seany65
Well-known
I thought it would be a good idea to start a thread about those odd/old shutter speeds and apertures that are on many old cameras. The main reason being that I recently bought a Welta Perle 6x9 from 1932-1936 and it's widest aperture is f6.3. Nothing too odd about that, but I was wondering:
Exactly where does f6.3 fit in between f5.6 and f8?
I presume some members will tell me with modern film it won't matter too much if I put the aperture slider too far towards f8, but that isn't really the point for me. I'm just curious.
I suppose f7.7 is so near f8 as to be more or less the same as f8?
I've also been thinking about shutter speeds. What started me off was thinking about what it says in a manual for an agfa super silette, about 1/300 being 1 1/2 stops from /125.
I realise that if wanted to use 1/300 I'd have to open the aperture by 1/2 an f-stop if I was 'bracketing' in one stop steps from 1/125 at f8.
But what about those cameras with 1/25, 1/50, 1/100 and a top speed of 1/150, or 1/175?
I've even seen cameras that go 1/25, 1/50, 1/100 and 1/125!
What's the point of such a small change and what are we supposed to do with the aperture if going from 1/100 to 1/125?
Exactly where does f6.3 fit in between f5.6 and f8?
I presume some members will tell me with modern film it won't matter too much if I put the aperture slider too far towards f8, but that isn't really the point for me. I'm just curious.
I suppose f7.7 is so near f8 as to be more or less the same as f8?
I've also been thinking about shutter speeds. What started me off was thinking about what it says in a manual for an agfa super silette, about 1/300 being 1 1/2 stops from /125.
I realise that if wanted to use 1/300 I'd have to open the aperture by 1/2 an f-stop if I was 'bracketing' in one stop steps from 1/125 at f8.
But what about those cameras with 1/25, 1/50, 1/100 and a top speed of 1/150, or 1/175?
I've even seen cameras that go 1/25, 1/50, 1/100 and 1/125!
What's the point of such a small change and what are we supposed to do with the aperture if going from 1/100 to 1/125?
lynnb
Veteran
Most films have enough latitude where half a stop isn't going to make an appreciable difference. If in doubt, overexpose. You could always look at a light meter scale to work out what intermediate equivalents to use for those "non-standard" shutter speeds and f-stops.
Transparency film is the only exception, where correct exposure really matters. If in doubt use a light meter and read between the scale markings.
Transparency film is the only exception, where correct exposure really matters. If in doubt use a light meter and read between the scale markings.
rbiemer
Unabashed Amateur
f/6.3 is 1/3 stop less light than f/5.6 I think.
Rob
Rob
mbisc
Silver Halide User
The maximum aperture is a simple mathematical formula (diameter of the opening vs. focal length), and given that most old lenses were in off-the-shelf leaf shutters (with a fixed "hole" size), it created some "unusual" maximum apertures -- with "unusual" I mean from the "new-ish" perspective of focal plane shutters where such considerations no longer matter.
css9450
Veteran
Imagine figuring "Sunny 16" with a fast film such as ASA 400... 1/100th at f32? Most of my vintage lenses don't stop down that far...
Dwig
Well-known
Actually, it is more like 1-1/3 stop from 1/125.
Usually, the shutter speeds will fit into one of the several conventional progressions, but the top speed is often whatever the shutter can deliver and doesn't fit any conventional progression. Not all of the old conventions followed purely geometric progressions.
f/stops also follow similar "rules". There were two common progressions that are almost always in 1/stop increments. The modern convention can be though of as starting at f/1 and the old convention uses 1 stop increments that are all 1/3 stop slower than the modern convention. In all cases the lens' maximum aperture it whatever it is and often doesn't fit any conventional progression.
f/stops are easy to deal with if you have the chops to deal with the math. They are a function of the area of the aperture, though marked based on the diameter. Remember, Area = Pi * Radius squares (yeah, yeah - Pie are rouund, cornbread are square...) and radius is 1/2 diameter. Also, "f/stop" is fraction notation and can be expressed in ratio notation; f/8 is the same as 1:8 and means the opening diameter is equal to the focal length divided by 8. The "f" is the standard letter meaning "focal length" is should always be lower case, never "F/stop" or the horrid "Fstop".
If you want to generate a table of f/stops you just need a good calculator. To get 1 stop increments you need to calculate the square root of 2 (1 stop is 1/2 or 2x the light and that the radius is squared). Multiply this by whatever starting number you want, "1" is the modern convention, and then multiply the result by the square root of 2 to get the next increment. to get 1/3 stop increments, use the sixth root of 2.
David Hughes
David Hughes
Hi,
Take the sequence that runs 20 40 80 160 and so on; it doubles each time.
Now look at the square roots of the sequence and you get:-
4.5 6.3 8.9 12.6 and so on; I hope everyone can see that makes f/4.5 then f/6.3 then f/9 and so on.
Our normal run of apertures start with the sequence 1, 2, 4, 8, 16 etc and give f/1 and f/1.4 and f/2 etc.
And the other sequence is based on 3, 6, 12, 24, 48 and so on and that gives f/1.8 and f/2.5 and f/3.5 and so on.
Only they don't all run logically. Some get rounded up or down to fit in the space available and others just seem odd to me. Anyway, it used to be called numbers theory but I expect I'm showing my age...
Regards, David
Take the sequence that runs 20 40 80 160 and so on; it doubles each time.
Now look at the square roots of the sequence and you get:-
4.5 6.3 8.9 12.6 and so on; I hope everyone can see that makes f/4.5 then f/6.3 then f/9 and so on.
Our normal run of apertures start with the sequence 1, 2, 4, 8, 16 etc and give f/1 and f/1.4 and f/2 etc.
And the other sequence is based on 3, 6, 12, 24, 48 and so on and that gives f/1.8 and f/2.5 and f/3.5 and so on.
Only they don't all run logically. Some get rounded up or down to fit in the space available and others just seem odd to me. Anyway, it used to be called numbers theory but I expect I'm showing my age...
Regards, David
Spavinaw
Well-known
One of the several different lens available on the Kodak Tourist was f/8.8. I don't know of any other camera with an f/8.8 lens. Wonder where they got that.
seany65
Well-known
Thanks to everyone for the replies and the detailed info.
@Lynnb: I understand about print film lattitude, and I use lightmeters, but I still use half steps on lenses that have that facility. I even use "just a bit past that f-stop or a little bit short of this f-stop" on my Jupiter 8. I suppose it's a bit pointless trying to be so precise but I think I find it a challenge to try not to rely on film lattitude.
@rbiemer: Thanks, that's exactly the sort of info I was hoping for. If my meter says f5.6 it won't matter much if I just use f6.3.
@Dwig: Thanks for the suggestion of making an fstop table, but the other apertures on that camera are the more modern f8, f11 up to f32. I just wondered how close to f5.6 the camera was starting at.
I understand the idea that the focal length divided by the biggest aperture size gives the maximum fNo. eg. a 50mm f2 lens will have a maximum aperture of 25mm.
Out of curiosity, how far apart are 1/100 and 1/125?
How far apart are 1/125 and 1/150?
How far apart are 1/125 and 1/200 and 1/200 and 1/250?
Is 1/175 half-way between 1/125 and 1/250?
@Lynnb: I understand about print film lattitude, and I use lightmeters, but I still use half steps on lenses that have that facility. I even use "just a bit past that f-stop or a little bit short of this f-stop" on my Jupiter 8. I suppose it's a bit pointless trying to be so precise but I think I find it a challenge to try not to rely on film lattitude.
@rbiemer: Thanks, that's exactly the sort of info I was hoping for. If my meter says f5.6 it won't matter much if I just use f6.3.
@Dwig: Thanks for the suggestion of making an fstop table, but the other apertures on that camera are the more modern f8, f11 up to f32. I just wondered how close to f5.6 the camera was starting at.
I understand the idea that the focal length divided by the biggest aperture size gives the maximum fNo. eg. a 50mm f2 lens will have a maximum aperture of 25mm.
Out of curiosity, how far apart are 1/100 and 1/125?
How far apart are 1/125 and 1/150?
How far apart are 1/125 and 1/200 and 1/200 and 1/250?
Is 1/175 half-way between 1/125 and 1/250?
Dralowid
Michael
In my experience it doesn't really matter. Many of the the old settings are roughly half way between the 'modern' ones so things even themselves out. If you really want to nail it find an old Weston light meter, they have all sorts of markings on them!
peterm1
Veteran
Yes I agree but in any event it is only really an issue when using a hand held meter and I needed to know what shutter speed to set on the camera. When shooting on film using an older lens with these aperture settings I just used the nearest equivalent setting and kept on shooting.
Richard G
Veteran
The progression 4, 5.6, 8, 11, 16 etc increments by a multiple of 1.4, the square root of 2, doubling the light with each stop opened.
The progression 4.5, 6.3, 9, 12.5, 18 etc is the same.
The difference between the two scales is a multiplication factor of 1.125 for the f stop, which is 1.27 increase in aperture area for each opening of the diaphragm, such 6.3 to 5.6 and so is close to a 1/3 stop but less than that.
With colour negative film one could just consider 4.5 is 4, 6.3 is 5.6, 9 is 8, 12.5 is 11 etc
With slides it might be better to do the opposite: 4.5 is 5.6 etc, but maybe not bother.
My Gossen meter gives one decimal place to the f stop e.g. f f4.8 which is close to 5.6. Despite what you read about meters and slide films, I have happily and successfully exposed Kodachrome in the past with just the sunny 16-like instructions from the box end. Guesses for evening worked too, but not so well indoors which I did from tables in the month I had no meter one holiday.
The progression 4.5, 6.3, 9, 12.5, 18 etc is the same.
The difference between the two scales is a multiplication factor of 1.125 for the f stop, which is 1.27 increase in aperture area for each opening of the diaphragm, such 6.3 to 5.6 and so is close to a 1/3 stop but less than that.
With colour negative film one could just consider 4.5 is 4, 6.3 is 5.6, 9 is 8, 12.5 is 11 etc
With slides it might be better to do the opposite: 4.5 is 5.6 etc, but maybe not bother.
My Gossen meter gives one decimal place to the f stop e.g. f f4.8 which is close to 5.6. Despite what you read about meters and slide films, I have happily and successfully exposed Kodachrome in the past with just the sunny 16-like instructions from the box end. Guesses for evening worked too, but not so well indoors which I did from tables in the month I had no meter one holiday.
JoeV
Thin Air, Bright Sun
I found it interesting that these "oddball" f/stop ratios showed up on my modern mirrorless cameras.
David Hughes
David Hughes
The modern range of f/1 then f/1.4 then f/2 and so on often has half stops on old film cameras (as click stops) and often one thirds on more modern ones where the camera sets the aperture in auto mode.
And the old aperture ranges correspond to halves and thirds.
As others have said, the film latitude, covers up a multitude of exposure sins and I'll add that I think the widest aperture on a lens - with a few exceptions that we all know - is designed to look good and give screen brightness in SLR's. Hence the advice to stop down always.
It's a bit like offering something on ebay at 4.99 instead of a fiver...
And then I remembered doing this on the spreadsheet a while ago:-
NB They run in thirds of a stop.
Regards, David
And the old aperture ranges correspond to halves and thirds.
As others have said, the film latitude, covers up a multitude of exposure sins and I'll add that I think the widest aperture on a lens - with a few exceptions that we all know - is designed to look good and give screen brightness in SLR's. Hence the advice to stop down always.
It's a bit like offering something on ebay at 4.99 instead of a fiver...
And then I remembered doing this on the spreadsheet a while ago:-
NB They run in thirds of a stop.
Regards, David
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dmr
Registered Abuser
I know some of them let you choose f-stop increments in 1/3 or 1/2.
Dwig
Well-known
Preface: one, all of these numbers get rounded off to neat values as excessively high precision is pointless. Two, the standard is to measure and label ISOs rounded to the nearest 1/3 stop increments, hence common f/stop and shutter speeds are usually in 1/3 stop increments.
To generate a table of shutter speeds choose a starting point (e.g. 1 sec) and multiply it by a fixed factor and then multiply the result by that factor and so for. The factors to use are:
- for 1 stop increments: 2, since 1 stop is either double or 1/2 the light.
- for 1/2 stop increments: square root of 2 ~= 1.4
- for 1/3 stop increments: cube root of 2 ~= 1.26
retinax
Well-known
What makes worrying about the differences and distances between these values even less necessary, apart from theoretical interest which I totally understand, but that has been covered by Dwig in post 6, is that most older shutters aren't so accurate. For third stops on the scale to matter, one would have know how long exactly one's exposure is, and that may easily be off a third stop to either side. And then we don't even typically know the transmission rates of our lenses.
giganova
Well-known
My Mamiya RZ67 has a maximum shutter speed of 1/400 sec. I guess that's about half way between 1/250 and 1/500, but for practical purposes, I treat 1/400 sec like 1/500 sec.
presspass
filmshooter
Some Sekonic meters can be set to show the older lens f stops and shutter speeds. They are added to the conventional ones, so the meters can be used for newer and older cameras. I have an incident meter and a combined incident/spot meter that I have set to do this.
citizen99
Well-known
The historical reasons why shutter speeds are marked the way that they are have been comprehensively covered by previous postings.
For practical use of my leaf-shutters I like to know what the actual opening durations are, so I got myself one of the photocell jobbies that plug into the computer sound card and am gradually working my way through the collection.
This refers to a collection of cameras that are at least 50 years old, and includes shutters by AGC (Prontor etc ...), Compur, Epsilon, Kodak, Agilux.
Even after servicing I have not yet come across any where the 'fast' speeds, say~1/200 nominal and faster, are anywhere near as fast as indicated. This included a Synchro-Compur, never fitted to a camera, in its original packaging. A full stop error is not unusual.
I record the results on a spreadsheet and print them on to a slip of paper to keep with the camera Then I have a good starting point for exploitation of the film exposure tolerance
.
For practical use of my leaf-shutters I like to know what the actual opening durations are, so I got myself one of the photocell jobbies that plug into the computer sound card and am gradually working my way through the collection.
This refers to a collection of cameras that are at least 50 years old, and includes shutters by AGC (Prontor etc ...), Compur, Epsilon, Kodak, Agilux.
Even after servicing I have not yet come across any where the 'fast' speeds, say~1/200 nominal and faster, are anywhere near as fast as indicated. This included a Synchro-Compur, never fitted to a camera, in its original packaging. A full stop error is not unusual.
I record the results on a spreadsheet and print them on to a slip of paper to keep with the camera Then I have a good starting point for exploitation of the film exposure tolerance
.