lens coverage, selection, cost.. was why Re: actual vs ratio sizes

[Robert Monaghan <rmonagha@xxxxxxxxxxxxxxxx>]

Dang! Now you have gotten me curious ;-) Since I'm hacking what amounts to
a shifting 6x14cm (really 55x130+mm), knowing _exactly_ how big the film
gate will be is handy to knowing where things should end up in the lens
circle of coverage, vignetting etc. and in picking the best lens for the $$
It will also impact how much of the lens angle I can capture on film or not?

Knowing the same thing about the various panoramics would seem to be
similarly useful as to potential for vignetting. Does the fuji beat the
linhof because it is a better lens, or because it is cropping the edge off
the 6x17 images with a smaller film gate than the Linhof 6x17? Does the 
silvestri have enough coverage for useful shifts, or will they be badly 
vignetted or soft in the corners? What effect does the built-in 8mm shift 
in the Linhof 6x12 have? 

Or how about why does a 90mm f/6.8 angulon cover and work on the
"Longfellow 6x17" (or 6x18) when it only (barely) covers 15 cm? That's
about a 400% difference in cost over deciding you really need the super
angulon or even worse the XL version to cover any 6x17 camera creation.
(see BJP Jan 15, 1997). Now the actual numbers are about 1.5cm short of 
the expected 17cm, so knowing _exactly_ what you need could save some $$

Finally, it just seems curious that if there is all this variation, that 
someone hasn't documented what camera does what. I mean, the cost for 
most panoramic cameras over the cost of 6x9 (actually 55x82 to 84mm) is 
about $100+ US per millimeter on up, depending on the camera model. ;-)

A 17cm length sounds like 6.8", the width of a 5x7" film, but if it is 
really 15.6cm, then it is 2.0 to 2.2cm shorter than a 5x7" film camera.
5x7" seems to be a lot wider, to me, if you really need the full coverage.
In other words, if a film back on 5x7 is going to be 2+ cm longer than a 
6x17, it is really a 6x19cm (so to speak) and even more panoramic, right?

curious and curiouser in Dallas ;-) 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, Ellis Vener wrote:

> i think trying to do such strict measurements will be fruitless. The
> Horseman 6x12 cm film gate is different in size from the Linhof and both
> are different from the size of the Noblex film gate. And the V-pan 6x17
> cm film gate is going to be different from the Art Pan, Fuji and Linhof
> gates, much less the Noblex and homemade 6x17 backs made from old Navy
> "torpedo" backs, plus we are all still waiting to see what the 6x17 back
> from Canham will look like. I think the best you can do is make the
> rough assumption that 17 cm means 17 cm, 12 cm means 12 cm, etc. I think
> none but the most anal of us are all that concerned with the actual
> dimensions of the film gate on a specific camera or film back. meanest 
> 
> Ellis Vener
> 
> Robert Monaghan wrote:
> > 
> > I would like to extend my actual vs ratio size table on my medium format FAQ
> > pages at http://www.smu.edu/~rmonagha/mf/mffaq.html, but before I do so,
> > I wanted to confirm that 6x12cm is really 2:1 based on 55mm (56?) x 110mm
> > or thereabouts, and 6x17cm is really 2.83:1 or 55mm x 156mm etc. Since
> > the "6cm" is really 55mm or 56mm long, then the longer axis has to be
> > less to keep the (printing) ratio. But I want to verify this assumption!
> > 
> > Are the formats of the Fuji 6x17cm the same as the Linhof 6x17 etc.? 6x12?
> > 
> > Thanks! it is a bit counter intuitive that 6x12 is really 11 cm long, or
> > that 6x17cm is really 15 1/2 cm long etc.
> > 
> > regards bobm
> > 
> > * Robert Monaghan POB752182 Dallas Tx 75275-2182 rmonagha@xxxxxxxxxxxxxxxx  *
>