Stacking lenses for more X (not telecentric)

[phero66]

I read awhile back on photo.net of people stacking a 50mm reversed onto a 100mm or 100mm macro to get 2x mag. Having the 100 macro and a 1.8 50mm I tried the above method handholding the lenses and looking through the rear of the 100mm. Surprisingly, the image got smaller, not bigger. 100mm normal, mated to 50mm reversed. Any ideas what I'm doing wrong? I'm thinking it maybe a focus issue or something simple that will be more clear once the lenses are attached to one another and I can work with the focus on each... am I thinking in the right direction?

--John

[DaveW]

First thoughts are that the 50mm is a non symetrical lens. So it's magnification is different according to which way around it is.

See:-

http://www.earthboundlight.com/phototip ... rsing.html

http://jimdoty.com/Tips/Closeup/closeup.html

DaveW

[rjlittlefield]

John,

This is a silly question, but by "handheld" and "looking through the rear" do you perchance mean that you had both lenses off the camera and were looking through the pair by eye? If so, be aware that that test can be extremely misleading because of the extra lens in your eye.

The only other way I can explain your result is that you had the 50mm so far away from the 100mm macro that the light was coming to a focus behind the 50, and you had the 100mm focused on that aerial image, which would in fact be quite small.

To work as normally described, the 50mm must be very close to the 100mm, essentially serving as an ordinary closeup lens, but very high power (+20 diopters!). The in-focus subject will be no farther from the rear (now front) of the 50mm lens than the film would be, if that 50mm were mounted on the camera in its normal configuration. Focus setting of the 50mm will matter hardly at all, and focus setting of the 100mm will matter much less than one might expect.

Operation of the pair can be understood in terms of a simple thin-lens model:

The 50mm lens focuses the subject (red box on left) so that it appears to be at infinity. The 100mm lens -- now focused at infinity, not macro -- forms its new image of the subject on the sensor, 100mm away. The image formed farther away is bigger, in proportion to the distance, hence 100mm/50mm = 2:1, the magnification ratio.

This simple model is not effective at predicting magnification when the 100mm lens is focused closer than infinity. The simplest model would predict that if you refocus the 100mm lens to its nominal 1:1 position, then it would be 200mm away from the sensor, the subject would focus 40mm away from the added lens, and the magnification would become 5:1. With real lenses, that model is way off.

For example, I just ran a quick test using a 55mm front lens and a Sigma 105mm macro rear lens. With the 105 focused at infinity, the magnification was about 2:1, as predicted. But refocusing the 105 to its nominal 1:1 setting increased the total magnification not even to 3:1.

I hope this is helpful. Personally I find that thinking of the added lens as just a very powerful closeup lens helps enormously to understand these pairs.

--Rik

[rjlittlefield]

John & DaveW,

One more minor thought...

I doubt that lens asymmetry plays much role here, since John will be using the 50mm lens in the same focusing configuration where that "50mm" was measured by the manufacturer. If the 50mm were not reversed, so that the subject was very close to the normal front of the lens instead of its normal back, then asymmetry would kick in.

--Rik

[phero66]

Guys,

Thanks for the replies. The 50mm and 100mm both have the same filter thread, and so I figure they would make a good pair. I didn't take into account my own "eye"! - They were held nose to nose.

Rik, your diagrams are very helpful. Everything is so much easier to understand with pictures

One more question. With quality output, stacking, and eventually stitching as considerations, what is the most X for my buck on a bellows (excluding the 50mm)? A fast 28/35mm reversed, a reversed lens stacked to my 100mm macro, a 20mm f2 macro bellows lens (olympus)?...I'm using the Olympus OM bellows system. I would be great to be able to get to 5x without multiple lenses, and then something higher from time to time.

Oh no, got one more... Rik since we are using the same bellows..the viewfinder head (of my 5D) gets in the way of mounting to the OM bellows (have an adaptor). I'm thinking a short extension tube on the back of the bellows would give me enough room. Would this cause any problems?

[DaveW]

phero66

"Oh no, got one more... Rik since we are using the same bellows..the viewfinder head (of my 5D) gets in the way of mounting to the OM bellows (have an adaptor). I'm thinking a short extension tube on the back of the bellows would give me enough room. Would this cause any problems?"

Nikon had the same trouble when they started putting those handgrip bulges and other projections on their cameras that got in the way of rotating to vertical format on bellows. Nikon advise a short extension tube on the back of their bellows to solve the rotation problem. This would cause no problems unless your Olympus, unlike Nikon, looses some additional automation?

A tube is only extension and will not affect image quality because no lenses are involved. It's only disadvantage is you increase the minimum focusing distance of your bellows because you have the thickness of the bellows camera standard plus that of the tube. But as your after more rather than less magnification this is not a problem

DaveW

[rjlittlefield]

One more question. With quality output, stacking, and eventually stitching as considerations, what is the most X for my buck on a bellows (excluding the 50mm)? A fast 28/35mm reversed, a reversed lens stacked to my 100mm macro, a 20mm f2 macro bellows lens (olympus)?...I'm using the Olympus OM bellows system. I would be great to be able to get to 5x without multiple lenses, and then something higher from time to time.

Short answer: "I don't know, it depends, and your mileage may vary."

Longer answer... See my post from Sept 10, 2006, Aperture and lens effects on stacking. Study the pictures, think carefully about what you want to do, shop around for prices, and see what feels best.

My personal favorite for stacking is the Olympus Zuiko Auto-Macro 38mm f/2.8 bellows lens. It's the lens that did my moth wings that you liked. See here for info about Olympus macro in general, here for information about that lens in particular. On the auto bellows, it's advertised to go from 2.3x to 6.7x. Your added extension will increase those numbers a bit. The optics for this lens are wonderful. Shortly after I bought it, I wrote to a friend as follows. "Imaging a 6.7mm field, this thing uses every pixel I have. Imaging a 2.55mm field, it doesn't use quite all the pixels, but I'm not going to casually reduce my image size, either. All this with a working distance of 33mm or more. Amazing." That's used with a 300D. To my eye, the field is dead flat, there's no CA, and I'm told that it's diffraction limited at f/4. On the down side, it cost $550 on eBay, and it (plus the bellows) would be pretty ungainly for field work.

If field work is important too, you should consider Canon's MP-E 65. Based on a short test sequence that I got from a friend, the MP-E's optics are noticeably softer than the best resolution of the Olympus 38, and from very limited hands-on, I'd say the Olympus is a lot easier to illuminate around. So for stacking, I'd use the Olympus. But the MP-E is compact, integrated, and gives great images stopped down a bit, so it would be much better for field work. (Charlie Krebs has even used it for stacking in the field! See here.)

For even higher magnifications, I recommend jumping straight to microscope objectives. They're relatively inexpensive and they give a lot higher resolution than the macro lenses (because of having wider apertures and being optimized to run wide open). In the posting I linked above, notice how much more detail pops out using a basic 10X achromat objective, versus the Olympus 38mm. Used as a macro lens at nominal magnification, the microscope objective will not fill your full 24x36mm frame with really good detail. But the center will be very good, as you can see in my comparison matrix.

Of the lenses in my matrix, if I had it all to do over again, I would skip the Luminar 16mm and Olympus 20mm on the basis of cost/performance compared to the other options.

At lower magnifications (2.2x and below), I like the Olympus Zuiko Auto-1:1 Macro Lens 80mm f/4. Again, at optimum aperture it uses every pixel in my 300D. See this post from both that lens and from a 10X objective. That lens is not so expensive -- I paid $275 on eBay. Again, it would be awkward for field use.

Another option I have thought about and find attractive, but have not pursued, is to use a Sigma 150mm f/2.8 EX DG APO AF Telephoto Macro Lens ($600) with extension tubes, teleconverter, and/or reversed 50mm. I doubt that that combination will reach 5X with the quality of the Olympus 38, but on the other hand it's much more flexible. Look through the forums for some of Jody Melanson's work -- it'll knock your socks off. A couple of good examples (and a photo of her equipment) are here and here.

And finally, if your head is spinning from all these ideas and prices, you might well just procrastinate until you have some more experience. Just mounting that 50mm on the end of your bellows (reversed, of course), will take you a long way toward 5X, and with stacking, the quality can be quite gratifying. See for example Figure 1 here.

Oh no, got one more... Rik since we are using the same bellows..the viewfinder head (of my 5D) gets in the way of mounting to the OM bellows (have an adaptor). I'm thinking a short extension tube on the back of the bellows would give me enough room. Would this cause any problems?

Nope, that's fine, for all the reasons that DaveW wrote.

--Rik

[georgedingwall]

Hi Rik,

Another option I have thought about and find attractive, but have not pursued, is to use a Sigma 150mm f/2.8 EX DG APO AF Telephoto Macro Lens ($600) with extension tubes, teleconverter, and/or reversed 50mm.
--Rik

I have the Sigma lens you mention, but I've not been able to use it with extension tubes or telecoverters, as it doesn't have an aperture ring. I don't know if the current version of this lens would have one.

Do you know how to force a stop down of the iris in a lens without an aperture ring?

[DaveW]

Found one on the web for Canon lenses George:-

http://www.photocritic.org/2006/stoppin ... n-ef-lens/

But I cannot find anything for stopping down Nikon "G" lenses. Nikon's lenses work the opposite way around to Canon's in that the aperture is held open for viewing against the diaphragm springs and the lens stops down when off the camera and the spring tension is released.

I suppose you might be able to make some sort of an adapter out of an old Nikon extension tube where you could move the stop down lever with some sort of screw adjustment to set the aperture, but it's probably easier to just use a more suitable "D" lens, or one of your enlarger lenses.

All the best as usual,

DaveW

[georgedingwall]

Hi Dave,

But I cannot find anything for stopping down Nikon "G" lenses.
DaveW

I wasn't really trying to use this lens with tubes etc, it was just that when Rik mentioned that he thought about using the lens in this way, I wondered if he knew of a way to stop the lens down when on a tube or extender.

For all high mag shots that I now do I always use my favourite enlarger lens which is a Schneider APO-Componon HM MC F2.8/40mm.

I might try one of Riks Olympus Zuiko Auto-Macro 38mm f/2.8 bellows lenses if I can find one on ebay that accepts paypal.

Bye for now.

[rjlittlefield]

I wasn't really trying to use this lens with tubes etc, it was just that when Rik mentioned that he thought about using the lens in this way, I wondered if he knew of a way to stop the lens down when on a tube or extender.

Well, maybe I'm just blissfully naive, but I'm under the impression that appropriate extension tubes and teleconverters will pass through the required electronic signals. These tubes, for example? Unfortunately, no doubt there are lots of older, simpler tubes & teleconverters that will not.

For all high mag shots that I now do I always use my favourite enlarger lens which is a Schneider APO-Componon HM MC F2.8/40mm.

Dang, I knew I forgot to mention something. Yes, top-notch enlarging lenses are reported to work fine, and they're great if you can get them cheap. I checked on Componon's just before I posted, but as I recall (can't access eBay right now), the buy-it-now price for that Componon was around $250. Personally, I guess I've never gotten my hands on a top-notch enlarging lens. The EL Nikkor I tested was not as good as my reversed 55mm. I gather there are some subtleties in the names that indicate lens quality, e.g. Componon vs Componar, but I haven't researched enough to know what's what.

I might try one of Riks Olympus Zuiko Auto-Macro 38mm f/2.8 bellows lenses if I can find one on ebay that accepts paypal.

Have you tried the microscope objective yet, George? They're great for high mag! And you can get a couple of really good ones for the price of the bellows lens...

--Rik

[georgedingwall]

Hi Rik,

Well, maybe I'm just blissfully naive, but I'm under the impression that appropriate extension tubes and teleconverters will pass through the required electronic signals.

I tried the lens with Nikon's own "Auto Extension PK Series Tubes", but it appears that you only get diaphragm control with AI lenses.

Have you tried the microscope objective yet, George? They're great for high mag! And you can get a couple of really good ones for the price of the bellows lens....

I did try the X10 supplied with my compound microscope. The results with this lens were interesting, but not all that successful. I have it in mind to get a better one and come back to microscope lens at a later date, but for now other things are occupying my time - and money.

What would you suggest would be a good X10 lens for me to get?

Bye for now.

[DaveW]

Rik,

Unlike Canon, Nikon's diaphragm control is by a mechanical not an eletronic linkage. This was maintained for backwards compatibility for old Nikon lenses. It has some advantages in that when you take any lens up to the "D" type lenses off the camera the diaphragm can be controlled by the aperture ring.

Nikon is however now going down the same path as Canon in that it is dispensing with aperture rings on its "G" type lenses solely designed for DSLR's and George has a similar independent lens without the diaphragm ring.

Nikon's extension tubes (and bellows) are still in the "Stone Age" in that they have no electronic contacts at all. Their tubes have only an AI indexing mechanism and a mechanical diaphragm coupling. The reason Nikon claims it has never updated them is because they believe all the modern electronics are unreliable at close focus distances. You certainly cannot rely on autofocus close-up, or any distance information from the lens. This presently applies to any make of camera, so Nikon do not provide for automation they consider may miss-focus or give wrong exposure in macro photography.

George,

My mention of an extension tube was for a reversed lens. Thinking about it further though I think the aperture is closed down by a rod or pin from the camera so unless you used an auto tube you probably would not be able to devise anything to fool this mechanism and stop the lens down. All my micro nikkors are "D" type lenses with aperture rings and also have a switchable manual focus ability.

DaveW

[georgedingwall]

Hi Dave,

George,

My mention of an extension tube was for a reversed lens. Thinking about it further though I think the aperture is closed down by a rod or pin from the camera so unless you used an auto tube you probably would not be able to devise anything to fool this mechanism and stop the lens down. All my micro nikkors are "D" type lenses with aperture rings and also have a switchable manual focus ability.

DaveW

I don't think I would even try to use this lens on tubes, even if I could. I have the old Nikon 105mm af-d macro lens, and that has an aperture ring, so it can be used the right way round, or inverted.

I also have the new 105mm VR macro lens, and that doesn't have an aperture ring.

Both the Sigma 150mm and the Nikon 105mm VR lenses do work with my 1.4X and 2X Sigma EX teleconverters within some limits. In some combinations you lose autofocus, but in all combination you retain diaphragm control. The VR is still available when either of the extenders is fitted to the 105mm VR lens. You can't, however, stack the two extenders on one lens due to the rear end construction of the extenders.

Bye for now.

[rjlittlefield]

Nikon's extension tubes (and bellows) are still in the "Stone Age" in that they have no electronic contacts at all.

How about third-party tubes? These from Kenko claim to provide diaphragm and meter coupling, though they are explicit that you have to focus manually and that "Nikon 'D' information is not transmitted because the lens is focusing closer than its programmed to focus".

What would you suggest would be a good X10 lens for me to get?

That's a good question, and one that I won't answer at the moment.

I've used mostly a Nikon 4X, the aus Jena 3.2X and 10X that came with my microscope, and an Edmund Optics 20X, most of them just basic achromats. These all work OK as macro lenses. They have some curvature of field, but that's no problem with extended DOF. They also have some visible CA that's removable with PTlens, and they get soft around the edges.

The reason I'm hesitant to recommend is that some objectives have large amounts of lateral chromatic aberration (LCA) designed into them and are intended for use only with matching eyepieces that have compensating negative LCA. The matched pair works great, but the objective by itself can be awful. See figure 17 and associated discussion in this article by Ted Clarke. Based on that article, I'd be inclined to avoid LOMO and Zeiss kpl lenses. But as I understand it, my "aus Jena" microscope is essentially East German Zeiss, so apparently just "Zeiss" is not a good indicator. Anyway, at the moment I'm aware that there's an issue and I don't know enough to feel comfortable making recommendations. Maybe it's a good time to ask my friends in the Yahoo Microscope group for some info/guidance.

--Rik