Re: Horizon 202 Questions

[petermarshall@xxxxxxxxxxxxxxxxxxx (Peter Marshall)]

In-Reply-To: <199809291352.PAA28908@xxxxxxxxxx>
> That should be about 26mm vs 43mm on a normal SLR 
> ( SQR (24^2 + 36^2) ) 

The figures I gave were for the RADIUS, which is half the figures for the 
diameter that you quote. For the swing lens camera it is difficult to know 
what the appropriate figure is as each point is imaged by the lens 
across the width of the travelling slit. Essentially we are dealing with 
half the height of the negative as the slit is relatively narrow - hence 
my figure of 24/2 = 12cm. Applying Pythagoras using half the slit width 
gives a slightly different figure - obviously depending on the slit width.

The two points I made are unaffected by any fractional differences in 
maths. First you need only have a much smaller image circle, and secondly 
there is no image fall-off in the corners (although there may be slight 
differences in sharpness towards the top and bottom of the frame, though I 
can't detect that in practice in my pictures.)

Peter Marshall

On Fixing Shadows and elsewhere:
http://www.people.virginia.edu/~ds8s
Family Pictures, German Indications, London demonstrations & 
The Buildings of London etc: http://www.spelthorne.ac.uk/pm/