Friday, August 05, 2011

Choosing An Alternative Mount Lens for an ILM Camera

In my last article I explained all about register and why ILM cameras allow such a wide range of off-system lenses to be adapted to their bodies. It's one of the main reasons these cameras (Olympus PEN, Panasonic G3 and family, Sony NEX) have proven so popular with aficionado photographers, many of whom have a standing investment in lenses from other systems.

In this article I'll list the systems we might want to use on our ILM and apply my own specific criteria of price, usability and form factor. Happily, a single mount choice will bubble to the surface. (If you apply different criteria you may get a different result.)

List of Lens Mounts
Here is a list of all the commonly-available lens mount systems that have a register under 30mm. I chose that value since it means I can use an adapter on my Olympus PEN E-P1 that maintains the small size advantage of the system. That's what makes the ILM so appealing in the first place. If I want a larger adapter I'll stick to my K-mount lenses. This first constraint limits the choices to old-school range-finder and half-frame systems.

I have rounded off the values slightly for ease of reading, and included the ILM systems in the chart for comparison.
C                 17.5 mm
* Sony NEX        18 mm
* MFT             19.25 mm
* Samsung NX      25.5 mm
Pentax Auto 110   27 mm
Leica M           28 mm
Leica M39         29 mm
Olympus PEN F     29 mm
Contax G          29 mm

I need to explain why "C" lenses are included even though their register is less than the ILM cameras. The reason is that adapters do in fact allow their use, since the difference is only a couple of millimetres. However, this means one needs to be careful that the chosen cine lens does not have protruding parts in the rear, since these might damage the camera. There are also issues of image circle compatibility, with many C lenses resulting in severe vignetting. Nonetheless, this mount has proven popular with certain adventurous photographers.

Applying My Selection Criteria
This list will be my starting point for deciding which third-party lenses to pursue. My goal is to find classic lenses with a nice manual focus feeling, since the MFT focus-by-wire system is poor. I am one of those people who prefers to focus manually, giving me optimal control over my pictures.

There are three more criteria: excellent image quality, reasonable close focus distance and affordable price. By that I mean under 200 monetary units (whatever they may be for you). I simply don't have much of a budget for off-brand lenses for my secondary camera system. So, applying the last criterion first, I eliminate the expensive Leica lenses, along with Konica M-Hexanon and similar compatible systems. This is by no means to slight their ability. If I had a couple of grand I'd be happy to buy one, but my current limit is an order of magnitude less.

The C lenses are also too expensive, but in this case not in an absolute sense. Rather, they are relatively dear for what they are, fetching prices way out of line with their image quality.

The Pentax Auto 110 is an insanely cute system with tiny lenses that nonetheless provide an image circle that covers the MFT format. However, this size was the result of a compromise that now has serious implications. The diaphragm was provided by the camera body. Thus, on an ILM camera, one must use them wide open at f/2.8. Their image quality at this aperture leaves a lot to be desired. In fact, they were never the best lenses from the stand-point of IQ. But no-one really demanded that of a normal lens that weighs 13g.

The Contax G lenses also have a peculiarity: they do not have a focus mechanism, since that was provided by the range-finder body. Various adapters exist that attempt to remedy this, but that jacks the price up. All reports are that the experience remains rather unwieldy. Despite the excellent quality of the standard lens, there are better alternatives. (I notice most who buy these on the volatile used market end up selling them on.)

Olympus PEN F System
That leaves only the Olympus PEN F lenses for consideration, perhaps appropriately enough; my Olympus E-P1 is a digital relative of the PEN after all. The PEN F was a half-frame SLR with a unique design, in that the mirror flipped side-ways into the body instead of upwards. This meant the camera could do without the viewfinder "bump" on top -- and it apparently made for a short register as well.

The PEN F had an uncharacteristically broad selection of lenses for a non-standard film size, though many of these go for a pretty penny on today's market (like any other unusual and potentially collectable lenses). Omitting two zooms and a mirror telephoto, this is what the line-up looked like:

G Zuiko AUTO W 20mm F3.5
E Zuiko AUTO W 25mm F4
G Zuiko AUTO W 25mm F2.8
F Zuiko AUTO S 38mm F1.8
D Zuiko AUTO S 38mm F2.8
E Zuiko AUTO S 38mm F2.8
E Zuiko AUTO MACRO 38mm F3.5
G Zuiko AUTO S 40mm F1.4
G Zuiko AUTO S 42mm F1.2
G Zuiko AUTO T 60mm F1.5
F Zuiko AUTO T 70mm F2
E Zuiko AUTO T 100mm F3.5
E Zuiko AUTO T 150mm F4
E Zuiko T 250mm F5
E Zuiko T 400mm F6.3

When considering which of these to purchase, I first eliminated the three wide lenses. That's because I already own the sharp and tiny Panasonic 20/1.7 in native MFT mount. In terms of image quality it is distinctly superior to other lenses in this system -- this is borne out through measurements, tests and hands-on use.

Likewise I eliminated the telephoto lenses of 100mm or greater as simply being too long for me, remembering that the 35mm equivalent focal length is double all of these values.

While I would love the super-fast 42/1.2, if it ever comes up for sale it would cost my arm. The same could be expected of many of the other less-common lenses.

However, the "G Zuiko Auto-S 40mm F1.4" is almost as fast, and can be found for a reasonable price, since as the kit "standard" lens it was produced in significant quantities. It's praised for excellent optics in a tiny form factor (165g and 43mm long). With a close focus distance of 35cm it meets all my criteria.

There other possibilities, but these hit the market less often. The 38mm F1.8 is that bit slower, but it has the same close focus distance and is even smaller (135g and 35mm long). Those looking for the ultimate miniature lens might hold out for the "E Zuiko AUTO S 38mm F2.8", which is a magical 70g and 14mm long. Of course something has to be compromised to make a lens this tiny relative to the larger "D Zuiko AUTO S 38mm F2.8". In this case it's the close focus distance, which gets bumped up to 80cm.

Like I said before, lots of choice!

I went ahead and located a 40/1.4 at below market value. In a future article I'll let you know how it works out.


No comments:

Post a Comment