Camera lens mount flange distance and implications for compact digital cameras with intercheangable lenses – Micro Four Thirds or Samsung NX?

Written by Gary on January 10th, 2010

The Micro Four Thirds camera system has surged to 3rd in popularity of “dSLR” sales in 2009 partly because of the versatility its short sensor to lens mount flange distance offers allowing almost any lens ever made to be used.

The recently announced competing system from Samsung which is a welcome competition for us all, may have a larger sensor and marginally less noise at high ISO, and less crop factor for 35mm lenses, but it has a number of disadvantages when compared to the Micro Four Thirds format.

To understand some of these issues, let’s first look at the implications of the sensor to lens flange distance – on the Micro Four Thirds cameras, this distance is 20mm, while on the Samsung NX system, it is 25.5mm.

One of the implications is the range of legacy lenses that can be mounted.

In theory, both systems should be able to have adapters made which allow infinity focus for most legacy lenses, HOWEVER, unlike the MFT cameras, it is uncertain if a Leica M bayonet lens would achieve infinity focus on a Samsung mount as Leica M flange distance is 27.8mm, only 2.3mm more than the Samsung and maybe too thin for an adapter.Other rangefinder lens mounts such as Leica M screw mount,  and Canon rangefinder, and the half-frame Olympus Pen should be possible  to make for the Samsung given they would require only 3.3mm thin adapters.

An important factor may be the difference in throat diameter – for example, the Canon EF is 8mm wider than the OM which may make a 2mm thin adapter design easier by allowing enough metal to give it strength, but more importantly, allows the narrower OM mount to fit inside the EF mount given there is no latitude to create a conical shaped adapter.

The Leica M throat is 44mm at the small end for SLRs and if the Samsung throat is 38mm, they will not be able to fit a Leica M mount inside it and thus it would appear one would not be able to fit rangefinder lenses such as a Leica M on a Samsung and still get infinity focus.

Without this capability, Samsung will struggle to gain support of photo enthusiasts who would be the early adopters, and without these early adopters and their ongoing support combined with the lack of goodwill in the SLR community, I would be surprised if Samsung make big inroads into this sector, however optimistic they may be.

A list of flange distances can be found on wikipedia and from this list you can see why you cannot use non-Nikon F mount lenses on Nikon dSLR as Nikon has one of the widest flange distance of 46.5mm, but you can mount Nikon F, Leica R, Yashica/Contax, and Olympus OM lenses on most other dSLR systems including Canon EF (44mm), Olympus Four Thirds (38.67mm).

You can also see that Sony/Minolta/Pentax lenses could also be used on Four Thirds but not on Canon EF cameras, but you need the mirror-less systems such as MFT and Samsung NX to use Canon FD/FL/R/EF lenses.

Optimal focal length for a compact pancake lens:

In order to make a pancake lens as thin as possible, the optimal focal length is close to the sensor-flange distance – this is why Olympus made its 17mm f/2.8 (34mm in 35mm camera terms) and Panasonic made its superb 20mm f/1.7 lens which is 40mm in 35mm camera terms, and presumably the reason Samsung chose 30mm f/2 pancake (48mm in 35mm terms).

For street photographers wanting a compact camera kit, a focal length of 30-40mm in 35mm terms is often the most desired focal length – obviously the 2 MFT lenses mentioned above fill this niche nicely, but the Samsung 30mm is too long – if they made a 25mm pancake which would equate with its flange distance, you could get a 40mm focal length reach in 35mm terms and still be a compact pancake lens.

They could make thin pancake lenses at focal lengths less than these, but I suspect the rear element may need to protrude into the camera or they would need to resort to a more complex lens design.

Short lens flange distances and sensor size:

As Leica have discovered, in order to make digital cameras using their 27.8mm flange distance for their Leica M lenses, increasing sensor size requires expensive specialised sensor design to ensure the light rays hitting the outer parts of the sensor are more consistent with the image characteristics of those hitting the central parts.

They appear to have finally achieved this in their Leica M9 full frame digital, but it is very expensive and does not offer live view for manual focus, nor movie capabilities.

Samsung with their NX-10 appear to have ignored this issue so it will be interesting to see how much vignetting, CA and poor image sharpness they will get in the outer areas of their images – there is always a compromise in photography – you can’t have your cake and eat it too!

Optical aberrations increase exponentially with distance from centre of the image, thus it will always be easier to make lenses with better edge-to-edge image quality on a 2x crop sensor compared to the NX 1.6x crop sensor.

Of course they could use in-camera digital corrections instead of expensive sensors but this would increase noise, and reduce image detail in the periphery.

Conclusion:

The Samsung NX is a welcome addition to the competition in the mirror-less interchangeable lens digital camera market as it will spur on further development and we should all benefit from that.

However, its design, whilst allowing similar size camera bodies to MFT, inevitably means potentially less versatility in what lenses could be adapted – in particular, they may not have access to Leica M  lens users, and their AF lenses will necessarily be larger than MFT lenses and with potential for less image quality in the periphery.

The 2x crop of the MFT sensor also means that focal length reach can be achieved in a much more compact lens than with Samsung’s APS-C size 1.6x crop sensor – you could easily design a compact 200mm f/2.8 lens for MFT or Four Thirds which would give high quality 400mm f/2.8 focal length reach in a very compact, hand holdable kit (please Olympus, bring one of these out soon), but to do so on a NX camera would require a massive 250mm f/2.8 lens with its much larger image circle.

Furthermore, Samsung does not have access to a range of AF lenses as does MFT with their MFT and Four Thirds lenses, and this as well as their lack of following, will limit their success.

It may though stimulate Nikon or Canon to enter this market, although I suspect Canon has the high end in its sights with some of its new lenses offering a 40mm image circle which allow for a larger than full frame sensor.

In comparison to the Samsung NX, the Micro Four Thirds format offers a better compromise on lens size, edge-to-edge image quality, greater hand holdable telephoto reach and compatibility with legacy lenses, and at present, a much greater range of dedicated AF lenses, much better video capability with only marginally less high ISO performance.

ps.. Novoflex has just announced its adapters for Samsung NX which include Nikon F, Canon FD, Minolta MD, Leica R, Pentax K, Olympus OM, M42 and T2, but as predicted, none for Leica M or Olympus Pen.

 

Comments Closed

8 Comments so far ↓

  1. John says:

    Do you like M4/3, right?

  2. admin says:

    Love M4/3, I think mirror-less systems are the way of the future for most photography.

    I would love the Leica M9 if it also had live view, EVF, and movie modes, and it was much more affordable – but M4/3 is a great compromise and beautifully complements a full frame dSLR kit.

  3. neekoh says:

    Was just searching for the sensor to lens flange distance… got a lot more information. Nice mini-article.

  4. smoke weed says:

    Hey, I’ve been lurking on your blog for a few weeks. I absolutely love your article and your whole blog! Looking forward to reading more!

  5. genji says:

    Well constructed article — both informative and persuasive. It’s indeed a shame that Samsung chose to develop a 30mm pancake when the 25mm alternative you suggest would have produced a field of view close to 40mm, my favorite full-frame focal length.

    One nitpick: the Olympus Pen F, with its 28.95 mm flange distance, was a half-frame reflex camera not a rangefinder. I have quite a few Pen F lenses and they are marvelous on m4/3.

  6. admin says:

    ah, yes, you are so right! will fix 🙂

  7. mircea Horia Dr.Mihu says:

    What about Sony NEX 5. Register 18 mm (lens mount diameter ?).I think that for this one there will be Leica M adapters.
    Regards

  8. admin says:

    I agtee, Sony didn’t make the same mistake as Samsung so we will see adapters for most lenses.

    The main problem with Sony in this regard is the same Leica faced – the larger the sensor at such short distances means image quality in the periphery will suffer.