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09-01-2014, 08:30 PM   #16
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QuoteOriginally posted by Na Horuk Quote
Wasnt it the other way around? 58mm and 55mm were out first, but then manufacturers started making them wider, to make them more appealing and faster aperture.
50mm lenses were common enough in the early days of 35mm photography. As for the definition of "normal", the length of the film diagonal is often given as an explanation. This is a convention, with some perceptual basis in that it is intended to provide a final print FOV of about 53 diagonal at normal viewing distance. See the Wikipedia article on "http://en.wikipedia.org/wiki/Normal_lens".

In practice, a variety of focal lengths have been "normal" on 35mm still cameras. The longest were about 58mm and the shortest generally about 40mm with the bias being towards the longer end. I have never read a good explanation as to why that may be except for something about the native magnification of the human eye at moderate distances. This is most evident with using a rangefinder camera with a 1:1 magnification viewfinder. With such finders it is common technique to have both eyes open when framing the subject. Sure enough, the viewfinder magnification (50mm focal length) is the same as the unaided eye. As a result, initial visualization can be very close to the final framing. (The assumption is that the photographer has internalized the dimensions of the frame.)

With SLRs, it is much the same. A common figure of speech regarding a bright, near 100% 35mm SLR viewfinder is that it is "like looking out a window" and with a 50mm lens, it surely is.


Steve

---------- Post added 09-01-14 at 08:44 PM ----------

QuoteOriginally posted by boriscleto Quote
The cine Biotar was 50mm...
Ummm...yes.

I am glad you brought this up because it addresses the most important part of the "normal" lens story. Cine for 35mm is half-frame and the convention for normal for cinema viewing is twice the frame diagonal due to the increased viewing distance. This results in a normal lens of 50-60mm. "Normal" is defined by the anticipated viewing distance for a print or projected image of a given size. Different camera and lens makers had various ideas of what that distance should be. The same was true in regards to depth of field calculation and the DOF scales on lenses from different makers.

As might be anticipated, photographers also had different opinions on what constituted normal for their work.


Steve


Last edited by stevebrot; 09-01-2014 at 08:47 PM.
09-01-2014, 09:50 PM   #17
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This is revealing - "The famous Leica 50mm f/3.5 Elmar lens released in 1920 was a Tessar type lens. After Leica introduced the first 35mm camera in 1925 .... "


This extract says 2 things, first, the very first 50mm lens destined for 35mm format was designed before the first 35mm camera was even built. second, it was a development of an earlier design.


I believe that the decision to go with either 50 55 or 58 was purely based on whatever criteria were deciding factors at the time of design and there was no conscious decision to use one or other focal length. we would have had 57 or 61 if it was convenient to design a lens of those focal lengths. I also believe that having a good consistent spread between lenses was important. Additionally focal lengths were either chosen for a specific purpose or for familiarity or for cheapness. In other words if customers wanted a 32mm they should get one


I think that once the manufacturer had a good range of focal lengths with even spread between them then the company would choose which of its range it would release with the camera.. The deciding factor was almost certainly cost, it being cheaper to make a 50 - 60 mm lens than other focal lengths other than maybe the 135mm.


Typical ranges were 24 35 50 80 135 200 300 400 600


Notice some interesting things, the 35mm was the expected focal length of fixed focal length 35mm cameras, the 35 doubled is 70, close to 80, which is the perfect portrait focal length, 135 was a cheap easy to produce lens and sufficiently far from the 80 to make a good jump, after 135 we return to multiples of 50.


Take out the 35 (which can be seen as a marketing ploy to give photographers used to fixed lens 35mm cameras a familiar focal length). and you have 24 50 80 135 200 400


Portrait photographers could go for 35 80 135. General photographers could go for 24 50 135. Additional longer lengths were handy jumps 200 400 even 600


Notice that the presence of a 55 instead of the 50 makes better mathematical sense, for General photographers, giving 24 55 135. Even 24 58 135 makes sense, there being not much difference between the FOV in each of the 50 55 and 58.


I have no reason to doubt that changing the glass formula allowed different control of aberration and may have contributed to the ability to design better lenses, but the existence of 50mm lenses in 1920 suggests this view is not the entire story.
09-01-2014, 11:10 PM   #18
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Two things to notice about the Leica 50mm f/3.5 Elmar lens. It was a Tessar type lens and only F3.5.
Tessars are of short construction, pancake lenses, so 50mm or 45mm fit fine onto an SLR but they don't have apertures bigger than F2.8. The challenge with SLRs with their 45mm flange distance was to built a short large aperture lens at the same time giving a good image. Large aperture requires something like a double Gauss or Sonnar. The Pentax F2 Sonnar was also 58mm and couldn't be made any shorter either. Certainly marketing, tradition, and customer preferences are important but Snell's law comes first.
09-04-2014, 03:45 AM   #19
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Interesting comments about 'normal' relative to viewing distance. I hadn't heard that before; mostly, hear about film diagonal. I don't know about 55mm. As far as ranges of focal lengths, many are separated by 1.5x 24 > 36 > 53 > 80 > 120 Not focal length but multiples of 1.5 above Close... I figured 1.5x was significant. 1.4x fit in the mix as well 28 > 39, 35 > 49, 50 > 75 Who knows I think favors 1.4x some. For the DA lenses. 15 > 21 > 29 > 40 with 50 > 70 The 29mm is missing, of course, and there is no room for 35mm with this theory. Take the 29mm and 1.5x to get 43mm. I think Pentax planned a 29mm lens. It is the missing link. It caused Janneman to die of a broken heart. Honestly, I prefer a 28mm on the camera over a 35...

---------- Post added 09-04-14 at 05:49 AM ----------

Sorry for the hash above. [br/] [br/] I don't have javascript enabled and saw I should use an HTML tag for the bold characters but didn't realize it was necessary for paragraph breaks. [br/] [br/] Looking at quoted text, it looks like they use an odd 'break' tag here [/br] [/br] Hopefully, I can figure it out soon...

---------- Post added 09-04-14 at 05:54 AM ----------

Oh, this might work </br> </br> Maybe ?

09-04-2014, 02:28 PM   #20
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QuoteOriginally posted by Tan68 Quote
Interesting comments about 'normal' relative to viewing distance. I hadn't heard that before; mostly, hear about film diagonal. I don't know about 55mm. As far as ranges of focal lengths, many are separated by 1.5x 24 > 36 > 53 > 80 > 120 Not focal length but multiples of 1.5 above Close... I figured 1.5x was significant. 1.4x fit in the mix as well 28 > 39, 35 > 49, 50 > 75 Who knows I think favors 1.4x some. For the DA lenses. 15 > 21 > 29 > 40 with 50 > 70 The 29mm is missing, of course, and there is no room for 35mm with this theory. Take the 29mm and 1.5x to get 43mm. I think Pentax planned a 29mm lens. It is the missing link. It caused Janneman to die of a broken heart. Honestly, I prefer a 28mm on the camera over a 35...

---------- Post added 09-04-14 at 05:49 AM ----------

Sorry for the hash above. [br/] [br/] I don't have javascript enabled and saw I should use an HTML tag for the bold characters but didn't realize it was necessary for paragraph breaks. [br/] [br/] Looking at quoted text, it looks like they use an odd 'break' tag here [/br] [/br] Hopefully, I can figure it out soon...

---------- Post added 09-04-14 at 05:54 AM ----------

Oh, this might work </br> </br> Maybe ?
Here is a link to the BBCode tag table for this forum:

PentaxForums.com - BB Code List


Steve
09-04-2014, 02:48 PM   #21
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I wouldn't have guessed that existed
Thanks
QuoteOriginally posted by stevebrot Quote
Here is a link to the BBCode tag table for this forum:

PentaxForums.com - BB Code List


Steve
09-04-2014, 08:33 PM   #22
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I'm surprised people feel the need to have a single reason for a lens's existence. I certainly am glad varying focal lengths exist. It also took me years to bond with my 50mm on 35mm film - really, I never did. It was neither wide enough nor telephoto enough but it absolutely did not look "normal" to me. It looked like a short telephoto. I would have preferred a 55 or 70, for sure.

In some motion picture lens systems, each focal length is an increase of 50% over the previous. That makes sense to me, with maybe some gaps being filled it. but the leap from 50mm to 85mm, in my opinion, is simply too large.
09-05-2014, 07:02 PM   #23
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QuoteOriginally posted by Tan68 Quote
I wouldn't have guessed that existed
Thanks
It, like the forum policies, is sort of hard to find. I am glad to be of assistance.


Steve

09-06-2014, 10:03 AM   #24
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50-58mm gives about the same perspective your eyes have (without glasses) on the old film SLRs. That is why they were standard.
09-06-2014, 12:09 PM - 1 Like   #25
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Also, in early SLRs it was easier to design fast lenses around 58 and longer, as simpler designs would clear the mirror (such as the Asahiflex 58 f2.4). Thus early SLRs often had 58 f1.4 or f1.2 while rangefinders would have 50mm as they had no mirror to clear. Later lens designs moved fast SLR lenses to 50 or 55 mm.

Remember the Pentax SV had 55mm f1.8, while the later Spotmatic added 50mm f1.4 where the rear element could be damaged if mounted on early SVs. Later SVs (orange R) were modified to work with the 50 f1.4
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