Reading mode: Light Dark

Why is the M4/3 mount so big

Go to last post
W

Wellington100

Veteran Member
Messages
11,810
Reaction score
5,360
Location
NZ
When I look at the M4/3 mount, I wonder why it has such a large diameter. The new Leica 25mm f1.4 lens is mostly plastic, only the centre of the lens is glass.

http://www.43rumors.com/good-news-folks-leica-25mm-lens-will-cost-around-650-euro/

The Panasonic 20mm f1.7 is an even better example of this:

http://www.dpreview.com/lensreviews/panasonic_20_1p7_o20/

Compare this to the Nikon 50mm f1.4. The glass fills the lens:

http://www.dpreview.com/lensreviews/nikon_50_1p4_n15/

Why didn't they go with a smaller diameter mount which would have allowed smaller cameras to look more balanced than they do now:

http://www.dpreview.com/news/1106/11061310panasonicGF3preview.asp
 
Two other reasons:

1) the ability to mount wide aperture longer lenses without being constrained in the capture angles at the sensor. It would be a shame if you had a mount that precluded a 50mm f1.2...

2) mechanical stability of telephotos and other heavier lenses and where you attach the camera to the lens rather than visa-versatile. Look at some of the AG-AF100 set ups and consider if they woul work so well with a smaller mount.

With the lens mount on a system like this you don't want to make compromises that you regret later - especially not for small gains in appearance.
 
Wellington100 said:
Compare this to the Nikon 50mm f1.4. The glass fills the lens:

http://www.dpreview.com/lensreviews/nikon_50_1p4_n15/
Click to expand...
Now compare this to the new Nikon AF-S 50mm f/1.8G:
http://www.dpreview.com/news/1104/11042710nikon50mmf1p8.asp

The glass doesn't fill this lens. Why? Because there is now a motor in the lens. Yes, that part of the lens not taken up with optics is required for the electronics & motors. So it's either motors in the body (and the motor has to be beefy enough to drive all lenses) which alllows smaller lenses but makes for larger bodies or motors in the lenses which allow smaller bodies (and lens optimized AF motors) but increase the size of the lenses.

--
Erik
 
Wellington100 said:
When I look at the M4/3 mount, I wonder why it has such a large diameter. The new Leica 25mm f1.4 lens is mostly plastic, only the centre of the lens is glass.

The Panasonic 20mm f1.7 is an even better example of this:

Compare this to the Nikon 50mm f1.4. The glass fills the lens:

Why didn't they go with a smaller diameter mount which would have allowed smaller cameras to look more balanced than they do now:

http://www.dpreview.com/news/1106/11061310panasonicGF3preview.asp
Click to expand...
On choosing a lens mount standard...small-ness must be balanced with other needs.

To me, the obvious fact is that both reducing the size of the image circle and eliminating the need to project rays past a no-longer-needed mirrorbox can allow you to reduce lens elements diameters. Yay. But the same reduction in scale cannot be said of the focusing components--the size of which is goverened less by optical formulas, and more by electro-mechanical characteristics. That's the obvious one.

Then...there are, I suspect, quite a few considerations they must take into account, the balance of which I suspect are largely ignored by us end users. But I can definitely speculate on some important aspects.

For instance, The lenses you happen to be comparing are relatively simple ASPH-enhanced lenses, which eliminates the need for that large front element that you are so used to seeing on DSLR-designed lenses. While some lenses can take very good advantage of modestly retro-focal designs, other (wider) lenses will still need to be somewhat retrofocally-severe, which would necessitate the large front elements you are so used to seeing. On the m4/3 mount, you'll see more pancake-ish lenses, around the normal focal lenghts, taking advantage of small/few lens groups, & no need for that large front element. But a system will certainly include some lenses that require those large elements (read: 7-14mm UWA). Shall you buid your standard around a diameter that works well at normal focal lengths, but is somewhat lacking at wide angle? Engineers would want to cover all of the system, not just the "smallest of them."

Then there's the structural consideration. Yes, you could hang 8lbs of legacy 4/3 lens off your pen mount & still autofocus a picture. The structural integrity of your mount is directly related to its diameter. This is why thin-walled structural elements are designed with wide diameters (think of OCLV carbon-fiber structural elements). If you had designed your mount to significantly smaller diameters, but had not beefed up the mount itself, you could exceed the structural properties of the mount itself.

That's just two off the top of my head.

It never occurred to me that some folks would actually think of the m4/3 lenses as "big" compared to other lenses. :)

--
'I have no responsibilities here whatsoever'
 
RoyGBiv said:
Wellington100 said:
When I look at the M4/3 mount, I wonder why it has such a large diameter. The new Leica 25mm f1.4 lens is mostly plastic, only the centre of the lens is glass.

The Panasonic 20mm f1.7 is an even better example of this:

Compare this to the Nikon 50mm f1.4. The glass fills the lens:

Why didn't they go with a smaller diameter mount which would have allowed smaller cameras to look more balanced than they do now:

http://www.dpreview.com/news/1106/11061310panasonicGF3preview.asp
Click to expand...
On choosing a lens mount standard...small-ness must be balanced with other needs.

To me, the obvious fact is that both reducing the size of the image circle and eliminating the need to project rays past a no-longer-needed mirrorbox can allow you to reduce lens elements diameters. Yay. But the same reduction in scale cannot be said of the focusing components--the size of which is goverened less by optical formulas, and more by electro-mechanical characteristics. That's the obvious one.

Then...there are, I suspect, quite a few considerations they must take into account, the balance of which I suspect are largely ignored by us end users. But I can definitely speculate on some important aspects.

For instance, The lenses you happen to be comparing are relatively simple ASPH-enhanced lenses, which eliminates the need for that large front element that you are so used to seeing on DSLR-designed lenses. While some lenses can take very good advantage of modestly retro-focal designs, other (wider) lenses will still need to be somewhat retrofocally-severe, which would necessitate the large front elements you are so used to seeing. On the m4/3 mount, you'll see more pancake-ish lenses, around the normal focal lenghts, taking advantage of small/few lens groups, & no need for that large front element. But a system will certainly include some lenses that require those large elements (read: 7-14mm UWA). Shall you buid your standard around a diameter that works well at normal focal lengths, but is somewhat lacking at wide angle? Engineers would want to cover all of the system, not just the "smallest of them."

Then there's the structural consideration. Yes, you could hang 8lbs of legacy 4/3 lens off your pen mount & still autofocus a picture. The structural integrity of your mount is directly related to its diameter. This is why thin-walled structural elements are designed with wide diameters (think of OCLV carbon-fiber structural elements). If you had designed your mount to significantly smaller diameters, but had not beefed up the mount itself, you could exceed the structural properties of the mount itself.

That's just two off the top of my head.

It never occurred to me that some folks would actually think of the m4/3 lenses as "big" compared to other lenses. :)
Click to expand...
I am not saying that the lenses are big in absolute terms, I am simply pointing out that the mount is big. If you compare the mount diameter vs the diameter on the front element of a m4/3 system to the equivalent ratio on an equivalent DSLR camera, it becomes pretty obvious that the m4/3 mount is very big relative to the front element size.

An excellent example is the just released GF3. The front of the kit lens is mostly plastic:

http://www.dpreview.com/news/1106/11061310panasonicGF3preview.asp

compare this to a Nikon D3100 which has a DX kit lens that is already smaller than the FF mount that Nikon DX attaches to:

http://www.dpreview.com/products/nikon/slrs/nikon_d3100

Full frame lenses bulge out significantly from the mount which is much smaller than the front elements:

http://imaging.nikon.com/lineup/lens/zoom/normalzoom/af-s_nikkor24-120mmf_4d_ed_vr/index.htm

Its just that it looks to me like a smaller mount would have allowed smaller diameter kit, prime and zoom lenses, which I think would have been a good thing. There is no way the motors in the lens need all that spare plastic real estate :-)

Lenses like the 7-14 could bulge a bit like SLR lenses do if they need extra large front elements.

To me the new shrunk down Panasonic looks a bit freaky with its oversized mount and tiny front lens element. Small is the direction the camera market is going in and the oversized mount looks like its too big for the currently desirable camera sizes, not to mention that the lenses seem to be bigger than necessary.
 
no text
 
Here is the Nikon D700 front view:

You can see how the sensor fills the space inside the lens mount, almost from end to end, whereas the Panasonic GF1 only fills half the space inside the mount area

All I am saying is that thats how much smaller the mount could have been. Its one reason why Leica users love their cameras so much, the lenses are compact. M4/3 lenses are far bigger than they need to be based on the size of the sensor.
 
Wellington100 said:
I am not saying that the lenses are big in absolute terms, I am simply pointing out that the mount is big.
Click to expand...
It's partly because of legacy: that's the size you needed on 4/3's to have fast telecentric lenses. Large enough to make a practical adapter for OM lenses may have played a part as well.

But you are looking at the wrong end of the telescope. Look at the back of lenses to see the mount diameter requirements. Take the most aggressive design you want to make (travel zoom, ultra fast prime, long tele, etc.) and calculate the rear diameter and light cone you need to cover your sensor. That's your minimum mount diameter. Canon chose theirs so as to make the 50mm f/1.0 lens possible.
Wellington100 said:
Its just that it looks to me like a smaller mount would have allowed smaller diameter kit, prime and zoom lenses, which I think would have been a good thing. There is no way the motors in the lens need all that spare plastic real estate :-)
Click to expand...
They need quite a bit as the Nikon 1.4 vs. 1.8 comparison shows. How much they need depends on what you are moving to focus. Kit lenses that just rotate the front couple of elements may need less than unit focusing designs that have to move everything. And with video AF, it's not just enough to move, but you need to move quickly and quietly as well.

It's all a compromise and they did not start with a clean sheet of paper. Could the mount be a few mm smaller? Probably, but that would not have much impact on the lens diameter after all of the construction factors.

--
Erik
 
Erik Magnuson said:
Wellington100 said:
I am not saying that the lenses are big in absolute terms, I am simply pointing out that the mount is big.
Click to expand...
It's partly because of legacy: that's the size you needed on 4/3's to have fast telecentric lenses. Large enough to make a practical adapter for OM lenses may have played a part as well.

But you are looking at the wrong end of the telescope. Look at the back of lenses to see the mount diameter requirements. Take the most aggressive design you want to make (travel zoom, ultra fast prime, long tele, etc.) and calculate the rear diameter and light cone you need to cover your sensor. That's your minimum mount diameter. Canon chose theirs so as to make the 50mm f/1.0 lens possible.
Member said:
Its just that it looks to me like a smaller mount would have allowed smaller diameter kit, prime and zoom lenses, which I think would have been a good thing. There is no way the motors in the lens need all that spare plastic real estate :-)
Click to expand...
They need quite a bit as the Nikon 1.4 vs. 1.8 comparison shows. How much they need depends on what you are moving to focus. Kit lenses that just rotate the front couple of elements may need less than unit focusing designs that have to move everything. And with video AF, it's not just enough to move, but you need to move quickly and quietly as well.

It's all a compromise and they did not start with a clean sheet of paper. Could the mount be a few mm smaller? Probably, but that would not have much impact on the lens diameter after all of the construction factors.
Click to expand...
You may be right that the size has been dictated by technological considerations, I have been wondering whether it was dictated by marketing considerations, ie, how to make a small lens look big, which might have been an issue when the the E series Olympus cameras were positioning themselves head to head against Nikon and Canon DSLR's but now the market wants small gear and it looks like m4/3 lenses could be much smaller in diameter than they are.

I bought my son an EP1 kit and the lens cover only goes around 2/3 of the diameter of the lens housing and the front element of the lens which is its biggest element is noticeably smaller than the cover. If you use that cover as a template for what size the lens could have been, I think you will get the idea. :-)

Its just that the Panasonic GF3 looks awful, as bad as the Nex3 really and all because of the lens mount diameter. Yet in use, it will have (relatively) huge lenses sticking off of it, which will offset its uber compact dimensions.

http://www.slim-digital-camera.net/2010/09/olympus-e-p2-special-black-editions/
Member said:
--
Erik
Click to expand...
 
Wellington100 said:
Here is the Nikon D700 front view:

You can see how the sensor fills the space inside the lens mount, almost from end to end, whereas the Panasonic GF1 only fills half the space inside the mount area
Click to expand...
I do understand your point. You're definitely not the first to observe the negative space inside the mount. My points remain valid though.
Wellington100 said:
All I am saying is that thats how much smaller the mount could have been. Its one reason why Leica users love their cameras so much, the lenses are compact. M4/3 lenses are far bigger than they need to be based on the size of the sensor.
Click to expand...
take a look at the newvoigtlander 25/0.95 for the m43 version of those leica m-mount lenses. I'd compare the leica 50/1.4 (a beast, by m-mount standards) vs the voightlander. Those are both benefitting from not having to accommodate lens motors. M-mounts don't have motors. Hence...they can be relatively compact.
--
'I have no responsibilities here whatsoever'
 
there's nothing stopping any manufacturer from taking any mount diameter & tapering down from the mount diameter to something narrower, if the lens components could fit in a smaller envelope. The lens mount diameter doesn't dictate how wide the oversll lens diameter is. In the same way that the summilux & noctilux lenses necessarily flare out to accomodatetheir massive optics, the reverse would be true too.

If you did this with every lens to theminimum it could be, you migt save some space. But you'd also have zero shared filter size for your system, which is also annoying. Ĥ

--
'I have no responsibilities here whatsoever'
 
RoyGBiv said:
Wellington100 said:
Here is the Nikon D700 front view:

You can see how the sensor fills the space inside the lens mount, almost from end to end, whereas the Panasonic GF1 only fills half the space inside the mount area
Click to expand...
I do understand your point. You're definitely not the first to observe the negative space inside the mount. My points remain valid though.
RoyGBiv said:
All I am saying is that thats how much smaller the mount could have been. Its one reason why Leica users love their cameras so much, the lenses are compact. M4/3 lenses are far bigger than they need to be based on the size of the sensor.
Click to expand...
take a look at the newvoigtlander 25/0.95 for the m43 version of those leica m-mount lenses. I'd compare the leica 50/1.4 (a beast, by m-mount standards) vs the voightlander. Those are both benefitting from not having to accommodate lens motors. M-mounts don't have motors. Hence...they can be relatively compact.
Click to expand...
Yes those are two very fine looking lenses. As you probably already know, the large aperture lenses on the Nikon system bulge considerably from the mount so accommodating the motors is not related to the mount size.

Where you benefit from a small mount is with the kit lenses which have small apertures and lower spec motors which are presumably smaller and of course the primes and pancakes that don't have VR in them either.

A small mount with a lens that bulges allows the camera body to shrink further because the oversized part of the lens is away from the camera body whereas a large mount that has a lens that tapers means the fattest part of the lens is always up against the camera body, which prevents the body from shrinking to a smaller form factor unless you go the ugly and compromised Panasonic GF3 route.
RoyGBiv said:
--
'I have no responsibilities here whatsoever'
Click to expand...
 
It
Wellington100 said:
Yes those are two very fine looking lenses. As you probably already know, the large aperture lenses on the Nikon system bulge considerably from the mount so accommodating the motors is not related to the mount size.
Click to expand...
It houses both the optics & the mechanics. Therefore, it necessarily neds to accommodate both. Therefore it's sizeis dictated by both. The fact that you don't accept that doesn't mean the engineers can disregard it.
Wellington100 said:
Where you benefit from a small mount is with the kit lenses which have small apertures and lower spec motors which are presumably smaller and of course the primes and pancakes that don't have VR in them either.

A small mount with a lens that bulges allows the camera body to shrink further because the oversized part of the lens is away from the camera body whereas a large mount that has a lens that tapers means the fattest part of the lens is always up against the camera body, which prevents the body from shrinking to a smaller form factor unless you go the ugly and compromised Panasonic GF3 route.
Click to expand...
You give me supreme confidence that you can engineer a system superior to m4/3 and sony.

--
'I have no responsibilities here whatsoever'
 
I think that the reasons Roy and Erik gave you are the good ones.

As an example the lens next to the 17mm, is the smallest one could adapt to M4/3, the Industar 69, a Tessar triplet from the Russian Chaika half frame camera. Of course it has no motor, no AF.

The Tessar triplet Could be the simplest devised: 4 lenses in 3 groups. Works with the M39 mount, which is smaller than m4/3.

However I also have the old 9-18 which has a huge front element, or an old 135/2.8 weighing 500 gr. The mount can still take it but I am carefult to hold the kit by the lens. Some have mounted bigger lenses, but one must be careful of the structural integrity of the mount, possibly with SHG zuiko lenses. Larger diameter helps to better distribute the weight.

So it's a matter of compromises. Some lenses can be small and still have big front elements, like some Leicas and CV, but I suppose that the exit lens will still be relatively small since it is so close to the film/sensor plane.

RF mounts like Leica, or half frame cameras' ones were smaller, but they accomodated only a limited range of lenses, not at the extremes of the focal range like a SLR had to do. It is interesting to see that the m4/3 mount is something in between the two.



--
Photostream: http://www.flickr.com/photos/amalric
 
Meuh said:
It would be nice if they used a bit more glass to give us FF equivalent DoF as well as the focal length :)
Click to expand...
You mean like the 25/0.95, errr, "50/1.8"? Considering the price (and the size) it entails, I think chasing the DOF ghost is a lost cause.

--
-CW

よしよし、今日も生きのいい魂が手に入ったな
 
RoyGBiv said:
Wellington100 said:
Yes those are two very fine looking lenses. As you probably already know, the large aperture lenses on the Nikon system bulge considerably from the mount so accommodating the motors is not related to the mount size.
Click to expand...
It houses both the optics & the mechanics. Therefore, it necessarily neds to accommodate both. Therefore it's sizeis dictated by both. The fact that you don't accept that doesn't mean the engineers can disregard it.
RoyGBiv said:
Where you benefit from a small mount is with the kit lenses which have small apertures and lower spec motors which are presumably smaller and of course the primes and pancakes that don't have VR in them either.

A small mount with a lens that bulges allows the camera body to shrink further because the oversized part of the lens is away from the camera body whereas a large mount that has a lens that tapers means the fattest part of the lens is always up against the camera body, which prevents the body from shrinking to a smaller form factor unless you go the ugly and compromised Panasonic GF3 route.
Click to expand...
You give me supreme confidence that you can engineer a system superior to m4/3 and sony.
Click to expand...
The bigger Sony sensor fills its mount area more than M4/3 does, this is the very point I am making, thank you for mentioning the Sony.

I can't engineer a system but happily Nikon and Pentax are both rumoured to be releasing new mirrorless camera systems so it will be entertaining to see how large their mounts are relative to their sensors.

I guess you guys are saying the mount size is an engineering issue whereas I am suggesting it might have been a marketing decision because compared to other systems including Sony and Samsung, the mount looks large relative to the sensor and relative to the diameter of the optics in all the popular lenses.
RoyGBiv said:
--
'I have no responsibilities here whatsoever'
Click to expand...
 
One of the marketed advantages of 4/3 system was said to be the telecentricity of the lenses.

With m4/3 they substantially gave it up, but it's possible they wanted to keep some of it.
 
You must log in or register to reply here.

Keyboard shortcuts

f
Forum
m
My threads
Mobile site
About
Editorial content
Cameras & Lenses
Community
All content, design, and layout are Copyright © 1998–2025 Digital Photography Review All Rights Reserved.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
When you use DPReview links to buy products, the site may earn a commission.
©GPS Media - Guides, Products, Services.
Back
Top