Barrel vs. Shutter: Why big difference in size ?

[Ken Lee]

On the left is a f/4.5 180mm Tessar in shutter. On the right is a f/4.5 250mm Tessar in barrel.
Both are identified as "Carl Zeiss Jena"
http://www.kennethleegallery.com/images/forum/twotessars.jpg

On the left is a f/4.5 210mm Heliar in shutter. On the right is a f/4.5 300mm Heliar in barrel:
Both are identified as "Voigtlander Braunschweig Heliar"
http://www.kennethleegallery.com/images/forum/twoheliars.jpg

I could understand if the 250mm Tessar were ~39 % longer than the 180mm Tessar, but it's more than twice the length. Similarly, I could understand if the 300mm Heliar were ~43 % longer than the 210mm... but it's roughly 3 times the length.

Why do we see such a disproportionate difference in size between the shutter barrel mounted versions of the "same" lenses ? Is there a difference in lens design ?

:confused:

[Arne Croell]

Well, for one your examples are not the same focal lengths. In each case your shuttered lens has a shorter focal length. The linear dimensions of a lens scale in direct proportion to the focal lengths, as you wrote, so the volume (and weight) scale to the 3rd power of it. This accounts already for a factor of 1.6 in volume for the top example, and a factor of 2.9 in weight and volume for the bottom one. In my experience, the difference is not huge for the exact same lens - some difference maybe due to the fact that the barrel versions use more blades in the aperture than the shutter often does, needing more room. Now, a weight difference is usually due to the fact that barrel mounts are often made from brass and shutters and the cells for shutters from aluminum. I'll provide some pictures with lenses of the same focal lengths later today.

[Ken Lee]

Thanks - That makes perfect sense.

I should have given a better title for the thread: Why big difference in length ?

[IanG]

Something Arne hasn't said is the use of those lenses.

The Tessar design in particular was used for different types of lenses of the same focal length. So a process lens may be larger than a normal camera lens. In addition the Tessar's were redesigned and the later shutter mounted lenses were longer, so my 1950's 150mm Tessar is longer and bigger than a 1919/20 165mm Tessar.

Ian

[ic-racer]

What is the front/rear element spacing on the barrel vs shutter lenses.

I don't know of any correlation between physical length of veiw camera lenses and their focal length.

[Ken Lee]

The Tessar design in particular was used for different types of lenses of the same focal length. So a process lens may be larger than a normal camera lens. In addition the Tessar's were redesigned and the later shutter mounted lenses were longer, so my 1950's 150mm Tessar is longer and bigger than a 1919/20 165mm Tessar.

Thanks - That is quite helpful: perhaps Tessar is less a specific design, than a trade name.

Others have explained elsewhere that the Heliar design was replaced with a Dynar design - but Voigtlander continued to brand them as Heliar. I guess the same is true of Tessars.

I'm looking to settle on a portrait lens in the 210mm length, and now I realize I will probably have to try out a number of them, before I find the one I like.

[EdWorkman]

What about coverage?
Do the huge lenses cover proportionately more than the focal length ratio?
And/or was the intent for critical work, that is, was the advertised angle of view restricted to a narrow zone that is the limit of low distortion or other special characteristic, as for repro work ? [and lots less than what works well for pictorial]

[IanG]

Tessar is a Zeiss trade name for the basic design, it was used by both East & West German arms of Zeiss after WWII, so passed to Doctor Optic who took over part of Carl Zeiss Jena.

While the original Tessar was a patented design Zeiss took out further patents over the years to cover Tessar variations, including the faster f2.8 Biotessar which is a different design to the Biotar.

Ian

[Dan Fromm]

What is the front/rear element spacing on the barrel vs shutter lenses.

I don't know of any correlation between physical length of veiw camera lenses and their focal length.Spacing is the same regardless. Otherwise the lens would perform worse in one mount or the other.

As Arne said, within a prescription, all dimensions of a lens scale linearly with focal length. Double the focal length, double the distance from the front element's outer vertex to the rear element's outer vertex. Note that this has nothing to do with packaging. Also note that not all lenses in the same design type, e.g., Tessar, have been made to the same prescription. To get a sense of the possible variations, visit www.dioptrique.info and look at the tessars ...

Cheers,

Dan

[Dan Fromm]

What about coverage?
Do the huge lenses cover proportionately more than the focal length ratio?
And/or was the intent for critical work, that is, was the advertised angle of view restricted to a narrow zone that is the limit of low distortion or other special characteristic, as for repro work ? [and lots less than what works well for pictorial]Ed as Arne wrote, within a prescription coverage scales linearly with focal length. Double the focal length, double the diameter of the circle covered.

It isn't aways clear what criteria manufacturers use to define coverage. As best as I can tell, Schneider and Rodenstock use the radius (or angle off-axis) at which MTF goes to zero to define coverage. Look at Schneider's MTF curves for, say, Xenars. Scary, eh?

For a contrary view from Rodenstock, look at the MTF curves for the 75/4 Apo-Rodagon D. They're nearly flat to the edge of the field, and then, at least with the one I had, there's no more image. I'd say that lens is a wide angle with deliberate mechanical vignetting to keep users from, um, misusing it.

Cheers,

Dan

[Nathan Potter]

Dan since you bring it up in this thread, I've always been confused by what exactly is meant by coverage. There seems to be no conveniently used criteria. For instance something like the amount of radial degradation in the COC at best focus - or some other metric with some universality to it.

Nate Potter, Austin TX.

[Arne Croell]

Here are the promised examples.
3 Tessars 210mm: 1 Carl Zeiss Jena in Barrel, 1 Carl Zeiss Jena in Prestor 3, one Docter Optic in Copal 3

2 Voigtländer Apo-Skopar 450mm (45cm), one in barrel, the other in a Compound IV

2 Voigtländer Heliar 210mm (21cm), one in barrel, one in Compound III

In all cases, the length of the mount is practically identical, give or take a mm.

[Ken Lee]

Wonderful - Your pictures are worth a thousand words !

Now (with mild fear and trepidation) if I may ask, concerning those three 210 Tessars: do they give different "looks" ?

From what I have observed comparing my Tessars to my Heliars, the differences seem most easy to discern, when shooting at or close to wide-open. Like the modern Cooke portrait lens, my Heliars (actually Dynars) exhibit some aberration that mostly disappears once we stop down past f/8. At smaller apertures, the difference between my Heliars and Tessars gets hard to judge: not coverage, but the overall rendering of both in and out of focus regions.

[Dan Fromm]

Dan since you bring it up in this thread, I've always been confused by what exactly is meant by coverage. There seems to be no conveniently used criteria. For instance something like the amount of radial degradation in the COC at best focus - or some other metric with some universality to it.

Nate Potter, Austin TX.Nate, coverage is in the eye of the beholder. The circle covered is the circle within which the image is sharp enough.

What's sharp enough? Beats me.

The closest I've seen to a sharpness criterion that makes sense is EKCo's much reviled Subjective Quality Index. It is tied closely to print size (enlargement, in a word) and the aperture at which the lens was shot. It is a system -- taking lens, film, film development, enlarging lens, paper, paper development -- measure, not necessarily a direct measurement of what the lens itself can do.

Next closest, and tied more closely to the lens itself, is Schneider's working definition. They seem to think that an MTF of around 10% at 20 lp/mm (or some combination like that) is the least acceptable. Whence the angle off-axis that gives the least acceptable MTF at frequency defines the limit of coverage. Still subjective.

Cheers,

Dan

[seawolf66]

Ken Lee go to the camera eccentric web stie and in their for sale section they have a pair of Protars same type but one in shutter and other with out :

[Sevo]

Now (with mild fear and trepidation) if I may ask, concerning those three 210 Tessars: do they give different "looks" ?


They should not - apart from minor changes in coating and assembly, the GDR Jena Tessars remained the same throughout, and Docter merely continued their production in the nineties.

Sevo

[Arne Croell]

They should not - apart from minor changes in coating and assembly, the GDR Jena Tessars remained the same throughout, and Docter merely continued their production in the nineties.

Sevo

Absolutely correct, they are all the exact same design - in this case from 1929 by W. Merté - so the only differences are the mounts and for the Docter version a slightly different coating.