[MattGunn]

Matt, you are a hero. Very impressive lens and adaption!

Thanks, It was fun to do and I think it will be a usefull lens although a bit heavy to carry any distance.

Not he best lens for bluebirds then

True. I have been playing a bit more and it appears to improve quite a bit as you stop it down. I should have some more example shots (with some blue in them) later.

Interesting thread. I was out of the digital slr game since recently I bought a K20D, but I was a Canon FD shooter before. Since the FD lenses are orphaned and I had a beat up but optically perfect 300/4 Canon lens that wouldn't sell for much I asked a good repairman to change the mount to K to work in preset mode. I'm getting it in the next days. Will post some pictures.

I look forward to seeing the results. Show us the lens / conversion as well, its always good to se how others adapt lenses and I know there is another another FD conversion to come in the near future (Ovim).

[max889]

Thanks for the interest Matt, I'll try to post pictures of the work. About your lens, ,ecause of the huge focal length, if I get it right you should be able to go for very small apertures before diffraction kicks in, so you results might even keep improving past f/32 (I don't know if the lens gets there though).

[MattGunn]

Thanks for the interest Matt, I'll try to post pictures of the work. About your lens, ,ecause of the huge focal length, if I get it right you should be able to go for very small apertures before diffraction kicks in, so you results might even keep improving past f/32 (I don't know if the lens gets there though).

If the subject is distant (focus near infinity) then the spatial resolution at the sensor is independant of the focal length:
The angular radius of the Airy disk is given by:

sin(A)=1.22 x l/d

where A is the angular radius, l is the wavelength of light and d is the aperture diameter. Now the aperture diameter is related to the F number (F) and the focal length (f) by:

F=f/d.

If the angular radius is small (as we hope it is) then the small angle aproximation holds and so sin(A)~A . Substituting these in gives:

A=1.22 x l x F/f

The linear radius of the Airy disk (r) is given by A x f and so finally

r=1.22 x l x F

This does not hold for macro photography where the subject distance is only a few times greater than the focal length where it gets a bit more complicated.
Also the smalest aperture of the lens is f/16.
There is a usefull tutorial on diffraction in photography here: Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

[Lowell Goudge]

.....The latest conversion is a Vivitar 55mm f/2.8 macro, originally in Konica AR mount. I know that this lens is available in K mount but I got it so cheep that I though it was worth a try in spite of the potential difficulties of acheiving infinity focus from a mount with a registration distance 4.8mm shorter than K mount.

The conversion involved dismantling the lens, removing about 4mm of metal from the back of the lens mount and the aperture ring, machining a new recess into the back for bits of the aperture mechanism, drilling and tapping new holes and fitting a flanged M42 adapter. So that I didn't have to stop the lens down before taking a picture I made and fitted a new aperture actuating lever so the lens workes as an M lens as the original K mount version did. It also reaches infinity focus.

As with previous conversions, I had a go at making it an A lens as can be seen from the photo. Unlike most of the previous lenses, in this one the aperture mechanism provides a linear change in aperture area with lever movement so I was hopefull it would be more sucessfull than previous attempts. However the aperture lever movement of the K AR lenses is greater that K mount. At the wide end it was OK but at the smallest aperture the exposure was almost 3 stops too high so I took the A pin out again and now just use it as am M lens. I haven't tested it much yet but it is another impressively sharp lens. A photo of the converted mount is shown bellow.

One thing I have noticed in converting vivitar and Kiron lenses from Minolta or nikon to PK mount is that you don;t have to remove any metal at all.

THe vivitars made by Kiron, and the Kiron lenses I have modified have a very long focusing helix. In fact I believe they did this as the means of accounting for all the lens makers in the main mechanical design.

THe focusing ring is attached to the helix by three screws visible when you take off the cosmetic collar at the front of the lens.

There is a small set screw and the collar threads off whe this set screw is backed out a little.

You can see past the fllange a at the front the 3 screws and large washers.

Just losten these off and you can modify the infinity focus point to suit the new mount distance as the focus limits are only based upon the focusing collar.

I will try to attach a few shots later or perhaps a sketch.

But I now have 2 fast wide angles, a 24mmF2.0 Vivitar by Kiron, with Nikon AI mount, and a 28mm F2.0 Kiron for Minolta MD mount, and both focus just fine to infinity after mounting flanged K mount M42 adaptors

[MattGunn]

I guess you have been lucky. The only lens I have had with enough extra focus travel to allow for an altered registration distance is a Super Takumar 300mm f/4. This had just enough extra travel to allow a flanged M42 adapter to be fitted and maintain infinity focus.
How thick were the original mounts of your vivitar / kiron lenses? I guess that if they were quite thick then replacing them with flanged M42 adapters gained you a bit in addition to adjusting the focus stop. With lenses with a significantly shorter registration than pentax such as Konica and Canon I doubt that any lens will have enough extra focus travel (building 5mm extra travel into the focus would be very wastefull). I would be interested to see your conversions though.

[MattGunn]

I took the wray 36" lens for an outing to the seaside last weekend. This seemed like an ideal place to test it as I could park close (this is not a lens to go hiking with) and there were plenty of willing subjects. During the winter months over half a million starlings frock here to roost under the pier so everywhere I looked there were birds to photograph. In spite of the poor results I have had previously with anything blue, some of these shots worked well as the lens improves as it is stopped down so it was used here between f/11 and f/16.


Pentax User Photo Gallery - Nature


Pentax User Photo Gallery - Nature


Pentax User Photo Gallery - Nature

[ovim]

Great shots Matt! I especially like #2. Would've liked #1 even more if it had that nice orange sky in the background. From how far away did you shoot these?

(btw I'm still waiting, but hopefully not for long)

[MattGunn]

Thanks Ovim I guess I must have been about 250M from the pier. The field of view with this lens is about 1X1.5deg on APSC. I went back yesterday and got some silhouettes against the setting sun but I haven't sorted the photos yet.
I'm sure your postman will be by soon...

[Lowell Goudge]

One thing I have noticed in converting vivitar and Kiron lenses from Minolta or nikon to PK mount is that you don;t have to remove any metal at all.

THe vivitars made by Kiron, and the Kiron lenses I have modified have a very long focusing helix. In fact I believe they did this as the means of accounting for all the lens makers in the main mechanical design.

THe focusing ring is attached to the helix by three screws visible when you take off the cosmetic collar at the front of the lens.

There is a small set screw and the collar threads off whe this set screw is backed out a little.

You can see past the fllange a at the front the 3 screws and large washers.

Just losten these off and you can modify the infinity focus point to suit the new mount distance as the focus limits are only based upon the focusing collar.

I will try to attach a few shots later or perhaps a sketch.

But I now have 2 fast wide angles, a 24mmF2.0 Vivitar by Kiron, with Nikon AI mount, and a 28mm F2.0 Kiron for Minolta MD mount, and both focus just fine to infinity after mounting flanged K mount M42 adaptors

go to this link for details

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/89824-adjustme...on-lenses.html

[ovim]

Sneak preview

[MattGunn]

Sneak preview

That should be a lot of fun, better hack the canon mount of quickly
I look forward to seeing what it can do and how it's put together, make sure you show us some images of the dismantled bits.

Here is another shot from the Wray 36", again of the pier on Aberystwyth seafront with the roosting starlings. Stopped down to f/16 and with next to no blue in the image I think it workes rather well. The narrow field of view allows the sun to occupy a fair proportion of rthe frame. I will have to get a solar filter and wait for the sun spots to show up...


Pentax Forums Home - Pentax User Photo Gallery - Settling down for the night

[ovim]

Nice shot Matt! The one bird taking off "in" the sun is the icing on the cake!

Here's my new project. A while back I spotted this Cannon FD 2.8/300mm L lens and a 4.5/500mm L on eekbay.co.uk both in very well used state. I had been looking for something long and faster than my russian 8/500mm mirror lens and was also considering converting something to K or M42 mount. The seller had stated that he would only ship within UK so I thought I'd let them go. But after seeing how the 4.5/500mm ended at a reasonably low price I started thinking about this 300mm again. And with only a few hours left before he bid would close I asked for MattGunns help and he was instantly ready to help out a fellow LBA victim from Finland .

There's also rumours of a new variation of LBA called LHA (LensHackingAddiction) which strikes those with poor funding and/or a great need for obsolete/old/exotic/fast/long/weird glass.



btw MattGunn the aperture works just fine. The breechlock just had to be locked. I had to push in something in the mount while twisting something else to make the lens think it's attached to a camera. After that aperture closes by moving the arm and the blades look to be in mint condition.

I'll start removing the mount hopefully later today.

[Nesster]

Appears B&L manufactured the Tessar under license from Zeiss, pre World War 1.

Here is one I bought today:



I think it was originally meant for one of the Graflexes - perhaps one of the reflexes - 3 1/4 x 4 1/4 on the lens, it has the aperture but no shutter. f/4.5 is the max aperture, as you see there is no focal length engraved on the lens.


Samples? Mounted to the rear tube from a Hanimar 135mm (as it's too large to fit my usual M42 ext tube) and then onto a Honeywell Pentax bellows. Nice focus to infinity, and as close as you want.

Kitty napping at f/11, flash on:



100% crop of the above - click through to flickr to get the true 100% view. Not too bad for a 100 year old lens...



@ f/8



@ f/5.6

[MattGunn]

It certainly takes good pictures, have you any idea of the focal length now you have tested it? How long was the total extension tube & bellows unit when set for infinity focus? What is the aperture range?
If all the Bausch and Lomb tessars work this well then it is definately time I tried the 24" Aero Tessar. Although I haven't done any tests to determine the registration distance yet, I think it may be very close to the same as the Wray 36" as the Tessar is a long prime focus lens and the Wray is a proper telephoto. If this turns out to be the case I will see if I can modify the lens tube for the Wray so the Aero Tessar can be fitted, making another tube this size is a lot of work.

[Nesster]

Thanks - yes, a Tessar is a Tessar... I think it is around 135mm or slightly longer.