Re: Horizon 202 Questions

[petermarshall@xxxxxxxxxxxxxxxxxxx (Peter Marshall)]

In-Reply-To: <199809261345.JAA15576@xxxxxxxxxxxxxxxxxxx>
> Thanks to all for the responses to my questions about the Horizon.  I 
> must
> say I'm overall very satisfied with the results I get with it.  
> 
> I've looked critically at my 14" prints thus far another time and really
> believe that any unsharpness I get along the top 1/8 of the image area 
> is
> probable related to some field curvature characteristic of the lens and 
> not
> a defect in my camera.  

This is not normal with the Horizon and I'd suggest you exchange it with 
another one as it sounds like a fault, though I can't think how it arises. 
The only thing I can think other than a undefined camera problem is that 
you are not getting the neg to lie flat in the enlarger

>The unsharpness goes away with objects imaged at
> certain distance/f-stop combinations - I'll just need to learn what they
> are.  The vignetting is ever so slight and is only along the very top 
> edge 

Again if this is happening in camera, either you have a seriously sick 
camera or there is something wrong in the way you are using it. I'd 
suggest careful examination of the negs using a low power microscope.

The only practical limitation I've found is one of depth of field at wide 
apertures - there is no way that you can get close objects sharp with the 
fixed focus.

Remember that the lens has a pretty easy job to do - unlike a normal 
camera lens to film distance is fixed across the whole negative, and you 
are essentially using a small strip from the centre of the lens across the 
whole neg. Any variation across the length of the neg can't be due to 
field curvature (though this could give a small vertical effect, uniform 
across the neg, but I haven't been able to notice it.) So you get uniform 
sharpness into the corner of the neg. The actual circle of coverage 
required is only about 12mm radius rather than the 22mm needed in a fixed 
lens 35mm camera. 

Peter Marshall

On Fixing Shadows and elsewhere:
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