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Dallmeyer LONDON PENTAC F/2.9 PATENT 4 1/4inch
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PostPosted: Sat Jan 07, 2012 12:10 pm    Post subject: Dallmeyer LONDON PENTAC F/2.9 PATENT 4 1/4inch Reply with quote








PostPosted: Sat Jan 07, 2012 1:44 pm    Post subject: Reply with quote
These lenses currently fetch quite some $$$$ in Asia now, most likelyx because of that very special bokeh.
From what I know Dallmeyer used rare earth doped glass for that Pentac lens design, so it it prone to browning.

Pictures are quite nice, a bit on the low contrast side since that lens is not coated (or is it?).


PostPosted: Sat Jan 07, 2012 2:35 pm    Post subject: Reply with quote
kds315* wrote:
These lenses currently fetch quite some $$$$ in Asia now, most likelyx because of that very special bokeh.
From what I know Dallmeyer used rare earth doped glass for that Pentac lens design, so it it prone to browning.

Pictures are quite nice, a bit on the low contrast side since that lens is not coated (or is it?).



Thanks Dr.Klaus to advise and comment that lens is not coated.


PostPosted: Sat Jan 07, 2012 3:20 pm    Post subject: Reply with quote
Perhaps not a sharpness wonder, but a very special lens indeed!


PostPosted: Sun Jan 08, 2012 7:46 am    Post subject: Reply with quote












PostPosted: Sun Jan 08, 2012 8:05 am    Post subject: Reply with quote
Most Pentacs weren't coated, the ones you find that are are from the 50s and later.

There is one Pentac that is still cheap - the common f2.9 8inch in wartime guise without Dallmeyer name (usually stamped A. M. for Air Ministry and with a crown or crow's foot) which is seen often on ebay, last few were not in good condition, so I'm waiting for a nice one to come along as I collect old British lenses, particularly Ross ones.

I'm surprised this Pentac isn't sharper, the 8inch one is very sharp, it was used for aerial reconnaisance.


PostPosted: Sun Jan 08, 2012 2:36 pm    Post subject: Reply with quote
Which camera did you use for these pictures? I've got an Air Ministry 2.9 8 inch and its image circle is huge. Using such a lens directly on a crop factor or full frame digital SLR means you use only a tiny portion of it. I've been considering making a DoF adapter, projecting the image circle of this lens onto a large ground glass and photographing that. That way you get the narrow depth of field but you'd probably lose a lot of the image quality.


PostPosted: Sun Jan 08, 2012 3:10 pm    Post subject: Reply with quote
Ian, if you look at Eric Beltrando's calculated performance for the Pentac (prescription taken from the patent, the lenses as made may be different) http://www.dioptrique.info/OBJECTIFS10/00472/00472.HTM you'll see that they don't have huge coverage and aren't that wonderful. He got much the same results for all of the fast heliar types whose prescriptions he was able to get. This includes the revered 100/3.5 and 105/3.7 Ektars.

In my tests, formal and informal, my 105/3.7 Ektars disappointed. My 101/4.5 Ektar has better image quality center and corner from f/4.5 down.

Eric found, however, that slow (f/9 and f/10) heliar types from Voigtlaender and Boyer are superb within their relatively narrow coverage. My Apo-Saphirs agree with him, my dialyte type Apo-Nikkors point out that there are better process lenses, at least centrally, from f/9 - f/16.


PostPosted: Sun Jan 08, 2012 10:49 pm    Post subject: Reply with quote
Nice series- I love #1 and #2 of both your series a lot. Very Happy , great captures.


PostPosted: Sun Jan 08, 2012 10:57 pm    Post subject: Reply with quote
Kathmandu wrote:
Nice series- I love #1 and #2 of both your series a lot. Very Happy , nice execution .


PostPosted: Mon Jan 09, 2012 1:55 am    Post subject: Reply with quote
dickb wrote:
Which camera did you use for these pictures? I've got an Air Ministry 2.9 8 inch and its image circle is huge. Using such a lens directly on a crop factor or full frame digital SLR means you use only a tiny portion of it. I've been considering making a DoF adapter, projecting the image circle of this lens onto a large ground glass and photographing that. That way you get the narrow depth of field but you'd probably lose a lot of the image quality.


on Panasonic G2


PostPosted: Tue Jan 17, 2012 11:55 pm    Post subject: Reply with quote
There's a 8"/2.9 for sale with no bids yet (starting price GBP 120, deadline in 12 hours), someone interested? I'll better leave it for someone with a bigger sensor-camera. Smile

Click here to see on Ebay


PostPosted: Wed Jan 18, 2012 12:01 am    Post subject: Reply with quote
Very nice. Love the "Jacob's Ladder" effect. Would love to shoot one of these if I had a FF camera.


PostPosted: Tue Jan 24, 2012 12:21 pm    Post subject: Reply with quote
With Canon 5d



























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