P3D Re: Realist Vignetting at f/16?

[Michael Georgoff <Michael_Georgoff@xxxxxxxxxxxxxx>]

RE: My f3.5 Realist vingnetting at f/16....

Jay Schumacher sent me a reply on this off-list, saying "seems to me that if
the cone of light were being blocked by something *inside* the camera then
it should happen at all apertures, not just small ones. My mental image is
of a cone that gets small enough at f16 and f22 that it doesn't quite reach
all the way into the corners of the film"

I've been thinking about what it looks like inside the Realist.  There is no
"something inside", Jay's right about that, so at f/16 and f/22 the "back
end" of the cone does not have enough image to reach the corners.  I imagine
a small circle "projection" not quite filling a rectangular screen, which is
the film plane.  Or a flashlight's round beam of light being shined on a
card so that the corners do not fill with light.

So, either the cone needs to be larger (as in larger aperture, so that the
front end in the lens is larger, and the back end "projection" ends up
larger, too) or the film plane needs to move back (as in focusing at a
closer distance).  No idea if closer focus (at f/16 or f/22) means the film
plane moves back far enough for the circle image to fill it. I do note that
on my Realist, when focused at infinity, the film plane is up as far against
the camera body as it can go.  Sort of infinity as "film plane parked"
position, and closer focus move the plane away from the body.  Total travel
maybe one eighth of an inch?

Still appreciate hearing more perspectives on vingnetting thing.  I'd hate
to have to shoot a f/11 or below to avoid it.

Michael Georgoff
San Jose, CA


------------------------------

End of PHOTO-3D Digest 2967
***************************