Extreme macro.

Discussion in 'Nikon' started by sim_m, Apr 30, 2008.

  1. I'm new to photo.net,
    I wish to obtain a greater magnification than a 1:1 but with quality results. I
    have thought of either attaching a canon 500D close up lens or using Kenko
    extension tubes with my 105mm macro lens which already produces a 1:1. my
    objective is insects face details. about 3:1.
    Any help please?
    Thanks, Simon.
  2. And what did you get when you tried those things? Was the magnification not enough, or what the quality bad?

    The old Minolta AF system used to have a special bellows mounted 1x-3x macro zoom that was reputed to be really excellent. And maybe a bellows might be something to try for you too. Do they make those for the Canon AF line?
  3. I assume you're talking about a 105mm micro Nikkor.

    To reach 3:1, you require an extra 140mm (the effective focal length of a 105mm reduces to 70mm at 1:1. That means, if you just buy the 36mm Kenko tubes, you require four of them. An awkward approach, at best. You'd probably need to build a stabilizing cradle bracket to get the lens extended out to that length.

    Even with the more powerful Canon 250D (skip the 500D for this one), you'd reduce the 105mm (really 70mm) to an effective 54mm. It's own 140mm extension at 1:1 gets you to 140/54-1 = 1.59:1. You need 76mm of additional extension to hit 3:1, two 36mm tubes are "close enough" at 72mm.

    You will also find that 3:1 makes handheld work virtually impossible, and you may want to invest in either a focusing stage (to move the subject in relation to the camera) or a focusing rail (to move the camera in relation to the subject) in order to focus.

    I would look at two other techniques. If you can get your hands on a Nikon PB-4 or PB-6 bellows, you can use a 50mm or 63mm enlarger lens to hit 3:1 magnification, and you will be able to vary the magnification. Additionally, the PB-4 and PB-6 have built in focus rails to make focusing much easier than other bellows suceh as Nikon PB-3 or PB-5, or those anonymous bellows from the auction site on the bay.

    Or, look at lens coupling. Put a telephoto face to face with a normal or wide, and you get magnification equal to the ratio of the focal lengths. 3:1 can come from a 50mm in front of a 150mm, or a 35mm in front of a 105mm. A used, manual focus 35mm f2.0 should be pretty affordable, definitely cheaper than four Kenko tubes, and easier to work with. You'll need a focusing rail to make this technique work.
  4. Assuming you are NOT using the AFS 105 VR micro, you can get up to about 1.6x magnification with the PN-11. You can increase that to about 2x if you add the PK-13 as well. I have had good results with this combination, This is a well balanced setup if the tripod mount on the PN-11 is used so handling is good. Assuming you have a camera like the D200 or D300 you'll still get AI metering.

    Adding a closeup filter like the Nikon No.4T or Canon 250D will increase the magnification a little further towards 3x.

    Another option might be to reverse a 50mm lens on the front of your macro lens. The 50mm lens will act like a very strong (and highly corrected) closeup filter. The aperture ring of the 50mm lens should be set wide open, and the macro lens used "normally". The magnification at "infinity" is the ratio of focal lengths: 105/50 = 2.1x. I guess magnification will go beyond 3x with the lens focused close. This combination will give you less working distance than above.
  5. If you have one, a reversed 55/2.8 AIS MicroNikkor is superb at magnifications above 1:1. It must be reversed, is better at f/4 than wide open.

    Nikon offers/offered all of the bits needed to use it. Bellows, reversing ring, auto-diaphragm ring, dual cable release, ...

    I've tested my 55/2.8 against 40/4.5 and 63/4.5 Luminars (google to find out what they are, short answer is more or less the best, although Macro Nikkors may be a hair better) and it is very competitive. If the extension needed can be managed a reversed 55/2.8 is a very cost-effective way to get magnifications above 1:1. For me it beats the alternatives suggested here.

    Oh, and by the way, I have the Luminars I mentioned. That's why I can say that they're better and that the 55/2.8 is much better than good enough. Luminars are rarely cheap, 55/2.8s usually are. If I'd known what a gem my 55/2.8 is, I'd not have chased Luminars.
  6. Simon, above postings offer good advice. You need a tripod, extension tubes, the right 105mm macro lens, not the VR version. And you can add teleconverters to increase magnification. If you can find it, the book, Close Ups in Nature by John Shaw tells you how to do it with Nikon equipment. The order of placement of the equipment affects the magnification. So does the focal length setting of the 105mm macro lens. That is why some of us use focusing rails to move the rig and not the lens barrel. Joe Smith
  7. A Nikkor 20/4 reversed on a bellows will give the following magnifications:-
    42mm lens extension gives a 5X magnification with 39mm clear working space;
    63mm lens extension gives a 6X magnification with 38mm clear working space;
    85mm lens extension gives a 7X magnification with 37mm clear working space;
    106mm lens extension gives a 8X magnification with 37mm clear working space;
    126mm lens extension gives a 9X magnification with 37mm clear working space;
    147mm lens extension gives a 10X magnification with 37mm clear working space;
    166mm lens extension gives a 11X magnification with 36mm clear working space
    186mm lens extension gives a 12X magnification with 36mm clear working space.

    See "How to select & use Nikon SLR Cameras" by Carl Shipman
    ISBN 0-912656-77-8
    Library of Congress Catalog Card: 78-52274
  8. Simon, if you must buy a book on closeup, get Heather Angel's The Book of Closeup Photography. She does the John Shaw thing much better than he does.

    If you want a clean explanation of "getting the magnification" with a 35 mm camera, buy A. A. Blaker's Field Photography. Shaw's material on that topic is cribbed from Blaker, and Blaker did it better.
  9. Roland, as much as I hate to contradict someone I respect as much as you, I have to take exception to your lens coupling advice.

    "The 50mm lens will act like a very strong (and highly corrected) closeup filter."

    I consider a "closeup filter" to be a lens significantly weaker than the lens that you're attaching it to, so that the optical characteristics of the whole system are dominated by the characteristics of the lens to which you apply the filter.

    A coupled lens system is exactly the opposite: the front (wide or normal) lens is dominant, it really defines the characteristics of the system. The rear (telephoto) lens functions merely as an infinity corrected bellows, like a modern "infinity optics" microscope.

    The front lens is normally one that does a good job of transforming an object near infinity to an image about 40mm from its rear element. So, when you reverse it, it transforms an object about 40mm from its "front" element to an image at infinity. Infinity is a little long for an extension tube or bellows, so we substitute a telephoto focused at infinity for an infinite bellows. This is nice, because the "virtual bellows" has a convenient finite length (roughtly the range from 50mm to 400mm) but infinity focus.

    Any good telephoto can be a satisfactory rear lens, and macro lenses are not known for their performance at infinity, so they're often not as good as more conventional telephotos. The old 105mm f2.5 is a wonderful rear lens.

    "The aperture ring of the 50mm lens should be set wide open"

    Again, I must disagree. No insult intended, I used to believe as you do, until Brian Caldwell set me straight. I have since put a lot of work into determining exactly how to control aperture. When the ratio of front lens to rear lens is fairly small (1:1 to 2:1) the best place to control aperture is between the two lenses, using the technique of "waterhouse stops". See the longer discussion, here.


    A 3:1 ratio is a bit of a gray area. But by the time it hits 4:1, the best place to control aperture is definitely inside the front lens. You start with the rear lens wide open, use the front lens aperture to control exposure and depth of field, and only adjust the aperture on the rear lens to serve as a flare reducing "baffle", making sure it doesn't cause vignetting or reduce exposure.

    Of course, this isn't as "convenient" as controlling aperture with the rear lens, but the increase in optical performance makes up for the inconvenience.

    "and the macro lens used 'normally'"

    You will find that the optical quality is only really good when you keep the rear lens focused in the range where the front lens does well. This is typically in the range from 6 feet to infinity, and magnification increases so little when you focus the rear lens from infinity back to 6 feet. You can focus the rear lens much closer, of course, especially if it is a macro, but the optical performance of the reversed front lens will decrease dramatically as you focus too close. So, while a 50mm f1.4 coupled to a 105mm macro focused to 1:1 (140mm) may be able to hit a magnification of 3.8:1, the 50mm f1.4 focused to 140mm is horribly soft, and has oodles of chromatic aberration, spherical aberration, and comma. It can be all "artsy" and "funky", but probably isn't exactly what you want or expect.

    I'll have to make a wizfaq out of this.
  10. Hi Joseph,

    Thank you for your post above, very interesting. As an "expert" on Nikon lenses it tempting to over-reach my area of knowledge and fill in the gaps with what I have read (poorly it seems)! I've read about reversing lenses, but never actually tried it, as I rarely need magnifications beyond about 1.5x. I have used Nikon closeup filters with various lenses, extension tubes, and lenses reversed on extension tubes - with good results.

    As you say, reversing a medium-short lens on a telephoto (eg 50mm reversed on 105mm lens) is probably similar to reversing a lens on a bellows or extension tubes, so you'd control the aperture with the front lens. Your comments about keeping the rear lens set near infinity is also interesting. I think I may have to try this technique now, so if the question arises again I'll know what I'm talking about.
  11. I suggest that you go to the internet and find a used copy of The Manual Of Close-Up Photography by Lester Lefkowitz. It's an excellent reference and it will show you how to use the various suggestions effectively. If I need high magnification I will use my 20mm f/2 or 25mm f/2.5 Minolta micro lenses on the Minolta Auto Bellows III. The only Macro Nikkor I have is the 120/5.6. This is optimized for reproduction in the 1:1 range so it wouldn't be good for high magnification work without a lot of extension. The Lefkowitz book will show you how to use enlarging lenses for high magnification. If you are shooting postage stamps indoors with controlled lighting then being close to the subject isn't such a problem. If you are in the field and need more working distance then you will need longer lenses and more extension. A teleconverter can be used to increase magnification but will slow you down and make focusing more difficult. It can also degrade the image somewhat. In some cases it is still a good tool to have. I have had some luck with the Vivitar 2X Macro Teleconverter and the Panagor Auto Macro Converter. There is a Panagor 3X Macro Converter but you lose so much light with it that it isn't really usable with live subjects.
  12. Jeff, you are aces in my book. I was planning to revisit this thread, because I realized that I forgot to recommend Lefkowitz. Granted, some of his stuff may be a little dated, but I still build brackets and tubes his way.

    Seriously, you have a 120mm Macro Nikkor? I don't think I've ever played with that one. I usually use Leitz Photars and Zeiss Luminars. I have the sequence of Luminars 16mm, 25mm, 40mm, 63mm, but not the 100mm. Do you use the Minolta bellows on a Nikon camera.
  13. Thank you all for your advice. Very interesting, I am considering the 28, 35 or 50mm prime lens either reversed on bellows or reversed to my 105mm which is the vr model. my doubts are if it would be a problem, as there is quite a difference in the filter thread sizes 62-52, In terms of vignetting.
    By the way Jeff I bought the book just now.
  14. Simon, vignetting is determined entirely by the locations of the entrance pupils of the two lenses. The filter size will not make a difference. Expecially with the combination of the 50mm and the 105mm. You can open both lenses up wide, focus them both to infinity, take a piece of black card, cut a 10mm hole in the center, center it over the 105, hold the 50mm reversed tightly to it, and you won't have vignetting. You're at the right point to "stop down" the combined lens.

    Beware off-the-shelf 62mm macro couplers. They flex a lot, and will tend to get stuck in your 105mm VR. Best way to couple a 62mm and a 52mm is to use a 52mm macro coupler and a 52-62mm step-down ring. The 52-62mm step down is very stiff, and won't get stuck in your 105mm VR. It might get stuck in the 50mm, but that's not as "mission critical" as the 105mm. If you want an adapter that can't get stuck in anything, get both the 52mm coupler and the 62-52mm step down very clean, and use a little Loctite when you mate them.

    Or use my favorite method, epoxy a 52mm and 62mm Cokin P-ring face to face, for a low cost, high quality, easy to remove adapter that cannot get stuck.
  15. When coupling lenses, should one focus them at infinity or at their respective optimal

    Never tried, but some combinations are told to work best when both lenses are in the
    normal position. How does this tandem coupling affect the settings?

    Cokin A-series rings are sufficient if you use three screws instead of epoxy. And you
    can nicely attach an aperture from, e.g., Edmund Optics in between.
  16. Hi Roland. Glad you found my post useful. Don't worry, some of the misconceptions you had are repeated so freqently that it's hard not to accept them as "truth". I've seen that "the reversed lens serves as a high power closeup lens" from respected sources such as John Shaw. Lefkowitz had a bit better treatment, but Dr. Caldwell was the one who put me on the path to understanding. I just built upon the clues he gave me, doing the math, the simulations, and a lot of real world testing.
  17. Come on, folks, the only reason not to use a proper macro lens is poverty. There's no other excuse for stacking lenses, using diopters, and so on.
  18. Come on Dan, there are many good reasons. Poverty? You must be kidding.

    I have more and better "proper" macro lenses than just about anyone else here: 200mm f4 AF micro Nikkor, the 60mm f2.8 AF micro Nikkor, 16mm, 25mm, 40mm, and 63mm Zeiss Luminars, a 25mm Leitz Photar, a 28mm f1.8 Ultra-micro Nikkor, three Nikon PB-4 bellows, several Epi-plan Nikon objectives for even slighty higher magnifications either on the bench microscope or the bellows, a floating macro bench (heavy platform on shock absorbers) with all sorts of movements and lighting gear, focusing stage, and a 6 axis computer controlled stage coming on line this summer.

    And despite all that, I frequently couple lenses, use closeup lenses, and use extension tubes. Why? Poverty, or something else? Well, take these in any order you like, it varies from day to day.

    A 25mm Photar has about 20mm working distance on a bellows at 10x magnification. A 20mm reversed on a 200mn has 40mm, which makes lighting a lot easier.

    I didn't "go digital" with the D3 and D2X that I currently use, my first digital was a Nikon D100. (Those were $2000 each in 1999, and I bought 2. Poverty?) D100 has no metering on a bellows. It does meter with coupled lenses, lenses on extension tubes, and lenses with closeup lenses. As far as current bodies, there are a lot of people out there with D40, D60, and D80, none of which can meter on a bellows, and all of which will meter with all those combinations of lenses, closeup lenses, and tubes. So, is everyone who doesn't have at least a D300 living below your "poverty line"? There's several million of those class of DSLRs in the field.

    The only macro lens that has a working distance similar to the 20-200mm f2.8 with a 500D closeup lens is the 200mm f4 micro-Nikkor. I take it that everyone who can't devote an extra $1200 for shooting the occasional butterfly is also cursed with poverty...

    Even though I vaccum and swab the insides of the bellows on a regular basis, they still throw a lot of dirt at the sensor. Coupled lenses keep the sensor much cleaner. This is especially important with the D3's reputation for attracting every stray bit of crud.

    A bellows, RMS adapter, extension tube, and case of Luminars adds about 3 pounds to my backpack, as well as taking up three regular lens compartments. The 200mm micro-Nikkor either displaces a general purpose 70-200mm f2.8 VR or 70-210mm f4-5.6 (OK< it's old, it's slow, but it's sharp and contrasty). So it requires a specific decision to go into the field on a "macro mission". A couple fo coupling rings, light enough to always reside in the bag, and I can get hign magnifications on a spur of the moment, on a mission that wasn't originally conceived as a macro day.

    An 85mm f1.4 with a Caono 250D diopted is effectively a 63mm f0.97. It's far from the sharpest macro lens you'll ever see, but the shallow DOF effects are quite beautiful, if done in moderation.

    Bellows are rather fragile in the field. They're easy to tear, and not at all weather proof. A drizzle of rain can do a lot more damage to a bellows than it will to a pair of reversed lenses. Even if the drizzle increases to a downpour, it won't compromise a D3, 70-200mm f2.8, and 500D closeup lens.

    Dan, there is poverty other than monetary...
  19. Come, on, Joe, you can't be serious about stacking lenses to avoid buying a macro lens. Extension tubes -- I use ELNY, they're inexpensive and can be coupled to nearly anything -- aren't expensive and are a good way of getting extension without using a bellows.

    And we're all going on about working far above 1:1 when all the original poster wants is 3:1. What he hasn't said is whether he'll be working in the field or in the studio/lab. If he's going to work in the field with live subjects, getting the magnification is the least of his problems.

    I'll say it again. Stacking lenses is for po' folks and those who don't want to buy the right tools.

    And this is a typical photo.net thread, with most of the posts devoted to chest-beating rather than probing the OP to be able to give him advice he actually needs.
  20. "Come, on, Joe, you can't be serious about stacking lenses to avoid buying a macro lens."

    Come on Dan, if you had bothered to read a single word I said, you'd be fully aware that's not the position I took.

    "And we're all going on about working far above 1:1 when all the original poster wants is 3:1"

    Apparently, you didn't read a single word that Simon wrote, either. As in "my objective is insects face details. about 3:1". Now, maybe you got a bit confused about what 3:1 means, but I'd think the addition of "insect face details" would make it clear to you that he is talking about "far above 1:1".

    "And this is a typical photo.net thread, with most of the posts devoted to chest-beating rather than probing the OP to be able to give him advice he actually needs."

    Actually, the second poster was the first one to start asking him questions. If there's a "chest beater" here, I'd have to vote for the guy who came in, started tossing around insults about poverty and how you can't do anything decent without investing in Ernst Leitz New York gear. Which, I imagine, is going to come as quite a shock to all the people who do manage to do some good work, and have some fun doing it, without any ELNY at all.
  21. Dan,
    Joseph is right. Even a millionaire buying the best 1:1 macro lens, he would never be able to photograph images that we cannot normally see regardless of the model. I had played with an MP-E65 which goes from a 1:1 to a 5:1, but I have nikon gear and am looking for an equvalent.
    As its hard for me to try before I buy due to shops being far away, I had asked an opinion of anyone that may have tried 3:1 and I am impressed with the help I had
    I do own a 1:1 lens ( Nikon 105 micro vr) so poverty has nothing to do here, I just wish to go behond. What's wrong with that, I find it fascinating ( see my image of a 3:1 with an MP-E65 (http://www.photo.net/photo/7224605) . Even if one is poor he also has the right to try out.
  22. By the way Dan If this thread helps people that cannot afford a real macro lens due to poverty then I am happy x2.
  23. Dan, somewhere above you said that I did not specify my intententions.
    As for subjects I intend the same as in my profile. The easiest live subjects I found so far are butterflies as after they come out of their cocoon the stay for some time to rest , giving me all the time to photograph. The worst were Ladybirds, they never stop moving.
    I had invested in the best possible gear, the D200 and the 105 vr micro, at that time could not find the earlier micro version, so I settled for the vr. As a support I use a manfrotto 190B (which today is discontinued) with a 410 geared head for precission and a velbon rail. I was looking for attachments that will not drop the quality of my images as their is no equivalent to the MP-E65. What is necessary to obtain the best images I will do. I am not perfect but I always try to improve my images. . My son owns Canon gear, I own Nikon. I like nikon gear and beleive they produce serious lenses.
  24. Cliff, I use manual focus Nikon gear and a variety of lenses, including a 100/6.3 Neupolar, on my 2x3 Graphics. I shoot the Nikons handheld up to the 105/2.8 MicroNikkor AIS' near focusing limit (0.88:1) with flash. Flash makes life much, much easier when dealing with live subjects. Dead ones are another matter entirely.

    When I shoot above 1:1, ok, 0.88:1, in the "studio" with a Nikon it is on a stand, in which case I have a variety of lenses available including the 55/2.8 reversed. This last wants more extension than is easy to live with by 5:1 so above 5:1 I use shorter lenses, e.g., 40/4.5 Luminar, 25/3.5 Luminar or 25/2.8 Summar. This last is a fixed aperture lens from a YELUU projection microscope attachment for some Prado projectors, is actually a hair better than the two 25 Luminars I've tested.

    When I shoot above 1:1 in the field, with Nikon or Graphic, the camera is on a 2-axis focusing rail on a tripod and I try to use flash illumination. With the Nikon, I get the extension needed with a combination of adapters, ELNY tubes, a Minolta Compact Bellows (contrary to Joe's assertion, this is quite robust) and use a Luminar. Not because the Luminars are better than a reversed 55/2.8 but because I find them easier to use. As I said earlier in this thread, if I had known that the 55/2.8 is so good reversed above 1:1 I'd not have bought the Luminars.

    Ease of use is worth a lot. These days I use the Neupolar on the Graphics much less than a 4"/5.6 Enlarging Pro Raptar. The EPR is nearly as good at all apertures at the magnifications at which I shoot (it tests as well as a known good 100/6.3 Luminar) and is much easier to use. Its aperture settings can be read from the side, the Neupolar's are visible only from in front. I bummed a nice mirror from my dentist, but still ... And I can attach a Jones macro-flash bracket to the EPR but not to the Neupolar.

    When shooting in the field I find flash to be a life-saver, use available darkness only with magnifications well below 1:1 and then only when shooting from tripod. With 35 mm, the subjects I shoot most often are live fishes in aquaria, flowers, insects.

    Oh, yeah. I don't shoot much above 2:1 with my Graphics. This is their limit with a 4" lens. With significantly shorter lenses, the front door can hit the subject. I like my Graphics, but for real close up on nominal 6x9 a real view camera or even a tailboard camera would be a better choice.

    I agree with you that Nikon's macro gear is first rate. But I respect Canon too and don't see the point of holy wars over which is in any sense better. Both seem better than good enough.
  25. Sorry, Simon, not Cliff.
  26. I think Dan is still pissed at me from the last post. I never said a thing here. That's funny...
  27. Right you are, Cliff. It was wrong of me to carry it for more than the time replying to you took. But I wasn't mad at Simon. He asked a sensible question to which I hope I gave an appropriate answer.
  28. Great, now that everybody has kissed and made up, let's try to observe the boring old forum protocol of mutual respect for each other's suggestions and opinions, as long as it doesn't involve playing in traffic.

    Personally, I'm proud of myself for not writing my first knee-jerk reaction to Joseph's posts regarding stacking lenses in an earlier thread, because I would have made a great ass of myself. I had disremembered a practice that worked very well for me - which happened to match exactly what he'd recommended - and would have in effect been at odds with myself.

    Specifically, I once believed it was best to adjust the aperture only on the lens directly mounted to the camera. In practice, however, stopping down this lens a little helped minimize internal flare, but stopping down the stacked lens proved far more effective.

    As for the po' folk argument ... no argument from me. I is po' folk and it works for me.

    Beyond that, puddup or shuddup. The proof is in the high resolution test photos done by whichever means you choose. Otherwise, it's just words, and black text against a white background always seems deceptively ... sharp.

    Might be interesting to conduct a shootout using various macro/micro techniques. Anyone interested?
  29. No worries Dan. You did give some good advice as well. I tried to look for a 55 mm but didn't find one yet, will keep trying.
  30. Simon, I don't know where you're located. If you're in the UK, now's a wonderful time to buy from the US, shipping charges and VAT notwithstanding. www.keh.com has a BGN grade 55/2.8 for $US 99 and a heap of 55/3.5s. I mention the /3.5 because, although I've never used one reversed, after a bit of palaver someone on the French LF board did and reported very good results.

    I understand why some are leery of buying 35 mm gear there, but the US part of the great auction site [photo.net wouldn't let me post the URL] has a heap of 55s on offer. Again, if you're in the UK now is a great time to buy from the US.
  31. Hey Dan, here's a peace offering...

    I agree on both the optical quality and the difficulty of using a 55mm f2.8. With over twice the diameter of a 63mm Zeiss Luminar it's just always getting in the way when you try to light the subject. And it doesn't help with it being 2x the length.

    But all that bulk is simply due to the enormous and complex double helicoid that lets the thing extend 27.5mm. The actual "optical capsule" is a compact unit, the size of a Luminar, Photar, or similar lens, and it's a compact "tube within a tube" that doesn't need the rest of the bulk to operate.

    I've removed similar capsules and remounted them. That's more a labor of love, it's almost never cost effective to do your own work on such things. But there are several shops that can do such work. You'll probably want to find one that can add a new, small aperture ring.

    I've also gone the other way around: I once remounted an older series 63mm El-Nikkor in the frame of a 50mm f1.8.
  32. BTW, a trick for protecting those delicate exposed rear elements of reversed stacked lenses: modify a rear lens cap to make a lens shade. A Dremel tool, hole saw or something similar would be quickest, but a starter hole with a cordless drill followed up with patient filing would do the trick as well.

    If you don't want to do this to a Nikon rear lens cap, the old Olympus Zuiko rear caps will also fit Nikkors! Not very tightly, but they will fit.
  33. Thanks for the suggestion, Joe. If I didn't already have the gear I do I'd be tempted to try it. As is, I'm temporarily poverty-stricken m'self. Just squandered more money than I should have on recordings of five operas by Rameau and two by Keiser. Broke R me.

    To get back on topic a little, Simon one of the advantages of using a short lens for a 35 mm SLR reversed, say a 20 or 24 Nikkor, instead of a macro lens such as a 25 Luminar is that the reversed lens for SLR will give greater working distance at the same magnification. I don't think it is appropriate to use any of these short lenses at magnifications as low as 3:1, but if you ever have to go a lot higher the trick may come in handy.
  34. Seen some results from this lens. Great. Just won the 3.5 AI version on ebay

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