Purchased a B&L Baltar 75mm f2.3 - now what?

John Lindroth · July 6, 2015

Hi all. This is my first post as a member. I'm thinking that this is the place to get some answers to a new project.

I recently purchased a Baltar 75mm f2.3 lens. I'm attaching a photo, that will show you the mount.

I got it at a deeply discounted price, so I thought that there are two possible options for it:

1. re-sell

2. find a way to convert/adapt the lens to be used on my Canon 5DMkII *** this is preferred, I'm a still photographer, but love old lenses

I have been searching online for companies that work with old lenses, and most will clean lenses, but do not offer conversion service. But I'm assuming that I'm looking in the wrong places.

So here are my questions so far, for which I have no answers:

1. what lens mount does this lens have?

2.Is there an adapter to EOS, or to another mount (M42?) that could be adapted to fit?

3. Doe this lens have the ability to focus, or is it in the camera mount?

4. I have seen this lens mounted into what looks like a Nikon 50mm f1.8 deconstructed lens. This might be interesting, but I can't find the person who is doing it, or any technical info on how to do the conversion.

Any other information about would also be greatly appreciated.

Thanks,

-John

Mark Dunn · July 6, 2015

It doesn't seem to have a mount at all.

If you look at this

http://www.ebay.co.uk/itm/like/251939825156?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&rlsatarget=&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

or this

http://www.ebay.co.uk/itm/like/181340832719?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&rlsatarget=&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

(this one is in an M42 mount which would adapt to EOS, so you know it can be done)

you only seem to have the bit at the end. You need the silver/black bit as well.. That's where the focusing rack is.

presumably you're referring to this

http://www.ebay.co.uk/itm/like/261073342723?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&rlsatarget=&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

which is indeed a gutted Nikon 50.

You need a friendly machine shop or another lucky eBay trade for the focusing rack.

Edited July 6, 2015 by Mark Dunn

John Lindroth · July 6, 2015

Thanks Mark. I think the second link might have the key to making this work. They have mounted the lens in an adjustable macro adjustment ring, basically adding both the mount adapter and focusing in one piece. Looks a lot like this one:
http://www.aliexpress.com/store/product/Adjustable-Focusing-Helicoid-Macro-Tube-Adapter-17mm-to-31mm-Suit-For-M42-to-M42-Lens/701997_1552455732.html

I won't have actual possession of the lens until FedEx delivers it this week, and I'll do a little testing for focus distances, but I think you've turned me on to something perfect.

They certainly do list for high prices. I'm hoping the glass is fairly clean in this one.

-John

Alex Nelson · July 7, 2015

Baltars generally didn't leave the factory in any kind of mount, or with any kind of focusing mechanism. Because of the variety of mounts and camera systems available at the time, it wouldn't have been worth it to Bausch and Lomb. Instead, rental houses and camera manufacturers installed the optical blocks (like yours) into some rudimentary thread-based focusing mount that suited their inventory.

You'll need to find the infinity position first, since that will be the closest the lens sits to the film plane and can usually offer a pretty quick answer as to whether or not a particular lens can be adapted to a particular camera system. In your case, 75mm is a pretty safe focal length, since longer lenses traditionally sit further from the film plane or sensor than do wide primes and are therefore less likely to interfere with mirrors or other internal obstructions.

You can work out which helical you need with a simple formula: d=f^2/(a-f) where d is the distance the lens travels from its infinity position in inches, f is the foca length in inches, and a is the close focus distance in inches. Say you want close focus at three feet, you would need to move your 75mm Baltar .27" from its infinity position.

I actually have a set of Baltars at home. If I can find my notes, I can tell you where infinity is on the 75mm.

Mark Dunn · July 7, 2015

Thanks Mark. I think the second link might have the key to making this work. They have mounted the lens in an adjustable macro adjustment ring, basically adding both the mount adapter and focusing in one piece. Looks a lot like this one:

http://www.aliexpress.com/store/product/Adjustable-Focusing-Helicoid-Macro-Tube-Adapter-17mm-to-31mm-Suit-For-M42-to-M42-Lens/701997_1552455732.html

I won't have actual possession of the lens until FedEx delivers it this week, and I'll do a little testing for focus distances, but I think you've turned me on to something perfect.

They certainly do list for high prices. I'm hoping the glass is fairly clean in this one.

-John

That item could be the beginning of a beautiful friendship for some old glass of mine. I'm thinking close-subject-distance-corrected enlarging lenses with no focusing rack of their own. Well spotted- I just googled, didn't even look at it.

Alex Nelson · July 13, 2015

At infinity, the image would land about 60.30mm from the front of the silver threads on the back. That is, for these purposes, your flange surface on the housing.

John Lindroth · July 22, 2015

Thanks Alex. I've been away on vacation, and I just saw your reply. I'll do a little testing myself, but this should make it simple to determine the right adapter. Does anybody know about the screw mount on the back of the lens? M42 is too large, M39 seems too small. Perhaps an "M40"??? I really want to keep the lens as intact as possible.

Alex Nelson · July 23, 2015

The threads are actually imperial (Bausch and Lomb being a US company), and are an arbitrary 1.560" x 40 TPI. It's not likely you'll find a ready-made adapter to match that, but if you know a machinist or have a reasonable garage shop, you shouldn't have any trouble fashioning something to couple it to a helicoid. It's too bad yours didn't come with any kind of mount, since that would have the mating threads and would open the possibilities for adapting the lens without incurring too great an expense.

John Lindroth · August 4, 2015

Thanks Alex. I'm doing some testing now, to see if I can make something unusual work. I've purchased some ApoxySculpt clay, and an M52-M42 17mm-31mm Helicoid Macro adapter. I'm planning to use the clay to create a lip inside the M52 that will hold the lens in place (coating it with machine oil, so it doesn't stick). I've done some testing, and the material is super strong once it's hardened, and I've used it in some test cases where I think it will work here too. I really don't want to ruin the lens, and stick it forever in the adapter, so I'm moving forward very carefully...

Alex Nelson · August 5, 2015

I don't know if you have any CAD experience, but you might try a service like www.shapeways.com to 3D print something more precise and finished-looking if your tests bear fruit.

John Lindroth · August 5, 2015

I'm still waiting for the helicoid macro adapter to arrive, but I've contacted a couple local machine shops to see what kind of quotes I can get. Sadly I have no experience with CAD. I've considered 3D printing as an option, but no idea how to make that happen. I'll check around with some stuff out there as well.

John Lindroth · August 27, 2015

I wanted to add an update, with many thanks to the folks who have replied to my initial post/question.

I've got the lens mounted in an M42 mountable, focusable piece.

I purchased an M52 to M42 Helicoid Focus Macro converter with 17-31mm range. Adding that onto the 45.46mm flange distance for the M42 put the lens right in range for the 60.3mm for the Baltar (thanks Alex!). My first thought was to find a machinist who could create an adapter between the two. This still might happen, but cost for a prototype was about $125. Very well within range for the actual value of the lens, but I wasn't sure if I wanted to spend that much starting off. So I searched and found an interesting compound called Apoxie Sculpt - an epoxy resin that stays in a sculptable dough for about 3 hours. Through some testing, I made sure that a good machine oil on a screw would not adhere to the resin once it hardened. With lots of measurement and testing, I created a piece to hold the lens at a distance that would put the lens a little past infinity (so I knew I could get to infinity on the camera) and molded the resin into place. It focuses to about 24" close focus.

As of this morning, I have a perfectly usable Baltar 75mm lens, and I can mount it on all three of my interchangeable lens cameras (Fujifilm X-E1, Canon 5DMkII, Sigma SD9).

Thanks to everyone for your help. Now comes the fun part of testing...

-John

Alex Nelson · August 27, 2015

That's great! Were you able to keep the lens flat and parallel to the film plane? It's not as critical as with wide-angle lenses, but I imagine your jig probably held it reasonably straight.

Can't wait to see what you shoot with it!

John Lindroth · August 27, 2015

I never measured to see if the lens is perfectly aligned, but the washers I used were all perfectly flat, so for a first attempt, I'm satisfied.

I'll try to shoot some test images to see if the edges are unevenly out of focus, but my thoughts were to use this for portraits, so there won't be any issues with edges, as I would want them out of focus.

From my first test shots (taken before I had this new setup), I was impressed by how sharp the images were. And the iris has 16 blades, and they appear circular, I can't see any pattern to the background all the way down to f16:

DSCF3943.JPG f2.3
DSCF3944.JPG f2.8
DSCF3945.JPG f4
DSCF3946.JPG f 5.6
DSCF3947.JPG f 8
DSCF3948.JPG f11
DSCF3949.JPG f16

Now to find some models...

Alex Nelson · October 20, 2015

Any photos to share yet?

John Lindroth · October 20, 2015

Hi Alex - most definitely! I really enjoy the lens. Not sure it's worth the prices asked on fleabay, but at $23 it's an amazing addition to my toolset. Here are some test shots, most at f2.3, but it's difficult to tell if it's stopped down because the aperture is always a circle! I've also used it for some headshots, and I really like the results (but don't want to add those photos here). I haven't used the lens yet on a full frame camera. All these photos, except the butterfly, were taken on a Fujifilm X-E1. Butterfly was with a Sigma SD9.
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