Similar Lenses.....

[AgX]

...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....

Can it not be, as I already assumed in this thread, that some Double Gauss designs just are built longer, thus also yielding less back focus?

I also hinted at the back focus distance just taken by the shutter assembly. A thicker assembly would require more back focus, unless one compensated for such by a shorter mirror or a novel way of mirror travel.

 

[guangong]

I didn’t mean my remarks on age to be anything more than provid a reference point with regard to prices, etc. With life in general there are old people who are chronologically in 40s and young people in their 90s.

 

[E. von Hoegh]

I didn’t mean my remarks on age to be anything more than provid a reference point with regard to prices, etc. With life in general there are old people who are chronologically in 40s and young people in their 90s.

That's exactly the way I took them.
At one time, the only people who had top-of-the-line equipment were the wealthy, and working professionals for whom the tool provided income; although there was always the odd enthusiast who budgeted & saved up for a particular piece of gear.

 

[Nodda Duma]

Can it not be, as I already assumed in this thread, that some Double Gauss designs just are built longer, thus also yielding less back focus?

Separation distance between the groups and the stop is important for aberration correction, so it’s not that straightforward. Aberration correction improves with a more compact group, so lengthening the design is a more difficult problem to solve. Additionally, longer designs are more sensitive to alignment (a cost driver). Longer designs are longer to accommodate a larger number of elements, but those designs still want to be compressed together. .

 

[E. von Hoegh]

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.

My Contax II with f:2 Sonnar, case, two filters, and lens shade came to RM 450 in mid 1937.

 

[flavio81]

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

At the risk of sounding redundant,

restricting ourselves to the SLR era,

in 1959 Nikon releases the 50/2.0 Nikkor-S. Why f2? Well, they couldn't make a faster 50mm for SLRs; in 1960/61 the f1.4 offering from Nikon was 58mm, not 50. (Same happened to other manufacturers).

So Nikon started with 50/2.0. Canon, 1959, had to one-up nikon in some way thus they managed to release a 50/1.8.

Later Pentax releases the first 50/1.4 lens for SLR cameras, soon Nikon and Canon follow.

The same will later happen with f1.2 standard lenses for SLRs, first it was 58mm (Canon 1962), then 55mm (Nikon 1965), and finally 50mm (Nikon 1978).

Nikon released a 50/1.8 in late 70s because they felt it was an improved.design over the 50/2, which was discontinued some years afterwards.

Canon released a 50/2 FD only for marketing purposes, internally it was the good old 50/1.8.

Pentax had the 55/1.8 along the 50/1.4 for at least 15 years (from M42 mount to the K-Mount era included); the Pentax 55 is a classic on its own right so I don't think discontinuing it was easy. Later they released 50/1.4, 50/1.7, and 50/2 in K-mount, to different price points and different optical designs.

 

[CMoore]

Ah,,,Thank You
I first go into photography circa 1978, and that for just a few years.. Was out of it until rather recently.
So you can excuse my ignorance of the design. My timeline experience was the 1,8.
Now that you mention it, it would make sense that the 2,0 came first, and then kind of lingered. Coming along 30-40 years later, it was easy to make the mistake of thinking that, for some weird reason, camera companies were actively making such similar lens at the same time.
Thanks Again for the info.