ZS/BTZS calibrations for different lenses?

[William Mortensen]

With all the discussion lately on the "scientific" approach to exposure/development control, (see what you started, Steve?), I was wondering... Do those of you who use a fairly formal system such as the Zone System or BZTS do separate calibrations for different lenses?

I use quite a few different lenses, from 19th century rectilinears to modern multi-coated lenses, and find (of course) that the contrast varies greatly (!) between them. Different light can significantly change the behavior of a single lens, especially with older uncoated optics prone to flare under harsher illumination.

I often hear of re-testing for a new film or developer, yet I never hear comments on doing separate testing for different lenses. Is this commonly done?

(BTW, my name keeps switching to "William Mortenson" on these posts. Whoever's doing that, cut it out!)

[Michael Graves]

Not only should you calibrate each lens; you should run a separate calibration run for each shutter speed. If you do that, you will discover the extra two zones I never told anyone about in my books.

AA

[Jorge Gasteazoro]

IMO it is not necessary with modern shutters, the margin of error is negligible. OTOH if you are using a 50 year old shutter, I would check to see the speeds are more or less in sync.......

[sanking]

Jorge: " IMO it is not necessary with modern shutters, the margin of error is negligible. OTOH if you are using a 50 year old shutter, I would check to see the speeds are more or less in sync..... "

Right. And make sure your exposure meter is calibrated, and that you know how to use it.

[Michael Graves]

I have a question that maybe Sandy can answer along these lines. I use a Soligor 1-degree spot meter for my metering. I seem to be noticing more and more that as the EV ratings rise above about 12.5 or so, I tend to get over exposures, and as they drop really low; in the range of 2 to 4, I get serious underexposures. Is there a method he (or anyone else, for that matter) can recommend for tracking the linearity of a meter? It doesn't seem to be very predictable. If EVs fall between around 6 to 12, the exposures are right on the nose every time.

I always take three readings. I meter for the lowest value where I want detail and place that on Zone II and then meter on the highest value that I want detail and calculate an estimated development factor. Then I try to find a place in the scene that I think SHOULD fall on Zone V and see what the meter thinks it will be. I don't do anything with that reading. Am I doing something wrong?

[William Mortensen]

I was presuming accuracy of basic equipment, though Jorge's and Sandy's points are well taken. But should one calculate exposure and development for, say, an uncoated 18" Rapid Rectilinear with the same BZTS numbers he derived using a multi-coated 450mm Nikkor-M?

For that matter, if I simply had Sandy King's BZTS numbers and used the same film, developer, agitation, and temperature, and we each had accurate shutters and meters, could I trust my negatives to be technically quite similar to his?

Just trying to imagine all the variables; lens character still seems to me the unspoken ghost in the machine...

[William Mortensen]

Michael- You didn't mention what your exposure times are, but could it be reciprocity failure?

[Jorge Gasteazoro]

For that matter, if I simply had Sandy King's BZTS numbers and used the same film, developer, agitation, and temperature, and we each had accurate shutters and meters, could I trust my negatives to be technically quite similar to his?

In a word, YES! this is one more of the wonderful things about the BTZS. I tend to use one thing and stick with it, but when Sandy was testing semi stand developing he e mailed me his plotter file. Instead of me re doing all the tests he did I just used his data with excellent results. Bear in mind that the variables have to be the same as you stated, same temp, agitation, developer and film. This is very important and cannot be stressed enough.

I would like to see Simmons provide data that allows everybody else to duplicate the tests as well as the BTZS does.

[Michael Jones]

When you compare the results from lenses of difference eras, say early protars to modern plasmats, the wild card is usually flare. Where in a modern lens, a great deal of attention has been paid to coating and internal light patterns, not much was done in the not so recent past (pre-WWII). In an uncoated lens, the flare will lower the contrast, especially in the shadows, increasing their density. This results from a change in the film curve that may require a change in exposure and increased development to tame.

Phil’s BTZS has testing procedures for flare and demonstrates its impact on an image, as well as how to ameliorate (or emphasize) its effects. If you use his calculator, after testing your camera and lens, you can program the “amount” of flare into the calculations for both exposure and development. While testing for each lens may be a bit much, a general understanding of the flare characteristics of your equipment allows you to be more precise. Joe Englander had a baseline testing procedure that had you metering off the film plane to get your exposure information for film speed and developing. This took internal bellows flare into account. That said, getting into the ballpark with Sandy’s BTZS numbers, as Jorge notes, may be all you need. Then you fine tune your personal technique with each exposure.

[sanking]

Jorge: "In a word, YES! this is one more of the wonderful things about the BTZS. I tend to use one thing and stick with it, but when Sandy was testing semi stand developing he e mailed me his plotter file. Instead of me re doing all the tests he did I just used his data with excellent results. Bear in mind that the variables have to be the same as you stated, same temp, agitation, developer and film. This is very important and cannot be stressed enough.

I would like to see Simmons provide data that allows everybody else to duplicate the tests as well as the BTZS does."

Jorge makes a fair point . And the obvious question is this. Has Steve Simmons ever actually tested BTZS? If so, why not publish his results so that all of us can evaluate them?

And, has he ever published in View Camera any comprehensive comparison of BTZS versus Zone testing? And if so, why not?