Kipon Baveyes Speedbooster + Mamiya 645 500mm 5.6 = Problem?

[Zack Birlew]

Hi, everybody, I’ve been toying around with a Mamiya 645 version of the Kipon Baveyes medium format speed booster and I had hoped to use it with the 500mm 5.6 but there seems to be vignetting of some kind. Has anybody else tested this combo? I’ve heard that certain Mamiya 645 lenses just don’t work with the Kipon Baveyes speed booster at all so is this one of them?

While I don’t have a Mamiya 645 film camera, the lens seems to work just fine with a straight Mamiya 645 adapter to my Sony A7S. I have had to take my Mamiya 645 500mm apart to clean it as I noticed some edge fungus or general dirtiness and I’m very sure I put it back together right optically according to a map diagram I found including most of the other Mamiya 645 lenses, however a flipped element is always a possibility. Naturally this happened before I could test it with the speed booster. Any help or advice would be greatly appreciated!

 

[Phil Holland]

Don't have that one here to test, but there's certainly a possibility on light occlusion when using focal reducers on some lenses.

In a perfect world they would be designed per focal length, even perfecter world, per lens; but I'm suspecting some of the projected image circle is getting chopped off before even getting into the glass of the speedbooster itself.

 

[Zack Birlew]

Well, I've tried flipping the middle front element and the rear element that I thought might be backwards by assembly accident during cleaning and everything leads to vignetting with the Kipon. Again, if anybody else has tested this combo and had the same result, I would love to hear it as that would help confirm whether I have this thing put together right or not. If it doesn't work with the Kipon then it's not too big of a loss as I could go into S35 mode without problems or know not to use the Kipon with this particular lens and still get some extra telephoto magnification with a straight dummy adapter.

On another note, I did try to use the Mamiya 500mm 5.6 for the Bethlehem Star recently and while I didn't get a chance to film or photograph it since it rotated out of view behind a mountain before being visible (doh!), I don't know if infinity was 100% accurate. Does anybody know how to adjust infinity with this lens? I've read that some Mamiya 645 lenses aren't very strong at infinity but being a 500mm lens, I would think this would be perfectly suited for infinity use. Any help or advice would be greatly appreciated!

 

[Zack Birlew]

Update! Since I didn't hear anything back from anybody and there were no user guides or manuals available, I decided the best thing to do was to take the lens apart myself.

As it turned out, the Mamiya 645 500 5.6 is VERY easy to take apart and adjust! I've found many 500mm lenses and bigger telephotos are easy to service and I theorize that since they're often used outside, they're more likely to get dirty or banged up so, thankfully, there was some kind of foresight by lens manufacturers to make maintenance easier to manage when they come in.

So, looking at the lens, you would think that adjusting infinity focus would require removing the three screws under the focus ring to open the lens up but, not so! The three screws are a nice maintenance point to access the internals of the lens, particularly the rear glass tube, as the entire back portion with the aperture dial and mount slides clean off and leaves you the remaining front of the lens, the rear glass tube, and two aperture levers, one sliding lever to control the aperture and one switch lever to control the Auto/Manual adjustment. This didn't help me as I wanted to adjust infinity focus, so the way to put the lens back together easily is to remove the rear mount from the back section so you can see better, manually set the aperture to the lowest or second to lowest point, flick the A/M switch to A so you can control the back pin for alignment of the A/M lever, and slide it all back together and possibly with a little twist, get everything locked back together. After screwing in one of the three set screws, test aperture to see if everything is aligned and clicking properly, if so, then screw in the remaining two screws and put the mount back on to close.

SETTING INFINITY

Okay, the front glass portion unscrews easily for cleaning and may be a little stuck like mine was so with that bulbous top unscrewed, you can look down and see two interior levels leading down to the rear glass and aperture blades. As it turned out, the first level with three screws is the part that needed to be adjusted in my lens and after unscrewing the three screws holding it, there was a clunk sound and I discovered that it was a helicoid unit. So, I tried to unscrew it a little and see if it was stuck or out of alignment but it unscrewed fine and came out easy and screwed back in as well. From what I could tell, alignment of the first helicoid would ideally be simple, however, I couldn't seem to get the helicoid to screw down any further than where it was at so that it could be screwed down in place but closer to the sensor as my lens stopped just short of infinity even with a dumb adapter on my Sony A7S.

Going further, I had to remove the rubber focus grip, just a couple of wood BBQ skewer sticks or long wooden Q-tip sticks slide under and can roll through the set stickiness smoothly and makes rolling the focus grip down a much easier job. With the focus grip rolled down, a row of six screws around the top of the grip can be seen and there's a couple of double screw spots that don't need to be touched as those are the stoppers for the focus ring. Removing the six rim screws is easy enough but you will also have to rotate the focus grip to see the silver lock screw through one of the two opening spots and once you remove that, the focus ring can slide off to reveal the silver rim of the secondary helicoid. The six rim screws hold the second helicoid in place so keep that in mind and note where the screw mark dots were in the deep middle line under the of the lip of the helicoid so you don't screw the focus ring back on the wrong segment.

Now, with the second helicoid exposed, that freed up the front helicoid a little and allowed for an easier grip and rotation. This arrangement was a little tricky as I had to hold the second helicoid down and rotate the first helicoid until it got to the almost flat of the inner set ring. I don't know if I just got cross eyed doing this several times but I remember the first helicoid being able to rotate completely in and out in one direction without rotating the other way, I could be wrong, however, so don't be worried if it does start rotating out, just try again. After a few tries and making sure to keep the secondary helicoid held in place, I got it to a point where I could rotate the first helicoid down to be flush with the inner ring and aligned with the screw holes. With both helicoids now rolled down in place, the next step is to get the inner lock segment that made the "clunk" sound back to the front of the lens. Thankfully, all you have to do is hold the lens upside down and it will fall back to the front with another "clunk", just reach under and screw back in the three lock screws and the front helicoid is locked down in place. Lastly, just put the focus ring back together starting with the silver lock screw and then the six rim screws, roll the rubber grip back on, and screw the front lens top back on and there you have it!

After adjustment, or in this case, zeroing out my lens' focus, I can focus to infinity and a little bit past which is good as I wanted to use this for astrophotography and the occasional moon shot. It's only a guess but I wondered if the person who had it before me adjusted the lens to focus closer or simply did a slightly botched CLA as the lens was otherwise mint. Also, since I got the front helicoid down flat on the inner ring, I would now be able to fine tune only the front helicoid if I wanted to adjust infinity by simply rolling it up a couple turns to the next screw alignment point. It was getting close to night by the time I got this done so I'll have to wait for daylight to see if perhaps the vignetting on the Kipon was due to this misplaced helicoid position invading the image. I'll post an update once I test it.

One other note, the Mamiya 645 500mm 5.6 definitely has a use limitation in that infinity on F5.6 or even F8 may not be all that sharp and stopping down to F11 would be the minimum for sharp infinity results, otherwise it's fantastic for mid and close (remembering the basically 30ft minimum focus range) at all apertures. Also, as with many long telephoto lenses, atmospheric conditions play a big role, especially at infinity, and can make what would normally be a crystal clear infinity focused landscape into a soft blurry mess as I found trying to check infinity on a distant mountain. Lastly, F11 may sound like having to stop down to the point of "Daylight-Only" but remember that Medium Format aperture ranges are a little different than 35mm, especially when used on 35mm sized sensors so it's not as dark as you would think.

 

[Zack Birlew]

Final update!

Okay, to finalize this thread, disassembly and cleaning of the Mamiya 645 500mm 5.6 is pretty straightforward and easy and, as I found out today, it is NOT compatible with the current iteration of the Kipon Baveyes Medium Format speedbooster. I tested one of my previous window test spots in my room and I can no longer focus close on the window frame like I could before my infinity adjustment but I can now clearly focus on the mountain across the valley and a little beyond, which confirms my hypothesis about the lens being improperly adjusted for closer focus for whatever reason. With the Kipon Baveyes, even after infinity adjustment, the image is still completely in a circle at Full Frame readout on my Sony A7S but is fine on APS-C crop which is okay, I suppose, but is a little bit of a letdown when the goal is to accurately mimic Medium Format coverage with this lens.

At least I can say I learned a lot more about a lens that doesn't have a lot of maintenance guides or repair videos online and I do still have a nice and sharp Mamiya 645 telephoto lens at the end of the day which will come in handy for astrophotography, nature, and effects shots regardless of sensor coverage with full frame cameras. The Kipon Baveyes, while not perfect, is still a handy tool for my other Mamiya 645 lenses I've tested so it's a nice solution until digital Medium Format becomes more affordable.

 

[Jacek Zakowicz]

I struggle to understand why you would want to use a sb on such a long lens? Isn't the purpose of long tele lenses to magnify as much as possible? Why not just use a shorter lens instead? They are usually faster so the speed factor is non issue, they are usually sharper, they have plenty of coverage since the angle of view is narrow. What is the point of this?

 

[Zack Birlew]

It's simply to utilize the full coverage of the complete lineup of my Mamiya 645 lenses. Much like how we see all the charts of using Full Frame lenses on S35 sensors, there's a visual difference and arguably a loss to the lens' look compared to using the lens on its designed sensor size, even though they may produce visually stellar images on smaller sensors in any case. I have a few 500mm options for Full Frame use but having a Medium Format option will come in handy as more Medium Format video options become available so, for now, using a speedbooster, I would like to test these Medium Format lenses and get an idea of the look they would give compared to smaller format solutions.

 

[Zack Birlew]

Alright, I have confirmed that the Kipon Baveyes Medium Format Speed Booster WILL NOT WORK with 500mm Medium Format lenses! I decided that since the Mamiya 645 500mm wasn't working I would try something else and I got a hold of a Pentax 6x7 500mm and a P67 1.4x Teleconverter to test. As it turned out, despite being slightly larger coverage than the Mamiya 645, the Pentax 6x7 500mm had the exact same vignette problem and the 1.4x Teleconverter didn't help. So, this was final confirmation that the Kipon Medium Format Speed Booster is optically limited to a certain range of focal lengths along with certain incompatibilities in between.