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07-12-2018, 04:21 AM - 10 Likes   #1
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Franken-adapter - Pentaka 8 lenses on the Q7

The Q is supposed to about fun and I have had some fun building a franken-adapter so I can use Pentaka 8 lenses on my Q bodies. I scavenged a Pentaka 8 bayonet mount off a Pentaka 8 movie camera (which can be had for next to nothing) and had it screwed it to a 2mm thick aluminium “washer” which was then fitted into the receiver part of a Pixco C-mount adapter. I knew the 2mm washer would put me in the ball park for focus because I measured the Flange Focal Distance from the camera before I scavenged the bayonet. I hit infinity focus a little before the infinity mark on the lens. I could get a bit shaved off the 2mm washer but it would take a bit of trial and error to get infinity right on the mark. For the time being I am happy with it as it is.

Was the exercise worth the effort? I think it was. Below are some images taken with the Q7, with 100 per cent crops where indicated (cropped to 800 pixel height). Except where noted, these pics were all shot at f4 but the lenses seem to be almost as sharp wide open (with less DOF of course).

Zeiss Biotar 25mm f2 My standard red-necked wallaby model – I only have to walk out the back gate to find one. This one is no lady. She practically mugged me to make me break off some kurrajong leaves for her to eat. But then she was good enough to pose.







The obligatory flower shot – bougainvillea in the back yard. I don’t think 100 percent crops are all that great on small sensors but they do show the lens and sensor at their limits.







A pic in mywool shed (Hand held, ISO 800 f4 1/13sec; I got lucky here – the cobwebs are pretty sharp)





Now for the Zeiss Sonnar40mm f2.8 Same red-necked wallaby. Note the ants in the whiskers.







A rose. Nice texture in the petals on the 100 per cent crop.









AustralianBrush-Turkey in the rainforest. This image was cropped for composition. (Hand held, ISO400 f2.8 1/25 sec; I got lucky here too. It was bobbing its head, feeding in the leaf litter, and (after a number of tries) I managed to catch it with its head at the top of “bob”.) In the 100 per cent crop at f2.8 the DOF is very thin but the lens is certainly sharp enough under fairly challenging conditions.








And finally,the Zeiss Biotar 12.5mm f2; This lens shows heavy vignetting on the Q7 and some vignetting on the Q10.




By my rough calculation, the Biotar 12.5mm f2 has an effective image circle of about 6.8mm.This is fine for 8mm film which has a 5.94mm diagonal. But it vignettes on the Q/Q10 sensor (7.7mm diagonal) and is much worse on the Q7 sensor (9.5mm diagonal). There are two other Pentaka 8 lenses : the Flektogon 5.5mm f2 and the Flektogon 12.5mm f2. However, the rear section of both these lenses projects well beyond the bayonet. The projection of the Flektogon 5.5mm f2 looks to be about the same as the Biotar 12.5mm f2,so I suspect it would vignette to a similar extent. The Flektogon 12.5mm f2 is even longer so I suspect would vignette even more.

Pentaka 8 lenses are comparatively cheap because there are no commercially available adapters. I paid just AUD$16 for my Biotar 25mm f2 (in virtually mint condition) and AUD$40 for my very clean Sonnar 40mm f2.8. It cost very little to put together my franken-adapter. My adapter piece could also slip into the receiver part of Pixco C-mount adapter for Nikon1 or m43 if someone wanted to try the lenses on those systems. My rough image circle measurements suggest they should give full coverage on a 1” sensor but show some vignetting on m43. For the time being I will stick with the Q system. On what I have seen so far, I think these two lenses make great manual primes for use on the Q. They are occasionally available in C-mount for around the USD$300 mark – but I don’tcall that “fun”!


07-12-2018, 06:19 AM   #2
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Excellent work, Pete - both with the adaptation of the lenses and the resulting photos!

Thanks for posting this... An enjoyable read!
07-12-2018, 06:54 AM   #3
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Lens junkies really love the Q line.
07-12-2018, 07:47 AM   #4
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Very nice results.

07-12-2018, 08:32 AM - 1 Like   #5
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Great results! Do you have any pictures of the "franken-adapter" and what the final result looks like mounted to the Q7? I might have to try something similar with my Q10...
07-13-2018, 12:35 AM - 7 Likes   #6
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Thank you all for the kind words

QuoteOriginally posted by WillWeaverRVA Quote
Do you have any pictures of the "franken-adapter" and what the final result looks like mounted to the Q7?
OK - these pics are a bit rough but I am supposed to be packing to head to Sydney in the morning:

The Pixco C-P/Q adapter disassembles into two pieces: the receiver part and the insert with the C-mount thread. Three grub screws (hex head) hold the insert in place. When they are removed the insert can be pushed out (there may be a bit of glue holding it in but I had no trouble separating them).




The 2mm aluminium "washer is made to the same diameter as the insert piece with a cut out to allow the Pentaka 8 bayonet to be screwed flat on it. It is not a complex job for anyone with the right tools (Not me - I had to get the piece made and tapped for the bayonet but it was not expensive).The Pentaka 8 bayonet will need to be scavenged off a Pentaka 8 camera. Then the "washer" with bayonet fitted is placed back into the receiver section and the grub screws replaced. When tightened they will grip the washer firmly but I used some very thin double sided tape to make sure there would be no slippage. The trick is to attach the receiver part to the camera, then attach a lens to the bayonet (on the washer) and insert the assembled lens/bayonet/washer so that the lens is in the correct position with focus marks to the top. Then tighten the grub screws. Too easy. The pics below show the finished adapter and the adapter on the Q7 with the Biotar 25mm f2 fitted. Looks "just like a bought one". I might get some aluminium black for the washer some time though.












These lenses were just made for the Q system. I think they look great on a Q (a piece of art hanging off the front of the Q) and they are certainly sharp enough. Below are the Sonnar 40mm f2.8 and the Biotar 20mm f2. The front elements are deeply recessed so a hood would never be needed. They look even better in the flesh - enough to make grown men weep.


07-13-2018, 01:54 AM   #7
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Thanks for the detailed instructions and the pictures.

Now I need to move on before the Q temptation gets me
07-13-2018, 10:49 AM   #8
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QuoteOriginally posted by PJ1 Quote
Thank you all for the kind words



OK - these pics are a bit rough but I am supposed to be packing to head to Sydney in the morning:

The Pixco C-P/Q adapter disassembles into two pieces: the receiver part and the insert with the C-mount thread. Three grub screws (hex head) hold the insert in place. When they are removed the insert can be pushed out (there may be a bit of glue holding it in but I had no trouble separating them).




The 2mm aluminium "washer is made to the same diameter as the insert piece with a cut out to allow the Pentaka 8 bayonet to be screwed flat on it. It is not a complex job for anyone with the right tools (Not me - I had to get the piece made and tapped for the bayonet but it was not expensive).The Pentaka 8 bayonet will need to be scavenged off a Pentaka 8 camera. Then the "washer" with bayonet fitted is placed back into the receiver section and the grub screws replaced. When tightened they will grip the washer firmly but I used some very thin double sided tape to make sure there would be no slippage. The trick is to attach the receiver part to the camera, then attach a lens to the bayonet (on the washer) and insert the assembled lens/bayonet/washer so that the lens is in the correct position with focus marks to the top. Then tighten the grub screws. Too easy. The pics below show the finished adapter and the adapter on the Q7 with the Biotar 25mm f2 fitted. Looks "just like a bought one". I might get some aluminium black for the washer some time though.












These lenses were just made for the Q system. I think they look great on a Q (a piece of art hanging off the front of the Q) and they are certainly sharp enough. Below are the Sonnar 40mm f2.8 and the Biotar 20mm f2. The front elements are deeply recessed so a hood would never be needed. They look even better in the flesh - enough to make grown men weep.

Really cool! I might have to look into doing something like this sometime since I haven't used my Q very much recently. Might be a worthwhile project. Thanks!

07-13-2018, 01:45 PM   #9
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QuoteOriginally posted by PJ1 Quote
Thank you all for the kind words
...
OK - these pics are a bit rough but I am supposed to be packing to head to Sydney in the morning
...
The pics below show the finished adapter and the adapter on the Q7 with the Biotar 25mm f2 fitted. Looks "just like a bought one"
...
These lenses were just made for the Q system. I think they look great on a Q (a piece of art hanging off the front of the Q) and they are certainly sharp enough. ... They look even better in the flesh - enough to make grown men weep.
Fantastic work. Really great job on the adapter... and yes - those lenses are beautiful!

Have a safe trip
07-13-2018, 01:57 PM - 1 Like   #10
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I love how Q users are into DIY projects that inspire the rest of us.
07-14-2018, 10:52 PM   #11
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QuoteOriginally posted by PJ1 Quote
Thank you all for the kind words



OK - these pics are a bit rough but I am supposed to be packing to head to Sydney in the morning:

The Pixco C-P/Q adapter disassembles into two pieces: the receiver part and the insert with the C-mount thread. Three grub screws (hex head) hold the insert in place. When they are removed the insert can be pushed out (there may be a bit of glue holding it in but I had no trouble separating them).




The 2mm aluminium "washer is made to the same diameter as the insert piece with a cut out to allow the Pentaka 8 bayonet to be screwed flat on it. It is not a complex job for anyone with the right tools (Not me - I had to get the piece made and tapped for the bayonet but it was not expensive).The Pentaka 8 bayonet will need to be scavenged off a Pentaka 8 camera. Then the "washer" with bayonet fitted is placed back into the receiver section and the grub screws replaced. When tightened they will grip the washer firmly but I used some very thin double sided tape to make sure there would be no slippage. The trick is to attach the receiver part to the camera, then attach a lens to the bayonet (on the washer) and insert the assembled lens/bayonet/washer so that the lens is in the correct position with focus marks to the top. Then tighten the grub screws. Too easy. The pics below show the finished adapter and the adapter on the Q7 with the Biotar 25mm f2 fitted. Looks "just like a bought one". I might get some aluminium black for the washer some time though.












These lenses were just made for the Q system. I think they look great on a Q (a piece of art hanging off the front of the Q) and they are certainly sharp enough. Below are the Sonnar 40mm f2.8 and the Biotar 20mm f2. The front elements are deeply recessed so a hood would never be needed. They look even better in the flesh - enough to make grown men weep.

Beautiful lenses and nice pictures!
07-16-2018, 03:11 PM - 1 Like   #12
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Thank you all for reading and commenting. The Q is a bit of a temptation for DIY and experimentation. I hope this little experiment will give others a bit of fun as well. Keep us posted!
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