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07-22-2020, 06:49 AM   #1
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Setting Aperture Manually 645 Lenses vs 67 Lenses

Hello,

When the 67 55mm (latest model) lens is unmounted and the aperture ring is turned I can see the aperture diaphragm opening and closing. With the 645 lenses the diaphragm stays wide open when rotating the aperture ring.

There are two different levers on the back of each of these lenses. One seems to control 'auto' aperture settings and the other 'manual' aperture settings. When either lens is set to manual, moving the aperture ring moves the 'manual' lever.

So when I set the aperture on a 645 lens manually the diaphragm stays wide open. If I then move the 'auto' lever with my finger it stops based on where the aperture was set. Is this a function of the depth of field preview? So the aperture is always wide open for focusing, but when a picture is taken the camera moves the 'auto' lever prior to exposure?

Is this just a difference in the way the lenses work mechanically? So the 'manual' aperture ring works on 645 lenses but only if they are mounted to the 645 body?

07-22-2020, 11:47 AM   #2
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Hi diggles,

The 645 lenses will not stop down manually like all the other Pentax lenses. When you mount them in reverse you need to use the Reverse Adaptor 645 as well as the Reverse Attachment 645.

it you check page 66 of my bellows eBook there is a better explanation.

The Pentax Bellows eBook - Articles and Tips | PentaxForums.com

Have a good one!

Murray
07-22-2020, 02:44 PM   #3
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Pentax 67 lenses only stop down with the lens off if you use the manual diaphragm lever on the lens.
07-22-2020, 03:30 PM   #4
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Thank you for the info. I was wondering if I was missing something, but it doesn't look like I did.

In addition to the 645z, I'm using these lenses on a Cambo Actus. My goal is to use the manual aperture on the lens instead of the lever of the lens board. The lever on the actus lens board uses a 0-10 scale so it doesn't directly relate to the f stops on the camera.

I did figure out a workaround though. If I put the lens on auto before mounting it to the lens board then move the lever on the lens board to 10 it closes the lens to it's smallest aperture. Then I can open the f stop to the setting I want for shooting, which is usually f11 for this setup.

With the 67 lenses I don't have to do the extra step.

07-24-2020, 04:08 PM - 1 Like   #5
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Mr O'neill, thank you for the kind offer you sent me today. When I got the 645 Auto Bellows, it came "naked", no User Guide, no Double Cable Release, just the apparatus with nothing else.

I found your eBook on Google and read the 645 Chapter. I figured I could use the Bellows with a single cable release to close down the 645 lenses' diaphragm before exposure and I knew the 645Z or the K3 would provide automatic exposure in Av mode (Aperture Priority).

On eBay, I found a brand new, boxed Pentax double cable release, a used Canon T3 cable and I was thinking about having the T3 modified with a common 2.5 to 3.5 stereo adapter plug. Then I discovered Canon was making an adapter cable (RA-E3) with their proprietary plug on one end and a 2.5 mm stereo plug on the other end. The length of both cables locked together is about 16 inches and should work seamlessly.

I'm still waiting for the 2 Canon cables to arrive in the mail, both have been shipped (the T3 cable from Italy and the RA-E3 cable from Japan). When I get them, I will try them to see if this combo works as I hope it does and, if everything is O.K., I will tape the junction of the 2 cables to keep them united for good.

Thank you once again and I will keep you informed if the double cable release plus the 2 Canon cables work correctly.

Regards


P.S. Using the 645 Auto Bellows is a "hell of a job" ... lol!
07-24-2020, 06:31 PM - 1 Like   #6
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QuoteOriginally posted by RICHARD L. Quote
P.S. Using the 645 Auto Bellows is a "hell of a job" ... lol!
Imagine what it must be like to use a Pentax 67 and its matching bellows. Humongous and slow plus add film. Whoa!
Thanks,
barondla

Keep posting the macros.
08-03-2020, 04:24 PM - 1 Like   #7
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QuoteOriginally posted by barondla Quote
Imagine what it must be like to use a Pentax 67 and its matching bellows. Humongous and slow plus add film. Whoa!
Thanks,
barondla

Keep posting the macros.
I don't have to imagine I have a 67 bellows as well, I am using a 645D body on it, not a 67, but it is a little like using an 8x10 view camera. I keep it disassembled in a 1500 Pelican case and assemble it when I want to use it. The bellows itself has a metal frame on both ends so it lends itself to that procedure nicely without risking damage.

Murray
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