Strange F-Stop Scale

[Thierry Schreiner]

Hi to all,

I just got my "new" Berthiot Stellor F3,5 F=360 No 6 Serie Ia.

It has a strange aperture scale, at least unknown to me, which goes as follows:

3.5 - 5 - 7 - 10 - 14 - 20 - 28.

I hope someone out there can help me to convert these into convenzional f-stops.

Thank you very much in advance and best regards form France.


Thierry Schreiner

[jetcode]

Hi to all,

I just got my "new" Berthiot Stellor F3,5 F=360 No 6 Serie Ia.

It has a strange aperture scale, at least unknown to me, which goes as follows:

3.5 - 5 - 7 - 10 - 14 - 20 - 28.

I hope someone out there can help me to convert these into convenzional f-stops.

Thank you very much in advance and best regards form France.


Thierry Schreiner

(your lens)
3.5 - 5 - 7 - 10 - 14 - 20 - 28.
(standard scale)
4 - 5.6 - 8 - 11 - 16 - 22 - 32

You have a lens that is about 1/4-1/6 stop more open than a standard aperature scale. I would use a standard scale, map it 1:1 to the scale on the lens, and know that you are opening up the lens a bit. Won't likely make much difference for exposing negative films.

[Ole Tjugen]

It's just 1/3 stop off. Many older French lenses are marked like that, just as many older German lenses are marked as 4.5 - 6.3 - 9 - 13 - 18 - 25 - 36.

Let's see... Does

- 4 - - 5.6 - - 8 - - 11 -- -- 16 -- -- 22 -- -- 32
3.5 - - 5 - - 7 - - 10 -- -- 14 -- -- 20 -- -- 28
- 4.5 - - 6.3 - - 9 -- -- 13 -- -- 18 -- -- 25

make sense?

[ic-racer]

Hi to all,

I just got my "new" Berthiot Stellor F3,5 F=360 No 6 Serie Ia.

It has a strange aperture scale, at least unknown to me, which goes as follows:

3.5 - 5 - 7 - 10 - 14 - 20 - 28.

I hope someone out there can help me to convert these into convenzional f-stops.

Thank you very much in advance and best regards form France.


Thierry Schreiner

To get the 'whole stops' multiply by 1.4, to get the 'half stop' series, multiply each by 1.185. I don't recall the multiplier for the 1/3 stop series but I suspect that is what is going on here. So, f7 is 1/3 more exposure than f8 and f14 is 1/3 more than f16 etc.

Here is a table also: http://www.riversidecardiology.com/fstop/f-stop.htm#4

[Thierry Schreiner]

Thank's a lot for sharing your knowledge, and for the speed of your responses.

Just good to know you're out there. Great.

Best regards to all of you

Thierry

[Jim Noel]

Regardless of the numerals engraved on the shutter, the openings are still one stop apart so it is easy enough to use them as is.

[domenico Foschi]

360 3.5...... I would love to own that lens.
Please let us know about performance, can you find it in any grocery store? :)