film shifting - a new idea? etc. Re: lens coverage, selection, cost.

[Robert Monaghan <rmonagha@xxxxxxxxxxxxxxxx>]

good points re: shifting; my 6x14cm design uses "film shifting" instead 
of lens shifting, which is an approach I haven't seen formally used on 
any other panoramic camera designs - new to me, anyway ;-) ...

with film shifting, you can have a rigid camera body (or bellows too) and
build the film channel say 25mm or so _larger_ than the actual film size.
Now you put the film on an extension adapter so it moves horizontally at
any desired point in that +/- 13mm shift range (fixed shift adapters or
turn screw to desired shift point on variable adapter).  Just be sure 
film is horizontal at the shifted point! ;-)

The film "floats" up or down in the actual film channel, which is
equivalent to shifting the lens up or down a similar amount, or equiv. to 
cropping a larger film size at that shift offset. You can keep the camera 
horizontal on a level tripod, but setup a film shift of +12mm, thereby 
minimizing converging verticals etc. by moving the film down into the 
lower (or upper) section of the lens coverage. Again, same as shifting 
the lens, but easier and lots cheaper to do with a rigid camera body, if 
the lens has the coverage as you noted...

the "gotcha" is that you have to select a film shift when loading the 
film, based on anticipated shift needs (in buildings or monument subjects)
or leave centered (for vertical shots or no shifts needed). Seems a good 
tradeoff, esp. if you shoot seconds of major shots and bracket ;-) 

Closest comparable camera is one of the 6x12cm (Linhof) which has a 
permanent 8mm shift reportedly built into the camera, which can't be 
removed, making it an issue for vertical shots and a middling shift amount
for times when you really need/want the full 12mm or more shift many 
panoramics offer. Film shifting provides the same built-in shift effect, 
but it is variable, and the lens is left centered on the camera. 
Naturally, you could shift the lens in a film shift camera (say 12mm) so 
when the film is at the top of the channel, no shift is selected (e.g., 
for verticals..); but shift up to 25mm or the full width of the film 
channel provided, as noted, the lens has enough coverage for such a 
trick! ;-) 

the film adapters/spacers are much simpler for a homebrew design than a
shift lens mount mechanism, more robust, and very cheap with the right
lens and starting camera body, and a rigid body rigid lens design is easy!

I'd be interested in any other camera designs which used this "film 
shifting" approach, since it seems both obvious and useful for many 
needs, but I have yet to see such an approach in any current panoramic 
cameras in the materials/books I have available...

regards bobm

* Robert Monaghan POB752182 Dallas Tx 75275-2182 rmonagha@xxxxxxxxxxxxxxxx  *
* Medium Format Cameras: http://www.smu.edu/~rmonagha/mf/index.html megasite*

On Mon, 3 Apr 2000 IAPPPresident@xxxxxxx wrote:

> One of the nice things about the V-Pan is WYSIWYG:  What you see is what you 
> get.  There is nothing sacred about 6 x 17.  If you look on the viewing 
> screen you may discover that the image circle is smaller than what you hoped 
> for, but the image works and you have only to do a little cropping.  Chet 
> Hanchett himself suggested putting some little black boards on the sides of 
> the film magazine to crop to 6 x 12, and there's nothing sacred about 6 x 12, 
> either.  And don't forget, the image circle thrown by the lens may just cover 
> the 6 x 17 format, but sometimes you want to shift the lens, and then the 
> bigger the image circle, the more room you have for shifts.  Chet recommends 
> an image circle of 200 mm for full coverage of the V-Pan frame.  There have 
> been times when shift was more important to me than frame size - so I just 
> shifted the lens, and later cropped the edges straight.  
> 
> Liz Hymans
> 
> In a message dated 4/3/00 4:27:31 PM Pacific Daylight Time, 
> evphoto@xxxxxxxxxx writes:
> 
> <<  As soon as I find a mm ruler I'll send you specs for my
>  V-Pan mark III. Do you want the film gate diagonal as well. You of
>  course are aware that published specs for image circles are often
>  conservative. And are talking about the older 90 mm f/6.8 Angulon or the
>  current or original version of 90 mm f/6.8 Super Angulon? Three
>  different lenses with different specs. >>
>