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Odd/Old shutter speeds and apertures
Old 11-30-2017   #1
seany65
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Odd/Old shutter speeds and apertures

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?
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Old 11-30-2017   #2
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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.
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Old 11-30-2017   #3
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f/6.3 is 1/3 stop less light than f/5.6 I think.

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Old 12-01-2017   #4
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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.
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Old 12-01-2017   #5
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Quote:
Originally Posted by seany65 View Post
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!
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...
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Old 12-01-2017   #6
Dwig
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Quote:
Originally Posted by seany65 View Post
...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.
Actually, it is more like 1-1/3 stop from 1/125.

Quote:
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?
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.
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Old 12-01-2017   #7
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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
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Old 12-01-2017   #8
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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.
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Old 12-02-2017   #9
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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?
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Old 12-02-2017   #10
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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!
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Old 12-02-2017   #11
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Quote:
Originally Posted by Dralowid View Post
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!


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.
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Old 12-02-2017   #12
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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.
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Old 12-03-2017   #13
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I found it interesting that these "oddball" f/stop ratios showed up on my modern mirrorless cameras.
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Old 12-03-2017   #14
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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

Last edited by David Hughes : 12-03-2017 at 03:26. Reason: Chart added.
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Old 12-03-2017   #15
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Quote:
Originally Posted by JoeV View Post
I found it interesting that these "oddball" f/stop ratios showed up on my modern mirrorless cameras.
I know some of them let you choose f-stop increments in 1/3 or 1/2.
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Old 12-03-2017   #16
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Quote:
Originally Posted by seany65 View Post
...
How far apart are 1/125 and 1/150?
...
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
As you can see using the 1/3 stop factor, the difference between 1/100th and 1/125th is 1/3 stop.
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Old 12-03-2017   #17
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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.
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Old 12-03-2017   #18
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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.
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Old 12-03-2017   #19
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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.
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Old 12-03-2017   #20
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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 :-).
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Old 12-03-2017   #21
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f value is just focal distance / aperture diameter. It used to be written as f/something, for instance f/8. The "f" being focal distance symbol in optics. In a 50 mm lens, f/8 would mean an aperture diameter of 50/8 = 6.25 mm

As said above each f stop is the previous one multpilied by square root of 2 (1.41 approx); so that succesive f-stops have one-half the area of the previous one, and therefore let half of the light pass through.

Current scale goes 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 and so on. The Germans started, I believe, from a famous 4.5 lens and built their scale from it. So, the 6.3 value belongs to the old German scale (4.5, 6.3, 9, 12...).

My old pre-war Summitar is marked in the German scale.
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Old 12-04-2017   #22
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Thanks to everyone for the further replies.
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Old 12-05-2017   #23
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I printed and laminated a small card with EV values of the weird and wonderful shutter/aperture combinations of the IIIb/Summar. Extract below (lose formatting on whole thing).

1 2 4 8 20
2 2.0 3.0 4.0 5.0 6.3
2.2 2.3 3.3 4.3 5.3 6.7
3.2 3.3 4.3 5.3 6.3 7.7


The calculation is... =(ROUND(3*(LOG($A2^2*B$1)/LOG(2)),0))/3
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Old 12-05-2017   #24
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A minor point, the letter "f" is the old hooked Latin version. So it goes ƒ/2 etc. Only I can't find one in Verdana but italics might look OK as f/2. A pity that we seem to have lost the "√" sign as well...

Regards, David
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Old 12-05-2017   #25
Richard G
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Quote:
Originally Posted by Dwig View Post
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
As you can see using the 1/3 stop factor, the difference between 1/100th and 1/125th is 1/3 stop.
Fortunately none of this is especially important, but I don’t agree with any of your calculations.

A half stop narrower is 50% less light rather than 100% so it is 2/3 of the area instead of 1/2. The f stop increment factor is therefore the square root of 1.5 (3/2) which is 1.22, not 1.4, which is the multiplication factor for a whole stop.

EDIT. And I’m swrong too. I shouldn’t have inverted it. A half stop wider is 50% more light but a half stop stopping down is 33% less, 2/3 of the area as above. Stopping down gives the figures above for the increase in f number. EDIT

The cube root of 2 never comes into any of this.
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Old 12-05-2017   #26
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Using the old APEX formulas

Ev = Av + Tv : (Ev at ISO 100)

Av = 2*log(base 2)N : (where N is the f/number)

Tv = log(base 2)D : (where D is the denominator of the shutter speed in seconds)
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Old 12-05-2017   #27
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I find, with the latitude of modern negative film, I just estimate when the aperture values fall between the usual f2.8, f4, f5.6 etc.

And the same with a recently serviced Leica Barnack, with 1/100th, 1,200th, etc shutter speeds.

When using old Kodak cameras like the Signet 35 or Medalist, even with a serviced camera, the odd higher shutter speeds are rather optimistic. My Signet 35 doesn't really reach 1/300th and my Medalist doesn't really reach 1/400th. So those need to be figured out by trial and error, or a good shutter speed tester, and then noted when figuring out exposure.

I thoroughly enjoy shooting the old cameras, they just need a little extra care.

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Old 12-06-2017   #28
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I suppose I'd better say "Thanks for the further replies" but it seems much of them have been translated to English from the original Chinese, by someone who only speaks/reads Icelandic, so I don't actually know if anyone's just insulted my grandmother or not.

@Richard G: "50% more light going 1/2 a stop wider, but 33% less light going 1/2 a stop down"?

So 1 stop wider is 100% more light and 1 stop narrower is 66% less light?

If you say "Nope, it's 100% less light" I'll officially bang my head against the wall.

@Timmyjoe: I also estimate where the aperture on the lens should be if the meter shows 'partway between marked values'.
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Old 04-01-2018   #29
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@David Hughes: I've been considering getting a Ferrania Elioflex 2 with apertures of f6.3, f9, f12.5 and f18, and I was going to ask about them, but I've just had another look at the aperture table you posted, and it has come in rather useful again. Thanks.

As I understand it, f6.3 is 2/3rds faster than f8, f9 is 2/3rds faster than f11, f12.5 is 2/3rds faster than f16 and f18 is 2/3rds faster than f22.

If that is correct, than perhaps both of my braincells may be edging towards a vague understanding of some photo theory.
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Old 04-01-2018   #30
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HI,

It's all part of the service.

You are spot on about 6.3 and 8 and so I guess you must be right about the rest of them.

For what it's worth, with cameras like that I use an elderly Weston meter that shows all the thirds for both speeds and aperture but you don't have to be that accurate as film has a fairly wide latitude. You can find it (the latitude range) by getting a DX decoder, which is nothing more than a lot of pictures of the squares and an explanation. They call it exposure tolerance btw.

There's one here:-

https://en.wikipedia.org/wiki/DX_encoding

Have fun, David

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Franz Stolze (1836-1910) & the first standard series of F-numbers
Old 04-01-2018   #31
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Franz Stolze (1836-1910) & the first standard series of F-numbers

Quote:
Originally Posted by seany65 View Post
@David Hughes: I've been considering getting a Ferrania Elioflex 2 with apertures of f6.3, f9, f12.5 and f18, and I was going to ask about them, but I've just had another look at the aperture table you posted, and it has come in rather useful again. Thanks.

As I understand it, f6.3 is 2/3rds faster than f8, f9 is 2/3rds faster than f11, f12.5 is 2/3rds faster than f16 and f18 is 2/3rds faster than f22.
I guess, it's easier if you forget the modern aperture numbering system for a moment.

Since about 1900 the major aperture numbering systems had in common, that full f-stops were a square root of 2 apart, and the F-number pattern was usually expressed with f/denominators, right?

And now, let's look at these figures:

10,000
7,071
5,000
3,535
2,500
1,767
1,250
883
625
441
312.5
220
156.25
110
78.125
55.24
39.0625

Confused?

Ok, *now* divide them by 100, and **now** you have the first standard series of F-numbers.

Hooray!

According to Rudolf Kingslake, it was the first standard series of F-numbers proposed by Franz Stolze (1836-1910), the same Stolze who was one of the fathers of photogrammetry.

As mentioned several times before, the square root of 2 does the trick. Why that? Because we have to think geometry, not arithmetics.
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Old 04-02-2018   #32
David Hughes
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Amazing how great minds think alike; here's the apertures as a percentage based on an f/1 lens being100%:-



FWIW it's a jpg.

I'm not sure if f/1.1 and f/1.6 are standard apertures but until I get an f/1 lens and stick it in a camera I'll manage somehow...

Regards, David.

PS I had the idea at well past midnight last night but did nothing until this morning. For once the time zones didn't work my way...
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Old 04-02-2018   #33
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Quote:
Originally Posted by David Hughes View Post
Amazing how great minds think alike; here's the apertures as a percentage based on an f/1 lens being100%:-

I like that, David

Here my thoughts --



-- admittedly, I cannot prove it, but I have the*very* strong impression that Archer and Adams weren't actually inventing their *zone system* at all, they've just very verbosely *recycled* the concise Stolze number system at a point of time when it started becoming *obsolete* (I know you like this adjective! ).
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Old 04-02-2018   #34
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Yes, and of course these days, thanks to the internet, the more you look the less you know; or perhaps the less certain you are...

F'instance, I know what a muffin is but the supermarkets are busy undermining me as we type and so on and so forth.

Regards, David
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Old 04-04-2018   #35
seany65
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David, Thanks for the link to the dx decoder page. I only use print film so film latitude is not too important to me, although I prefer to not use latitude at all by trying to give as near to the 'correct' exposure as possible. Just call it 'over-fussy' or 'silly pedantic-ness' or something.

That's even though I know there's no real point at trying to be so 'accurate' because film has latitude.
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Old 04-04-2018   #36
David Hughes
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David, Thanks for the link to the dx decoder page. I only use print film so film latitude is not too important to me, although I prefer to not use latitude at all by trying to give as near to the 'correct' exposure as possible. Just call it 'over-fussy' or 'silly pedantic-ness' or something.

That's even though I know there's no real point at trying to be so 'accurate' because film has latitude.
What baffles me is that I've only ever seen one camera with all 12 DX contacts; it was a Minolta Dynax 7000i and one camera (some Yashica MF???) had just one DX contact...

Theory and practice I suppose.

And I noticed years ago that bracketing and then giving the film to most labs produces three 99% identical prints and you have to look at the negative to see which was right, if that word can be used about exposure; I've my doubts at times.

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Old 04-05-2018   #37
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Life was a lot simpler years ago...





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Old 04-05-2018   #38
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What baffles me is that I've only ever seen one camera with all 12 DX contacts; it was a Minolta Dynax 7000i and one camera (some Yashica MF???) had just one DX contact...

Theory and practice I suppose.
...
There were a number of cameras that had only one DX contact. These were all P&S models that were targeted at "snapshooters". They only supported 2 ISOs, 100 and 400. The contacts would read the 400 patch. If blank (naked metal), the camera set ISO 400 and if not it set 100. With anything faster than 400 it would set 400. With anything slower it would set 100. The target user would be a color negative shooter. At the time the films had massive latitude and were only sold as ISO 100, 200, 400, 1600. All color negative films sold at the time would work adequately.
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Old 04-05-2018   #39
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Thanks, the one I saw was a Yashica MF-2 Super; vintage 1986-ish. It baffled me at the time.

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Old 04-06-2018   #40
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In addition to some more conventional shutter speeds, my Leica IIIf has some closely spaced (slower) shutter speeds:
1, 1/2, 1/4, 1/10, 1/15, 1/20, 1/30, 1/40...

This to go along with an Elmar with the earlier aperture scale of f/3.5, f/4.5, f/6.3, f/9, f/12.5 and f/18.

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