Re: [OT] Lenses [Was: [OT] Cameras again]

In article <98ea5e14d%Graeme@xxxxxxxxxxxxxxxxxxxx>, Graeme Wall
<Graeme@xxxxxxxxxxxxxxxxxxxx> wrote:

> In message <291220051957312042%nospam@xxxxxxxxx>
> Elliott Roper <nospam@xxxxxxxxx> wrote:
>
> > In article <4c2fffe04d%Graeme@xxxxxxxxxxxxxxxxxxxx>, Graeme Wall
> > <Graeme@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> >
> > > At 35mm (50mm on a 35mm film camera) the perspective of the view is very
> > > similar to the human eye. Shorter focal lengths expand the perspective
> > > introducing increasing distortion until you eventually get the fisheye
> > > effect. Longer focal lengths compress the perspective.
> >
> > Just for the fun of arguing, and from a little bit of 'satiable
> > curtiosity'[1], how can you tell?
>
> Very easy at the extremes.
>
> >
> > Human eyes don't have a flat plane of film at a fixed distance from the
> > optical centre of the lens. In fact they act like a view camera with a
> > maniac in charge of the swings and tilts and lifts. Furthermore,
> > depending on what you are looking at, they appear to switch off more or
> > less of the retina (CCD) when it suits.
>
> Optically the human eyeball is crap, all the images have to be computer
> processed before they are any use[1].
OK, that's what I meant. The link between the optics and the human
photoshopping is pretty close. If you enlarge a tiny fraction of an
image taken with a 28mm lens, it will have the same perspective as the
same image as a full frame telephoto subtending the same angle.
Does not your eye/brain system act a zoom lens in the same way?.

> And if my failing memory[2] is still
> functioning, the retina is at a fixed distance form the optical centre of the
> lens. It is this that gives the eye a wider field of view than a camera lens
> of the same effective focal length.

Ah yes. Well spotted, although don't you mean 'depth of field'?
>
> > Compare looking into the far distance to see if that is legs walking off
> > the footpath as seen under a car parked 200m ahead, and catching sight in
> > the side mirror of the glove of a biker about to do a loony mezzanine lane
> > stunt behind you. In 35mm terms, that's a 18-500mm zoom in less than 0.2
> > sec.
>
> No it isn't, because the perspective hasn't changed, you've merely altered
> the focus, you don't see the distant object any larger or the near object any
> smaller.

I strongly disagree with that. Your eye/brain is changing perspective
in a very agile way between concentrating on fine detail in the far
distance right in the middle of whatever bit of retina is best at that,
and then on a close by blur exciting some other bit on the periphery
just before the aforementioned bloke on the Yammy in the mezzanine lane
almost clips your mirrors.

To sort-of answer my own question, but really to ask a deeper one, how
about comparing photos of faces taken with various length lenses? At
what focal length are the most flattering portraits taken? Would that
be the natural "field of view" for looking at people? What about the
same question with respect to scenery? What role do swings and tilts
play in architectural photography? Why does mucking about with the true
perspective of vertical lines make the picture of a building look
better? What about the related question of the most natural aspect
ratio for film or video?

I truly believe there are no easy to prove answers to any of this.
You are a cine cameraman are you not? Is there a good reference book?

Preferably one that does not try to snow me with golden means and
stupid looking blokes with long arms standing in a circle.

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To de-mung my e-mail address:- fsnospam$elliott$$
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