Camera lens mount, comparing the brands and engineering

I still remember the days when I first started photography, I asked my friends the most commonly asked question, ‘what camera should I buy?’ Everybody seems to have their own biased opinions about the brands, some called themselves the canon fan boys, nikonians, pentaxian and so on.

Therefore I would like to share my views purely on the engineering aspect with my limited engineering knowledge and a little background, hoped to clear the clouds and differences once and for all, and maybe this can help you decide on your next camera. I maybe wrong on some details, so please correct me if you must!

Introduction, flange distance, adaptability of SLR, DSLR and mirrorless.

Before I compare the brands and engineering, I have to explain the flange distance for the benefits for those who are not familiar.

To put it simply, the brands that chose shorter flange distance will gain accessibility of third party designed adapters to fit other legacy lenses (other factors includes the thickness of the adapter, material, design, and even lens mount diameter). In general, the shorter the flange, more lenses they can use, but not necessarily better, which I will explain later on Sony’s E-mount.

MicroFourThirdsDiagimage source: dpreview

As illustrated above. You can see some popular lens mount and their flange distance here:

Mount Description Focal Flange Distance [mm]
Q Pentax mirrorless 9.2
1 Nikon mirrorless 17
C 8mm, 16mm video lens 17.526
X Fujifilm 17.7
E Sony mirrorless 18
m4/3 Micro Four Thirds mount Olympus/Panasonic mirrorless 19.25
NX Samsung 25.5
M Leica rangefinder 27.8
m39 screw mount Old Leica rangefinder 28.8
Pen F Olympus half-frame 28.95
FT (4/3) Olympus, Panasonic DSLR 38.67
A/R Konica 40.5
FD Old Canon 42
MD Old Minolta 43.5
EF Canon 44
EF-S Canon (crop) 44
B Praktica 44.4
A Sony/Minolta 44.5
K Pentax 45.46
m42 screw mount Old Pentax and some others 45.5
OM Olympus 46
F Nikon 46.5
R Leica SLR 47
PL Arri 52

I will skip the detail on the sensor size and focal length in terms of adaptability.

Post introduction and assumption in engineering

Thanks for some first feedback on the bias on electronics and failure rate. I am stating the assumptions here.

1) Priority in production engineering, number of flips for machining that can contribute in production time and cost.

2) Second priority in engineering simplicity in packaging. Eg. use of electronics to replace certain mechanical components to improve on speed, ease of use and possible reduction in overall cost.

3) Though there’s no data on actual comparison of mechanical/electrical failure, coming from general mechanical characteristics- Number of parts (less the better), number of moving parts (less the better).

Popular lens mount

Canon DSLR, EF/EF-S, EF-M

Canon has one of the world’s largest market share in DSLR. Back in the days switching to electronic and auto-focus, Canon ditched the old FD design (thank god) because FD mount is basically shit, reversed the bayonet, a lot of moving mechanism on the lens and its a pain in the ass to disassemble and repair (personally I have a lot of problem doing that).

The FD 'reversed bayonet'
The FD ‘reversed bayonet’

In addition, FD mount flange is long, and the new EF has one of the shortest flange distance in any full frame DSLR, that makes EF one of the most adaptable DSLR on the market. Canon chose to put the AF motor in the lens, powered from the camera body to provide current and signal. Which was a wise move back then, which all following modern design lenses followed the same concept.

Modern EF electrical contacts
Modern EF electrical contacts

The disadvantage? There’s no in-body image stabilizer. Canon lenses with IS can be a few hundred dollars more expensive than the non-IS. A master repairman once told me that the sensor stabilizer is prone to spoil when the camera drop. Come on, Olympus did it, Pentax did it, Sony even did it with full frame sensor, my Olympus dropped a few times and the sensor shift stabilizer still works fine. The only benefit to have in-lens IS is to have optical preview, or Canon engineers are just lazy.

EF-M on the other hand, is a huge disappointment when it was announced. It has nothing in superior comparing to other mirrorless mounts. The Canon fan boys are utterly disappointed that it’s not a full frame.

Nikon F, AIS, 1, whatever

Apologies for revealing some personal biased opinion, but I will explain why! There is such a long complicated code names for Nikon lenses, mount variations, and even the earlier Nikon DSLR model naming is confusing. Nikon has one of the largest collection of legacy lenses available. Back in the days switching to electronic and auto-focus, they chose a different strategy from the rival Canon – Keep the loyal Nikon owners happy by sticking to the old lens mount, which is not wrong. BUT, the existing Nikon F mount design has a lot of problems.

1. The flange distance is longer than Canon EF, which is why Nikon lenses can be used on Canon but not vice versa. I am not too sure if longer flange complicates lens design. Just comparing Nikon 17-55mm 2.8 and Canon 17-55mm 2.8, Canon counterpart is shorter and cheaper.

2. Smaller lens diameter, which makes lens design harder, thicker, which is why modern Nikon lenses are generally more expensive than Canon.

3. They chose to keep on modifying the lens design, some were driven by a small motor in-built from the camera body. It’s a clever design back then so you use a single motor to drive all mechanical lenses to auto focus. It’s not future-proof, little did they know some years later somebody designed the modern piezoelectric motor for lens, makes it simpler in terms of engineering packaging, maybe lighter, most importantly quieter and faster. The old design is obsolete and inferior, but Nikon has to stick to it because of their strategy. It makes the mechanical engineer VERY complicated, increased production cost and repair cost.

1. The unnecessary protrusions obsolete designs 2. Mechanical aperture 3. Perpendicular electronic contacts
1. The unnecessary protrusions obsolete designs
2. Mechanical aperture
3. Perpendicular electronic contacts

4. Positioning the electronic contacts, Nikon chose to put it perpendicular to the lens mount, spring-loaded, ball-loaded, which is again, very complicated to design, engineer, package and repair. Therefore costlier as well.

Nikon 1 however, has some mixed feedback. I have yet to try it yet nor to disassemble it. There are some people who loves the compact design and high speed video recording, some just do not like the small sensor. One thing for sure, there was a huge disappointment on the Nikon mirrorless websites and rumor sites when it was announced.

Sony A, mirrorless E mounts

Sony A mount was bought over from Minolta. Similar to Canon, they separated the lens bayonet and the electronic contacts, which is good for engineering and packaging, except that it has slightly longer flange distance than Canon. Like Nikon however, some models are compatible with older Minolta lenses to have the mechanical aperture and AF motor. While having this compatibility is a major set-back in terms on modern engineering, the newer Sony lenses are comparatively simpler to design and manufacture than Nikon.

1. Electronic contact 2. Aperture control 3. AF motor
1. Electronic contact
2. Aperture control
3. AF motor

E mount is an interesting mount. In terms of packaging, it has one of the most straight-forward simplicity design. However, I suspect the engineers did not consider the fact of future design of bigger sensor, OR, they optimized it too much that it is ‘just-nice’. In fact it is too small. Quote from Kenrockwell:

The same $3,000 LEICA lens looks horrible on the Sony. This is because the Sony’s sensor is obviously not happy with lenses with their rear nodal points this close to the sensor, while the LEICA cameras are designed to work well with these LEICA lenses. I saw the same thing shooting the LEICA SUMMILUX-M 35mm f/1.4 ASPH on the Sony. This is the world’s best 35mm lens, yet it was soft on the sides when shot on the A7.

The full frame sensor is almost too big than the mount itself.
The full frame sensor is almost too big than the mount itself.

(2014 Oct 27 update: Quote from Sigma CEO Kazuto Yamaki with his DSLRmagazine interview:

I’ts a bit more difficult to make ART lenses for the Sony FE system because of the not so large diameter of the mount. We don’t know why Sony did this. Likely because the E-mount was meant for APS-C first and only after that they did use it for FF too.

This confirms my hypothesis for the small diameter Sony FE and Nikon F mounts.)

So, this is bad. What about the crop sensor? E mount has among the shortest flange distance and biggest sensor yet to offer, are the crop sensor NEX cameras good?

The first generation of standard kit lens comparison.
The first generation of standard kit lens comparison. Photo from dpreview.com

By comparing the first generation of standard kit lens, Sony E lenses looks humongous compared to the slim body of NEX (the newer generations are much smaller). Is shorter, smaller and slimmer body always better? I tried for myself, the weight balance is a bit weird, and I suspect one thing from the lens design: the engineering design for short flange big sensor with AF is difficult. Why? here’s the reasoning:

The 50mm lens design for a ‘normal’ legacy SLR with about ~40mm flange distance is probably the cheapest and easiest thing to manufacture. Even the modern Canon 50mm 1.8 cost about US$100. For some reason I do not know why the basic E-mount 50mm cost more than double, and its bigger and heavier. Now why don’t they just keep to the old design and add spacer to provide the same flange distance? It may be smaller and cheaper.

It’s either that, or I am wrong about the optic engineering and Sony just want to make more profit. If shorter flange distance is a problem… why are the Leica M-mount lenses so small?

One note on the advantage. For some reason its either Sony is open about their mount technology or the reverse engineering is simple, apparently its pretty easy to decode the electrical signal of the Sony mount, and third-party ‘smart adapter’ is available to allow AF of Canon EF lenses on the E-mount. This is however not possible with the m4/3 mount with Canon. So… Sony is secretly friend with Canon. (correction, Metabones just release a new smart adapter to allow aperture control of Canon lenses on Olympus/Panasonic bodies.)

Pentax K

There’s always a very happy group of Pentaxian out there even though Pentax has some interesting strategy – crop sensor, premium body low price, expensive premium APS-C lenses, skipped the full frame and went straight for digital medium format. But hell, the mount is another pain in the ass to manufacture.

1. Electronic 2. AF motor 3. Aperture control
1. Electronic
2. AF motor
3. Aperture control
Update 2 Nov 2014. I managed to get my hands on attempting to modify the kit lens DA 18-55mm II. I am both impressed and frustrated the same time.
Update 2 Nov 2014. I managed to get my hands on attempting to modify the kit lens DA 18-55mm II. I am both impressed and frustrated the same time.

Update 2 Nov 2014 on the DA 18-55mm II assembly:

– Is surprisingly well built for the cheapest kit lens as compared to the Canon/Olympus counterpart.

– Is expectedly pain in the arse to assemble, more parts, more components, user-unfriendly assembly of the cam system, took me 3 hours to learn to reassemble back. You can call it poor engineering as it is much more complicated than other brands’ engineering in general.

– Plus point on the engineering: There’s many self-lock mechanism and reduce the use of screws.

Similar to Nikon, they modified the old lens design to have electronics. Instead of placing the electronic contacts outside of the bayonet, they put it ON the bayonet (not to mention another 2 more pins on the body, I suspect is the + and -). Positioning is difficult in a radius, machining is troublesome. Some Pentax lenses are spring loaded to control aperture, so that means you can’t play with ‘freelensing’ unless you tape up the lever. It’s not surprising that some of their lenses are generally more expensive than other brands. But hell, a 21mm F3.2 lens for US$600?! You got to be kidding me. Not to mention the ridiculous 31mm 1.8 for more than 1k. Now I know you get close to a standard 50mm focal length, but I just mentioned that the standard 50mm 1.8 is one of the cheapest thing to manufacture, why would anyone want to buy a 47mm* 1.8 for more than 1k that can’t even cover full frame? Even a m39 Leica 50mm F2 Summitar is cheaper.

One good thing about the motor design, they make some really uniquely small lenses that made use of the advantages of in-body-motor (unlike Nikon for which they can’t decide what they want). But then, the unique 40mm 2.8 XS with a small piece of glass without motor shouldn’t have cost more than US$200 as listed price considering the China made C-mount 25mm 1.4 with multiple glasses cost less than 10 USD in China retail.

 

..That’s all for now, but stay tune

Stay tune, I will update this page from time to time. Olympus/Panasonic coming next.

The writer is an automotive research engineer, whom on his free time disassemble, repair and modify lenses. He shoots mostly with Canon and Olympus/Panasonic, secondary with Pentax and Nikon, and very little with Sony. Any feedback is welcome.

Advertisements

One thought on “Camera lens mount, comparing the brands and engineering

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s