Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-10-2019, 10:31 AM   #1
Junior Member




Join Date: Oct 2016
Posts: 47
K-mount on 645

Doesn't seem to be any existing system to mount a K-mount lens (35mm image circle) on a 645 camera..

I understand that it won't cover the entire sensor, and also the focus distance is much greater on 645... but even within limited focus range / non-infiinty, etc... I could see it useful to use my fisheye, or 31 limited, or 77 limited on a tilt/shift etc.. on a 645Z sensor. even if it was just as a special effect

I can't be the first person to think this .... has anyone ever jerry-rigged something like this together?

If not, anyone got an old broken lens I can buy the body mount from to experiment?

12-10-2019, 10:48 AM   #2
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 3,852
The large difference in mount-to-sensor distances (70.87 mm - 45.46 mm = 25.41mm) has a huge effect on infinity focus, especially for wider-angle lenses.

With a 31mm K-mount lens sitting flush with the 645 mount ring (assuming that is even possible), the focus point with the lens set to infinity would be only a couple of inches in front of the lens. The good news is that at that macro-range distance, the projected circle of the 31 would certainly cover the entire 645 image circle!

A fisheye lens would probably not work at all -- the infinity focus point would be so close, it would be inside the lens.

On the telephoto side, a 300mm K-mount lens would ∞-focus at about 4 meters which might make it OK for less-fearful wildlife.

If you want to play with this at zero cost, just hand-hold whatever lens in front of a 645 camera, look through the viewfinder, and see where it focuses.
12-10-2019, 10:51 AM   #3
Pentaxian
bertwert's Avatar

Join Date: Jun 2015
Location: Golden, BC
Photos: Albums
Posts: 11,558
It would be, at minimum if you had no longer extra length to the adaptor, a 25mm extension. This would mean it would only really be suitable for macro, as with a 50mm lens, this would be a max focal distance of 15cm, resulting in a magnification of 1:2.
12-10-2019, 11:15 AM   #4
Loyal Site Supporter
Loyal Site Supporter




Join Date: Sep 2017
Location: Medellín
Posts: 1,206
QuoteOriginally posted by loji Quote
Doesn't seem to be any existing system to mount a K-mount lens (35mm image circle) on a 645 camera..



I understand that it won't cover the entire sensor, and also the focus distance is much greater on 645... but even within limited focus range / non-infiinty, etc... I could see it useful to use my fisheye, or 31 limited, or 77 limited on a tilt/shift etc.. on a 645Z sensor. even if it was just as a special effect



I can't be the first person to think this .... has anyone ever jerry-rigged something like this together?



If not, anyone got an old broken lens I can buy the body mount from to experiment?
You can use your 31 Limited for macro with the 645 reverse adapter set which happens to be 58mm. You just need an 58mm thread extender, which is available from many Chinese suppliers.
If you want to compose and focus wide open, you'll need the front standard of an auto bellows and use a double cable release.



12-10-2019, 12:19 PM   #5
Site Supporter
Site Supporter
EssJayEff's Avatar

Join Date: Jul 2011
Location: Hillsborough, NC
Photos: Gallery | Albums
Posts: 313
Do you mean other than the "Pentax Adapter K for 645 Lens?" (I couldn't find it in the Accessories Reviews section, so that link goes to a past Marketplace listing.)

Last edited by EssJayEff; 12-10-2019 at 12:23 PM. Reason: typos
12-10-2019, 12:34 PM   #6
Pentaxian




Join Date: Jan 2018
Photos: Gallery
Posts: 560
If you couldn't imagine why not before, you know now. I'll add another – to be useful at other than macro range, the lens would have to be sunk into the 645 body. Pentax don't do mirrorless, but you'd probably have a 645 mirrorless after the first release of the shutter. (and a damaged rear element too)
12-10-2019, 12:50 PM   #7
Loyal Site Supporter
Loyal Site Supporter




Join Date: Sep 2017
Location: Medellín
Posts: 1,206
QuoteOriginally posted by StiffLegged Quote
If you couldn't imagine why not before, you know now. I'll add another – to be useful at other than macro range, the lens would have to be sunk into the 645 body. Pentax don't do mirrorless, but you'd probably have a 645 mirrorless after the first release of the shutter. (and a damaged rear element too)
If the P645 cameras had a manual mirror override like the Mamiya M645's, one could certainly use a lens like that with the addition on an external viewfinder. Makes me wonder if there's a 135 format 24mm tilt/shift lens that has enough clearance from the mount in order to be adapted.

12-10-2019, 01:13 PM   #8
Site Supporter
Site Supporter
MossyRocks's Avatar

Join Date: Nov 2017
Location: Minnesota
Photos: Gallery | Albums
Posts: 1,214
QuoteOriginally posted by EssJayEff Quote
Do you mean other than the "Pentax Adapter K for 645 Lens?" (I couldn't find it in the Accessories Reviews section, so that link goes to a past Marketplace listing.)
Other way around they want to stick a K lens on a 645 camera, not a 645 lens on a K camera.

12-10-2019, 01:20 PM   #9
Site Supporter
Site Supporter
EssJayEff's Avatar

Join Date: Jul 2011
Location: Hillsborough, NC
Photos: Gallery | Albums
Posts: 313
QuoteOriginally posted by MossyRocks Quote
Other way around they want to stick a K lens on a 645 camera, not a 645 lens on a K camera.
Ah...got it.
12-10-2019, 08:25 PM   #10
Site Supporter
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 6,413
I've used my Takumar 28/3.5 lens reversed on my Pentax 6x7 for about 5x magnification.

Pentax 6x7 Reverse Adapter 49mm & 67mm reviews - Pentax Camera Accessory Review Database

I'm sure there is a similar adapter for the 645 system.

Phil.
12-12-2019, 09:21 AM   #11
Site Supporter
Site Supporter
MossyRocks's Avatar

Join Date: Nov 2017
Location: Minnesota
Photos: Gallery | Albums
Posts: 1,214
QuoteOriginally posted by gofour3 Quote
I've used my Takumar 28/3.5 lens reversed on my Pentax 6x7 for about 5x magnification.
How sharp was running it like that? I've done about a 3x with it but anything beyond that I have problems from vibration because I have to do a very long exposure and have kids so everything is blurry.
12-12-2019, 10:39 AM   #12
Site Supporter
Site Supporter
gofour3's Avatar

Join Date: Oct 2008
Location: Vancouver, Canada
Posts: 6,413
QuoteOriginally posted by MossyRocks Quote
How sharp was running it like that? I've done about a 3x with it but anything beyond that I have problems from vibration because I have to do a very long exposure and have kids so everything is blurry.
I got really good results with the 28/3.5 reversed and using the 6x7 Helicoid extension tube.

There is a picture in my review of the Super Takumar. It's a bead you put on a DIY jewlery:

S-M-C/Super Takumar 28mm F3.5 Reviews - M42 Screwmount Wide-Angle Primes - Pentax Lens Reviews & Lens Database

Phil.

Last edited by gofour3; 12-12-2019 at 10:46 AM.
12-12-2019, 01:34 PM - 1 Like   #13
Site Supporter
Site Supporter
MossyRocks's Avatar

Join Date: Nov 2017
Location: Minnesota
Photos: Gallery | Albums
Posts: 1,214
QuoteOriginally posted by gofour3 Quote
I got really good results with the 28/3.5 reversed and using the 6x7 Helicoid extension tube.

There is a picture in my review of the Super Takumar. It's a bead you put on a DIY jewlery:

S-M-C/Super Takumar 28mm F3.5 Reviews - M42 Screwmount Wide-Angle Primes - Pentax Lens Reviews & Lens Database

Phil.
well it is good to know that I could go above 3x magnification and still get good results if the kids would quit bouncing around the house so much. With the M42 to 49mm reversing ring, M42->K adapter, a couple of sets of M42 extension tubes and an M42 helicoid I have plenty of gear to use with my 28/3.5
12-12-2019, 04:49 PM   #14
Loyal Site Supporter
Loyal Site Supporter




Join Date: Sep 2017
Location: Medellín
Posts: 1,206
QuoteOriginally posted by gofour3 Quote
I got really good results with the 28/3.5 reversed and using the 6x7 Helicoid extension tube.

There is a picture in my review of the Super Takumar. It's a bead you put on a DIY jewlery:

S-M-C/Super Takumar 28mm F3.5 Reviews - M42 Screwmount Wide-Angle Primes - Pentax Lens Reviews & Lens Database

Phil.
Lol, I have that same lens and it's even easier to use with the 645 reverse adapter because they're both 58mm. It's a very cheap and good option for extreme tabletop macro.

12-31-2019, 06:35 PM   #15
Pentaxian




Join Date: Nov 2015
Location: California
Posts: 620
QuoteOriginally posted by loji Quote
Doesn't seem to be any existing system to mount a K-mount lens (35mm image circle) on a 645 camera..



I understand that it won't cover the entire sensor, and also the focus distance is much greater on 645... but even within limited focus range / non-infiinty, etc... I could see it useful to use my fisheye, or 31 limited, or 77 limited on a tilt/shift etc.. on a 645Z sensor. even if it was just as a special effect



I can't be the first person to think this .... has anyone ever jerry-rigged something like this together?



If not, anyone got an old broken lens I can buy the body mount from to experiment?
It is possible and would have to go mirrorless to make it happen, Such as the gfx. not all lenses work though, some are better then others. The one part that they are able to do, is if they don't completely work, they cut out part of the sensor to turn it into the full frame camera. Also all lenses turn into manual lenses as far as using k mount lenses.

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
645d, 645z, camera, focus, k-mount, lens, medium format, sensor
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
645-A 150mm or 645-A 80-160mm jumbleview Pentax Medium Format 8 05-25-2018 03:26 AM
For Sale - Sold: Pentax 645 w/ 55mm, 75mm, 120mm Macro, 150mm and more. FULL 645 Kit! Free shipping gdneil Sold Items 4 04-13-2018 04:42 PM
Pentax Adapter K for 645 Lens (645 to K mount) Read more at: http://www.pentaxforums Uplander Pentax K-1 5 10-05-2016 11:41 AM



All times are GMT -7. The time now is 08:28 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top