M To N

 

The Sony NEX mount was made for sad old gits like me. “Hold on Paul…” I can hear you say “do you mean that Sony engineered a whole camera line specifically for you?”. No! There was a happy accident that had some unforeseen benefits. I’ll explain. This is going to be a bit beardy and nerdy.

The first commercial 35m film camera was produced – the Tourist Multiple. made by Herbert & Huesgen of New York

Just over 100 years ago, or to be precise in 1909, the film (or movie depending upon where you are from) industry standardised on a film format of 1.37 inches in width with four perforations per frame. The decision was economic, it meant that cinemas didn’t have to have different sized film projectors. In 1913 the first commercial 35m film camera was produced – the Tourist Multiple. made by Herbert & Huesgen of New York. Unfortunately this achievement is largely forgotten because the story of Oskar Barnack inventing 35mm film for stills and the Leica camera has become the accepted history, but that is FAKE NEWS as a certain orange haired buffoon is apt to say. Not long after these small format cameras as they were then known took two distinct evolutionary paths the rangefinder (which was the first) as pioneered by Leica and the Single Lens Reflex as pioneered by K. Nüchterlein’s when the Kine Exakta launched in 1936.

The first Single Lens Reflex was the Kine Exakta launched in 1936.

 

Looking through a rangefinder viewfinder. Illustration p.31 London, B et al Photography, 7th Edition, Prentice Hall, New Jersey, 2002.
How range finder focusing works. Illustration from p.31 London, B et al Photography, 7th Edition, Prentice Hall, New Jersey, 2002.

Rangefinder cameras initially were very popular. The technology was available and relatively simple and the cameras and lenses were very compact. The photographer looks through a window on the camera and sees an image with a fainter duplicate from a rotating prism over laid. The photographer adjusts the rangefinder until the two images match up exactly, then the image is in focus. This system was called the split image rangefinder and had been developed to sight artillery pieces and was well understood at the time. The disadvantage is of course that the photographer is not seeing what the lens sees, only an approximation which can lead to inaccurate framing due to parallax errors. Interchangeable lenses were facilitated by having a screw mount and Leica adopted as their standard the L39 or LTM (Leica Thread Mount) which is 39mm in diameter with a Whitworth thread of 0.977 pitch and a flange distance of 28.8mm. Other manufacturers made variations on a theme i.e. the Canon M39 (aka J Mount) and the FED 39 which all share the same diameter but the thread pitch and flange distances are different. By the 1950’s photographers were looking for a faster way of changing lenses and so short throw bayonet mounts were developed. In 1954 Leica introduced the M mount and this is characterised by it having an external diameter of 44mm, a bayonet consisting of four claws and a flange distance of 27.8mm.

With the advent of digital imaging camera designers were suddenly allowed to consider alternative designs where there were no moving parts. It was hoped that eliminating the mirror and using an Electronic Viewfinder (EVF) and taking a direct readout off of the sensor would allow cheaper and easier manufacture. The autofocus system would be more accurate because the readings could be taken directly off of the sensor and the use of electronics allowed more accuracy than mechanical linkages. With no flappy mirror to interfere with things the flange distance could be reduced along with it’s radius. So the Sony NEX mount has a flange distance of 18mm and a diameter 41.6mm which means that just about any lens can be mounted to a NEX body via an adapter and as long as it has an imaging circle big enough so that an image can be projected on the sensor. The NEX mount covers both so-called full frame format (35 x 24mm) and the APSC format (24 x 16mm). This is the happy accident because I’m sure that when Sony adopted this standard they didn’t realise that it would allow legions of photographers all over the world to mount legacy lenses (lenses made for cameras that are no longer produced) to be mounted to the new Sony mirrorless cameras. Now I am the first to admit dear reader that as a photographer I have been promiscuous. I have not stayed faithful to one brand or lens mount which means that I have a fair few lenses sitting in a shoe box that I no longer have camera bodies for. Now I’ve already talked about mounting my old Olympus OM Zuiko lenses on my Sony A7r here. This and a few subsequent posts are going to be about using L39 and M mount lenses.

The Fotodiox DLX Stretch is a clever M mount to NEX adapter that has a built in adjustable extension tube to allow a degree of close focusing with any M Mount lens.

“So who in their right mind would want to do this?” Well you’re probably right to want to do this would be a sign of mental infirmity to some, but for many people (myself included) auto everything cameras are a bit boring and modern lenses while being technically very good can be a bit characterless. While Leica lenses are wallet puckeringly expensive there are plenty of more affordable alternatives made by Minolta (now absorbed by Sony), Konica (initially taken over by Minolta and then swallowed up by Sony), Ricoh, Voigtländer, Rollei (both of these as part of Cosina’s licensing of their names) Zeiss and those produced in Russia such as Zorki and Fed. These lenses are beautifully made with metal barrels and mounts, buttery smooth focusing, and exquisite clicking aperture rings. I’ve got a Canon L macro lens, and while it produces wonderful images the plastic body is somewhat underwhelming considering the price Canon charge for it and it’s not something I’d pick up for the tactile experience and as for the whole joy of ownership – well let’s not talk about it. These older lenses just feel so satisfying in the hand that makes you want to do some serious lens fondling. They just engender a joy of ownership that plastic can’t. I told you there are mental health issues with this.

SLRs have a big flippy flappy mirror between the lens and the film/sensor. Illustration p.38 Parish, S; Photograph Australia With Steve Parish, Steve Parish Publishing, Brisbane, 2003.

Another reason why rangefinder lenses are attractive is that there are fewer optical design compromises. SLRs have a big flippy flappy mirror between the lens and the film/sensor. This meant making wide-angle lenses next to impossible because the rear lens element would foul the mirror. In 1950 Pierre Angénieux invented the retrofocus lens which is a kind of “reverse” telephoto design where the lens elements closest to the film plane have a negative effect making the image smaller. The downsides are more glass elements means more air to glass surfaces which means more refraction which means more potential chromatic aberration and distortion. More glass means more weight. Here’s an interesting fact – a cubic centimetre of glass is heavier than a cubic centimetre of concrete. Range finders are mirrorless cameras so there isn’t a restrictive mirror flapping about, this has the net effect that your 28mm lens can be a true 28mm lens without a whole bunch of extra glass causing problems. It also means that rangefinder lenses are much smaller than their SLR counterparts.

The retro focus lens design invented by Pierre Angenieux.

However, it is not all unicorns at the bottom of the garden. Rangefinder lenses were designed for use with film and the silver halide crystals in the film emulsion did not care at what angle lights hits them to provide the necessary reaction to form the latent image. But with a digital sensor it is a whole different ball game because the sensor is no longer just a gelatine substrate coated with an emulsion containing silver halide crystals it is a complex sandwich of filters, lenses and electronic componentry as the schematic from whatdigitalcamera shows. For best performance the light needs to enter micro lenses at 90º, when the incidence of the light is severely off perpendicular then not all of it reaches the pixel at the bottom of its well this can cause vignetting, smearing with loss of detail, and severe colour fringing. This is what stopped Leica initially developing a digital range finder. Kodak developed a special sensor with offset micro lenses for Leica M8 to help overcome this along with in camera software correction the digital M became a reality.

The many layers that make up film emulsion. The silver halide crystals respond to light hitting them at any angle. Illustration from London, B et al; Photography, 7th Edition, Prentice Hall, New Jersey, 2002.

 

Anatomy of a sensor. A – Colour filter array
. B – Low-pass filter / Anti-aliasing filter
. C – Infrared filter (hot mirror). D – Circuitry
. E – Pixel
. F – Microlenses. G – Black pixels

. For light to hit the pixel in its well it needs to travel as near to perpendicular to the sensor plane as possible. Illustration from http://www.whatdigitalcamera.com/technical-guides/technology-guides/sensors-explained-11457

 

Why not buy a digital M and be done with it? There is no way I could afford a digital Leica as I’m not a “Trustafarian”, and also and perhaps more importantly, my lenses are not made by Leica they are the much cheaper Voigtländers so I’m not going to drop nearly $10K AUD just to use them again. But as I had a Sony A7r for experimenting with my collection of Olympus OM Zuiko lenses I thought I’d just buy a M to N adapter. Because the Sony NEX mount is a much shorter flange distance than a conventional DSLR its sensor does have micro lenses to cope with the native wide angles. However, the fly in the ointment is that just having them alone does not fix the problems with M mount lenses because there is no in camera correction via firmware. So straight away the situation is more complex than using old SLR lenses. The answer is obviously to fix the problems in post. Users of Lightroom can rejoice as there are profiles for Voigtländers lenses in the developing module. They are easy to use but given that they are somewhat generic they sometimes don’t fix the problem entirely requiring a little extra fiddling about. If you are really keen then you can build your own profiles using Cornerfix.

The Voigtlander M to Nex adapter allows users of M mount lenses from Leica, Zeiss and Voigtlander to mount their lenses on Mirrorless cameras from Sony

Well now we’ve got that out of the way lets talk about adapters. At their most basic an adapter is just a tube with a male bayonet mount at one end and a female at the other. For the sake of brevity I’ll limit this to just dumb adapters i.e. you’re not trying to get auto focus and stabilisation to work. There are a huge range of prices for essentially the same thing. I’ve paid as little as $15 including postage from China to as much as $200. So what do you get for your money? Not a lot. I got a Voigtländers VM II Adapter – Leica M Lenses to Sony E Mount for $200 AUD from an Australian seller. It looked nicely made but it had a serious flaw, there was no spring in the lens release button which means that your lens could fall off as it wasn’t secured. I don’t know if that is typical but I had no luck with trying to exchange it with the seller so I was kind off put off spending a lot of money. The next adapter I bought was from a Chinese seller on eBay and it cost a grand total of $15 AUD and it worked fine. A little agrarian in the looks department but it did the job nicely. Then I noticed that Voigtländer made a close focus adapter which took my fancy. Generally rangefinder lenses only focus down to 1 metre and I like to use wide angles closer than that for dramatic effect and it also meant that my 75mm was suitable for tight portraits. So my interest was definitely piqued, but my wallet was a little bit shy about coughing up $389 AUD after my experience with the other one. Then I discovered the Fotodiox DLX Stretch for $170 AUD from B&H Photo and for half the price of the Voigtländer coupled with B&H’s excellent customer service I was in like Flynn.

The Fotodiox DLX Stretch is a clever M mount to NEX adapter that has a built in adjustable extension tube to allow a degree of close focusing with any M Mount lens.

When the DLX Stretch arrived in its plain brown wrapper I quickly reassured the significant other that it wasn’t anything X rated (“No luv I said photographic accessory not pornographic accessory!”) and got down to playing with it. Basically what it is is an adapter with its own built in variable extension ring. The extension is achieved via a helicoid with a long throw. The amount of extension is not great about 2-3mm but that is enough to reduce the minimum focusing on my Voigtländer 35mm f2.5 Color Skopar from 70cm to 30cm. As my Voigtländer 15mm f4.5 Super-Wide Heliar and Voigtländer 75mm f2.5 Color Heliar are both L39 screw fitting I promptly ordered two L39 to Leica M adapters so I could use them with the Fotodiox DLX Stretch and the results were just as impressive. For the 75mm the minimum focus is 100cm and is then reduced to 65cm, and for the 15mm the minimum focus was reduced from 30cm to 12cm.

The Voigtlander 15mm f4.5 Super Wide Heliar normally has a minimum focusing distance of 30cm but when used with the Fotodiox DLX Stretch at full extension the minimum focusing distance becomes 12cm.

In terms of construction the DLX Stretch is reassuringly weighty (unlike the cheap Chinese adapters which feel so light that they may be made from a lacquered toilet roll tube). Both the male and female mounts are chrome plated brass. The aluminium body is anodised a natty orange colour that matches the orange lens mount trim on Sony A7 series cameras. The ring that moves the helicoid is knurled and has a prominent finger tab and has a nice smooth action although saying that it is difficult to use while videoing without creating camera shake. There is no wiggle or play with the extension and the unit attaches to cameras and lens snuggly with evidence of any play or light leaks. To further install confidence in the product Fotodiox warranty the adapter for 24 months.

The Cosina Voigtländer 35mm f2.5 Color Skopar mounted to a Sony A7r via a Fotodiox DLX Stretch M to E lens adapter.

 

A photo of bowl of curry laksa taken with the Voigtlander 35mm f2.5 Color Skopar lens on a Sony A7r at the lenses normal minimum focusing distance of 70 cm.

 

The same bowl of Laksa with the same camera and lens but this time the Fotodiox DLX Stretch is extended to give a minimum focusing distance of 30 cm.

Overall I can see some photographers scoffing at the concept saying they have no need. Myself I like it very much and am using it a lot especially with the Voigtländer 15mm f4.5 Super-Wide Heliar.

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