Old Lens Question- Old F/Stop Markings?

[Nokton48]

Hi All,

I have a Plaubel Makina wide-angle lens (a 7.5cm Orthar) that has a funny progression of F/stops marked on the barrel

6.8 9 12 18 25

I guessing this is an older system of marking the iris.
Are there equivalent F/stops? I'd like to start using this lens.

Incidentially, this one appears to be quite sharp to my eye.
I've heard from others that it's quite sharp when enlarged.

2016-07-26 13.12.00 by Nokton48, on Flickr

 

[giganova]

What do you mean by "equivalent F/stops"? It's a linear, continuous scale. So f/8 is right in the middle between your 6.8 and 9 marks.

 

[tunalegs]

Those are f/stops. They're just not the numbers you're used to. It's not like the Uniform System or other non f/stop systems, if that's what you're concerned about. On old lenses it was not unusual for the progression of numbers to be determined by the maximum aperture, so you get "weird" f/stop values.

 

[Nokton48]

OK Cool. Yes that was my concern, that it was a non-f/stop system.
Funny I haven't come across this before. Most of my LF lenses are 50's-60's ish

 

[tunalegs]

OK Cool. Yes that was my concern, that it was a non-f/stop system.
Funny I haven't come across this before. Most of my LF lenses are 50's-60's ish

You usually only see these odd progressions on prewar lenses. I think I've only got one postwar lens in my collection with a non-standard progression.

 

[Nokton48]

Good info. Thanks!

 

[Dwig]

Hi All,

I have a Plaubel Makina wide-angle lens (a 7.5cm Orthar) that has a funny progression of F/stops marked on the barrel

6.8 9 12 18 25
...

As others have noted, these are standard f/stops. This "odd" progression was actually very common prior to WWII and lasted for a little while afterwards. The 1-stop progression is:
4.5 - 6.3 - 9 - 12 - 18 - 25

This "old style" progression uses marked f/stops that are 1/3 stop smaller than the modern convention of 4 - 5.6 - 8 - 11 - 16 - 22 ... . The 1/3 stop progression in round numbers would be 6.3 - 7 - 8 - 9 ... . Start with 1.0 and multiply it by the sixth root of 2 and then multiply the result by the sixth root of 2 again over and over to get a 1/3 stop progression starting from f/1.0.

 

[David Hughes]

Hi,

Now you just need an old meter to show these f/stops and so on...

Regards, David

PS On more modern meters the in between stops are sometimes marked by lines, like rulers show ½, ¼, ⅛ etc.

PPS FWIW, both have been checked and the Weston was re-balanced and the Leica meter was fitted with a new cell.

 

[Roger Hicks]

The next largest modern-type stop will be 1/3 stop faster than the marked stop, i.e.

f/25 is 1/3 stop slower than f/22 (or f/22 is 1/3 stop faster than f/25)

f/18 is 1/3 stop slower than f/16 (or f/16 is 1/3 stop faster than f/18)

f/12 (or f/12,3, or f/12.5) is 1/3 stop slower than f/11 (or f/11 is 1/3 stop faster than f/12)

f/9 is 1/3 stop slower than f/8 (or f/8 is 1/3 stop faster than f/9)

f/6.3 is 1/3 stop slower than f/5.6 (or f/5.6 is 1/3 stop faster than f/6.3)

f/4.5 is 1/3 stop slower than f/4 (or f/4 is 1/3 stop faster than f/4.5)

f/3.2 is 1/3 stop slower than f/2.8 (or f/2.8 is 1/3 stop faster than f/3.2)

f/2.2 is 1/3 stop slower than f/2 (or f/2 is 1/3 stop faster than f/2.2)

As with many lenses, the maximum aperture doesn't necessarily fall on the whole-stop scale of either the modern scale (1 - 1,4 - 2 - 2.8 etc) or the old "continental" scale as on your lens . I have or have encountered lenses with such maximum apertures as f/1.5, f/1.7, f/1.8, f/1.9, f/2.3, f/2.5, f/2.9, f/3, f/3.5, f/4.2, f/4.8, f/5, f/5.8, f/7.7 and f/9.

Also (a) many aperture numbers are roundings, cf. f/12-12,3-12,5 and (b) they aren't always that accurate anyway, so you might find that the speed of two lenses with the same marked aperture is not quite the same. This is one reason for T/stops, which deal with transmission, not theoretical aperture.

Cheers,

R.

 

[Robert Lai]

The easiest solution are the Weston meters. They have these now intermediate f/stops directly on the dial.

 

[Nokton48]

Thanks everyone for your responses. All is sorted now.
Looking forward to more lens testing up ahead. 🙂
There is a learning curve with this funky fiddly old gear;
I enjoy figuring out how to use it properly.

 

[David Hughes]

Hi,

It's worse than Roger says as not all are rounded properly but are made to "run" in a logical sequence.

f/8 is f/8 but

f/11 is really f/11.3137084990 which rounds down to f/11 and

f/8 is f/8 but

f/22 is really f/22.6274169980 which rounds up to f/23 in my little world and so on.

The now standard series is actually the square roots of the series 1, 2, 4, 8, 16, 32 and so on, which ought to be obvious...

Regards, David

PS To compare off the scale values, of course, you square the number first.

 

[Richard G]

Note the progression. Each f stop is a number which is double the previous f stop but one, indicating a halving and halving again of the area: f4.5, 9, 18. From each of those just halving the area is 6.3, 12, 25, where that progression is also a doubling, roughly, of the f number progressively.

 

[Dwig]

...
The now standard series is actually the square roots of the series 1, 2, 4, 8, 16, 32 and so on, which ought to be obvious...
...

it is to those that know that the effect of the aperture opening is a result of its area and we've chose to mark the aperture opening using the diameter. That is, the diameter of an equivalent area true circle in the case of apertures controlled by irises generating slight different shapes. If you know the formula for the area of a circle you realize how the area change is related to the diameter.

If the progression bothers you then blame Pythagoras and his chums.😀

 

[David Hughes]

... If the progression bothers you then blame Pythagoras and his chums.😀

Hi,

I think he was as upset by them as any other Greek, as they called them irrational numbers. It's a good thing the Sumerians etc had done the ground work for them and knew of "his" theorem a lot earlier (say 1800BC). Although I often wonder who should have got the credit for it.

BTW, I just saw the f stops as a logical numerical sequence, 1.4 and so on being a dead give away. Sorry, didn't mean to get that serious ;-)

Regards, David

 

[Spavinaw]

There was a 200 pound squaw seated on a hippopotamus hide, a 100 pound squaw seated on a deer hide, and another 100 pound squaw seated on a bear hide which conclusively shows that the squaw on the hippopotamus was equal to the sum of the squaws on the other two hides. My hunble appologies to Pythagoras.

 

[Nokton48]

I also have this ancient Depth of Focus Table made by Plaubel for the Makinas. The four principal lenses are listed, along with hyperfocal lens settings. Everything in Meters and using the old-style lens f/markings. So a very handy thing to have (say with the 73mm Orthar which can be easily scale-focused on the later Makinas).

2016-07-30 11.59.29 by Nokton48, on Flickr

 

[Muggins]

May I just mention what a beautiful thing that Weston Leicameter is!

Adrian

 

[David Hughes]

Hi,

And very easy to use now it's been sorted out. I like to have the right outfit in use and it goes with all the old Barnacks.

Regards, David

PS And the older stuff is great fun to use; obviously I'm not a serious photographer...

 

[graywolf]

Actually there were at one time 3 different f-stop scales: American, British, & French. But they were all f-stops the starting point was different.

Before that there were several different aperture systems, none of which were base on f-stops. You really have to do your research to figure those out. However, most of those date from before the 1920's.

Any meter that reads in 1/3 stops can be easily used with any of the f-stop systems. Except the early Westons, which used a different index than ASA/ISO. However they worked OK for B&W. For slides you had to convert your ASA rating to Weston ratings.

There was a time when you really had to be knowledgable to be a photographer. Now you don't even need a camera just a smart phone.