I wonder, how much $ to have a lens cleaned and calibrated. KEH?
All you need is to to determine what the true speeds are, then you can keep the exposure corrections on the lensboard and refer to them later. You can do a quick soso job yourself with instant film that should be fine if you are working with print film.
Please dig out an old Ansel book that talks about the difference between coated and uncoated lenses. (With illustrations) Read your Kingslake. This is a fundamental part of Photography that has slipped out of community wisdom because the folks who dealt with it and knew it are at least 55 years old, and the newcomers simply haven't dealt with it.
1. The number of air-glass surfaces, of ANY era, reduce the amount of light that is transmitted to the film.
2. Some classic lens designs were meant to limit that loss.
3. Some designs have higher natural contrast.
In the old days, you might choose a Zeiss Protar, or Goerz Dagor, as an all around lens. Wide coverage, and moderate contrast, and 4 air-glass surface, it was a safe choice for folks working in flare prone conditions.
The Tessar, having higher natural contrast than a Protar, was a great choice for folks who needed to shoot in flat lighting. But with 6 air-glass surfaces, the deep shadows were often lighter than anticipated. Why ?
Flare (or light that is not transmitted through a lens, but reflected within the lens) affects the shadows, and not the highlights. You have a harder time separating Zone I from Zone II because FLARE functions as fill flash, or base fog, (otherwise known as non-image density).
In similar conditions which cause an uncoated Tessar to image a foggy Zone I, a Protar will image a clean Zone I.
On your negative
Zone O: 0 exposure units
Zone I: 1
Zone II: 2
Zone III: 4
Zone IV: 8
Zone V: 16
Zone VI: 32
Zone VII: 64
Zone VIII: 128
A lens with a small amount of flare might add 1 exposure unit to the film. It raises Zone 0 to Zone I, Zone I to Zone II, and Zone II almost to Zone III. You lose your pure black, your threshold black, and fine shadow detail become murky and empty... unless you account for it.
But 1 exposure unit does not affect Zone IV at all.
Some classic lenses could not be used in all conditions. The classic Plasmat, with its 8 air-glass surfaces would give accurate midtones and highlights, but unless very carefully controlled, gave soft shadows because the flare inherent to the design provided built-in pre-exposure in the form flare.
This flaw, however, encouraged an aesthetic of soft, gravure-like, glowing blacks in the '20s and '30s. The Plasmat is the design which later became the Symmar, and the most common commercial design after WW2. Not at all, in its mulicoated form today, conducive for glowing shadows !
Some classic designs, like the Planar, had 10 or more air-glass surfaces and regardless of their high speed, were flare prone and impossible to shoot at all in many settings. After WW2, and lens coating was not a military secret, PLanar type lenses became the standard for small and medium format lenses,and fast view lenses.
Coating also made possible advanced wide field lenses, like the Biogon or Super Angulon, whose 8 or more air-glass surfaces were completely dependent upon coating to make them practical.
As lens coating became 'the thing' after the war, many photographers had their old lenses coated, and there were surprises sometimes. In a letter to Ansel Adams in the early 1950s, Paul Strand ruefully described the effect of having his trusty Dagor coated. It seems the delicate shadows of Strand' negatives was destroyed by the coating. The lens had become harsh, and hard... and Strand had to cope with a pure black Zone I. Adams and Strand coped with this 'improvement' by changing how they exposed and developed film. Just like us !
As late as the 1980s, commercial shooters took advantage of lens designs to support their work. Coated Artars and Symmars were relied upon in the studio and in carefully controlled settings, but Tessars ( Commercial Ektars ) were still relied on to give the most contrast on a sheet of film. Even coated, a Tessar still rendered cleaner blacks.
When Multicoating technology finally permeated the large format world, in the 1980's, the issue of variable lens contrast was pretty much resolved. There were differences to be sure, but one could go about their business without having to take lens contrast into consideration.
In my own work, I bought a brand new 8x10 lens over the winter, replacing my well loved Protar. As I near 60, I'm not able to focus as easily as I used to. I dislike darkcloths in the studio, and it had become too hard to focus the old lens. The new, multi coated lens does the trick.
Of course, I had to completely change how I exposed and developed film, but change is just part of life.
Please excuse any errors in this post to late nights in the darkroom, and too much coffee in the morning. PLEASE don't take my word on any of this, but check Adams, or, even better, Kingslake's, "History of the Photographic Lens" or, the Bible, "View Camera Technique" by Leslie Stroebel.
Last edited by df cardwell; 05-09-2008 at 07:57 AM.
Reason: tpyt tpoy topy TYPOS !
Interesting post, df. What I find interesting is that classic 6/4 fast double Gauss type lenses (think TTH OPIC, Panchro, Speed Panchro, ... and Boyer f/1.4 and f/1.9 Saphirs) were taken up, and eagerly, by cinematographers (think "Hollywood") but shunned by still photographers. I've never understood how movies, with their extremely stringent image quality requirements, could be made using lenses that weren't good enough for still photographers, by definition less demanding.
Since you have a newer lens to compare with, I think I would first try a quick set up with a side by side comparison viewing through the lenses with a light background and a means to trigger the shutters simultaneously, or close to it. It would certainly be obvious at the slower speeds if one is different than the other but might be slightly more difficult at the higher speeds.
It certainly would be worth a try before blindly shipping the lens off to get repaired before the root cause is identified.
Alternatively, if you find the Ektar is slow, you can easily compensate for the time being although a slow shutter will most likely become slower with time, negating your 'quick fix'.
If you find the lenses are close in terms of shutter speeds, I think a test might in order at shutter speeds that are identical and determine if indeed the Ektar is a more contrasty lens and then make allowances to correct development for that situation.
Fred
Last edited by Fred Aspen; 05-09-2008 at 09:47 AM.
More exposure is not more contrast, but can often be misconstrued as such, so do check the shutters. I tape the actual shutter speeds, rounded to the nearest 1/3 stop onto the lensboard.
Having a development adjustment factor for lenses with low contrast (read lots of scattering) is a good idea. If indeed it is a contrast increase and not overexposure, then do a few tests. Choose your most reliable lens (e.g. a well-calibrated coated plasmat or tessar type lens) as standard and match you others to it. Start with a couple test negs, +10%, and +20% to compare to. You might even have to decrease exposure a bit to get the negs to match.
After you have arrived at a development adjustment for each lens, just note it in your already extensive exposure record and develop accordingly (maybe saving up batches from each lens to develop together?).
On the other hand, if the contrast increase is small enough that you can easily compensate for it in printing, then you can ignore it at the shooting stage. You will have to decide what is appropriate.
Since you have a newer lens to compare with, I think I would first try a quick set up with a side by side comparison viewing through the lenses with a light background and a means to trigger the shutters simultaneously, or close to it. It would certainly be obvious at the slower speeds if one is different than the other but might be slightly more difficult at the higher speeds.
It certainly would be worth a try before blindly shipping the lens off to get repaired before the root cause is identified.
Alternatively, if you find the Ektar is slow, you can easily compensate for the time being although a slow shutter will most likely become slower with time, negating your 'quick fix'.
If you find the lenses are close in terms of shutter speeds, I think a test might in order at shutter speeds that are identical and determine if indeed the Ektar is a more contrasty lens and then make allowances to correct development for that situation.
Fred
I just set the two lenses up side by side on two of my 4x5s. The funny thing is, the newer lens (the 90mm) is the slow one. It's doing twice the time (2 or more secs : 1 sec) as the Ektar, at least, at what should be a 1 second exposure. So I set it at 1/2 sec & the Ektar at 1sec and exposed a few sheets. They sounded pretty much in sync. I don't know about the other settings yet, but for now at least I know that my 90 is way off. Sounds like something is wrong with it. I always thought it was just too cold (shooting the frozen lake in winter). I was thinking another way would be to put them both on bulb - at least they'd be the same exposure. - One test at a time!
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Originally Posted by djkloss
