Archived posting to the Leica Users Group, 2016/09/16

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Subject: [Leica] How did 50mm become the "normal" lens for 35mm cameras?
From: hlritter at (Howard L Ritter Jr)
Date: Fri, 16 Sep 2016 23:31:09 +0200
References: <> <>

I?m not sure I understand what you mean, Bill. This looks like circular 
reasoning: no magnification or reduction with respect to what standard? Only 

The size of the image on the film has no inherent relationship to the 
subject itself unless it?s taken with a macro lens at 1:1 reproduction 
ratio. Anything else is an arbitrary representation that depends on the 
focal length and distance to subject. Pick a print size and a viewing 
distance. Choose the FL to be that which gives the same image scale on the 
print as the scene that you?re viewing from the same point as the camera. 
Maybe for one person that?s 50 mm, maybe different from others. The process 
would be totally arbitrary.

Is it that 50 mm gives a unity-magnification view in the viewfinder of a FF 
SLR? That?s dependent on the apparent size of the focusing screen produced 
by the FL of the VF eyepiece. Again, arbitrary. Designers could make the 
image formed by a 35-mm lens on the screen appear at unity magnification by 
using a wider-field eyepiece on the VF.

Any focal length for any film frame size is totally arbitrary. The human eye 
takes in nearly 180 degrees, so one ?no magnification or reduction? standard 
would be a fisheye lens. OTOH, the field of foveal vision, full resolution, 
is a fraction of a degree, so another standard would be a 1000-mm lens. 

I?ve heard it said that the field of attention of the human eye-brain 
system, the principal stuff that we apprehend when we look at a scene, is 
about the same as that captured by a lens whose FL is about the same as the 
diagonal of the film frame. So a FL in the range of 40-50 mm would fit that 
bill. That?s also full of assumptions and arbitrary decisions. The 50-mm 
decision is probably rooted in many things, including what?s in this 
paragraph and what was available when 35 mm photography was evolving.

Simple P&S cameras had 35-mm lenses when they were FF film cameras and that 
seemed to make most users happy. Today the few fixed-lens FF digital 
cameras, I suppose the only two, in fact, use 28 and 35 mm, respectively: 
the Leica Q and the Sony RX1. 

I use 35 mm as the default lens on my 240 and MM when I head out. I don?t 
even own a modern 50-mm lens.

The bottom line is: Normal FL is what the photographer regards as such. But 
it doesn?t have to do with a zero point between magnification and reduction.


> On Sep 16, 2016, at 6:17 PM, Bill Clough <billclough042541 at> 
> wrote:
> It's called a normal lens because it neither magnifies or reduces the 
> image.
> --Bill Clough
> On Fri, Sep 16, 2016 at 11:15 AM, Adam Bridge <abridge683 at>
> wrote:
>> I?m just wondering if anyone knows since 43mm would be the more rigorous
>> focal length for tradition 35mm film.
>> Thanks!
>> Adam Bridge
>> _______________________________________________
>> Leica Users Group.
>> See for more information
> _______________________________________________
> Leica Users Group.
> See for more information

In reply to: Message from abridge683 at (Adam Bridge) ([Leica] How did 50mm become the "normal" lens for 35mm cameras?)
Message from billclough042541 at (Bill Clough) ([Leica] How did 50mm become the "normal" lens for 35mm cameras?)