Can anyone help? I am looking for a ‘how to’ guide to using the Rodenstock depth of Field Calculator (the little plastic dial which they recently stopped making).

Here’s why I need it: I am relatively new to large format photography, having recently got hold of a lovely old Sinar Norma on eBay.

I want to make some accurate depth of field calculations for some night-time landscapes I am working on using the Norma and its Schneider lenses (90mm and 150mm). Some shots need details in focus from about 6 metres to 25 metres away; others from 6 metres to infinity. Despite that, I ideally want to open up the aperture as wide as possible so that I am not forced to take hour-long exposures. I know about the refraction and diffraction, hyperfocal distance and focussing ‘one third in’, but am after some very precise measurements!

The Rodenstock calculator is confusing to use without any accompanying instructions. I have had no luck searching online or contacting Rodenstock themselves. There is also a ‘depth of field scale’ referred to on the monorail clamp for the Sinar, but I don’t have the actual scale itself….

With thanks,

J Coombes