8" Air Ministry Pentac question

[John Kasaian]

I know this will cover 5"x5" straight on, but has anyone tried it on a 5x7? If the last 1" on the short sides goes to the worms thats OK but I was wondering if these lenses have mechanical vignetting that would cut the image off?

Thanks!

[Jason Greenberg Motamedi]

There was a huge amount of variation among the AM Pentacs, but they will illuminate 5x7. Corners on most AM Pentacs will be quite fuzzy, but not so with the original Dallmeyer Pentac.

[John Kasaian]

Thanks Jason!

[william linne]

All the ones I've used do pretty well on 5x7. I've even used front tilt with some of the Air Ministry lenses with no problem. Lots of fun!

[John Kasaian]

Thanks william!

I suppose it is simply a matter of the "luck of the draw" when it comes to Pentacs with the Dallmeyer being a shoe-in, then?

[Jason Greenberg Motamedi]

John,

A bit of what I have learned obsessively buying Pentac lenses: Assuming you want a sharp lens your best bet is to try to find an AM Pentac with a removable flange. These lenses were made by Dallmeyer and mounted in his factory. These have removeable elements (not burnished in, so the omnipresent haze between the first and second groups can be easily cleaned) and a standard 77mm filter thread. For all intents and purposes these are identical to those lenses made by Dallmeyer for the commerical market except they (usually) aren't branded. Failing that, the AM lens with an integral flange but the initials JHD stamped in white on the side of the barrel appear to have glass made in Dallmeyer's factory but were mounted elsewhere. These seem to be better quality glass, but often the mounting is poor resulting in a bit of spherical aberration and reduced coverage.

[John Kasaian]

Thank you Jason, that gives me a better idea of what to look out for!