HERMAGIS 440mm Aplanat No.4 Series II - and iris as f numbers - little help

[fotoresearch]

Welcome everyone,

I just became the owner of this lens: HERMAGIS 440mm Aplanat No.4 Series II. // Serial number: 36070 //

I have only one problem with it, on the lens iris - instead of the aperture markings I have the number markings

1
2
4
8
16
32
64

What aperture corresponds to these numbers?

It is difficult for me to determine whether I should use the US or French measure
How can you check it?

Someone told me that the initial f value of my lens should be: focal lenght divided by the diameter.
In my case it will be: 440mm / 60mm (about) = 7,33
So should I assume that my lens start from f/8 and this is French system?

Best
Lukasz

[Two23]

I'm going to assume that 1 means fully open, 2 means half as much light, 4 means a fourth as much light.......


Kent in SD

[pgk]

Might be worth looking at: http://www.earlyphotography.co.uk/si...diaphragm.html

[fotoresearch]

Thank you for your answer.
The material is interesting, it didn't give me an answer in 100% - straightforward, but at least I know in which direction I'm going.
I will have to do some tests - I'm lucky that I have cheap mammography films - financially, the tests won't hurt.

[fotoresearch]

When I was looking for answers on the web, it was not explicitly stated where it meant ... so I will have to test

[Andrew Plume]

Hi

".....focal lenght divided by the diameter......." of the width of the lens element/glass is exactly what I would be doing

good luck and regards

Andrew

[Ari]

I had the same query years back. All I remember was someone telling me "f/16 is f/16".
I guess what he meant was that f/16 is the same in the US or standard system. The other stops you'll have to figure out.

[fotoresearch]

Somewhere on the net I found this representation of value.

Iris No | f value
1 = f/10
2 = f/14
4 = f/20
8 = f/28
16 = f/40
32 = f/56
64 = f/81

At the beginning I thought that my initial value of f is 8, .... but during the test on f / 9, and saw that the picture is underexposed.
So it may turn out that the following values will match.

Tomorrow tests for each aperture value.

[quickeye]

I found this on the internet some time ago and use it with my Hermagis lens.

[lungovw]

It is not that difficult to measure them: https://apenasimagens.com/en/measuring-lens-aperture/