That's down to subject distance - our brains compensate for it so we don't see it with our eyes in the same way as the camera does. It happens less on longer lenses because the differences in subject to camera distance vary less significantly accross the frame when the subject to camera distance is greater.
Depends on camera type and camera to subject distances and orientation. On a longer lens you get the effect of compression, beloved of Murray Walker in his F1 commentary.
The human eye, is a remarkable thing, the information it acquires, is then 'manipulated' by the most complex organ in our body, the brain. We can instinctively zoom in and out from some form of default viewing angle, but this may well vary depending on how far or near what we are 'interested' in, happens to be from our body. Therefore, I think we need to specify the angle of view of our vision, and then work out what focal length fits the film/sensor size we are using. Obviously a person's vision, is going to vary, as it can be restricted by things like tunnel vision. For instance, I get the impression that if I am in a room, with a group of people in front of me, my angle of vision, 'seems' to widen, and I find that I need to use a wider angle of lens, to get what I see, whilst if that same group of people (were positioned exactly the same, and at the same distance from me) were outside, with a pretty nondescript background behind them, I get the impression that I would select a lens with a slightly narrower angle of view, so that the perspective of the scene in front of me, 'looked' correct. Do we know, or can quantify how much 'work' the brain is doing in the background? I doubt it. For instance, it could be that when something 'catches our eye' in the scene in front of us, whilst our angle of vision might well be the same, our brain 'highlights and 'focusses in' on that part of the scene, without us probably noticing that we are indeed doing this. Therefore (and I haven't any data etc to back this assertion up) the 'angle of view' of our eyesight varies from one moment to another, and this 'difference' in angle, might well be greater than we think it is, and my reason for saying this, is vaguely based on the different lenses people on this thread, have cited as delivering what they think, gives them the most 'natural' viewing angle. My apologies to those who may find my reply somewhat convoluted!
And it's what I was talking about, too. I haven't looked but I'm sure Langford & others cover it in their books on photography. The focal lengths of lenses on cameras bring their effects to the two dimensional images that we make with them. BTW, the quality of lens design has an effect on the curvilinear distortion. This maybe what bobatkins is on about. Unfortunately despite the hour, just before 10a.m., my brain appears not up to it at the moment, on a B/H morn! I was having such interesting dreams just before waking at 7-ish! I will re-read it later. I may have spotted a potential mistake, though! I think 40mm lenses were not commonplace, and generally were not available on interchangeable lens 35mm cameras until after 1970; definitely not in the 1950s & 1960s.
I would say the subject and context you wish to place it in will determine the focal length, regardless of sensor size.
Or this will ... [h=2]Poll - Which focal length, on a full-frame camera,[/h]would you use to create a sense of reality? ... to take you back to the OP's original question.
That's my answer to the very question the OP posted. Frankly, the question is a bit of a red herring.
You were a little vague. I think Damien wanted your choice of a specific focal length. The Polls have a chequered history. I think they have a value if composed well (with the right options) and the voting buttons work!
