Dallmeyer Series 3B Lenses Differences?

[Jay Decker]

I have two recently acquired Dallmeyer 3B lenses. One lens has an iris that opens to f/3.5 and has instructions on the barrel to unscrew the front element for soft focus. The other lens has does not have an iris, the lens has a slot for water stops, and an measured and calculated maximum aperture of f/3. Are these two lenses the same optical lens design with only mechanical differences? Can I get the same soft focus effect by unscrewing the front element on either lens? Is there any reason why someone would want to have these two versions of this lens?

Thanks,

Jay

[goamules]

The 3B patent lens did change over the years, it was made for many decades. You have a later one with the iris and provision for turning the barrel to adjust soft focus. Your other one is earlier, and probably has a series of notches on the rear element's knurled bezel. On these you must reach your hand into the back of the camera to turn the bezel to adjust soft focus. Not very convenient, hence the other design. You can look up your serial number to date here: http://www.antiquecameras.net/petzvallens.html

Garrett

[Jay Decker]

The 3B patent lens did change over the years, it was made for many decades. You have a later one with the iris and provision for turning the barrel to adjust soft focus. Your other one is earlier, and probably has a series of notches on the rear element's knurled bezel. On these you must reach your hand into the back of the camera to turn the bezel to adjust soft focus. Not very convenient, hence the other design. You can look up your serial number to date here: http://www.antiquecameras.net/petzvallens.html

Garrett

Garrett - thanks for the information. Based on the table at antiquecamera.net the lens without the iris was made around 1880 (yes, it does have notches in the rear bezel), and lens with the iris was made just after the turn of the 20th century. I did not know that they were over a hundred years old... both lenses are in great condition and produce a beautiful image on the ground glass.

[Jim Galli]

Pictures please. Unscrewing the front element doesn't make sense, nor would it change the lens softness. Dallmeyer over the years used different and increasingly sophisticated methods of accomplishing the same task of separating the 2 rear elements from each other. With the earliest lenses, you simply unscrewed them from each other. Simple, straight forward, but a pain in the butt to take the lens off the camera or the back off while your subject is twiddling their fingers waiting for the bone head photographer. The later lenses had you twist the front barrel which accomplished the same thing through some mechanical means but you did it from the front which was much faster. Often, especially on the later aluminum mounts, dissimilar metal corrosion can cause this function to have locked up forever. Not sure why one is 3.5 and one is f3. Anyone?

[Jay Decker]

Pictures please.

Here you go...

http://monkeytumble.com/tmp/P1010007.jpg

http://monkeytumble.com/tmp/P1010005.jpg

http://monkeytumble.com/tmp/P1010003.jpg

http://monkeytumble.com/tmp/P1010004.jpg

[Jim Galli]

That's what I thought. It means you grab the whole barrel and turn. The flange thread obviously has to be well seated so that it just doesn't break loose and unscrew from the flange. The part in the flange stays put and the entire barrel turns which brings the front lens of the rear 2 forward. If it's stuck, get some "rubber buffer" at the Auto Parts store and keep patiently working it with liberal application of the liquid. It dries with no residue and is harmless. Great for sticky shutter mechs too.

[Jay Decker]

Excellent information. Thank you gentlemen!

[PawelR]

Not sure why one is 3.5 and one is f3. Anyone?

I was digging a lot for answer to this question... Anyone? :)

[Steven Tribe]

Lenses are the same. But the presence of an iris with its blades inside the barrel means that the maximum aperture is less than in the WHS version which has a narrower stop framing system.

[PawelR]

Thank you Steven.

I have two dallmeyer 2b, same design, same dimensions of glasses but one is a little bit longer (focal length 222mm), second one is a little bit shorter (focal length 210mm). My point is the diameter of glasses was always the same but they change length of lens for change focal length for customer needs? So, shorter focal length is slighlty faster?

Please correct me Steven if i`m wrong.

[Steven Tribe]

I know the 3B has been described as both 11.5" and 12". I think it is the earliest models which are the shortest. Dallmeyer did not give focal lengths (efl or back focus) in early catalogues/adverts. My "knowledge" is just what I have read. All 4 3Bs I have played with were all 12". Perhaps the earlier 2B's were also slightly shorter?

[Steven Tribe]

Back to the OP's question!

A couple of years ago I discovered a complete set of lens cells for the "turn the barrel/iris" model of the Dallmeyer 3B. I made a new brass setting for this lens set, making a replacement WH slot instead of an iris. I have described this here - but what I didn't mention was the loaner (and eventually, purchaser) of this lens actually compared it with a standard 3B. He virtually accused me of witchcraft as the home assembled 3B was quite a lot faster than the ordinary 3B. I did try to explain it away with new balsam, but I realise now that it was just due to increased aperture possible due to the WHS system.

[PawelR]

My lenses:
3b is 300mm 121XX serial number
2b is 220mm 271XX serial number
2b is 210mm without cellar..

[goamules]

Here is what I believe accounts for slight variances in focal lengths of the same manufacturer's lenses. This probably applies up until the 1920s, when manufacturing became a lot more standarized, including the types of glass. There are actually two things going on here:

1. As is documented, lens makers had to test each new lot of glass that they got. They tested the glass' variation in refractive index, mainly. Each lens was then ground and optimized for several critical optical parameters, such as spherical aberration (sharpness), field curve, etc. They did NOT try to standardize the exact focal length to the fraction of an inch. Instead, they ensured each lens was as optically perfect as it could be, even if the focal length varied a few fractions of an inch. You will note some manufactures acknowledged this variation. Taylor, Taylor and Hobson for a period would engrave the exact focal length on the barrel like this one that is 10.65". If you bought another from them that month, it would be slightly different, and marked so. I'm sure this convinced TTH customers they were buying a precisely measured and build lens. Dallmeyer didn't worrry about it.

https://c1.staticflickr.com/1/763/23094263164_0c25bab841_b.jpg

The one thing that was standardizes was their brass barrels. So you don't get fluctuating barrel lengths, another way they could have possibly standardized the focal length. So they let the focal length fluctuate, and ensured the barrels were physically the same, and the quality of each lens was the same. These lenses were all hand made, matched, and optimized, each element for each lens.

2. The other thing is that during different periods, the lens designs and manufacturing were slightly updated. Again, the companies knew large format lenses were put on focusing body cameras. It didn't matter if what they called an 8" lens was actually 8.39" or 8.2" etc.

[goamules]

This brings up a very important consideration. These lenses were hand made, and hand fitted and optimized. They were not standardized in terms of swappable parts. Many times over the years I've heard people say "I have a XYZ petzval, missing the rear crown glass element....and need to find one..." I keep my mouth shut, but know that if they find a piece of glass that physically fits into the brass, they are NOT going to get the precision and quality that the original maker intended. Because each piece of glass was matched up, in each individual lens.

[Steven Tribe]

I agree with almost all of the foregoing. But I always thought (and still do!) that the two decimal points on early T,T&H represent the efl of all the lenses made for a particular format. Although The Lens VM doesn't actually say it, it does give two decimal point figures for a few of the early lenses, but mostly just refers to format sizes.

What especialy makes me think that same two decimal point figure appears on all lenses is the casket RR/WAR/RV set I have. The same barrel has all three efls engraved. RV is 8.72, RR is 7.28 and WAR is 4.12. I don't think T,T&H would manage to coordinate the measuring of 3 different efls and engrave them. The serial number is 5235 - a set for 1/2 plate

[goamules]

Here is how my hypothesis can be proven. If anyone has another 5x8 R.V. can tell us if it says exactly 10.65, like mine, or something different and specific to the lens, like I suppose. I sold another to Gandolfi, but can't remember what it was engraved with.

I just called a friend who has a casket set, and his WAR is engraved 5.44".
Yours WAR is 4.12 so those are fairly different lengths.

But here are two more casket sets, with these WARs listed:

WAR ser no. 3969 listed as 4.13" focal length
WAR ser no. 5802 listed as 4.11" focal length
http://www.earlyphotography.co.uk/site/entry_L24.html

I believe TTH engraved the exact FL of each lens. I rest my case!

[Steven Tribe]

Well done - and the variation is far more than I thought possible. So selection of paired lenses for stereo use must have been tricky!

My 1/2 plate set is simpler than the first set shown in earlyphotography, but is probably the same as the second one, not illustrated. It is also closer in serial number and with the other RR and WAR efls.

For future reference, the figures for these two no. 3 caskets for 1/2 plate from T,T & H are:

no. 5802. RR. 7.41" WAR. 4.11" RV. 8.68" (ex. from earlyphotography)
no. 5235. RR. 7.28". WAR. 4.12". RV. 8.72" (my own)

[Emil Schildt]

I sold another to Gandolfi, but can't remember what it was engraved with.



The one you sold me is 8x5 RV 10.56"

[goamules]

Thanks, that also helps.