[LargeFormat] Focus Shift on Stopping Down

[Clive Warren]

We have heavy rain here in Bristol this weekend - at least it's not too cold 
- the British obsession with weather is really only due to the large number 
of wet weekends in Winter and sunshine during the week - for me that is when 
you can't take the time out to do personal photography.....

Anyway, on this rather damp Saturday morning I was wondering about focus 
shift on stopping down. Some lenses are more affected by this than others - 
can be a bit of a pain if you are using compact field lenses that have small 
apertures. Checking the ground glass is difficult enough when wide open, let 
alone checking for focus at smaller apertures.

So, which lense types are most affected by focus shift?  For example the 
very bright Wollensak Velostigmat Series II 12" is affected....

Anyone have rules of thumb?

Cheers,
       From the rain soaked leave strewn streets of Bath today,
Clive



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