2 questions for the lens gurus amongst us.

[smieglitz]

1) Is/was there a standard for lens series size designations that related to specific formats? For example, can I presume a #3 covers 4"x5", that a #5 lens was meant for the 10"x12" format, etc.? If possible could someone list the equivalencies please?

2) Can someone describe how lens reflections indicate lens designs? I understand strong reflections indicate air to glass interfaces while faint reflections indicate cemented glass surfaces. Could someone post a visual example for each showing what might constitute a number of strong or weak reflections and how they would be counted?

I guess that was more like 8 questions... :rolleyes:

Joe

 

[KarenB]

I don't know if this may answers some of your questions or not, but have you seen these lists?

http://www.largeformatphotography.info/lenses/

Karen

 

[JG Motamedi]

... Is/was there a standard for lens series size designations that related to specific formats? ...

I wish there was. As far as I know the only universal is that the larger the number the longer the lens. Many lens manufacturers even changed their numbers over time. For instance, a lens we both have, a 16" Vitax, has been designated as both a no. 3 (before ~1910) and a no. 5 (after ~1910).

A Dallmeyer 5D is 19" and covers 10x12 while a Dallmeyer 5A is 22" and covers 12x15. On the other hand, a no. 5 Dagor is 10 3/4" and covers 8x10, and a Voigtlander "Quickworker" no. 5 is about 9" and covers 5x7, while a Voigtlander "Portrait Euryscope" Series II no. 5 is 11.5" and covers 8x10. However, a Voigtlander "Portrait Euryscope" Series III no. 5 is 13" and covers 10x12. Did I mention that the Voigtlander "Extra Rapid" Euryscope no. 5 is 17.5" and covers 11x14?

Sorry for the asinine answer. I never thought of myself as a lens guru, maybe more of an optics imam...

 

[Dan Fromm]

Standards? You want standards? Are you nuts? Rhetorical question, of course you're nuts.

As far as I can tell, each manufacturer had its own relationship between the lens "number" and format covered. B&L had at least two, one for tessars badged B&L Zeiss and another for tessars badged Zeiss Kodak.

Counting reflections? Its a good way to tell a Dagor from a dialyte, to tell a tessar from a triplet. I'm non-, not anti-, digital so can't post examples.

What I do to try to see reflections is close the lens diaphragm as far as possible or (better) remove one cell from the barrel or shutter, then look at it under a single light. Rock it back and forth, look to see what I can see. When the cell will come apart, then I check front and rear sections. This last is useful for telling, say, what's probably a 6/4 plasmat like a Symmar from a 6/4 double Gauss like a Xenotar (some aren't 6/4). Weak reflections can be very hard to see.

I've never learned how to tell which piece of glass is curved which way, so can't make fine discriminations among the many flavors of tessar, ... Triplets and dialytes are easy to recognize, everything else is harder. It helps to have something like the Vade Mecum ready to hand when trying to tell what type a lens might be.

But there are some lenses that don't fall nicely into well-known categories. Try counting reflections from a 210/9 Konica Hexanon GRII. It isn't a 6/4 plasmat, even though everyone knows that's what process lenses are. Try counting reflections from a Lomo RF-3, -4, or -5. I dismantled my RF-5, looked at the curves. Its a 4/4 double Gauss, not a 4/4 dialyte, even though everyone knows that's what process lenses are, except, of course those pesky f/10 Process Nikkors. They're 4/4 double Gausses too.

Just remember, when all's said and done either a lens shoots well enough or it doesn't. Knowing what design it is won't change that, is useful mainly for one-upsmanship. What the lens does is all that matters.

Cheers,

Dan

 

[smieglitz]

...
A Dallmeyer 5D is 19" and covers 10x12 while a Dallmeyer 5A is 22" and covers 12x15. On the other hand, a no. 5 Dagor is 10 3/4" and covers 8x10, and a Voigtlander "Quickworker" no. 5 is about 9" and covers 5x7, while a Voigtlander "Portrait Euryscope" Series II no. 5 is 11.5" and covers 8x10. However, a Voigtlander "Portrait Euryscope" Series III no. 5 is 13" and covers 10x12. Did I mention that the Voigtlander "Extra Rapid" Euryscope no. 5 is 17.5" and covers 11x14?...

That's what I was a fraid of.

But, your answer is helpful as I was considering the purchase of a Dallmeyer 5D since I thought it might cover 11x14. Looks like I'll have to watch for a 6D (? fat chance) or a 5A. I was hoping a #1 lens might be sixth-plate and #2 @ quarter-plate, but that seems unlikely given the nonstandardization you point out.

As you know, I also have a copy of the Lens Collectors' Vade Mecum and while helpful, I'm still confused by several of the lenses I have. For example I recently bought a small projection lens off eBay. I was hoping it was a small Petzal but it turned out to be a 15" focal length at about f/10 as near as I can tell. Yet, when I open it up it has a cemented front doublet and air-spaced rear doublet but doesn't quite match any diagram in the vade mecum. F/10 seems terribly dim for a Petzval design, doesn't it?

Also, I'm wondering what Seroco f/5 series II Portrait Lenses may be since I can't remove the front group. (The rear group is a pair of air-spaced lenses.) In the front group, I see a huge bright reflection and then a pair of faint ones, the first (?) smaller than the second, followed by a larger brighter reflection at the rear. Does this indicate a cemented doublet at the front and thus a Petzval design?

Thanks for all the other responses as well.

Joe

 

[JG Motamedi]

Well, the 5D will cover 11x14 at infinity without actually vignetting. It has some pretty fierce fall off, but is ok for head and shoulders shots. I use one pretty frequently, since my 5A is anything but portable.

I am pretty sure the Seroco f/5 is a rebadged Wolly Vesta, which is a Petzval.

I have never been able to figure out design by reflections. I take a more direct route by just opening them, of course this doesn't always work.

 

[jonw]

I recently picked up a Dallmeyer 5D (19") portrait lens, but the the soft focus ring does not appear to move. Not being familar with this lens' design, can someone please confirm whether or not one of the two rear set of lens should rotate to create the softening effect? The only way the barrel on this lens will rotate is if I remove the set screw which is located close to the inside rear set of lens and then the rear lens can be removed completely from the barrel.

If in fact the rear two sets of lens should rotate and thus are stuck, what would you recommend be done to "unstick" it? I have tried using a hair dryer to heat it up in the event there is old hard lubricant, but no luck yet.

The lens does have an aperture lever and it does move freely. But none of the lens can be removed from the barrel, except for the rear set of two lens groups which can only occur with the removal of the set screw mentioned above.
Any thoughts, on either confirming this lens is designed to work properly by removing the set screw or advising what steps need to be taken to get my "new" lens to work properly, are appreciated.
Jon

 

[Ole]

This is one of the reasons I prefer German lenses: There seems to be at least a HINT of concistency.

No.1 is usually meant to cover 9x12cm, 2 for 13x18, 3 for 18x24, 4 for 4x30 and so on. Most No.0's were for 6.5x9cm.

But that doesn't always work - wide angle lenses in particular follow their own "logic". My Busch WA Aplanat Ser.C No.2 is a 150mm, which covers 24x30cm with movements and more...

I'm getting good at reading reflections, but it's hard to explain. Practice with a lens of known design is the best advice I can give - that's how I managed to find out that my Leitmeyr Weitwinkel-Anastigmat is an Angulon clone. Most of them are not...

 

[JG Motamedi]

JonW,

There are two styles of the Dallmeyer Patent Petzvals; in the older style (usually brass barrels) the glass element closest to the film rotates. If you look on the rear of the lens you will notice small indents or notches, ranging from one to four. These are the "softness" marks, rotate the final element around so the notches matches the little brass screw/stem which sticks out. The second newer style (usually black lacquer or aluminum mounts) the entire barrel turns on the mount.

I have never had any luck whatsoever with these defocusing devices on either Dallmeyer or the Wolly Vitax--they never seem to do very much.

 

[jonw]

JG, my Dallmeyer 5D lens is the newer version.

Thus JG, if I am correctly understanding your response, my newer version lens is designed so that its set of two rear lens groups are suppose to be stationary in the lens board and the "softness effect" is designed to be created by loosening or removing the set screw and then unscrewing the barrel unit in front of the two rear lens group until the desired effect is obtained. If correct, then presumably, one would then tighten down the set screw so that the barrel is ready to be used at the desired focus set up?!Otherwise, this newer verision design can be unscrewed to the point that the front barrel unit of the Dallmeyer 5D can be removed. If this is correct, it does seem strange when compared to the diffusing rings one finds on some of the Wolly Velostigmat lens and/or the Ilex Portrait Lens. Do you just keep your lens adjusted to the point where the maximum softness effect is always set and the set screw is tightened down?

JG, I have seen your nice portraits you have posted and especially like the ones where you used your Dallmeyer 5D lens. I hope I have as much success with my Dallmeyer 5D lens as you do. I have exposed two sheets of 8x10, but have not had a chance to put them in the JOBO.

Jon

 

[JG Motamedi]

John,

Thanks for the kind words. I think I didn't describe the defocusing mechanism very well. With the newer black lacquer or aluminum barrels, to obtain defocus you need to move the actual barrel. The flange, which is attached to the lensboard, stays in place (hopefully) and as the barrel rotates it changes the space between the two components in the rear element. You shouldn't need to loosen any screws. With the older mechanism, you reach into the rear of the camera, and turn the ring holding the closest component of the rear element. I attached a jpg of the rear of the older mechanism. The newer one looks like this one:

Stolen from: http://blogs.salon.com/0004217/2005/07/18.html. Note that the soft image he has on this page, of the woman with the umbrella is probably NOT from a Dallmeyer Petzval. They won't (in my experience) produce that sort of halation.

jason

 

[jonw]

That is what I was afraid of. The rear unit which has the two sets of lens appears as if it should rotate, but it is frozen tight. The set screw I was referring to is located immediately in front of the "rear unit" and if the screw is removed, then the front of the barrel can be removed with the aperture ring and the front lens group.
I have believe the old aluminum lens housings are frozen tight due to age etc. I would assume there should be some lube inside the defuser ring which if I understand you JG, would be the second set of the lens which should rotate and which is near the rear of the barrel, but not the last set of the lens group which in fact attaches to the flange/lensboard.
With this say, any suggestions on how to unfreeze my diffuser ring on this Dallmeyer 5D? All help is appreciated. Thanks. Jon

 

[JG Motamedi]

Not surprising. All of my older lenses have had similar problems. There is not clear-cut answer. A small amount of penetrating oil might do the trick, but then again it might seep through and get on your glass. You can use strap wrenches (leather or plastic) to forcibly unscrew the two components, but again, you risk stripping or otherwise ruining them. Of course, you can always send it to Grimes and pay for them to do the work. Were it me, I would GENTLY use a pair of strap wrenchs. If it didn't come loose I would leave it be. The defocusing doesn't do much anyways.

 

[JG Motamedi]

Two images to help:

 

[jonw]

Yep, that is what I thought. The softer mechanism is frozen. I will take your advise and trying shooting it a while and see how the pictures turn out. I am afraid it paid too much for this lens, especially since it did not have a flange. However, the bright note is that it does fit another flange which goes with a large wet-plate brass lens I have and the glass is clean for its age.
PLUS, I also picked up a 14" Vesta in a working studio shutter. I probably will end up trying the Vesta out, but eventually listing it on APUG classifieds. I truly need to narrow my collection of portrait lens.

Thanks again for all your assistance. Jon

 

[acroell]

Back to the lens reflection question. Dan gave you already a lot of good suggestions. Let me point out a few more things.

It is possible to determine whether a reflection is from a surface that is convex towards you or concave. A convex surface acts as a convex mirror, which always produces a virtual erect image. In other words, if you move the light source to the right (or the lens to the left) the reflection moves to the right. the same is obviously true for flat surfaces. Concave surfaces are a bit more complicated, as they have a focal point in front of the surface. If your light source is further away from the surface than the focal point (most cases) then moving the light source to the right (lens to the left) side, will result in the reflection moving left, i.e. the image is reversed. When your light source is at the focal point there should be no discernable image of the source as the surface produces a parallel beam of light (for a point source). If you're even closer to the surface it'll react like a convex surface in orientation (source moving right, mirror image moving right). The latter two cases can happen for very large concave (shallow) radii. It is therefore important, to turn the lens around as Dan mentioned, because then the concave surface will be convex and vice versa. Doing that, it should be possible to deduct the surfaces and their orientation (but not their order).

It is also a good idea to vary the distance of the light source and the lens, to not overlook any reflections. Reflections from small radius surfaces can be quite small.

Cemented glass interfaces can be easy to see or very faint - it depends on the difference of the refractive index of the glasses. They are never colored like the ones from coated interfaces. There is a pitfall with uncoated lenses in that a _multiple_ reflection from a glass-air surface can resemble a very faint reflection from a cemented interface. I had that happen with a Rapid Rectlinear which showed 2 "cemented" interface reflections although I knew there was only one. This can be checked by adjusting the light source such that the suspected 1st main reflection is cut off by the mount; if the other faint reflection disappears at the same position it is likely a re-reflection.

 

[rrankin]

Jason,

I have a 4D (old style from your description) but haven't had much chance to use it yet. I have used it with no turning of the rear element and was very pleased with the results.

When I played with it, I saw no discernible differences on the GG as I went from notch one to 4. This seems to be in acordance with your experience. What exactly is SUPPOSED to happen? Is it meant to introduce some spherical distortion around the edges, put the entire image out of focus, or what?

Cheers,
Richard

 

[JG Motamedi]

Richard,

I knew the design introduces spherical aberration, but I was unclear to what end, so I looked up the patent (US no. 65729, UK no. 2502/66).

The defocusing arrangement is described to:

"... adjust at the will of the operator, to obtain for the moment any desired amount of distribution of definition over several planes, simply by an alteration in the distance or separation of elements composing, as in the lens described, the back combination, without at the same time deranging any other necessary corrections of the entire objective..."

"... With a lens or objective so constructed the operator can, by sacrificing intense sharpness of definition on one plane, distribute the definition over several planes and so obtain a more artistic and pleasing result... "​

I think it safe to say that the defocusing arrangement serves to increase the apparent depth of field ("distribution of definition over several planes") by increasing spherical aberration and decreasing sharpness. In any case, I can't imaging that soft focus was much of an attraction in 1866, when the lens was designed. Later in the early 20th century, when SF lenses were in vogue, the lens was repackaged. Of course, perhaps it was just a way of patenting the information.

jason

 

[rrankin]

Jason,

Thanks for the info - that has caught my interest for sure now. I'll have to go and burn some film with this thing and see if I can detect any differences. I suppose using APH is cheap enough to waste...

What would be a good target subject to check this out, do you think? I have one of those Air force charts but that would be a near focus and probably not useful. This is when the Flatiron Building might come in handy, but there's nothing like that around here that I know of. Seems to me a good subject would need a definite pattern distribution across the entire image plus receding objects along all the edges.

Any ideas on that?

Cheers,
Richard