[MF3D.FORUM:394] Re: MF DOF(was Re: Dream Camera)

["Bill Glickman" <bglick@xxxxxxxx>]

Sam

      When tilting for train tracks, you always tilt the front standard to
change the plane of sharp focus, tilting the rear standard would cause the
scene to distort the image....you have to tilt the lens forward.... you are
partially right about the persons head being out of focus... this would be
determined by the lens fl being used, because the distance of the point
under the camera in which the plane of sharp focus will begin at - and then
spread out like a cone is a function of the fl.  A simple formula to get you
close to that point is fl/(j*5) = tilt angle (Degrees) ... where j is the
distance in feet below the lens where the plane of sharp focus extends
outward towards the scene.  The longer the fl lens the harder it is to get J
up high...(because the greater the tilt angle)  remember, that you can not
arbitraly allow any tilt angle.... tilt angles are limited by the size of
the image circle lens you have... as you tilt the lens downward, the image
circle moves up over the film..... until at some tilt angle no light is
hitting the film area at all!  Also as you move closer to the edges of the
image circle you are confronted with Cos^4 theta light fall off.... an issue
with ALL lenses at the edges of their image circles... this can mean a stop
or 2 of light loss.  So, there is several things to consider when tilting...

If anyone is interested, there is an excellent graphic and quick time movie
by Merklinger referencing the relationship between the tilt angle and plane
of sharp focus...Seeing this is much better than trying to envision
it......I will try to dig up the URL  and post it if anyone wants to see
it...

Regards
Bill G


----- Original Message -----
From: Sam <3dhacker@xxxxxxxxxxxxx>
To: Medium Format 3D Photography <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Tuesday, April 04, 2000 1:38 PM
Subject: [MF3D.FORUM:392] MF DOF(was Re: Dream Camera)


> At 11:08 AM 4/4/00 -0700, you wrote:
> >Bill Glickman wrote:
> >> ...MF will most likely be my mainstay due to the DOF limitations
> >> with the longer fl lenses used in 4x5.
> >
> >That's odd.  I was leaning in the opposite direction, figuring view
camera
> >movements would be the best way to deal with shallow DOF.
>
> Wouldn't that depend on your subject? If you are shooting train tracks,
> then yes you could tilt the back to compensate for the foreground and
> background in focus. Stick a person in, say 8 feet from the camera, and
> their head will be out of focus. No advantage to LF if background detail
is
> directly in line with a foreground subject.
>
> Speaking of Large format stereo, my restoration of a Farrow 5x8 Stereo
> Tailboard camera is nearly finished. I should have some pix later next
week
> to share with y'all.
>
> Sam
>