Tilting the lens tilts the image plane. Actually, it also tilts the
object plane. The idea is that the film is further from the lens for
close objects than far objects to both are in focus. View cameras can
also offer this kind of movement although some offer only a parallel
movement by having a rising or falling front. This has another effect.
Its usually used to eliminate the "distortion" from perspective.
Actually, the image presents true perspective when the lens is centered
but pictures are so often viewed at the wrong distance for the image
size that the object appears to be distorted. I have difficulty
explaining this in words alone but a drawing makes it clear. Note that
this applies to lenses that are orthogonal (I think this is the correct
term), that is, straight lines in the object are presented as straight
lines in the image. If you imagine a square box with several square
compartments each with a sphere in it, a photo may appear to make the
squares larger as you move away from the center and the spheres will
become egg shaped with the narrow end toward the center. When such an
image is viewed from the equivalent of the taking distance (that is from
a distance equal to the lens to object distance times whatever
magnification there is in printing) the objects will appear rectilinear,
i.e., no geometric distortion. When viewed at too far a distance you
will see the distortion. This is also what causes the "distortion" in
wide angle lenses (but not fish-eye lenses since they are not
orthogonal). Here again, viewing from the correct distance makes the
"distortion" disappear.
On 3/26/2017 7:21 PM, CarlosMFreaza wrote:
Hello Richard:
The SL66 is not like a View Camera, it only allows to tilt the lens like you could tilt a cardboard as John explained; the purpose is to increase or to diminish the DOF beyond the limits you could reach playing with the f stops keeping in mind it's a MF camera with advantages and disadvantages regarding a View Camera. The function is very useful to photograph a group of items keeping their depth and sharpness, but you couldn't correct perspective distortions like a building or a church vertical lines, you need a View Camera (or PS) for that purpose. I think this SL66 function is aimed at commercial photography mainly, but it can be used for other purposes too, BTW.
I I hope a quick improvement for your carpal tunnel problem.
Carlos
2017-03-26 22:25 GMT-03:00 `Richard Knoppow <dickburk@xxxxxxxxxxxxx <mailto:dickburk@xxxxxxxxxxxxx>>:
I think it helps to visualize the image plane. Moving either the
front or back of the camera is like extending the image beyond the
normal limits of the film. You select the part of the image you
want. This is where the lens and film planes remain parallel. When
the lens or film is tilted it really changes the direction the
camera is pointing. When either the image plane or lens plane is
tilted it really also tilts the object plane. The plane of focus
really remains the same but is tilted in space to the film plane
cuts through it. The effects become obvious if you have a good,
wide coverage, lens on a camera with adequate movements and play
with them. I am not sure what movements are available on the
SL-66 (I don't have one). Tilting the lens or film plane have
different effects than moving them in parallel. The effect of
either on illumination becomes clearer when one pictures how the
image, object and lens plane interact.
I really MUST get my carpal tunnel problem fixed. I can hardly
type any more. UGH!!!
On 3/26/2017 5:33 PM, CarlosMFreaza wrote:
Yes John, I called it the Scheimpflug angle in my post, they are
really the angles of the Scheimpflug principle, the Scheimpflug
intersection is where the angles of the subject plane, the lens
plane and the image plane have an intersection.
I watch the DOF effect whilst tilting the lens in the focusing
screen directly, however you could lose some details sometimes
because the screen loses luminosity for some areas according you
tilt the lens, the Scheimpflug indicator cards can help for a
better planning, I don't have the original transparent, it would
be nice to have the 80mm lens indicator at least, I'll write you
off list tomorrow, thank you very much John.
Carlos
2017-03-26 20:11 GMT-03:00 John Wild
<jwild@xxxxxxxxxxxxxxxxxxxxxx <mailto:jwild@xxxxxxxxxxxxxxxxxxxxxx>>:
Carlos, that's a nice collection.
I'm sure you know that with the Scheimpflug principle, when
tilting the lens with respect to the film plane, the plane of
focus is no longerparallel to the film but, with respect to
the SL66, it leans forward like a piece of cardboard.
With the focus hood, being taller than the rest of the items
it goes above the plane of focus, a bit like the items being
tilted and submerged underwater but the top of the camera is
above the surface and so it is no longer in focus.
Do you have the Scheimpflug calculation cards for the SL66? I
think I have a spare if you would like one.
John
------------------------------------------------------------------------
*From:* rollei_list-bounce@xxxxxxxxxxxxx
<mailto:rollei_list-bounce@xxxxxxxxxxxxx>
<rollei_list-bounce@xxxxxxxxxxxxx
<mailto:rollei_list-bounce@xxxxxxxxxxxxx>> on behalf of
CarlosMFreaza <cmfreaza@xxxxxxxxx <mailto:cmfreaza@xxxxxxxxx>>
*Sent:* 26 March 2017 12:35
*To:* rollei_list@xxxxxxxxxxxxx
<mailto:rollei_list@xxxxxxxxxxxxx>
*Subject:* [rollei_list] Rollei SL66 Distagon 4/80
I took yesterday a photograph about the equipment my father
often used when he had photography as a hobby;it's from the
'50s and I'm still using it. The Rolleiflex 2,8C Xenotar and
the Gossen Sixtomat and the Walter Voss Diax IIb are in
perfect working order.
The image was taken with the Rolleiflex SL66 CZ Distagon
4/80, Kodak Tmax 100 developed with Romek PQ7 1:3. I used the
camera capability to tilt the lens, the 2,8C viewfinder hood
is out of focus slightly and its Xenotar lens is in focus, it
happens due to the Scheimpflug angle, I need a bit more of
practice:
-- Richard Knoppow
dickburk@xxxxxxxxxxxxx <mailto:dickburk@xxxxxxxxxxxxx>
WB6KBL
