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Kimunor 500mm f/8 mount - Help needed !
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PostPosted: Mon Oct 16, 2017 3:20 am    Post subject: Kimunor 500mm f/8 mount - Help needed ! Reply with quote

Hello,

I purchased a very cheap Kimunor 500mm f/8 pre-set lens with Minolta, Nikon and Pentax adapters.
I thought it was a T-mount lens but I don't recognize the mount on it.

I want to have a T-mount on it.
What is this mount ? Is that an incomplete T-mount?

Here are some photos of the mount





PostPosted: Mon Oct 16, 2017 7:43 am    Post subject: Reply with quote

Let's see the adapters...


PostPosted: Mon Oct 16, 2017 7:52 am    Post subject: Reply with quote

I think it is missing the mount part altogether. These types of lenses are usually for many mounts just changing the rear part. You can guess the mount lenght needed by measuring the register distance and trying to figure out how many millimeters are missing. My guess is about 10-15 mm.


PostPosted: Mon Oct 16, 2017 9:04 am    Post subject: Reply with quote

Probably the same as this lens reviewed on The Pentax Forums, which looks as though it's a T mount.

https://www.pentaxforums.com/userreviews/quantaray-500mm-f8-f32.html


PostPosted: Mon Oct 16, 2017 9:12 am    Post subject: Reply with quote

I think it is missing the leftmost part in this picture:

https://www.pentaxforums.com/userreviews/showfull.php?product=871&bigimage=The_Five_Star_Lens_tn1.JPG

You can see the little screws that hold (probably T-) mount to the lens.


PostPosted: Mon Oct 16, 2017 1:16 pm    Post subject: Reply with quote

What I think you are looking at is the internal collar of a t-ring (= mount) stuck on the t-mount (the t-mount is sensu stricto the lens side of things). My usual trick in these situations is a bit of boiling water to expand the joint, then judicious use of an appropriate wrench, protecting the metal with a bit of leather or tape as desired, to unscrew it. NB it is possible to wrench out the entire mount from the end of the tube if its really stuck, there is usually just a little grub screw locking it in.


PostPosted: Mon Oct 16, 2017 2:05 pm    Post subject: Reply with quote

Try the register distance first:

1 set the lens to minimum focusing distance (ok, that is a slight problem with these 500mm)
2 set a light source, lamp or something to that distance in dark / dim place
3 move a white plane behind the lens behind the rear of the lens until the picture is sharp
4 measure the distance between rear of the lens and the white plane

if the distance is more than 55mm you are missing some parts


PostPosted: Mon Oct 16, 2017 2:28 pm    Post subject: Reply with quote

Let's see the adapters... Smile

Lenses screw into all my t mount adapters...this one appears like the inner part of the mount, but it screws into, not on to the lens barrel.

The other possibility is the lens is an early version of t mount, a universal type mount with t mount aspirations, but abandoned for the spec'd newer t mount, however, the lens doesn't look that old...


PostPosted: Mon Oct 16, 2017 4:46 pm    Post subject: Reply with quote

marcusBMG wrote:
What I think you are looking at is the internal collar of a t-ring (= mount) stuck on the t-mount


edit: it looks a bit large to be t-mount. diameter should be much less than 42mm Confused


PostPosted: Mon Oct 16, 2017 5:13 pm    Post subject: Reply with quote

It certainly looks like the inner part of a T-mount, however there are some of these that can fool you.
Best to check by unscrewing that rear bit. This will reveal a M42x.75 thread if it is a true T-mount.

However, some of these things are not actually T-mounts. The manufacturers of some of these cheap lenses at some point started making fake T-mounts, I think in order to reduce machining operations such as cutting threads, so the flange there could just be part of the mount-end sleeve. In that case the adaptation to a camera mount becomes more complicated.

BTW, this is definitely a later lens - 1980's at least if not later. T-mounts came in around 1961.


PostPosted: Mon Oct 16, 2017 5:23 pm    Post subject: Reply with quote

Yes, it's half of the T mount, in the last picture you can clearly see the V Groove where the grub screws of the outer part of the mount locate. If that inner part wont unscrew use the outer from another mount.

Here's a picture of a complete T mount off the lens, showing the thread on the back of the lens.


PostPosted: Mon Oct 16, 2017 6:10 pm    Post subject: Reply with quote

Hi,

Thanks for your answers.

I did research on my side too.
This lens I got came with three adapters (Canon, Minolta and Pentax K) that fits perfectly in this mount.
The flange is correct with an analog Pentax camera.

But there are two versions of this lens :
- The one I have with this strange proprietary mount
- The T-mount version

I initially wanted to use it on a C-mount camera. But, by adding The Pentax-K adapter and a Pentax to C-mount adapter gives a too much long flange distance. So it doesn't focus well.
Unfortunately, I only have 2 options left to use it on my C-mount camera:
- Cut the strange mount to readapt a T-mount, so I can use a genuine T-mount to C-mount adapter
- Make my own "strange-mount" to C-mount adapter (and computing the correct flange distance).


PostPosted: Mon Oct 16, 2017 7:22 pm    Post subject: Reply with quote

Cheaper to just buy another 400-500mm with a proper T-mount.

These are very cheap in the used market.


PostPosted: Mon Oct 16, 2017 8:40 pm    Post subject: Reply with quote

You're right, Luis ! I think I'm good to resell it.


PostPosted: Mon Oct 16, 2017 8:40 pm    Post subject: Reply with quote

How was too long flange length determined? I ask because 500mm focal length on c mount camera is extreme long telephoto, with sturdy mounting necessary...ie, the Pentax to c mount adapter should have worked...


PostPosted: Mon Oct 16, 2017 8:41 pm    Post subject: Reply with quote

The more I look at it, the more I think Luis got it right - faux t-mount. But if its intended for t-mounts, with or without internal collar, the flange distance should be correct.
With a 500mm lens a few mm out on the flange distance will make very little difference to focus range - the moon might be a bit OoF. Bear in mind the loooong close focus distance of .. I see 10m/32' on the distance scale.


PostPosted: Mon Oct 16, 2017 11:41 pm    Post subject: Reply with quote

I deducted the flange distance problem from the impossibility to go to infinity focus.

Pentax lenses + K-to-C adapter to C-mount cam : OK
Kimunor + K adapter to Pentax Cam: OK
Kimunor + K adapter + C adapter to C-mount cam : KO (No infinity focus)

For information, My C-mount cam is a modified Yi 4K+ . Maybe the x5,5 crop factor amplifies defaults from the Kimunor.


PostPosted: Tue Oct 17, 2017 12:06 am    Post subject: Reply with quote

If this is all correct -

"Pentax lenses + K-to-C adapter to C-mount cam : OK "
"Kimunor + K adapter to Pentax Cam: OK "

Then the problem is likely to be a minor error in infinity setting on the Kimunor lens that may not be apparent on a Pentax body. This is not unusual in long tele; the usual case is to set these to go past infinity a bit to allow for errors.

Your 5.5x crop very likely does magnify a bit of lack of infinity focus in the Kimunor.

There should be a way to adjust these lenses for infinity. I can't say in your case.


PostPosted: Tue Oct 17, 2017 2:22 am    Post subject: Reply with quote

Just to be clear you can obtain focus at distances closer than infinity?

I understand the focus adjustment tolerance increases with focal length. Wide angle lens proper focus adjustment range is much smaller than for telephoto's. I don't know if that applies here...


PostPosted: Thu Oct 19, 2017 3:46 am    Post subject: Reply with quote

visualopsins wrote:
Just to be clear you can obtain focus at distances closer than infinity?

I understand the focus adjustment tolerance increases with focal length. Wide angle lens proper focus adjustment range is much smaller than for telephoto's. I don't know if that applies here...


Yes, I can obtain focus at closer distances.
I didn't investigate much on the lens these days, because I was working on other lenses.