Microscope objectives and bellows

I've been playing around with some recent acquisitions, a Zeiss 16mm f2.5

Luminar, and several Zeiss and Nikon microscope objectives, and an old favorite

of mine, the 25mm f2.5 Leitz Photar.

 

The Zeiss Luminar, Leitz Photar, and Nikon Macro (not "micro") Nikkors are

basically long working distance objectives, mounted to be a little more friendly

for macrophotography. This consists of giving them marked aperture controls

(some microscope objectives have aperture controls, but they're typically

unmarked, like my Nikon U10 and U20), black exterior finishes, and are labeled

in focal length and f stop, instead of "X" (magnification) and "NA" (numeric

aperture) like microscope objectives. The lens mount for the Photars, Luminars,

and Macro Nikkors are identical, all use the RMS (Royal Microscopy Society)

screw mount.

 

Fortunately, they're easy to convert. Older microscope objectives were made to

the "160mm tube" standard. That means focal length = 160mm / magnification.

Aperture is a little more difficult, the conversion involves cosines and arc

cosines, but for NA 0.33 or smaller, it's approximately f=1/2NA. NA 0.5 is about

f1.2, if I've got the math right. Common microscope objectives were 2.5x and 5x

(low magnification "scanning" objectives for "navigating" around your specimen)

then 10x, 20x, and 40x. These are focal lengths of 10 The Zeiss Luminars come in

16, 25, 40, and 63mm focal lengths (there are a couple of longer lengths, like

the 100mm, are not microscope objective designs, and use larger mounts. They

won't work on a standard microscope, but they do work on monsters like the Zeiss

Ultraphot). The Leitz Photars are 12.5, 25, 50, and 80mm. The Nikon Macro

Nikkors are 19, 35, 65, and 120mm. This suggests to me that the Zeiss are

standard microscope objectives,

 

So, here's my results, so far, on a Nikon bellows, at extensions of about 100mm

and 200mm, with a D2X. I'll try to post some shots later this week. I'm assuming

that any lens that isn't specifically labeled as having a tube length other than

160mm adheres to the 160mm standard.

 

4-5mm

 

Zeiss L.D. EPIPLAN 40/0.60 (4mm f1.0). Fair. Not impressed by the contrast, or

the chromatic aberrations. The working distance is near non-existent, about 4mm.

even with a tapered "bullet nose" tip, it's hard to light a subject from above.

This really is a microscope lens, intended for use with translucent subjects,

lit from below. I have two sepcimines of this lens, one appears to be totally

uncoated, and the other is not coated on at least half the elements.

 

Nikon M Plan 40 0.5 ELWD (5mm f1.2). Good. Its marked 210, which means the 40x

is relative to a 210mm microscope tube, not the old 160mm standard. The ELWD

stands for "extra long working distance", and it lives up to that. The "M Plan"

lenses have good flat fields and excellent color correction. It's got modern

coatings which help the contrast. The coatings are all different colors, not

just purple and amber, so I assume it's a very modern lens. When I put enough

light onto the subject, this lens is a joy. At 100mm, it's 20x, and an effective

aperture around f24. That's a bit much for a Nikon "DX" sized camera, which has

a diffraction limit between f16 and f22, but definitely not a show stopper. This

lens has no aperture control, nor does it need one. Hard to think of an f1.2

lesn as "slow", but on a bellows, it is, and you couldn't stop it down even if

it had an aperture control. The contrast and sharpness are excellent, the field

flatness is impressive. At 200mm, the effective f48 limits both my resolution

and ability to see. I lit the subject very brightly (maybe 4x daylight). If I

pull away from the viewfinder and look directly at it, my eyes sting. The

working distance is about 12mm, which for 20-50x magnification is just a dream.

Now, if I can come up with some interesting and creative ideas for macro at

20-50x. Now, as far as the joys of 20-50x on a bellows, that's an article in and

of itself.

 

8-10mm

 

Nikon U 20 0.33 (8mm f1.6, assuming 160mm standard). Very good. This lens has an

aperture control. It's not marked, but I can't see shooting it anywhere other

than wide open. At 100mm, it's 12.5x magnification, and f20. Even on a full

frame DSLR or 35mm film, I wouldn't want to stop down a full stop to f28. You'd

only stop this one down if shooting medium or large format. At 200mm, we're 25x,

but f40. Coatings appear decidedly more primitive than the M Plan, but the

contrast is still pretty good. May be subjective, but I don't think it matches

the M Plan for contrast. Working distance around 15mm, which can be quite handy.

 

Nikon M Plan 20 0.4 ELWD (10mm f1.4). Excellent. Like the M Plan 40, this is a

210mm tube objective. At 100mm, it's 10x and f14. It's actually below the

diffraction limit, and it's tack sharp and beautifully corrected. At 200mm, it's

20x and f28, but still an impressive performer. Like the M Plan 40, it needs no

aperture control. Again, working distance is about 12mm. I can see using this

lens around 10-20x, but never less than 10x. I can get 10x out of my 25mm

Photar, with a longer working distance.

 

16mm

 

Nikon U 10 0.22 (16mm f2.27). Excellent. This lens has an aperture control. It's

not marked, and I may stick an aperture scale on it. 100mm she's 6x and f14.

There are times I can see stopping it down a stop, even on a D2X. 200mm gives

12.5x and f28, so we're back to being wide open. Good sharpness and flat field,

and I'd have to say better contrast than the U 20. Also better than my other

16mm, the new Luminar. The 15mm working distance is sweet.

 

Zeiss Luminar 16mm f2.5. Very good. Has an aperture control, marked in tiny,

dark, hard to read numbers 1, 2, 4, 8, 15. Those are area, not "stops" (which

are based on diameter). I can only see using 1 and 2. The "15" setting is f20,

and if you extend it just 80mm on a bellows, that's f100, totally useless mush.

I was expecting this thing to beat the tar out of the U 10. I was surprised. The

contrast and sharpness are slightly inferior to the U 10. And it's so much

harder to use. The working distance is under 8mm, and the front of the lens is

bigger than that of the U 10, so lighting the subject is much harder. For

transmission microscopy, this wouldn't be a problem, but I use it as a macro lens.

 

25mm

 

Leitz Photar 25mm f2.5. Excellent. Tack sharp, good contrast. Aperture control,

marked in large white numbers in real f stops. A joy to use. A mix of coated and

uncoated elements, but it doesn't seem to hurt the performance of the Photar

design. Working distance about 20mm.

 

Leitz Summar 24mm. Good. Aperture not marked, calculated at f5 based on rear and

front element diameters. Came with an RMS to M39 adapter marked "Repro Summar"

but the 24mm and 42mm are also referenced as "Macro Summar" lenses. A very tiny,

hard to hold lens. Aperture control marked 2, 6, 12. A mix of coated and

uncoated elements. At 100mm an effective f20, at 200mm an effective f40, so the

strangely marked aperture control would probably never be used.

 

40-50mm

 

Leitz Summar 42mm. Good. Aperture not marked, calculated at f4.2 based on rear

and front element diameters. A very tiny, hard to hold lens. Aperture control

marked 2, 6, 12. A mix of coated and uncoated elements. At 100mm an effective

f8, at 200mm an effective f16, it can be stopped down a stop or two, and only

reaches acceptable sharpness at an effective f22, a narrow valley between poor

contrast and correction and diffraction. Id jump right from the 25mm Photar to

the 63mm Luminar and skip this lens in normal shooting.

 

Leitz 3.5/0.10 170 (48.6mm f5). Fair. This lens has no aperture control, no

coatings, and noticeable curvature of field. And the working distance is about

15mm, very short for a 50mm lens. The rear element is so much larger than the

front element that I'd say this lens is actually a reversed telephoto. It's

built to allow a long focal length lens to be par-focal, to live on the same

lens turret as the working 10x, 20x, and 40x lenses, without much refocusing

when you rotate the turret. Highly undesirable for macro photography on a bellows.

 

63mm (winner, Zeiss Luminar)

 

Zeiss Luminar 63mm f4.5. Excellent. Aperture control, marked 1, 2, 4, 8, 15,

30, 60. Working distance is fine, contrast and sharpness are simply amazing.

I've shot other lenses in this area, Nikon and Leitz, but the Zeiss holds its own.

 

Olympus MPlan 2.5 0.10 (64mm f5.0). Fair. No aperture control, poorly corrected,

and poor contrast. A mix of coated and uncoated elements. Very weird working

distance of about 30mm. It's too short for good bellows work, but too long to be

parfocal with any of my microscope objectives on the scope.

 

Out of this set, I'd pick these for the macro bench

 

5mm Nikon M Plan 40

 

10mm Nikon M Plan 20

 

16mm Nikon U 10

 

25mm Leitz Photar

 

40mm (need to get that Luminar from Vivek)

 

63mm Zeiss Photar

 

I'll see if I can shim and space these to work on my microscope in a coherent

fashion

 

3.5x Leitz 3.5x 0.10

 

10x Zeiss 16mm Luminar

 

20x Nikon U20

 

40x Zeiss EPIPLAN

 

wizfaq

 

Excellent info! Could you also post pictures of your favorite microscope objectives when you post the images they produce Joseph? Also, I was unaware nikon made a RMS adapter. Did you create this item for your bellows or did nikon make a royal microscope thread mount adapter?

 

Lindy

Nikon did make an RMS to M39 to Nikon F, two-part adapter as part of their multiphot system. It is currently pretty rare and expensive. One of the RMS to M39 adapters is currently for sale on that auction site for something like $400.

Lindy, I have two Leitz M39 to RMS adapters. One Leitz adapter came with the 25mm Photar (and I have the original Leitz box that's made to hold them both). The other adapter is identical except that it has "Repro Summar" printed on it in large, white, nicely engraved lettering.

 

I have a couple of M39 to Nikon F adapters. One is an aftermarket part, built specifically to be an M39 to F adapter, and of very good quality. The other is a "T-2" type T-mount adapter, the kind that's made in 2 or 3 separate parts, with a threaded insert. I had a machine shop make me a new M-39 threaded insert.

 

I'll post an image of one of the objectives on the adapter on the bellows.

 

I'm currently having some brass RMS to T-mount adapters tooled up. They're 50mm (2 inches) long, and taper from the T mount to the RMS end so that they give you more working room to around the lens.

 

I don't have any of those $400 collectible adapters Ian mentioned. I do have some collectible Nikon 28mm f1.8 Ultra Micro Nikkors, very high resolution repro lenses that have some interesting macro potential.

I've got a couple RMS adapters but I only have one microscope lens. One RMS adapter is Canon FD to RMS along with their 20mm f3.5 microscope thread bellows lens and the other adapter is pentax K mount to RMS adapter. I can cobble the Canon FD RMS adapter to Canon made leica 39mm and then that to Nikon F to 39mm to use on my PB4 bellows. I can adapt either a Eos body or Canon FD body to PB4. Nikon used to make F to 39mm adapters and thats the one I've got. At the moment I'm using K Mount 6mp dslr, my first dslr. I seem to be lacking the overwhelming lighting needed for the 20mm bellows lens.

 

I found the link to the RMS to 39mm adapter $395 auction. Thats alot of money.

 

Lindy

Joe, there's a big difference between microscope objectives and photographic objectives such as Luminars, Photars, Mikrotars, Summars, Milars, Neupolars, Micro Tessars, MP-4 Tominons, ... Microscope objectives are designed to be used in optical systems with two stages of magnification and, as you pointed out, a fixed-length tube separating objective (stage 1) and ocular (stage 2). Photographic objectives are designed to be used by themselves without an eyepiece. It is easy to confuse a photographic objective in RMS thread with a microscope objective.

 

I'm not clear on how you tested. It isn't clear whether you tried each of your objectives to find the range of magnifications for which it is optimized. Some are very good over only a small range of magnifications, so being fair to the lenses requires testing in the right range for each. The 19/2.8 Macro Nikkor, for example, is much better at 15:1 than at 10:1 or 20:1.

 

About female RMS-to-male T adapters. Edmund Industrial Optics offers them. And SRB offers them at UKP 35. See http://www.srb-griturn.com/index.asp?function=DISPLAYPRODUCT&productid=258

Hi Dan.

 

I'll be the first to admit that my testing is very subjective. And I didn't do a serious hunt for the optimal distance, just a quick check at two easy to attain distances, 100mm and 200mm. Sounds like that 19mm Macro Nikkor of yours hits its stride at 300mm, and that's major league different from microscope objectives designed for 160mm.

 

I quite agree, there are a many interesting differences between most microscope objectives and macro lenses. I just seem to have hit on a few where the differences aren't all that big. One thing that isn't too critical is the issue of a 1 stage or two stage design. Good objective and eyepieces are designed to go from a plane at the subject distance to an intermediate plane (used to be at 160mm, now 210mm is common) to another plane at the eye. If they do this well, you can substitute a "real" plane, like film or a sensor, for the virtual one. The big problem is working distance, and the fact that most microscope objectives just aren't that well corrected.

 

I've never seen the SRB-Griturn adapters. How deep are they? He doesn't have pictures of the RMS adapter, but he calls it an "insert for T-mount", which is the same term he uses for this M-39 adapter.

 

http://www.srb-griturn.com/index.asp?function=DISPLAYPRODUCT&productid=246

 

That puts the objective pretty much flat against the front standard of the bellows (like the Canon RMS adapter that Lindy uses). The Edmund is 11mm thick (not including the M42 threads), which is better than nothing, I guess.

 

That's one thing I like about the Leitz RMS to M39 adapters, they're 25mm (again, not including M39 threads) long cylinders, and the flat RMS end is 43mm in diameter. Much easier to work around than the 85mm square front standard of the bellows.

 

But I want to go one step beyond that. I want my truncated cone to have a 25mm front, and a 50mm length past the M42 threads (although a shorter cone may lower cost substantially). That gives me a range of about 100mm to 250mm on the bellows, and that should hit the sweet spot of just about any objective or macro lens.

p.s. I took an instant dislike to SRB-Griturn after looking at his site just now. The M39 adapter page I pointed out says "Enlarging lenses make good macro lenses as they are corrected for short working distances and flat field."

 

And the RMS, C, and D mount adapter page that you pointed out says "RMS objective lenses from microscopes, C-Mount lenses from 16mm movie or CCTV cameras, and D-mount lenses from standard 8mm movie cameras, make very strong macro lenses when used with extension tubes or bellows."

 

Cine lenses only perform well as macro lenses if you reverse them. This is also true of enlarger lenses. Most modern (as in the last 30 years) enlarging lenses are asymmetrical. Shorter focal lengths (40, 50, 63, 75, 85, 100mm) perform badly on a bellows, unless you reverse them.

 

But you don't need SRB-Griturn's adapters if you're going to reverse lenses. That is done with off-the-shelf step up rings and reverse mount adapters.

Joe, what you wrote about the need to reverse enlarging lenses when shooting above 1:1 is generally accepted as true. But and however, there are exceptions.

 

H. Lou Gibson wrote in Kodak Publication N-12B (I think that's the number, may be mistaken) that the 50/4.5 and 75/4.5 Enlarging Ektars work very well above 1:1 when mounted normally. I've tried 'em out, and he's right. These lenses are heliar types, seem to be symmetrical except for the diaphragm's placement. And my 4"/5.6 Enlarging Pro Raptar just about matches a 100/6.3 Luminar at f/11, f/16, and f/22 from 1:8 to 1:1 and wide open from 1:1 to 4:1. I've never had, so have never tried out, a 50/9 Apo Saphir. These are symmetrical, diaphragm placement aside, heliar types and have been used, according to a friend who used to be very close to Boyer, as macro objectives.

 

You don't seem to be aware of Linhof's female RMS-to-male various adapters. These usually come attached to Luminars. I have one that goes to 25x0.75, a standard Schneider enlarging lens thread, had and sold one that went directly into a #0 shutter. I use my RMS-to-25 mm adapter on a conical plastic (cheap) 25 mm to #1 shutter adapter.

 

I also have the Edmund adapter. There'as an attachment that makes it easier to use, one wants their NT52-301 "T-Mount Microscope Objective Lens Ring Mount", also their NT52-298 "T-MOUNT DOUBLE MALE THREAD".

 

Cheers,

 

Dan

Check out Dr Klaus Schmitt's web site on macro lens and adapters. He has the most complete list of macro lens. Here is a link to the adapter page. There are a number of the cone shape adapters available. The one that is not on this page but also meet what you need is the Topcon adapter for their 35mm macro, 65mm long and a tiny bit wider then the RMS tread.

 

BTW: It may be easy/better plus cheaper (<$100, at time) if you hunt for a Tominon 17mm then using a microscope objective.

 

http://www.macrolenses.de/adapter.php

The RMS to X adapters are easy to cobble together if you find the Zeiss microscopic objective plastic containers. They have metal RMS rings. Just pop them out and glue them properly (to ensure it stays in one plane) to whatever you need.

 

Interesting mini review, Joe. I have the Zeiss magnification charts/info leaflets somewhere (also available on ebay from some folks as scans). Will dig it up.

 

Major factor in using all the high magnification lenses is the lighting. Not easy at all. There are books on these topics but no one can follow any "recipes" to achieve certain results. It is a learn as you go type of thing and is quite challenging.