I wrongly thought the statement "Although 35mm in focal length (normally
63 deg angle of view), the lens is essentially equivalent to a 24mm lens
in angle of coverage (actual 83 deg)." in esif pretty much meant the
view was the same as a 24mm. It isn't. The 35mm shifts far enough that
it will cover more than what I see in a 24mm lens. The only explanation
I can imagine for why 83 deg at max shift for the 35 is bigger than the
84 deg of the 24mm fixed lens is that the shift lens 83 degree angle
covers from one corner to the opposite corner when the lens is shifted
in only the vertical direction. Since the width of the combined image is
narrower than the image of the 24mm lens, the top most part of the
combined image and bottom most part of the combined image have to be
further apart.
The easiest way to see what it will cover is to point a 35mm lens with
the bottom of the frame at the horizon, then point the lens with the top
of the frame at the horizon. The sum of the two is the coverage provided
by shifting vertically.
The most common way I compare lenses of different focal lengths is by
using the narrow dimension of coverage of a wider lens to estimate the
wide dimension of coverage of the next step longer. The 35mm shift
provides greater vertical angle coverage in landscape orientation by
shifting than by keeping it fixed in portrait orientation (which is
consistent with it providing more vertical shift coverage in landscape
orientation than the fixed 24mm covers).
So Piers is right 83 deg of coverage is greater than 84 deg ... I'll
bet my description is perfectly clear.
-jeff
(I'm assuming the 24mm shift without shifting is the same as a 24mm non
shift lens - I think that is a safe assumption - as typical the two
shift lenses are what I have with me)
----- Original Message -----
From: "Piers Hemy" <piers@xxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Wednesday, June 04, 2003 3:20 AM
Subject: RE: [OM] Re: Shift Lenses
> No, I don't think that is correct, Peter.
>
> I think the point is that the plane of view when the lens is shifted
is not
> at 90deg to the lens axis. So as you shift, the angle of view
increases.
> And thus if you take two images at full shift each way as you
describe, you
> will get more than a normal 24mm coverage.
>
> But that is just my impression, open to challenge!
>
> I would offer to test on my 35/2.8 shift, but it's not a Zuiko, so I
suppose
> that would be off-topic! (and it's not a shift, it's a T&S)
>
> Piers
>
> -----Original Message-----
> From: owner-olympus@xxxxxxxxxxxxxxx
[mailto:owner-olympus@xxxxxxxxxxxxxxx]
> On Behalf Of petertje@xxxxxxxxxxxxx
> Sent: 04 June 2003 09:25
> To: olympus@xxxxxxxxxxxxxxx
> Subject: [OM] Re: Shift Lenses
>
> --snip
>
> The way I understand this comparison of a 35mm shift to a 24mm is the
> following: if you shift it all the way up and mark what you see, then
shift
> it all the way down and mark what you see, then the complete image
covered
> by those 2 marks will correspond to the image of a 24mm. Is that
correct ?
>
> --snip
>
> Peter.
>
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