help needed: Steinheil lens

[Emil Schildt]

I have been looking at a lens for my biggest camera...

I found a Steinheil 27 Lin Aplanat that looks fine.

I wrote the seller to ask, whether the 27 meant 27" focal length, and got a "yes it is", but I am in doubt.

Anyone have a good guess? Or more knowlegde than me in this area............

a 27" would be perfect for my use...

look at the images.

thanks

[eddie]

How big is it? That will give a pretty good indication if if is 27 inch.

[Emil Schildt]

How big is it? That will give a pretty good indication if if is 27 inch.

dunno - I must write the seller again...

[Steven Tribe]

Well Steinheil invented the Aplanat (Dallmeyer was no.2) so you can't go wrong.
This has still it's original flange with indentifying numbers. I seem (will check!) to recall that the 27 refers to the iris width in mm rather than inches, though.

[Emil Schildt]

Well Steinheil invented the Aplanat (Dallmeyer was no.2) so you can't go wrong.
This has still it's original flange with indentifying numbers. I seem (will check!) to recall that the 27 refers to the iris width in mm rather than inches, though.

thanks - but 27mm iris - that's small (?)...

I wrote the seller about physical mesurements.

[Steven Tribe]

VM says Aplanat Lin 11 has a focal length of around 6".
Could this be 11cm efl? "Yours" being 27cm?

Alternatively, following the iris size and VM data:

If Lin 11 is 150mm, then Lin 27 will be around 270mm?

[Emil Schildt]

sounds right, but then again: if Lin 11 is approx 6", then Lin 27 definitively isnt 27".....

[CCHarrison]

I learned the answer to this many years ago when I came across a tiny Steinheil Aplanat of just 7 LIN...

Here is the answer according to a Steinheil catalogue:

""The openings are exceptionally stated here in lines (of Paris) [labeled LIN on the lenses], since aplanats were made and named according to these units and because these names are still used by the public."

LIN was the lines of measurement of the opening (aperture) to a lens.... An inch of Paris = 27mm and there were 12 lines in an inch, i.e. a line was 2.25mm

So, a 27 LIN lens has an aperture of 27 LIN times 2.25mm per LIN = 60.75mm take that and divide by 25.4 mm per imperial inch and that equals = 2.40 imperial inches for the max aperture.

If the lens is a max aperure of f/8 which most olde Aplanat's do, then by math, the focal lenght is about 19.2 inches in focal length.

That was easy....


Dan

[Steven Tribe]

Imperial inch is 25.4mm.
If I understand you right Dan, then Emil's Lin 27 is 27 lin - which is 270 lines equivalent to 23.7".
Going back to VM's example. 11 lin is 110 lines, which, (110/12) is 9.16 parisian inches. 9.16 x 27/25.4 which is just over 9.7 inches? Which is quite a lot more than their guestimate of 6"?

[CCHarrison]

Steven, you need to follow the math above: 27 LIN max aperture translates to ~19.2 inch focal length

VM: 11 LIN x 2.25mm Paris lines = 24.75mm aperture opening. If f/8 lens, than focal length is 7.8 inches focal length.

Because the Aplanat's are generally f/8 lenses, a quick and dirty math trick is to just take the lenses LIN number and multiply it by .70 to get the rough focal length.

For example, 27 LIN x .70 = 18.9 inches....close to the actual of 19.2 inches
For example, 11 LIN x .70 = 7.7 inches....close to the actual of 7.8 inches

Best
Dan