Re: [gentoo-user] merging or fitting images together

[Philip Webb <purslow@ca.inter.net>]

120520 Stroller wrote:
> Zoom lenses were much less common even 2 or 3 decades ago.
> For a long time, a 50mm prime was the common kit lens,
> rather than the 18-105mm zoom which is sold today.
> This was because on a camera using 35mm film, a 50mm focal length
> gives a field of view very close to that seen naturally by the human eye. 
> Wikipedia states that "the first modern film zoom lens was designed c 1950
> by Roger Cuvillier" and Canon's official website (the "Canon Camera Museum")
> states that "The history of Canon's zoom lens goes back to 1954."
> Since the photos are stated go have been taken in 1953
> it seems highly unlikely that the photographer was using
> a highly expensive and cutting-edge zoom lens. I doubt many people
> would have been able to afford these zoom lenses when first released. 
> It seems to me safer to assume that the lens is a 50mm.

In fact, looking more closely at the picture of a ZI
which I've put up in my I/net 'test' dir (found on the I/net earlier),
it says 'F = 7,5 cm', so the lens appears to have been a  75 mm .

> I guess focal length may change fractionally during focussing
> -- as lenses are moved back and forth during as the focus ring is turned --
> however it may also be that a camera manufacturer designs a lens
> with a 48mm focal length because that's easier to construct for some reason
> or produces better images and decides to sell it as 50mm
> because a 2mm difference makes no difference to the photographer. 
> Or it may be that the distortion is caused by lens distortion
> perhaps Hugin is trying to compensate for that, and straightening up lines. 
> In any case, I might try re-doing the stitch a few times,
> each time telling Hugin the lens is 47mm, 48mm, 49mm, … 51mm, … 53mm.
> Perhaps you may find that one of those is perfectly spot on.

Thanks for the further lesson ! -- it sb tried at  75 mm .

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