Dichroic Calibration - Worth It?

[RalphLambrecht]

filter changes always require an exposure correction. it's un avoidable no matter what the filter manufacturer's claim may be.

 

[ic-racer]

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.

 

[RalphLambrecht]

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?

 

[nworth]

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. ...

Adams once recommended a test for developing time. He exposed a series of step tablet images such that they centered the entire range of reproduced steps. Then he developed the images for various times until he found the time where the greatest number of steps was reproduced. That was the optimal developing time. With the papers of that era, this could be a critical test, since after a while fog and extra contrast appeared and the range decreased. With today's papers, that generally doesn't happen to any extent, and you more or less develop to completion. With Dektol, that happens in about a minute and a half; with other developers it may be different. It may also vary with the paper.

 

[ic-racer]

yes, but it's a promise no filter supplier has been able to keep yet,

The Ilford set I had was very close when I tested it. At least as close as I could test with a 21 step wedge.

which midtone gray is supposedly to staying constant?

The Ilford set I tested the gray stripe on the step wedge exposure was somewhere near the geometric center of the grays visible. I did not measure the exact reflection density.

and second, is that always the right tone the exposure is judged by?

Well that is the tone you need to use to use the filter set correctly. If you try to judge exposure based on black, white or some other gray, you are not using the filter set properly as designed. I'd ignore criticism of a product what was used incorrectly.

 

[Bill Burk]

If you try to judge exposure based on black, white or some other gray, you are not using the filter set properly as designed. I'd ignore criticism of a product what was used incorrectly.

It works as designed, but I think Ralph is levelling his criticism at the design.

The calibration technique from Paul Butzi in the original post describes calibrating to have consistent exposure for the highlights, which I think is what Ralph wishes the filter manufacturer had done.

So if you have a Dichroic head, you have a choice of approaches.

p.s. I use graded paper, so maybe I don't know what I'm talking about.

 

[Rafal Lukawiecki]

0.60 logD over paper base is the ISO paper speed point. My 500H, when adjusted, seems to produce this midtone at all grades at the same exposure, for a given negative, which I believe is the meaning of a speed-matched system. This agrees with what I read in Ralph's book, which shares useful suggestions how to take this fact further, and to arrive at an equal highlight while changing grades, which may be more useful than trying to keep a rather dark midtone constant.

 

[bvy]

More frustration. I ran the safelight test and everything came out "safe." I notice the enlarger has -2 EV attenuator plugged in. Don't know if that makes a difference.

This was done with a grade 3.5 filtration dialed in (75M+15Y) for 7 seconds (f/8). Ilford MG RC paper, 60 sec. in Ilford PQ.

 

[Bill Burk]

bvy,

If you'd like to send out one of the negs, I'd be happy to check to see if the problem lies in a thin neg. Send a pm... I'm sure others would be happy to make similar offer... It might be one of those things that is easy to see once its in hand.

 

[RalphLambrecht]

exactly.keeping a meaningful highlight density constant is what a truly matched exposure system delivers. anythin else is a nice try.

 

[RalphLambrecht]

It works as designed, but I think Ralph is levelling his criticism at the design.

The calibration technique from Paul Butzi in the original post describes calibrating to have consistent exposure for the highlights, which I think is what Ralph wishes the filter manufacturer had done.

So if you have a Dichroic head, you have a choice of approaches.

p.s. I use graded paper, so maybe I don't know what I'm talking about.

i could not have said it better myself.

 

[Bill Burk]

...but this print/scan looks as though the negative is quite thin (ie underexposed) and also possibly underdeveloped....

Then the solution would be to find out why the film didn't get as much development as it needed.

Since you got the time right...

Check the D-76 developer temperature isn't/wasn't/couldn't have been too cold (if so, warm it up to 68-degrees F).

Or maybe it's just that your shots were in flat light (was the crowd shot on an overcast day?), in which case you would expect to print on higher grades.

I'd go back to the Ilford reference on post #3 from Michael R 1974. To simplify while things aren't going well, simplify. Use the single filter settings chart. (Adding Yellow doesn't help higher contrast grades).

 

[bvy]

I'm going to back to some prints I made last year (well, 2011) that had better contrast. I rescanned two of them tonight (side by side) using my current workflow, to reduce or eliminate the scanning variable. (I placed the print I posted previously in the background for comparison.)



Print #1
enlarger exposure: f/11 for 5 sec
filtration: none
paper: Ilford RC Pearl Gr. 2
developer: Ilford PQ 1+9 60 sec.

Print #2
enlarger exposure: f/8 for 6 sec
filtration: Ilford multigrade #1 filter
paper: Ilford MG Pearl
developer: Ilford PQ 1+9 60 sec.

I made #1 first and decided it was too contrasty. For #2, I switched to MG paper and added a filter; I thought it looked better.

Both #1 and #2 were made on my Omega B600 condenser enlarger -- not on the Omega C760 with dichro head that I'm currently using.

I'm a little nervous about sending my negatives out, but to compare, I scanned them side by side. The top negative was made with the Olympus XA4, the bottom with the Yashica T5 with on-camera flash. Both are Kodak Tri-X 400 developed in D76 1:1 at 68F for 9:45.



(Thanks again everyone. Your patience and good advice prompted to me to renew my membership -- something I would have done anyway, but it's good to be reminded why this community is so valuable. Happy New Year to all...)

 

[Bill Burk]

I get it, I once gave a prize-winning negative to a co-worker because he wanted an example to try to match, and I never got it back.

Frames 17 and 26 show sufficient density in the highlights. This tells me you developed the film enough. But the frames you printed are thin. I think it's the scene lighting (flat light in the first place). So the advice to develop longer... would apply... if you get into the same situation again with the same kind of dull light. Otherwise, it's OK to stick with your current developing plan.

Your print #1 looks pretty good to me. Since it was done on a Condenser enlarger, you would need to use a higher grade to get the same look from your C760.

For the next print experiments, don't be afraid to overshoot and give filtration for Grades 4 and 5. At least then you'll know you went too far.

 

[Rafal Lukawiecki]

It's not easy for me to judge the film you are using, as I'm not familiar with that version of Tri-X, but the frames in question seem a little underexposed, considering the other points mentioned earlier.

Congratulations on having a safe safelight—surprisingly, not a common feat.

 

[Bill Burk]

Well, the negatives still look significantly underexposed to me.

Right! Try shooting at EI 250 or 320 instead of 400, see if that helps things

 

[bvy]

Thanks again. The negatives look a tad underexposed and/or underdeveloped to me too. But if we agree that the two frames under consideration (15 and 27) have roughly the same density, I'm confused as to why I was able to get a really contrast print on grade 2 paper (frame 27, print #1). I might have to pull the B600 out of the garage and hook it up again...

 

[Bill Burk]

A condenser enlarger will gain about a grade in results. The Callier effect is named as the reason.

You don't need to go back to that enlarger... just go up a grade.

 

[pentaxuser]

But if we agree that the two frames under consideration (15 and 27) have roughly the same density, I'm confused as to why I was able to get a really contrast print on grade 2 paper (frame 27, print #1).

If you are referring to the two pictures of the boys then the more contrasty print was in fact grade 2 as the paper's natural grade is 2 without any filtration. On the other you have used a grade 1 filter which is why it is less contrasty and flat looking. I much prefer the non filtered print but I'd give a grade 1.5 a try as the unfiltered grade 2 might be just slightly too contrasty but we are getting into a very subjective area now

pentaxuser

 

[Jim Rice]

The original negative (15) looks thin from underexposure to me. You might try to intensify that negative. I believe the issue is in the negative.

 

[Ronald Moravec]

It would be easier for you to produce negatives that print well on grade 2. Develop them longer and you won't need to use grade 5.

Yes 4 sure. Exposure controls shadow detail. Development controls highlight density. With more highlight density, you can expose longer and get blacker blacks. Another way to think is longer print exposure will get the blacks you desire, but the whites will grey. If they had more density, light would be held back more and they would stay white.

 

[PKM-25]

I'll see how I get along with black and white on a color head I guess. I have a Beseler 45S coming tomorrow and plan on hooking it up to my StopClock Vario, can't decide if I will use the spare sensor in it or not.
I also got two brand new boxes of Ilford MG filters in 3.5x3.5 for my mural enlarger and students, nice to fall back on if I hate the Dichroic head I guess...also bought Ralph's book, look forward to learning a lot.

 

[bvy]

Thanks again everyone. I'm still not convinced. I won't argue that my negatives aren't thin and/or underexposed. But the print I got of the boy (#1) has much more contrast than the prints I'm producing today (from similarly thin/underexposed negatives).

I bought my Ilford multigrade developer (PQ) 13 months ago, but it has always been kept full in an airtight bottle. I wouldn't expect it to be bad, but I might pick up a fresh supply anyway.

 

[Richard Jepsen]

I once had a Leitz V35 with speed matched contrast steps. Later I got a LPL color head and found myself using under the lens filters or dialing in only megenta. If your negatives normally print within a one contrast grade spread, (2.5 to 3.5) just using magenta is easy.

I print test strips when changing contrast and the magenta only technique does not slow me down. I have learned instinctively when to add a second or two when increasing contrast. Megenta only allows you to avoid printing though higher density and avoid exposure times over 30s.

If you do complex manupulation or print balancing this will not be as convenient as dialing in speed matched contrast changes. Good negatives with simple techniques produce good results with less frustration. Its all in a properly exposed negative.

 

[ic-racer]

I would agree with this post and go further by saying that you should (where possible) produce negatives that require no filtration, given your film development procedure and enlarger type/set up.

Actually Steve Beskin posted information that negatives processed to print on Grade 3 paper yeild the least distorted tonal reproduction scale. Also, when using multigrade paper, exposing without a filter negates any benefit of the multigrade technique.