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CMoore · Apr 24, 2018

Not just these two, but 45mm (not sure of the aperture) and the 50mm f/2.0.
Especially to the beginner, hobbyist, uninitiated to all the nuances of Camera and Lens gear.....what drove the development of these types of lens.?
I think most all 35mm SLR had a 50mm 1.7 or 1.8.
What did a 45mm offer that the 50 did not.....size i guess.?
I suppose the bigger "mystery" is the 50/2.0. Why would Canon, Nikon, or whoever decide to have a 1.8 and a 2.0.?
Thank You

MattKing · Apr 24, 2018

45mm is a lot closer to the so called standard focal length for 135 film, because the diagonal of a 135 frame is about 43mm.
My sense is that you will find more 45mm lenses on fixed lens cameras, which usually don't have a mirror that needs to clear the back of the lens.
In comparison, designers of SLRs need to concern themselves with such clearance issues, so tended toward longer standard focal lengths.
Early on there were SLRs with standard lenses with focal lengths like 58mm - Konica comes to mind.
And as for the f/2.0 vs. f/1.8 question, the lenses probably were designed based on other considerations first, including questions of manufacturing standards and glass availability and existing sources for aperture mechanisms, and the maximum aperture number that they ended up with would have been the result.
A 50mm f/1.4 lens (for example) used to be seen as an expensive and exotic lens. Any design that emphasized maximum aperture tended to be a specialty product,

Oren Grad · Apr 24, 2018

CMoore said:
I suppose the bigger "mystery" is the 50/2.0. Why would Canon, Nikon, or whoever decide to have a 1.8 and a 2.0.?

During the manual-focus SLR era, at least, offering both an f/1.8 and f/2 lens was a marketing decision, not a technical one. The f/2 version was pretty much always intended as a companion for the company's budget model - for example, Pentax promoted f/1.8 normal lenses with the Spotmatic series and the KM/KX/K2, but f/2 normal lenses with the SP500/1000 and K1000.

Nikon never did this - they abandoned 50mm f/2 for 50mm f/1.8, presumably because having f-one-point-something was easier to market when all the competitors had it. But they economized in various ways with their f/1.8 lens - for example, by offering the more plasticky Series E version, initially with the low-end EM camera.

AFAIK, Canon never offered an f/2 normal with its SLRs - at least not for as long as I've been following, which is since the early '70s. Nor did Olympus. Minolta did offer f/2 normals, both 50 and 45; again, these were promoted as budget options especially with the low-end models.

By the time AF SLRs rolled around, the standard kit lens for bottom-of-the-line models was a cheap zoom, not a normal prime - first 35-70, later 28-70 and other 28-to-something options - and it no longer made sense to devote resources to manufacturing both f/2 and f/1.8 or f/1.7 versions of a 50 - though Canon, at least, did radically cheapen the design and construction of the second generation of its 50mm f/1.8 EF-series lens.

E. von Hoegh · Apr 24, 2018

At one point, in the early '30s, f:2 was the holy grail, Leitz had the Summar, Zeiss had Sonnars 50 & 85. Then Zeiss rapidly follwed up with the 50/f:1.5 Sonnar, viewed then as miraculous and it was very very expensive, around 1/3 the price of a small inexpensive car.
Pentax had screwmount 55mm Super Takumars in 1.8 and 2, but this was pure marketing, they shared identical glass; the f:2 version had a restrictor next to the aperture.
The Nikkor 50/2 was introduced 1965, as a relatively inexpensive, but still fast and highly corrected lens. It was replaced 14(!) years later with the f:1.8, the only noticeable difference being the 1.8 had the very slight barrel distortion of the f:2 better corrected (I have 5 of the f:2s, the distortion is really very slight - negligible unless you look for it).
The 45mm lenses - usually f:2 or f:2.8 - in addition to being closer to the format diagonal of 43mm are very compact, also an outfit of 28-45-80/85 is very nicely spaced.
Once upon a time, lenses faster than f:2 were regarded as exotic special purpose lenses, it is much more difficult to design a really good f1.4 than an f:2 lens - now the bokeh nuts use the f:1.4 & 1.2 lenses to give "good bokeh" to their contentless pictures.
55 & 58mm lenses were popular because to clear the mirror, a "normal" lens has to be a bit retrofocus, they involved fewer design challenges & compromises & usually had little to no distortion.

benjiboy · Apr 24, 2018

I'm afraid you're wrong Oran, Canon did make an F.D.50mm f2 lens there are. several for sale at the moment on eBay.
https://www.ebay.co.uk/itm/CANON-NE...rom-Japan-086/273173804447?hash=item3f9a6d759 As far as I recall they were supplied as a kit lens with some of the cheaper FD bodies like the T50

guangong · Apr 24, 2018

EvH gave a good explanation. Younger folks on APUG ( those below 70 yrs) have no idea about how expensive cameras and lenses were in the good ol’ days and how difficult and costly lens design was in the age of the slide rule and limited kinds of optical glass.
In older movies, one way to hint at substantial wealth of a character was to have him own a Leica, and to show that somebody had really big bucks, a Contax. The hero in Hitchcock’s rear window was a professional, but he “only” had an Exacta. Now, on APUG we talk about how many Leicas and Nikons we own along with a multitude of lenses.

E. von Hoegh · Apr 24, 2018

guangong said:
EvH gave a good explanation. Younger folks on APUG ( those below 70 yrs) have no idea about how expensive cameras and lenses were in the good ol’ days and how difficult and costly lens design was in the age of the slide rule and limited kinds of optical glass.
In older movies, one way to hint at substantial wealth of a character was to have him own a Leica, and to show that somebody had really big bucks, a Contax. The hero in Hitchcock’s rear window was a professional, but he “only” had an Exacta. Now, on APUG we talk about how many Leicas and Nikons we own along with a multitude of lenses.

Hey, I've had multiple Leicas, back when you could get really clean M3s with a Summicron/Summarit and case for $200 to $250 youngsters don't remember that either.
But, even thirty years ago it was too expensive to put together an outfit, and to make $$ I needed SLRs.

AgX · Apr 24, 2018

benjiboy said:
I'm afraid you're wrong Oran, Canon did make an F.D.50mm f2 lens there are. several for sale at the moment on eBay.
https://www.ebay.co.uk/itm/CANON-NE...rom-Japan-086/273173804447?hash=item3f9a6d759 As far as I recall they were supplied as a kit lens with some of the cheaper FD bodies like the T50

Here a bit more info on that lens(es)
http://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/50mm.htm#f2.0

Oren Grad · Apr 24, 2018

benjiboy said:
I'm afraid you're wrong Oran, Canon did make an F.D.50mm f2 lens there are. several for sale at the moment on eBay...

AgX said:
Here a bit more info on that lens(es)
http://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/50mm.htm#f2.0

Thanks to both of you - I happily stand corrected! An interesting little byway on Canon FD lens history...

AgX · Apr 24, 2018

E. von Hoegh said:
55 & 58mm lenses were popular because to clear the mirror, a "normal" lens has to be a bit retrofocus, they involved fewer design challenges & compromises & usually had little to no distortion.

Retrofocus is a certain design type, not applied to 50mm lenses for 35mm format.
But I assume some early designs following the Double Gauss principle either had been still too extended to give enough back focus, thus clearance for the mirror, at 50mm, or back then one considered more clearance more advantageous. Thus those 58mm and 55mm versions were designed.

We should keep in mind that within that back focus distance not only the mirror has to be placed , but also the shutter.

E. von Hoegh · Apr 24, 2018

AgX said:
Retrofocus is a certain design type, not applied to 50mm lenses for 35mm format.
But I assume some early designs following the Double Gauss principle either had been still too extended to give enough front focus, thus clearance for the mirror, at 50mm, or back then one considered more clearance more advantageous. Thus those 58mm and 55mm versions were designed.

We should keep in mind that within that front focus distance not only the mirror has to be placed , but also the shutter.

50s for SLRs are indeed retrofocal, for instance flange focus on a Pentax is 45.5mm, the outer surface of the rear glass is maybe 3-4mm behind that, say 41 or so mm from the film.
The prewar f:2 Sonnar is a mild telephoto, too.

Nodda Duma · Apr 24, 2018

The Double Gauss design as for 35mm format is not considered a retrofocus design, as it does not meet the criteria for such. It is symmetric, with both groups having positive optical power and the entrance/exit pupils being approximately similar in apparent size.

Ref the Augenieux design, which is synonymous with retrofocus and commonly used for wide angle lenses.

darkosaric · Apr 24, 2018

I have heard that Nikkor 105mm/2.5 and Summicron-M 90mm are similar... anybody used both of them?

MattKing · Apr 24, 2018

guangong said:
Younger folks on APUG ( those below 70 yrs) have no idea about how expensive cameras and lenses were in the good ol’ days and how difficult and costly lens design was in the age of the slide rule and limited kinds of optical glass.

Thanks for classifying me as one of the "younger folks" - I've got more than 8 years to go before I lose my status! .
I started selling cameras just about the time that things really changed. In the early to mid-70s the 35mm SLR went from being a specialist piece of kit to being found in department stores. And I was there, in my teens, ready to sell you one!

Sirius Glass · Apr 24, 2018

CMoore said:
What did a 45mm offer that the 50 did not.....size i guess.?

The 45mm offered a slightly wider angle than 50mm and some preferred that for snapshots and travel. Some just liked the wider angle.

CMoore · Apr 24, 2018

guangong said:
EvH gave a good explanation. Younger folks on APUG ( those below 70 yrs) have no idea about how expensive cameras and lenses were.

I suppose APUG Members of 70+ must be suffering Dementia.
As a 20 year old, in 1980 (that means i was born circa 1960) i can assure you that we were Very Aware of how expensive a Nikon/Olympus/Canon/Pentax SLR was.....the big cost of the lens also did not escape us.

ic-racer · Apr 24, 2018

In the 35mm systems I use, there is no 45mm lens. Too bad because it would provide an angle of view more consistent with the 'normal' lenses of all the other formats I use.

Sirius Glass · Apr 24, 2018

guangong said:
EvH gave a good explanation. Younger folks on APUG ( those below 70 yrs) have no idea about how expensive cameras and lenses were in the good ol’ days and how difficult and costly lens design was in the age of the slide rule and limited kinds of optical glass.

Crapola and $#!+ on a shingle, now I am old. Damn!

E. von Hoegh · Apr 24, 2018

CMoore said:
I suppose APUG Members of 70+ must be suffering Dementia.
As a 20 year old, in 1980 (that means i was born circa 1960) i can assure you that we were Very Aware of how expensive a Nikon/Olympus/Canon/Pentax SLR was.....the big cost of the lens also did not escape us.

Going back 40 years or so, they were even more expensive. Compare the price of a Leica or Contax in say 1936 to the average yearly income for a working man and the price of a small car, say a Ford or Chevy econobox.

AgX · Apr 24, 2018

A Leica II with Elmar was at 240 RM in 1936. The average income then was 145 RM a month. And about 50% had to be used on food alone.

E. von Hoegh · Apr 24, 2018

Nodda Duma said:
The Double Gauss design as for 35mm format is not considered a retrofocus design, as it does not meet the criteria for such. It is symmetric, with both groups having positive optical power and the entrance/exit pupils being approximately similar in apparent size.

Ref the Augenieux design, which is synonymous with retrofocus and commonly used for wide angle lenses.

I'm aware of the Angenieux design, where the rear node can be outside the physical lens, but what is the correct term for the Gauss type when the rear node is so far back in the rear group?
I have a textbook somewhere describing the placement of the node so far back as being a design challenge in the early days of fast 50s for slrs, and how using 55/58mm made things easier.

CMoore · Apr 24, 2018

E. von Hoegh said:
Going back 40 years or so, they were even more expensive. Compare the price of a Leica or Contax in say 1936 to the average yearly income for a working man and the price of a small car, say a Ford or Chevy econobox.

Are you concocting some bizarre kind of "Harder For Me Than For You" contest.?
A working man in 1936 would have been born in 1916...102 years ago. NOBODY on APUG was buying Cameras/Lens then.
Of course, taking this "logic" further, we could rewind it to 1889.
You young guys have no idea what it was like to have to carry all of our gear with us, including the coating chemicals, glass, and a darkroom tent.
Yep, you guys born in 1916 had it Pretty...Darn...Easy.

E. von Hoegh · Apr 24, 2018

CMoore said:
Are you concocting some bizarre kind of "Harder For Me Than For You" contest.?
A working man in 1936 would have been born in 1916...102 years ago. NOBODY on APUG was buying Cameras/Lens then.
Of course, taking this "logic" further, we could rewind it to 1889.
You young guys have no idea what it was like to have to carry all of our gear with us, including the coating chemicals, glass, and a darkroom tent.
Yep, you guys born in 1916 had it Pretty...Darn...Easy.

Are you insane?

CMoore · Apr 24, 2018

E. von Hoegh said:
Are you insane?

I suppose that is possible, hinging partly on your definition of insane. Would that be circa 2018, or 1936.?
At least i was recounting personal experience.....from a time frame that i actually live in.
Have A Good Night

Nodda Duma · Apr 25, 2018

E. von Hoegh said:
I'm aware of the Angenieux design, where the rear node can be outside the physical lens, but what is the correct term for the Gauss type when the rear node is so far back in the rear group?
I have a textbook somewhere describing the placement of the node so far back as being a design challenge in the early days of fast 50s for slrs, and how using 55/58mm made things easier.

There’s no real distinction made, sort of how a car with disc brakes vs a car with drum brakes are still both cars. The approach to image formation and aberration correction is the same. Notwithstanding the accommodation for the mirror, all Double Gauss designs implement design symmetry to accomplish both objectives. The front and rear groups are both positive and nearly equivalent. The relative focal lengths set the back focus, which is trivial to conceptualize so I don’t have insight into why some designs had a longer focus...perhaps it was a tolerancing or fabrication limitation.

Contrast this to a retrofocus which has a negative front group and a stronger positive rear group to push the exit pupil out past the rear of the lens. The really wide angle lenses take this form.

When it comes down to it, in modern optical design clearing the mirror is just one constraint (or one operand in the optimization merit function) among thousands and not really where the main design effort for a Double Gauss is focused. The main focus of the designer is usually on reducing glass cost and sensitivity to assembly tolerances.

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