Micro 4/3 for photomacrography
As discussed here and here, I took the decision of moving from Nikon APS-C DSLRs to the Micro 4/3 format. I had recognized since 2010 that moving to a mirrorless system was the logical step and only a matter of time, but the available systems were not satisfactory, and their future development too uncertain, until 2012.
By 2014, I had gotten rid of almost all my Nikon lenses and Nikon DSLRs. Among cameras, I kept only a D70s converted for multispectral photography, for the simple reason that it would have been difficult to sell it at a price worth going through the hassle of advertising it on eBay. I am now using only Micro 4/3 cameras. I kept only four Nikon-mount macro lenses because they come in handy on Micro 4/3 now and then:
One of the characteristics of the Micro 4/3 format is the low registration distance (19.25 mm) and relatively small diameter of the lens mount. Both characteristics, together with the sensor size (with a 17.3 x 13 mm imaging area - not total sensor size), allow small and compact lenses to be built. The low registration distance allows a large choice of lenses to be attached via adapters, and to be used in manual mode focused up to infinity. Literally dozens of adapters are available for this purpose. A side effect of the availability of adapters is that the Micro 4/3 format is a dream come true for photomacrographers, who are now free to experiment with almost any camera lens, movie lens and microscope objective ever made.
The build quality of these adapters is quite variable. An example is shown above. Cheap, no-brand adapters made in China have two main drawbacks: the front and rear bayonet mounts are usually made of anodized aluminium (see the above example), and mechanical tolerances are often poor. This causes the adapter to wiggle and scrape back and forth within the camera body when turning a focusing ring or aperture ring. Some slightly better adapters have a front mount in chrome-plated brass, but the rear mount, which is the really important and most frequently used one, is still aluminium. Anodized aluminium is an especially poor choice of material for a lens mount. Aluminium is too soft for this purpose, and deforms easily. The surface film of anodized aluminium is essentially composed of fine alumina (aluminium oxide) crystals with added color. Alumina is a widely used industrial abrasive (incidentally, the crystalline form of aluminium oxide is called corundum, and is also widely used as an abrasive and in cutting and drilling tools) and having it scrape back and forth within the lens mount of the camera body cannot be a good thing. Friction of the adapter within the camera body also causes the underlying aluminium to deform and alumina particles to break off as a very fine dust. I certainly dislike the thought of a source of highly abrasive metal and mineral particles inside the camera and close to the sensor, shutter and rear lens element. Unfortunately, several of the current Micro 4/3 adapter types, including one that is particularly desirable for use in photomacrography (see below) are so far only available with aluminium rear mounts.
A few brands make better Micro 4/3 adapters. Metabones is the best brand I am aware of. Their adapters are roughly ten times more expensive that the cheapest ones, but worth the cost. The Metabones Nikon F to Micro 4/3 adapter shown above at the left has the best female Nikon bayonet of any adapters or extension tubes I have ever seen (including Nikon's own extension tubes). The rear Micro 4/3 male bayonet fits without play on my Panasonic and Olympus bodies. The Metabones C to Micro 4/3 adapter shown above at the right is also very precise, and machined in a single metal piece. In spite of its high price it is the cheapest source for a high-precision male Micro 4/3 bayonet I know of, and I recommend it as a component to be built into home-made equipment (the C mount may need to be widened in order to avoid vignetting with certain combinations of optics and cameras, and must also be blackened to avoid reflections).
Another possible source of well-made male Micro 4/3 bayonets are the 4/3 to Micro 4/3 adapters by Olympus and Panasonic (above). Third-party adapters of the same type have appeared recently, but I have no direct experience with them.
Old lenses (preferably from the discounted "trash" bins of camera shops, especially in Japan) are the customary source of lens bayonets for DSLRs, including Canon, Nikon and the third-party lens brands. The Micro 4/3 lens market is still a bit too new for this to be a reliable source at present.
Unlike several of the cheapest DSLRs, all Micro 4/3 cameras that I know of can shoot with non-CPU lenses (this is often called "shooting without lens" in configuration menus), so the practice of "chipping" an adapter with electronics salvaged from an old lens is not necessary. This is a consequence of the Micro 4/3 policy of supporting the broadest possible range of lenses, rather than trying to "lock" users into a specific brand or recent subset of lenses as sometimes done by DSLR makers.
Kipon makes better-than-average adapters, albeit not as good as Metabones. All Kipon Micro 4/3 adapters I have handled, unfortunately, have aluminium rear mounts. Mechanical tolerances are looser than in the Metabones adapters.
It seems that virtually all lens adapters for the Micro 4/3 format are designed to provide infinity focus with their respective lenses. As a result, most adapters are bulky, with a length of a few cm (e.g., above left). The no-brand adapter above at the right is an exception. It is, fundamentally, an ordinary C-mount adapter that provides infinity focusing with the C video lenses equipped with a lens base narrow enough to fit into the recessed portion of the adapter. What makes this adapter remarkable is that the edge of the recessed portion carries an M42 female thread, almost as an afterthought. This thread is too close to the camera body to allow focusing with an ordinary M42 lens, but the M42 thread opens up a whole range of possibilities.
For instance, a focusing helicoid with M42 mounts at its opposite ends can be attached there, with an M39 enlarger lens (typically devoid of a focusing helicoid) attached at the front via an M39-M42 adapter ring (see the leftmost example above). I only wish that Metabones would make a similar M42 and/or M39 short adapter with better metal and mechanical tolerances (without the C thread, which I don't really need, and with a larger central hole or a rectangular baffle to avoid the risk of vignetting).
A short Nikon F adapter would also be useful, for instance to attach a Micro 4/3 body to Nikon bellows. If no company will sell good-quality adapters of these types, eventually I will make my own by modifying Metabones adapters and old extension rings.