Re: Slit width - Distance to fim plane

[Alan & Shari Kafton <shmooze@xxxxxxxxx>]

Robert Durn wrote:
> 
> Hello to all,
> Does any one have any thoughts or answers to how wide a slit should be and
> how far it should be from the film plane? I have been building a camera with
> a 24mm Nikon lens using 120 film stock and a 1mm slit placed 10mm from the
> film plane.
> I still can't get a really sharp image even at f16. The film transports
> around a drum omega style and has an image of 149.5mm for 360 degrees.
> Also, I know that the rule says 2 x focal length x Pi or 150.796mm but is
> 149.5mm close enough?
> 
> Can any one help?
> Many thanks, Rob Durn Stockport UK
> 
> also at Robert.Durn@xxxxxxxxxxxxxxxxxxxx

Dear Rob,

One other thing you may want to consider is that often the published
focal length in not correct -- for wide angle lenses, the actual FL
tends to be a bit longer.  So if your lens is really 24.5 mm, the
calculated drum diameter should be almost 154 mm which is now quite a
bit off of what you actually have.

It turns out that the Roundshot Super 35 or 220VR users manual lists
actual focal lenghts for some Nikon lenses that must be programmed into
the camera computer.  If you respond with more details on what lens you
actually have (i.e. f2.0, f2.8 etc, AI, etc) perhaps one of our list
readers will look to see if the manual has your lens listed.

While I've never built a camera, I think you'll find the slit-to-film
distance for most panoramic cameras is closer than 10 mm.  1 mm slit is
a bit on the narrow side compared to most -- the narrower the slit, the
more banding-prone your camera will be.  On the other hand, the narrower
your slit, the LESS prone your camera will be to apparent
synchronization (out of focus) problems due to your drum being the wrong
diameter!!

Ah....to be able to afford that great Roundshot Super 35 or 220VR!!!

Best of luck,

--Alan Kafton