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.

Three Lenses

This post came about as a response to post on a Google+ group I belong to. The post contained a link to an article at the website Olympus Passion by Chris Corradino (whom I don’t know) called “Full Frame vs Micro 4-3 Revisited with Pro Olympus Lens” where a canon EOS 6d with 17-40mm f4 L lens was compared with an Olympus OMD EM10 with 12-40mm f2.8 Pro lens. Nothing wrong with that, it serves as a potentially useful comparison of two popular cameras and lenses. In the article he posts two pictures of the same scene taken around a year apart, one used a polarizing filter one didn’t and the Canon 17-40L is not the best lens in the line up, and comparing a wide-angle zoom to a standard zoom doesn’t really tell anything. Also Olympus uses in camera software correction of its lenses to the RAW files whereas the Canon doesn’t and one has to manually apply correction when processing in Lightroom or ACR. So I thought about it and decided to do my own test. Now before I start I’d like to say that testing zoom lenses is fraught with difficulty and the reason why is very ably demonstrated by Roger Cicala’s excellent article “Painting Zoom Lenses with a Broad Brush – Roger’s Law of Wide Zoom Relativity” which is enough to make any sane person throw up their hands in horror at the enormity of it all.

 

The file from the EM1 with the Olympus 12-40mm f2.8 opened in Lightroom.

 

If we look at the lens correction box it shows that a built in lens profile has been applied.

 

I’m not really the scientific type, but I know that to make any form of comparison you have to compare like with like and remove all variables. The cameras and lenses tested were as follows:

  • Olympus OMD EM1 mki with Olympus m.Zuiko 12-40mm f2.8 pro
  • Canon EOS6d with Canon EF 24-70mm f4 IS L
  • Sony A7r with Sony FE 28-70 f3.5-5.6 OSS

Why three cameras and three lenses, well mainly a case of why not, but also I wanted to see how a budget kit lens performed against the two “pro” lenses, and I was using it as a control as I had previously looked at it. Each lens was shot at the wide end and the long end, with the wide end an architectural shot to look at how the lens behaved at infinity and close-ups at the long end.

 

Holy Trinity York provided the wide-angle subject.

 

Typically standard zooms behave best at the wide end and the performance deteriorates as you zoom into the long end. All the lenses were tested at an aperture of f8 for the two shots previously mentioned and wide open to test for vignetting. For each shot the camera was mounted to a tripod, there were no filters on the lenses, any image stabilisation was turned off and the shutter was tripped via the self timer. All metering was done using a handheld incident light meter – Minolta Auto Meter V f. Because the base ISO of the EM1 is 200 all the images on all cameras were shot at value. The only DSLR in the group was used in live view mode to avoid mirror slap. The images were all shot as RAW files and then converted to 8 bit jpgs using RawTherapee (version 4.2.1) which allows you to switch off any embedded lens correction. There was no sharpening, noise reduction or correction for chromatic aberration. Ok that’s the methodology lets look at what happened. Click on the images to see them at full size.

Phillip the photographic bear provided the tele test subject

 


Olympus OMD EM1 mki with Olympus m.Zuiko 12-40mm f2.8 Pro lens

The Olympus m.Zuiko 12-40mm f2.8 Pro lens was announced as Olympus’ high end standard zoom in 2013 to accompany their then flagship camera the OMD EM1.

 

Built for the micro four thirds system this lens is equivalent to a 24-80 mm lens and that’s all the talk of equivalency you’ll get out of me, if you want more see this. The lens was launched at the same time as the EM1 in 2013 and it heralded a new line of “Pro” lenses. Of the three lenses here it is the only one with a metal outer construction and it has a splash proof and dust proof design. Its vital statistics are 84mm in length, a diameter of 69.9mm, has a filter thread of 62mm and weighs in at 382g. Not that it counts for much, but it feels nice in the hand and the manual focus clutch (reminiscent of the ones found on Pentax’s 645 range of lenses, is a very nice touch. Optically there are 14 elements in 9 groups – there are 1 aspherical element, 1 dual-sided aspherical element, 2 ED glass elements, 2 HR glass elements, 1 EDA glass element, 1 HD glass element. It is the most optically complex lens of the group. For bokeh aficionados there are 7 rounded aperture blades. The minimum focusing distance is 0.2m.

 

At the wide end the centre of the image is what you’d expect from a modern zoom, it is sharp and contrasty. At the edges the image is still sharp but the contrast has fallen off a little giving the appearance of softness. The chromatic aberration (CA) is very apparent. At the long end in the centre the image is still sharp but the contrast is lower than what we found on the wide end. The edges exhibit a little softness. The CA virtually non-existent. The results from the long end caused me a little consternation as it was the first time I’d seen images without any in camera correction applied so I repeated them just be sure and got exactly the same result.

The lens resolution chart shot at 12mm wide open to show any vignetting or lens distortion.

 

Testing for vignetting and distortion I found that the lens exhibited marked vignetting and barrel distortion at the wide end at f2.8. The vignetting had disappeared on stopping down to f5.6.

 

This time at 40mm wide open.

At the long end there is only slight vignetting and very mild pincushion distortion. What is interesting is that there is significant variation in the exposure, remember these were metered using a handheld incident meter. The long end is nearly a whole stop darker than the wide end. This shouldn’t happen with a constant aperture zoom.


Canon EOS6d with Canon EF 24-70mm f4 IS L lens

The Canon EF 24-70mm f4 IS L lens was introduced in 2012 as Canon’s budget (if that term can be used at this price) L series standard zoom lens.

 

This is the most expensive lens in the group with a retail price of around $1200 AUD. It is also worth pointing out that this is the budget standard zoom in Canon’s L range. This lens was introduced in 2012 and was intended to be a kit lens for then newly announced Canon EOS6d. The body is made of some variant of ABS plastic which is somewhat disappointing considering the price, but with a weight of 600g it has a satisfying heft. The optical construction is 15 lens elements in twelve groups with 2 aspherical and 2 UD elements. The aperture diaphragm is comprised of 9 rounded blades. Unsurprising it is the biggest lens of the trio being 93mm long, 83.4mm in diameter and has a 77mm filter thread. Image stabilisation is built into the lens and is good for four stops. The minimum focus distance is 0.38m, but the lens has a rather nifty macro feature where you press a button and turn the zoom ring and that takes it down to 0.2m and a maximum magnification of 0.7x.

At 24mm the centre of image is extremely sharp and contrasty and the edges are the same. At the tele end it is a repeat. Chromatic aberration is non-existent at both extremes.

The Canon EF 24-70 f4 IS L at 24mm wide open

 

Shooting wide open at 24mm vignetting is very apparent, I would say that there’s probably 2 stops difference between the corner and the centre. The barrel distortion is not excessive but is noticeable. At 70mm a small amount of vignetting can be seen and there is some mild pincushion distortion.

 

The Canon EF 24-70mm f4 IS L at 70mm wide open.

Sony A7r with Sony FE 28-70mm f3.5-5.6 OSS

 

The Sony 28-70mm f3.5-5.6 OSS was introduced in 2013 as the budget kit zoom to accompany the Sony A7 mirrorless camera.

 

The joker in the pack and the cheapest on test at just under $350 AUD, and boy when you pick this one up it certainly feels like it. When I originally wrote about it on 3rd July 2016 I was very skeptical of its durability, well nothing adverse has happened to mine, but, Kirk Tuck wrote today that his met a tragic end courtesy of a dog’s tail and a hard floor. Well what do get for your $350? Well unsurprisingly at this price point this is largely made of plastic – the cheap kind – and is very light coming in at 295g. There’s not a lot of glass either just 9 elements in 8 groups made up 1 extra low dispersion and 3 aspherical elements. The simpler optical design and low price makes this the only variable aperture lens in the test group. The aperture diaphragm is made up of 7 blades. Size wise it is a compact 83mm long, has a diameter of 72.5mm and has a filter thread of 55mm. The plus points are that it is dust and moisture resistant, has built in image stabilisation, has a respectable minimum focusing distance of 0.4m and comes with a lens hood. As an aside I believe that every lens should come with a hood.

 

 

At 28mm the lens is again just like any other modern lens – sharp and contrasty. At the edges there is a drop off in contrast but they remain sharp. Chromatic aberration is very well controlled and easily fixed in Lightroom. The slow variable aperture means that vignetting is not a problem and there is only slight barrel distortion. At 70mm the centre is sharp and has good levels of contrast, the edges are sharp with a slightly lower contrast. There was also some evidence of coma. Again very little vignetting and a slight trace of pin cushion distortion.

The Sony 28-70mm f3.5-5.6 OSS lens at 28mm wide open.

 

The Sony 28-70mm f3.5-5.6 OSS lens at 70mm wide open.

 


Conclusion

So is the Olympus 12-40 the Canon killer that Chris Corroding says? Well without in camera software correction it is only just a bit better than the Sony which is half the price. It is the correction that elevates this lens to very good. Having said that the Canon 24-70 f4 is probably one of their very best zoom lenses and produces very good images straight out of the camera. Apply the Lightroom lens profile and it is even better. Is that surprising? No considering its cost I would hope it be optically very good. This is the rub – for $350 AUD you get a surprisingly good lens with the Sony and most people would be very happy with it. The Olympus at $870 AUD sees some significant improvement. The Canon at $1200 AUD sees only incremental improvement over the Olympus. The law of diminishing returns is very clearly at work here.

When it comes down to sensor performance the Sony A7r rips the head off of the EM1 and EOS6d and spits down the stump. I have been amazed by how well it performs – the dynamic range is very, very good, the lack of an anti-aliasing filter means that with good lenses insane amounts of detail can be rendered, and the high ISO performance is also very good. The Canon EOS6d’s sensor is capable of very nice colour rendition, especially skin tones, but it is not the best when it comes to dynamic range. It is what I’d call workman like. For the Olympus EM1, well the dynamic range is very good, high ISO performance not so. The lack of anti-aliasing filter helps you get the best out of the lenses. I really like my m4/3 Olympus cameras and lenses, I use them more than anything else, but I really feel that the sensors are holding them back. I’ve yet to get any long-term usage out of the new 20Mp sensor that is found in the EM1 Mkii, but I do think that if they got access to the latest BSI sensors from Sony and reduced the base ISO to 100 that there would be quite a sizeable performance boost. But all this is moot as all three are capable of excellent results if I do my part.

It is important to remember that I only have access to one of each lens so I have no idea of what the sample variation is for any of them. What does this all mean in terms of real world usage? Well I’ve used my Olympus 12-40 far more than the Canon 24-70 and I am more than happy with how it performs. I hardly ever use the Sony 28-70 as I only really use the A7r with legacy lenses.