. They could be fading or faded. One thing I didn't consider is that a dialed-in filtration and a physical filter give the same constrast but at different exposure times. Anyway, I'd like to get away from the filters altogether, which is why I thought the calibration would be worthwhile.
Originally Posted by BMbikerider
I have a new supply of paper arriving today. I'm going to test my safelight to make sure it's safe. Run some more tests...
If you are set on using a dichroic head then have a look at Ralph Lambrecht's site "Darkroom Magic". He very helpfully gives correction exposure factors when you need to change contrast grades. I have never found the Ilford or anyone else's dual filtration to give a constant exposure when changing grades although the exposure differences are relatively small over say half a grade say grade 2 to 2.5 but beyond this the exposure difference is enough to give a different print from the one you'll get if you stick to the same exposure
filter changes always require an exposure correction. it's un avoidable no matter what the filter manufacturer's claim may be.
Changing contrast grade without changing the midtone gray level is the whole idea behind dichroic head calibration and the Ilford filter set. I'm glad both methods work in my darkroom.
yes, but it's a promise no filter supplier has been able to keep yet, and the reason is obvious. first,which midtone gray is supposedly to staying constant?, and second, is that always the right tone the exposure is judged by?