Site Sponsors
Results 1 to 20 of 20

Thread: Pentax 110 lens with aperture control

  1. #1
    turbo
    Guest

    Pentax 110 lens with aperture control

    A day off, a bunch of camera parts (size 00 shutter + Pentax 110) and an idea.


    The finished product will screw into a C-mount adapter, provide infinity focus and f-stops from 2.8 to 11 and a smidge. The 50mm lens will not fit in the adapter. The bottom picture was taken with the 18mm at f8.

  2. #2
    ChrisJ
    Guest

    Re: Pentax 110 lens with aperture control

    I've been looking for a way to do this myself, even wide open the lenses are good, stopped down they would be really good.

    Where did you get the shutter mechanism?

    Chris

  3. #3
    turbo
    Guest

    Re: Pentax 110 lens with aperture control

    The shutter was off of a Konica I, a Konirapid shutter, but any
    size 00 shutter will work. I started to use a compur shutter from a
    Kodak but the aperture lever was behind the shutter so could not be
    accessed when mounted.

  4. #4
    Subscriber Member
    Join Date
    Jan 2008
    Location
    Toronto, Canada
    Posts
    3,026
    Post Thanks / Like
    Images
    1117

    Re: Pentax 110 lens with aperture control

    Quote Originally Posted by turbo View Post
    The shutter was off of a Konica I, a Konirapid shutter, but any
    size 00 shutter will work. I started to use a compur shutter from a
    Kodak but the aperture lever was behind the shutter so could not be
    accessed when mounted.
    Briliant

    Keith

  5. #5
    Ranger 9
    Guest

    Re: Pentax 110 lens with aperture control

    VERY spiffy build!

    Am I correct in thinking you removed the actual shutter assembly (blades, master ring, timing geartrain, etc.) from the shutter housing, and just used the diaphragm assembly?

  6. #6
    Senior Member pellicle's Avatar
    Join Date
    May 2009
    Location
    Southport, Australia
    Posts
    1,429
    Post Thanks / Like

    Re: Pentax 110 lens with aperture control

    lovely ... did the threads match easily?

  7. #7
    Member
    Join Date
    Mar 2009
    Posts
    90
    Post Thanks / Like

    Re: Pentax 110 lens with aperture control

    I used to think that no 00 shutter is too small for homemade lens. Now you find a new value of that. Good job!

  8. #8
    Super Duper
    Senior Member
    Vivek's Avatar
    Join Date
    Apr 2008
    Location
    Netherlands
    Posts
    13,601
    Post Thanks / Like
    Images
    21

    Re: Pentax 110 lens with aperture control

    Awesome! I might have a few shutters around.

    The 18/2.8 (especially stopped down, sample is real nice) kicks the Oly-D 17/2.8 in terms of performance (flatter field and no CA).

  9. #9
    turbo
    Guest

    Re: Pentax 110 lens with aperture control

    Yep, stripped the shutter of everything but the housing and aperture. Mounted the 110 mount flange to the shutter's speed dial retaining ring and glued the ring to the shutter body.

    The shutter mounting thread is the same diameter, but a different pitch. That's OK though because you don't screw it in very deep (about 1/2 turn). Use the shutter mount ring and shim/grind to adjust infinity focus.

    I made the mistake of gluing the flange assembly to the body without the lens mounted, so there was not enough clearance between the flange and shutter to mount the lens. Since the flange can be removed, I shimmed the flange to provide the needed clearance.

    One thing missing is a DOF scale. Have to judge sharpness in the finder. In the attached photo the focus was on the truck front tire.

  10. #10
    simplebot
    Guest

    Re: Pentax 110 lens with aperture control

    That's awesome! I also built one, but I used an iris from an old broken pentax 50mm lens, and mounted it into the c-mount adapter. I wasn't able to achieve infinity focus due to the bulk of the mechanism, so I've kind of shelved it for now, unless I need to do some close up photography.
    Here's a pic:

    I don't have any f-stops set, so I just wing it for DOF through the viewfinder. It's fun, but not very usable right now. Congrats on yours!

  11. #11
    echols
    Guest

    Re: Pentax 110 lens with aperture control

    Would you be interested in selling your adapter?
    echols

  12. #12
    Senior Member m3photo's Avatar
    Join Date
    Dec 2008
    Posts
    1,043
    Post Thanks / Like
    Images
    28

    Re: Adapter for sale

    Quote Originally Posted by echols View Post
    Would you be interested in selling your adapter?
    echols
    I'd also be interested in having a pre-made diaphragm adapter for PENTAX-110 lenses - anyone up to it? On the G1 they're certainly good even at f/2.8, I reckon the 18mm could be an excellent street lens with the possibility of stopping it down.

  13. #13
    turbo
    Guest

    Re: Pentax 110 lens with aperture control

    Quote Originally Posted by echols View Post
    Would you be interested in selling your adapter?
    echols
    I don't have any more defunct shutters to build another adapter. I collect and rebuild 50-80 year old German cameras which frequently use the compur #00 shutter. I find that a lot of the cameras I buy for parts end up being repairable. I'm the only person I know that can end up with fewer parts after buying a parts camera. Sigh!

    Maybe one of the adapter makers will see the interest in this and build an aperture Pentax-110 mount. Hmmmm. Maybe I should start buying 110 lenses.

    turbo

  14. #14
    Member
    Join Date
    Sep 2009
    Posts
    233
    Post Thanks / Like

    Re: Pentax 110 lens with aperture control

    Could you just stick a black disk with a hole into the c-mount adapter, to at least be able to stop it down to a preset aperture?

    If that is possible, then you can at least switch between 2.8 and say f8 for lots of DOF. Not exactly convenient, but a nice option I think.

  15. #15
    Senior Member m3photo's Avatar
    Join Date
    Dec 2008
    Posts
    1,043
    Post Thanks / Like
    Images
    28

    Re: Black disk

    Quote Originally Posted by madmaxmedia View Post
    Could you just stick a black disk with a hole into the c-mount adapter, to at least be able to stop it down to a preset aperture?

    If that is possible, then you can at least switch between 2.8 and say f8 for lots of DOF. Not exactly convenient, but a nice option I think.
    Funny that, I was thinking of exactly the same thing driving to work this morning! F/8 as it happens is what I usually stop down to to get the best out of most lenses.

  16. #16
    Senior Member
    Join Date
    Aug 2009
    Location
    Sydney, Australia
    Posts
    347
    Post Thanks / Like
    Images
    1

    Re: Pentax 110 lens with aperture control

    Quote Originally Posted by turbo View Post
    Maybe one of the adapter makers will see the interest in this and build an aperture Pentax-110 mount. Hmmmm. Maybe I should start buying 110 lenses.

    turbo
    Quite probably a good idea. The way C-Mount lenses and OM lenses have increased in value since MFT isn't funny anymore (unless you already have what you want).

  17. #17
    turbo
    Guest

    Re: Pentax 110 lens with aperture control

    Quote Originally Posted by madmaxmedia View Post
    Could you just stick a black disk with a hole into the c-mount adapter, to at least be able to stop it down to a preset aperture?

    If that is possible, then you can at least switch between 2.8 and say f8 for lots of DOF. Not exactly convenient, but a nice option I think.
    Waterhouse stops. Back in the days when the lens cap was your shutter, one of the ways to change f-stop was with thin metal sheets with different sized holes that were slipped into a slot behind the lens.

    You could cut 3x5 cards to size with an f-stop (and painted Sharpie black, of course) and tape it to the back of the adapter. That should work.

  18. #18
    Member
    Join Date
    Sep 2009
    Posts
    233
    Post Thanks / Like

    Re: Pentax 110 lens with aperture control

    Great! I will start playing around with aperture disks, as soon as I get my hands on a 110 lens. The 18mm 2.8 is really the only Pentax one I want, not sure if there are any other good ones from other cameras.

  19. #19
    ChrisJ
    Guest

    Re: Pentax 110 lens with aperture control

    The only problem with this approach is that the actual diameter of the f stops is dependant on the focal length of the lens. The physical aperture diameter is just focal length divided by f number.

    So for the 18mm lens they would be;-

    f4 = 4.5mm

    f5.6 = 3.21mm

    f8 = 2.25mm

    f11 = 1.63mm

    f16 = 1.125mm

    Whereas the apertures for the 24mm lens would need to be;-

    f4 = 6mm

    f5.6 = 4.28mm

    f8 = 3mm

    f11 = 2.18mm

    f16 = 1.5mm

    For the 50mm and 70mm lenses - well you can work it out yourself.

    For the 20 - 40mm zoom it would be high on impossible to get the right aperture.

    Whether any of this actually matters is a moot point really, by making an aperture disc with a diameter of 2.75mm it would be wider than f8 when used with the 18mm lens and smaller than f8 when used with a 24mm lens. If you used it with the 50mm lens it would be an effective aperture of f18! But you would still get the increase in DOF, in fact you would get the same DOF as a 21mm lens at f8, but your shutter speed would be slower!

    It all ties together (I think!) and the hours spent in the optics lectures I attended (over 50 years ago) is finally paying off.

    Chris

  20. #20
    Member
    Join Date
    Sep 2009
    Posts
    233
    Post Thanks / Like

    Re: Pentax 110 lens with aperture control

    Thanks Chris, I was just wondering what size the hole should be- I am mainly interested in the 18mm lens anyway and will probably end up just making just a f8 disk for now.

    I actually ended up winning a auction for Pentax 110 and both 18mm and 24mm lenses though (and a couple of filters to boot). So your info is very helpful. Thanks!

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •