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...

[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.