[rollei_list] Re: Verticals at edge of frame
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Mon, 12 Dec 2011 20:05:56 -0800
----- Original Message -----
From: "Kirk Thompson" <thompsonkirk@xxxxxxxxxxx>
To: "Rollei List" <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, December 12, 2011 3:24 PM
Subject: [rollei_list] Re: Verticals at edge of frame
I'm still not sure, Carlos, that I'm following you.
Presumably you took the picture knowing you'd use a
perspective crop on it, so there's no loss of information,
other than resolution, from what was intended.
Or alternately you mean that if you didn't have cropping in
mind when you took the picture, cropping it later will leave
something out – as is always the case. As Jeff said, you
have to plan ahead and leave enough foreground (or enough
sky above your church cross) for the crop.
Anyhow here's an example. I tried half a dozen places in
the alley before I got the framing I wanted. The image was
taken so that after perspective crop, (a) the 'E' in 'Hope'
would be included, along with its light standard; and (b)
the diagonal wire at the left would make contact with a bit
of building and not just wander off the left margin. The
perspective crop has of course interpolated pixels at the
top, and in that sense there's technically a loss of
resolution, but with no visible effect. All intended
information is included; nothing left out or lost.
But back to the original post: the problem was probably
just camera angle. As in this photograph, you get more
perspective convergence if you shoot from the waist or
chest. If you want a straightforward representation of
architecture, it's best to use a prism and shoot from eye
level, which will end up looking more natural to the viewer.
(Or abandon Rollei for view camera or tilt-shift DSLR lens,
but that's a whole different story.)
It's interesting, though, that commercial photography and
sometimes even architectural magazines don't always correct
for perspective. We have a kind of secondary vision: the
eye tricks us into seeing verticals when we walk around in
the world, but people have become so accustomed to viewing
wide-angle camera shots that they accept some convergence of
verticals in photographs. The 'tippiness' becomes part of
the dynamics of the composition.
Kirk
PS: In practice I often take out some vertical convergence
in an image with Photoshop, but also leave some.
Date: Mon, 12 Dec 2011 15:15:48 -0300
Subject: [rollei_list] Re: Verticals at edge of frame
From: cmfreaza@xxxxxxxxx
To: rollei_list@xxxxxxxxxxxxx
Note that perspective "correction" is really trading
one optical illusion for another. The effect appears to the
eye partly because prints are viewed from the wrong distance
(same as "wide angle" distortion) and partly because we
mentally compensate for dimininshing perspective on
verticals when actually viewing them.
The same correction as produced in a computer image
editor can be doen by tilting in an enlarger. However, the
focal length of the projection lens must be correct, and,
ideally, both negative and paper must be tilted. That
creates a problem with the light source but the method does
work with some care. The effect of correcting perspective in
an existing photo never quite duplicates the effect of doing
it in the camera, for instance the planes of focus can not
be changed while in the camera they do change.
Even in the camera the cropping is changed from what it
would be if the camera were simply pointed at the object. If
one knows that the image will be manipulated later some
account of that can be made in the original framing.
BTW, I've seen a lot of view camera images where the
camera over-compensated for the verticals resulting in an
image which actually becomes larger at its most distant
points!
Another BTW, there is a curious effect when looking at
a panoramic picture, especially one taken with a rotating
camera. When views with the image flat the surfaces, say of
a building, appear to curve away from the viewer but, when
viewed from the center of a curved print the image looks
right. The image IS right, providing its viewed from the
right place.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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