normal lenses

benjiboy · Dec 22, 2013

AgX said:
The commonly reported reason for less than 100% coverage is to compensate for cropping due to mounting a transparency in a slide-mount.
I do not find this very convincing. Tolerance in manufacture may be another reason.

This is true I had a Nikon F2 and was shooting slides exclusively with it and was losing a significant amount of the image area after mounting, and this also applies to enlarger negative carriers if you don't file them out to accommodate the full negative area. I find the ideal viewfinder coverage for film is that of my Canon New F1's which is 97%

mikebarger · Dec 24, 2013

I'm a little surprised by the interest in 43/45mm lens.......I always thought the 105 was normal for a 35mm frame. If I have to go to a wide; I just go to the 18mm.

mawz · Dec 26, 2013

The reason for why not 100% and 1x in the finder is simple, you have to give up eyepoint to achieve that, making it difficult to actually see the entire field of view (and for some, actually painful). Both the OM-1n and the Pentax MX (which actually has the highest finder magnification) have major issues for eyeglass wearers due to the very low eyepoint, and personally I find the MX literally painful to shoot (major eyestrain issues). The best all-round finders are either the 100% ~0.8x finders in cameras like the F2 or non-HP F3 or for eyeglass wearers the high-eyepoint finders in the F3HP, F4 and F5.

dynachrome · Dec 27, 2013

I don't think Nikon ever claimed 100% in all circumstances for the F or F2. It claimed 100% with a 50mm lens at inifnity.

RalphLambrecht · Nov 27, 2014

gleaf said:
Normal essentially is what you normally see when you look. Or near when focal length equals the diagonal of the selected image size.

interesting that our eyeballshave a focal length of about 17mm in average.the aperture ranges from f/2 to f/8 from dim to bright light but I don't know what the film format is

Old-N-Feeble · Nov 27, 2014

An old thread but...

Ralph, our eye vision is essentially ultra-wide. My peripheral vision used to be significantly greater than 180 degrees (now it's less) but that's just the way my eyeballs see, not the way my brain sees. Our human brains concentrate our attention on primarily the center few degrees of what our eyes see... almost like having long lenses rather than wide. However, we move our eyes in all directions and our brains "piece together" a fuller view of our surroundings. It's a far more complicated process than I care to study about.

I'd say, for most folks, the age-old way of calculating lens normal focal length works fairly well. For me, I think I see wider than that but I do tend to look around a bit more than most folks so maybe that's why. I also tend to prefer wider horizontal images at 1:2 or 1:2.5 ratios moreso than other formats perhaps because in the real world I find it easier to turn my head right/left and move my eyes horizontally rather than move my head up/down and move my eyes vertically. So I guess I have a less tall and wider view of the world.

At any rate, our "vision" is more of a brain thing than the actual view seen by our eyeballs.

KenS · Nov 27, 2014

‘bubble thinks’… wait a few…

Was not the 35mm film frame of the day 24mm by X mm wide since it went through the ‘movie’ film gate in a different direction. The ‘diagonal’ of the frame is now ‘smaller’ that what we get with a 36 x 24mm image area and should we now ‘disregard’ that aspect ratio as a function of ‘normal’ field of view?

Ken

Old-N-Feeble · Nov 27, 2014

^^^ That's not what I wrote.

Peltigera · Nov 28, 2014

Movie film is 24 x 18 but still 35 mm format has usually been 24 x 36 (24 x 24 and 24 x 32 not uncommon).

Xmas · Nov 28, 2014

Wooooa Batman another old thread resurrection.

Cost is the big driver 6x6 cameras have similar focal length rule sets, 6x7, 6x9, etc.

Technology has improved optical glass with

refractive index 1.9, wide range of dispersions
multi coating
high refractive index glass fluid at very low melting temperatures, high precision ceramic molds
poly carbonate
CNC machines

Only a few design innovations, (like Konicas 40mm Pancake patent)

Ive no problems with OM1s with the x0.9 finder magnification eye relief and eye glasses, in dim light I need to wind the variable dioptre of OM4s to one extreme to use matt/micro focusing, with my current spec prescription.

Nikon F and F2 were expensive for the additional tolerances needed (and materials for motor drive use).

Robin

ic-racer · Nov 28, 2014

RalphLambrecht said:
a 'normal focal lengthlens is typically defined as havinga focal length equal to the film-format diagonal. in case of 35mm film that is close to 43mm. so, why, I ask don't we see lenses with that focal length?; we have many close to it; 35 or 50mm,but I've never seen 43 or ;let's say 45mm.why do you think that is?I use 35 and 50mm a lot and can see 43 or 45 having an advantagein viewing angle and weight over the typical 500mm normal.confused:

If you look at the long dimension of the contemporary 35mm format frame opening, it forms a square with a diagonal of 50mm. This is just an observation and it does not answer your question.

flavio81 · Nov 28, 2014

Xmas said:
Wooooa Batman another old thread resurrection.

Cost is the big driver 6x6 cameras have similar focal length rule sets, 6x7, 6x9, etc.

Technology has improved optical glass with

refractive index 1.9, wide range of dispersions
multi coating
high refractive index glass fluid at very low melting temperatures, high precision ceramic molds
poly carbonate
CNC machines

Only a few design innovations, (like Konicas 40mm Pancake patent)

+1

Add to your list:

Extra low dispersion glass comparable to Fluorite
Anomalous dispersion glass
Injection-Molded non-glass aspherical lenses (Canon)
Molded glass aspherical lenses (Canon)

Design innovations since the 60s:
Extreme ultra-wide-angle lenses like the 220° fisheye (Nikon)
Floating elements (Nikon)

Design innovations since the 80s:
Diffractive optics (Canon)
Image stabilization (Canon)
Designs with Inner element focusing, particularly for AF use... for example the Canon FD 85/1.8 is very different from the following EF 85/1.8; the former is unit focusing while the latter moves an internal group for focusing.

wiltw · Nov 28, 2014

ic-racer said:
If you look at the long dimension of the contemporary 35mm format frame opening, it forms a square with a diagonal of 50mm. This is just an observation and it does not answer your question.

Huh?...opening the back of my Olympus OM-4 I measure 43mm diagonal opening.

flavio81 · Nov 28, 2014

wiltw said:
Huh?...opening the back of my Olympus OM-4 I measure 43mm diagonal opening.

You're correct.

24mm x 36mm ---> hypotenuse is about 43.266mm

But he means that the square of 36mm would have a diagonal of about 50mm. He's correct as well.

And it's a very interesting observation.

So for 6x7 format, for example (about 56x70mm) --> "normal" could be rather than 98.99mm rather than 89.64mm

and for 6x4.5 format (about 56x45mm? ) --> normal could be 79.19mm instead of 71.84mm

wiltw · Nov 28, 2014

flavio81 said:
You're correct.

24mm x 36mm ---> hypotenuse is about 43.266mm

But he means that the square of 36mm would have a diagonal of about 50mm. He's correct as well.

And it's a very interesting observation.

So for 6x7 format, for example (about 56x70mm) --> "normal" could be rather than 98.99mm rather than 89.64mm

and for 6x4.5 format (about 56x45mm? ) --> normal could be 79.19mm instead of 71.84mm

Thx, I misunderstood what he meant.

OTOH, your dimensions for 645 do not really match any 645 SLR manufacturer's measurements (Mamiya, Pentax, Bronica) for actual frame size...42.5 or 43mm height, 55 or 56mm frame length...70-71mm actual diagonal vs. 78-79mm computed diagonal using long dimension square vs. 75mm standard FL.

Old-N-Feeble · Nov 28, 2014

ic-racer said:
If you look at the long dimension of the contemporary 35mm format frame opening, it forms a square with a diagonal of 50mm. This is just an observation and it does not answer your question.

Interesting. Is this how you calculate normal focal length lenses for the way you see? You calculate the hypotenuse of the square of the long edge of the format you shoot?

Arklatexian · Nov 29, 2014

I have always heard that a 50mm lens on 35mm cameras approximates what the eye sees. Each format size has its "normal" focal length and again, I have always heard that in each case they "approximated" what the eye sees. Please note the word "approximates", hence the 80mm lens on Hasselblad and 75mm on some Rolleis. I don't think you will find very many retrofocus lenses on RF cameras. I think they are mostly found on SLRs.....Regards

Arklatexian · Nov 29, 2014

Dan Fromm said:
Emil, as has already been pointed out, Leica started it. Zeiss-Ikon and Nagel copied Leica. That historical accident is the reason 35 mm cameras with 24 x 36 gates have 50 mm (or so) lenses as standard, but no one's explained the historical accident.

The Leica was initially conceived as an exposure test device for 35 mm cinema. The 35 mm cine camera's gate is 24 x 18 mm. That's the so-called Edison format and yes, T. A. Edison invented it. By convention -- set to gain working distance -- the "normal" focal length for 35 mm movies is ~ 50 mm. That's what Oscar Barnack used on his exposure tester. When the exposure tester grew into a camera that should double frame 35 mm (24 x 36) the 50 mm lens was retained.

Barnack was testing a lens for motion picture cameras when he made the pre-Leica. When it was decided to manufacture a still camera they doubled the size of a movie frame (Edison format) and made what we still call "Double Frame" today and you can still buy "Single Frame" cameras today. I think the Olympus Pen was one.....Regards

Dan Fromm · Nov 29, 2014

Old-N-Feeble said:
Interesting. Is this how you calculate normal focal length lenses for the way you see? You calculate the hypotenuse of the square of the long edge of the format you shoot?

No, no and no again. The idea "normal lens" reflects two conventions.

The first, used in all still camera formats except the cine camera-derived 18x24 (single frame in cine parlance, half-frame in still photographer) and 24x36 (double frame in cine, full frame in still) is the gate's diagonal. Diagonal, not hypotenuse. Rectangles have diagonals, right triangles have hypotenuses.

The second, used with still cameras that use 35 mm film is arbitrary and reflects cinematographer's practice. Edison format (yes, TAE invented the motion picture industry) is 24x18 and the so-called normal focal length for the format is 50 mm, not 30 mm, the format's diagonal. This was adopted to keep the cine camera off the stage. It was retained by Barnack when he made an exposure tester for cinematgraphers. The original Leica camera was developed from the exposure tester. And that's why people who shoot double frame 35 mm take 50 mm as normal rather than 43 mm, the format's diagonal.

These conventions have been accepted since the beginning of photographic time. To avoid confusion, accept them and don't trip over each other trying to explain them. They're conventions and that's all, don't follow from laws of nature. Honor the conventions and people will understand you. Don't honor the conventions and you'll spread confusion. Ever widening circles of confusion.

Interestingly, in the late '50s through late '60s 35 mm SLRs were offered with "normal" lenses as long as 58 mm. This because the 6/4 double Gauss lens type that is the basis for nearly all of the fast "normal" lenses for 35 mm SLRs of that era is somewhat telephoto, i.e., has a shorter back focus than expected given focal length. Until SLR manufacturers managed to compute 50 mm 6/4 double Gauss types with long enough back focus to clear their cameras' mirrors and good enough performance they simply offered "normal" lenses with enough back focus. As I said, convention and nothing more.

Old-N-Feeble · Nov 30, 2014

ic-racer said:
If you look at the long dimension of the contemporary 35mm format frame opening, it forms a square with a diagonal of 50mm. This is just an observation and it does not answer your question.

Old-N-Feeble said:
Interesting. Is this how you calculate normal focal length lenses for the way you see? You calculate the hypotenuse of the square of the long edge of the format you shoot?

Dan Fromm said:
No, no and no again.<snip>

Dan, I was asking ic-racer if that's the way HE calculates for normal lens focal length.

EDIT: Sorry for abusing the term "hypotenuse".

Dan Fromm · Nov 30, 2014

Old-N-Feeble said:
I was asking ic-racer if that's the way HE calculates for normal lens focal length.

There are rules. Not everyone knows or follows them. These days many people who don't know just make things up. The younger generation -- that includes you, kid -- isn't as well-educated as it used to be.

Old-N-Feeble · Nov 30, 2014

Dan Fromm said:
There are rules. Not everyone knows or follows them. These days many people who don't know just make things up. The younger generation -- that includes you, kid -- isn't as well-educated as it used to be.

I agree with you. I was bringed up and teeched in Texas.

RalphLambrecht · Nov 30, 2014

That's quite alright. if smart people would be half as smart as they thinkthey are,they would be twice as smart as they actually are.

ic-racer · Nov 30, 2014

RalphLambrecht said:
interesting that our eyeballshave a focal length of about 17mm in average.the aperture ranges from f/2 to f/8 from dim to bright light but I don't know what the film format is

In a way it is like a large format scan back. The only area that has fine resolution is the fovea which has a very narrow angle of view. It scans on demand. Any area you look at is clear and sharp, giving an impression your whole field of view is clear and sharp.

ic-racer · Nov 30, 2014

Old-N-Feeble said:
Interesting. Is this how you calculate normal focal length lenses for the way you see? You calculate the hypotenuse of the square of the long edge of the format you shoot?

I'd say "Normal Focal Length" is, by definition, the diagonal of the film format. Too bad the common english word "Normal" is part of the term, that leads to a lot of confusion. Making people think there is some connection between "Normal Focal Length" and the way humans see.
"Normal Focal Length" is kind of like "Normal" in chemistry, which is simply defined as "milliequivalents per liter," and has nothing to do with normal human physiology.

normal lenses

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