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Archive 2012 · Leica M Lenses: an interesting look into the past
  
 
zoffdino
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p.1 #1 · Leica M Lenses: an interesting look into the past


I just purchased a 90mm Elmarit-M and was curious about its capabilities. Long story short, I went Leica's support and found a book written by Erwin Puts in 2002: Leica-M Lenses: Their Souls and Secrets.http://en.leica-camera.com/assets/file/download.php?filename=file_1756.pdf

Among the interesting tidbits I've found (I focused mainly on the 90mm focal length):


  1. Leica 90mm lenses have been in continuous production since 1931.
  2. 90mm as a "portrait lens" is a oxymoron invented by the sales people to describe the slightly soft image of the Summicron-M 90mm in 1980 (the last pre-ASPH design).
  3. Nobody knows why 50mm is called "normal". The human vision field range from 6 to 130 degrees depending on what criteria you are looking at. The tradition of the 50mm as a lens on which each maker is evaluated started with Oskar Barnack when he chose a 42mm lens on the Ur-Leica. It may have moved to 50mm because for ease of construction (and rounding).


Overall a very good read, doused in history lessons and overexposed in thoroughness. The trademark Erwin Puts' style is on display, but at a scaled down level where each lens is only endorsed with a design diagram, two MTF charts , a vignetting and a distortion chart.



Aug 05, 2012 at 12:48 AM
lovinglife
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p.1 #2 · Leica M Lenses: an interesting look into the past


Thanks for the link..
I will read it.



Aug 05, 2012 at 08:14 PM
carstenw
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p.1 #3 · Leica M Lenses: an interesting look into the past


Here is a link which works better for me: http://en.leica-camera.com/assets/file/download.php?filename=file_1756.pdf


Aug 05, 2012 at 08:23 PM
thrice
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p.1 #4 · Leica M Lenses: an interesting look into the past


It is called a normal lens because of the ratio of size difference between near and far objects appears the same based on the distance from the ~50mm lens or an eye.

True 'normal' is 43mm. That is, on a 24x36mm imaging area.

A portrait lens is usually a medium telephoto, the reason being that perspective distortion from wide angles enlarges protrusions (nose, forehead, chin) on a subject and is deemed unflattering. A mild degree of telephoto flattening is flattering, a bit too much and people lose dimension.

An oxymoron is an adjective next to a noun which can be seen as opposing, like "cheap leica".

Puts has his moments. Understanding field of view and english obviously aren't his strong suits.



Aug 08, 2012 at 08:58 AM
carstenw
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p.1 #5 · Leica M Lenses: an interesting look into the past


thrice wrote:
It is called a normal lens because of the ratio of size difference between near and far objects appears the same based on the distance from the ~50mm lens or an eye.


I don't quite get this description. As far as I am aware, the ratio of near and far objects is only a question of where you stand, not which lens you use.



Aug 08, 2012 at 09:34 AM
edwardkaraa
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p.1 #6 · Leica M Lenses: an interesting look into the past


carstenw wrote:
I don't quite get this description. As far as I am aware, the ratio of near and far objects is only a question of where you stand, not which lens you use.


I think both are correct. It is a matter of where you stand (to fill the frame with the same subject).

In this case, a WA will cause perspective distortion and a tele will cause compression.

Of course, if you shoot from the same position, and crop a WA shot, you will get the same perspective as a telephoto. But in practical use, I wouldn't shoot a portrait at 1.5 meter with a WA and crop the frame. Nor could I take a group photo with a 90mm lens even if I wanted to for lack of room space.


Edited on Aug 08, 2012 at 09:48 AM · View previous versions



Aug 08, 2012 at 09:47 AM
thrice
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p.1 #7 · Leica M Lenses: an interesting look into the past


Sorry, I should have added "for compositions having the same comparative size of the near object but different focal lengths"


Aug 08, 2012 at 09:48 AM
carstenw
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p.1 #8 · Leica M Lenses: an interesting look into the past


Okay, I understand what you meant now

But I am not sure how that description can yield a working method for determining the correct focal length for a normal lens?



Aug 08, 2012 at 09:51 AM
thrice
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p.1 #9 · Leica M Lenses: an interesting look into the past


The angular field of view is the same, between 42 and 56 degrees.

Of a single eye.

If you're looking at the scene, and you have the near object the same approximate size in relation the rest of the scene in your finder/groundglass as you see it when looking through one eye straight into the scene then it is pretty approximate to normal.

If it is larger through the lens relative to the rest of the scene then you're wider, if it is smaller then you are longer.
I don't quite understand what you're struggling with.



Aug 08, 2012 at 09:57 AM
edwardkaraa
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p.1 #10 · Leica M Lenses: an interesting look into the past


I think what thrice says makes sense, at least to me

We always get confused by scientific definitions, but in practical terms, if you stand at the same camera to subject distance (no matter if close or far), and shoot with a WA, standard, and tele, the perspective is different, unless you crop, which I suppose no one wants to normally do.



Aug 08, 2012 at 10:04 AM
 

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carstenw
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p.1 #11 · Leica M Lenses: an interesting look into the past


thrice wrote:
The angular field of view is the same, between 42 and 56 degrees.

Of a single eye.

If you're looking at the scene, and you have the near object the same approximate size in relation the rest of the scene in your finder/groundglass as you see it when looking through one eye straight into the scene then it is pretty approximate to normal.

If it is larger through the lens relative to the rest of the scene then you're wider, if it is smaller then you are longer.
I don't quite understand what you're struggling with.


But wait: now we are back to my first point, which is that the relative sizes of objects in the scene is only dependent on where you stand, not which lens you use. So given that you and your camera are standing at the same place (approximately), you will see the same as your lens sees, no matter what lens you use... I mean, that is what photography is, right, an image of what you see with only the exposure and colour sensitivity differing from what you see, but not the perspective or geometry (fisheye lenses excluded).

I thought that normal lenses were defined by the angle of view of one eye, as you say.



Aug 08, 2012 at 10:36 AM
carstenw
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p.1 #12 · Leica M Lenses: an interesting look into the past


edwardkaraa wrote:
I think what thrice says makes sense, at least to me

We always get confused by scientific definitions, but in practical terms, if you stand at the same camera to subject distance (no matter if close or far), and shoot with a WA, standard, and tele, the perspective is different, unless you crop, which I suppose no one wants to normally do.


Hmm, I am not sure what you are getting at either If you stand in one place, and shoot with 3 lenses, you do indeed get exactly the same photo, with extra around it, the wider the lens. The central parts are the same.

But I thought Daniel was talking about varying the subject distance to keep the main subject the same size (a boulder, say), and observing the relative sizes of the objects in the scene. The thing is that if you put your eye where the lens is, you will always see the same as the lens sees, no matter what focal length (except fisheyes, and ignoring other kinds of distortion).

And that is the normal state of things. The camera *of course* makes a photo of what you see, with the same proportions. What else could it do?



Aug 08, 2012 at 10:43 AM
edwardkaraa
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p.1 #13 · Leica M Lenses: an interesting look into the past


carstenw wrote:
Hmm, I am not sure what you are getting at either If you stand in one place, and shoot with 3 lenses, you do indeed get exactly the same photo, with extra around it, the wider the lens. The central parts are the same.

But I thought Daniel was talking about varying the subject distance to keep the main subject the same size (a boulder, say), and observing the relative sizes of the objects in the scene. The thing is that if you put your eye where the lens is, you will always see the same as the lens sees,
...Show more

Of course, in order to do what Daniel is saying, you will have to vary the shooting distance according to the lens, so closer with a WA and further away with a telephoto, which will inevitably alter the perspective, which is dependent on the distance to the subject as you rightfully said earlier.



Aug 08, 2012 at 10:53 AM
Makten
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p.1 #14 · Leica M Lenses: an interesting look into the past


Carsten is right; if you crop a picture taken with a wide lens, it will look exactly the same as with a corresponding longer lens. Perspective is only a function of distance, and there is no such thing as "perspective distortion", even if it's a decent term.

In my opinion, 50 mm is too long on 24x36 compared to my eyes active field of view. Horizontally, yes, but not vertically. I believe the nearest "true" normal is 80 mm on 6x6 in that sense.



Aug 08, 2012 at 11:13 AM
edwardkaraa
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p.1 #15 · Leica M Lenses: an interesting look into the past


Makten wrote:
Carsten is right; if you crop a picture taken with a wide lens, it will look exactly the same as with a corresponding longer lens. Perspective is only a function of distance, and there is no such thing as "perspective distortion", even if it's a decent term.



I have the impression we are all saying the same thing differently

Practical example:

Camera on tripod in a flat landscape setting including sky, horizon and foreground. 2 lenses are used, say 21mm and 200mm to accentuate the effect. The 200mm frame includes horizon and objects as close as, say 20 meters. If you crop the 21mm shot, you will get exactly the same frame as the 200mm, but only in the frame center. The thing is, the 21mm shot includes foreground elements as close as 1 meter. The perspective in relation to the lens/subject distance is certainly quite different. That is why a WA shot has several angles of perspective in one frame, while the longer the lens, the more homogenous the perspective.



Aug 08, 2012 at 11:32 AM
Makten
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p.1 #16 · Leica M Lenses: an interesting look into the past


I don't think I would use the word "perspective" for your descriptions, Edward. But in everything else, we agree.


Aug 08, 2012 at 11:58 AM
edwardkaraa
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p.1 #17 · Leica M Lenses: an interesting look into the past


Makten wrote:
I don't think I would use the word "perspective" for your descriptions, Edward. But in everything else, we agree.


I wouldn't use it either, but I'm short of vocabulary



Aug 08, 2012 at 12:02 PM
carstenw
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p.1 #18 · Leica M Lenses: an interesting look into the past




One minor point: in your example, if you point the 200mm lens anywhere in the scene, whether at 2m, 20m or infinity, it will see the same as that part of the wide angle shot (ignoring distortion), so it isn't perspective, but more simply field of view.

The one caveat is that if you take a super wide shot, the corners look distorted or stretched, because we simply do not put our head in the right place to give the correct effect when viewing the photo. If we would, they would look the same.



Aug 08, 2012 at 12:38 PM
edwardkaraa
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p.1 #19 · Leica M Lenses: an interesting look into the past


carstenw wrote:


One minor point: in your example, if you point the 200mm lens anywhere in the scene, whether at 2m, 20m or infinity, it will see the same as that part of the wide angle shot (ignoring distortion), so it isn't perspective, but more simply field of view.



It is true that if I point the 200mm anywhere in the 21mm frame, I will get the same angle and same framing.

However, the 200mm shot has "flattened perspective" because in the entire frame the lens to subject angle is quite similar. However in the WA shot, in the same frame there are different angles from 180 degrees in the center to almost 90 degrees in the foreground. This in my opinion is what creates the "dynamic perspective" of wide angles.




Aug 08, 2012 at 12:54 PM
carstenw
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p.1 #20 · Leica M Lenses: an interesting look into the past


Yes, it is true that the wide angle lens appears to have more variety in the composition, but if you used the 200mm lens to stitch, you would still get the same results, so it isn't fundamentally different.


Aug 08, 2012 at 01:08 PM
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