35mm Film — Negative Format Oddities…

[radi(c)al_cam]

No question, I'm aware, since some 90 years the «standard» format or more recently «full frame» is 24mm x 36mm. The diagonale of that format is an odd 43,266615305… mm.

Of course we have (or have had) «single frame» or «half frame», 18mm x 24mm, or the other way round 24mm x 18mm — having exactly 30mm of diagonale, and hence a 30mm standard lens.

Then we have 24mm x 24mm (e.g.: Robot, Tenax, …), diagonale 33,94112549… mm (so the standard lens should have been a 34mm one can guess).

Early Minolta (Nikon too?) RFs had 24mm x 32mm, I guess; the diagonale of that format is exactly 40mm.

My question is:

When we insist, that for a «full frame» 50mm is the standard lens, and the focal length in question is derived from the negative format's diagonale, why did I never hear from that format:

24mm x 44mm ? (or more exactly 24mm x 43,863424398… mm 😉)

 

[grouchos_tash]

I heard that it was just happened to be the lens that Oskar Barnack had lying around to stick on his prototype miniature camera.

 

[Bille]

When we insist, that for a «full frame» 50mm is the standard lens, and the focal length in question is derived from the negative format's diagonale

Well, is it? I When using an SLR a 50mm lens will give about the same magnifaction of the scene as the human eye. You can confirm this with both eyes open. Does this have to do with the dimensions of the negative? I dont think so.

 

[johnf04]

I like a 58mm standard lens, like the Helios 58mm f2.

 

[radi(c)al_cam]

Well, is it? I When using an SLR a 50mm lens will give about the same magnifaction of the scene as the human eye. You can confirm this with both eyes open. Does this have to do with the dimensions of the negative? I dont think so.

No, that's an illusion. Don't underestimate the human brain when it combines the two pictures — it can compensate at least +/- 1 dioptre.

 

[radi(c)al_cam]

I like a 58mm standard lens, like the Helios 58mm f2.

So do I — regarding SLRs, my favourite standard lens is a 58mm Rokkor 😀

But that doesn't have to do with the «ideal» negative format 😉

 

[Bille]

No, that's an illusion. Don't underestimate the human brain when it combines the two pictures — it can compensate at least +/- 1 dioptre.

Wrong. Try it yourself and compare with wider and longer lenses. If you are still having "illusions" maybe consult a professional...

 

[radi(c)al_cam]

Wrong. Try it yourself and compare with wider and longer lenses. If you are still having "illusions" maybe consult a professional...

I did, even with several cameras. And: Each camera model had a slightly different magnification — let alone when one changes the particular finders, it's again different 😉

 

[waileong]

Some say 50mm was chosen to allow some looseness in framing as 100% viewfinder slr's hadn't been invented yet. But does it really matter why 50 mm was chosen.

 

[sevo]

Well, is it? I When using an SLR a 50mm lens will give about the same magnifaction of the scene as the human eye. You can confirm this with both eyes open. Does this have to do with the dimensions of the negative? I dont think so.

No. It has everything to do with the magnification of the viewfinder - the entire 35mm SLR viewfinder system traditionally was tuned to have a roughly 1:1 magnification at 50mm. But at that, it is arbitrary and merely a matter of convenience with the focal length that was most common (but my no means physiologically "normal") when SLRs grew popular. With the "normal lens" being replaced by zooms by the 1980s, it was sometimes abandoned for a higher eye point.

 

[E.M]

So Alexander , you went to a professional with several cameras , wat was his answer ?

 

[David Hughes]

Hi,

Can't say I've ever seen a 43mm lens.

My guess is that 2 inches or 50 - ish mm was a standard lens size and one was picked up. Perhaps used in the eyepiece of a Leitz microscope and the lens barrel from the same source as they (microscope eyepieces) could be moved up and down to vary the magnification slightly.

I doubt if Barnack did anything more complicated as what did he have to go on? The diagonal was used for some formats but he obviously didn't use it. Or perhaps one of the other 35mm camera makers did. Also he worked for Zeiss and could have had an easy source there...

As for 50mm being normal, that was traced to a magazine article in the 30's and, if I could remember where I posted it, I'd tell you where to find it.

Regards, David

 

[sevo]

No question, I'm aware, since some 90 years the «standard» format or more recently «full frame» is 24mm x 36mm. The diagonale of that format is an odd 43,266615305… mm.

It is twice the Pathe/Edison 18x24 frame - as such, a artefact of using cine film.

When we insist, that for a «full frame» 50mm is the standard lens, and the focal length in question is derived from the negative format's diagonale...

You are already misled at that point. 50mm is a convenient agreement, but no natural parameter. And even "normal is the length of the diagonal" is just a rule of thumb that happens to be close to other definitions, not the physical parameter which our definition of normality is derived from.

First of all, forget about lengths - these are an artefact of film size, the only thing that matters is FOV, in degrees (of angles). Now, "normal" is defined as the human FOV. But the eye is no camera, human vision is complex and the eye is a permanently moving, scanning device, with a static FOV below 10° and (motion only) edge vision past 100° - and we've got two of them. Whan we usually consider the normal human FOV is that of the stereoscopic field in roaming binocular vision - around 30-70° in a healthy uncorrected pair of eyes, where 40-55° was considered the sweet spot within that range a century ago. But much of that is a cultural definition, defined by habits, our modern culture might actually need a far more individual interpretation. And even half a century ago 47° (50mm) was by no means the only normal lens proposed or used (42mm to 58mm have been common as normal lenses on 35mm cameras).

 

[radi(c)al_cam]

So Alexander , you went to a professional with several cameras , wat was his answer ?

😀

Sevo explained it a lot better than me — although I neither know whether sevo is a «he», nor whether sevo is a «professional» — btw, the term «professional» without any detailed definition sounds very weird to my ears, but telling too much could be a — wait for it — «professional misconduct» 😉

 

[squirrel$$$bandit]

Hi,

Can't say I've ever seen a 43mm lens.

There's this one—and it's a good one!

 

[michaelwj]

50mm?

Everyone knows a 35mm is the standard lens. Why else would it be called 35mm film 😀

 

[radi(c)al_cam]

50mm?

Everyone knows a 35mm is the standard lens. Why else would it be called 35mm film 😀

Yes, sure, 35mm is the standard lens —— for a 24mm x 25,475478405…mm negative format 😉

 

[tunalegs]

Do not confuse "standard" and "normal". Nor place too much importance on the correlation between the diagonal of the negative and the focal length of the lens. In practical considerations this is a trivial matter. Few cameras in any format have lenses with focal lengths that match the diagonal dimension of the negative. There are just too many more important considerations when creating lenses.

Nor would I necessarily consider 50mm "standard" among 135 format cameras. Excepting interchangeable lens cameras, where considerations about accommodating the mount in the camera body, the shutter, etc. come into play - plenty, if not most, fixed lens cameras use focal lengths shorter than 50mm. Interestingly this could be said for other formats, most 6x6 fixed lens cameras use 75mm lenses for example.

Beyond that, the number printed on the lens is usually nominal, rather than a precise measurement of the lens' actual focal length. There are a lot of 50s, which I suspect are somewhat shorter or longer than what is indicated on the front ring.

 

[radi(c)al_cam]

[…] Nor would I necessarily consider 50mm "standard" among 135 format cameras. Excepting interchangeable lens cameras, where considerations about accommodating the mount in the camera body, the shutter, etc. come into play - plenty, if not most, fixed lens cameras use focal lengths shorter than 50mm. Interestingly this could be said for other formats, most 6x6 fixed lens cameras use 75mm lenses for example. […]

Thank you, in deed «normal» and «standard» are not exactly the same, my bad.

But: the diagonale of the so called 6cm x 6cm format (rather: 55mm x 55mm) is 77,781745930… mm — hence quite in the middle between the common 75mm, or also usual 80 mm 🙂

 

[Jake Mongey]

Im blind in one eye and although i haven't specifically tested it mm seems to fit well to what i see. Obviously it could just be me wrongfully thinking that but usually what i see i usually get something very similar with a 28mm