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Canon camera mounts and change

  |   Article, Articles and reviews, Canon EOS R, Lens, Personal views, Rumour lens article   |   No comment

Changing Canon camera lens mounts

How might the RF mount affect you?


It seems that Canon’s choice of an all new ‘RF’ mount for their mirrorless EOS-R camera might cause difficulties for existing camera and lens users.

Does it really?

Keith has been looking at Canon’s range of lenses past, present and future and wonders if in time the fuss will subside and we’ll get on with taking photos…

canon rf mount

We’re all doomed – or not

Already I’m seeing articles and comments about Canon’s move to the RF mount that are not even wrong in their level of their cluelessness about optics and the camera market(s) around the world.

The sky is not falling – perhaps some context and history will help.  In a few years all will be well, but probably better ;-)

Canon lens mounts – A brief history

Canon changes lens mounts and systems – some people are left behind, some move on.  With the new RF mount there are many questions as to what it means for different categories of Canon camera user. This note aims to show a bit of historical context for the change – noting that past changes didn’t have the echo chamber of the internet to contend with…

I’ll mention some of the older lens mounts first, since many modern DSLR users may not even know this aspect of Canon’s lens history.

Canon R mount

Let’s go back to 1959 – the Canonflex 35mm SLR is launched using the R lens mount. It used a breech-lock style of mount to attach the lens (i.e. lens doesn’t rotate in camera as you attach it).

Canonflex camera trio

Quite a range of lenses are launched – note the 1000mm and 2000mm

Just the one zoom: 55-135mm f/3.5 (1963)

35mm f/2.5 (1960) 100mm f/2 (1959) 200mm f/3.5 (1959)
50mm f/1.8 I (1959) 100mm f/3.5 I (1961) 300mm f/4 (1960)
50mm f/1.8 II (1960) 100mm f/3.5 II (1963) 400mm f/4.5 (1960)
50mm f/1.8 III (1963) 135mm f/2.5 (1960) 600mm f/5.6 (1960)
58mm f/1.2 (1962) 135mm f/3.5 I (1959) 800mm f/8 (1960)
85mm f/1.8 (1961) 135mm f/3.5 II (1961) 1000mm f/11 (1960)
85mm f/1.9 (1960) 2000mm f/11 (1960)

I should note that with mirrorless cameras, suitable adapters will let you use any of them on the new EOS-R

For more historical detail start with the ‘R Mount’ at WP or the Canon camera museum

1964 The FL mount

Canon_FL_58mmA breech lock mount lens that was used from 1964 to 1971

Improving optical design produced a few more zooms

55-135mm 3.5
85-300mm 5
100-200mm 5.6

Wider lenses too

19mm 3.5
19mm R 3.5
28mm 3.5
35mm 2.5
35mm 3.5
P38mm 2.8

Lot’s of ~50mm
50mm 1.4 (1965)
50mm I 1.4 (1966)
50mm II 1.4 (1968)
50mm 1.8 (1964)
50mm II 1.8 (1968)
50mm M 3.5
55mm 1.2 (1968)
58mm I 1.2 (1964)
58mm II 1.2 (1968)
85mm 1.8
100mm 3.5
M 100mm 4
135mm 2.5
135mm 3.5
200mm 3.5 I
200mm 3.5 II
200mm 4.5
300mm 2.8
300mm 5.6
400mm 5.6
500mm 5.6
600mm 5.6
800mm 8
1200mm 11

1971 The FD mount

Time for another change. This mount was introduced in 1971 with the Canon F1 and lasted until the EF mount was introduced in 1987.  The FD allowed for closer integration (mechanical) between lens and body. All lenses I’ve mentioned so far (R/FL/FD) were manual focus.  Canon produced 134 FD lenses. These ranged from 7.5mm to 1,200mm in 17 different fixed focal lengths and 19 zoom ranges.  I’ll not list all the lenses – there were a lot of them – see the WP article for a lengthy discussion.

1987 The EF revolution

The EF mount introduced electronics into the lens – that and a focus motor.

It’s a bayonet type mount which means that unlike the earlier breech-lock designs, the lens contacts rotate against the corresponding camera parts. Breech lock mounts are great for mechanical coupling since they reduce physical wear and misalignment. They are slower to swap lenses with though.

The EF mount extended the flange distance (film/sensor to front of camera lens mount) to 44mm meaning that FD lenses couldn’t make use of a simple physical adapter (they had a 42mm flange distance).

The 54mm mount diameter was significantly larger than any competing system at the time and gives lens designers some additional freedom in design.

The EF system includes over 80 lenses – for details of -all- of them see our http://EFLens.com site

2003 EF-S for smaller cheaper lenses

ef_s18-55_35-56 versionsThe EF-S mount is a minor mechanical variation on the EF mount, meaning that you can use EF lenses on an EF-S camera, but not vice versa. It still has the same 44mm flange distance. There are just over 20 EF-S lenses, many being updates of previous versions, such as the ubiquitous 18-55mm, where I’ve an article on the EFLens.com site just showing how versions differ

The back of the lens can protrude into the camera body. Add to this the smaller APS-C sensors and it makes for slightly more flexible lens design.

The prime driver, if you look at the EF-S lens range is manufacturing cost. There are none of the premium ‘L’ series of lenses and only a few prime lenses. That’s not to say there are not some good EF-S lenses (see my EF-S 10-18 review for example) but Canon’s message was always – quality comes with EF.

2012 The smaller EF-M mount

The EF-M mount was introduced in 2012 for the small EOS-M range of mirrorless cameras.

The lack of reflex mirror meant the flange distance could be reduced to 18mm from 44mm.

In what I thought was an interesting move at the time, the mount throat was also reduced from 54mm to ~47mm. A look at the EF-M mount suggests that if you want to put a 35mm full frame sensor behind it, then there are going to be lens design restrictions from the small aperture.

compare ef and ef-m

What did the EF-M mount say about mirrorless for Canon? To my mind it suggested a small camera aimed at those wanting modest image quality and a market where relatively few owners would ever change a lens (a bit like EF-S but perhaps even more so).

If you wanted to use your EF300 2.8L IS lens then you could, with an adapter. Whilst some of the armchair experts decried the limitations of the range of lenses and performance compared to say the larger Sony mirrorless cameras, I saw a range of cameras that would probably sell well to a particular market.

Whilst on the subject, I’d notice that Sony goes for an 18mm flange distance with the FE mount and has a slightly smaller throat diameter (46.1mm vs 46.7mm). My suspicion is that the diameter of the FE mount is not a favourite with Sony lens designers – note how with Nikon’s new Z6/7 lens mount they have gone for a wider mount and specifically said that it helps them with lens design.

2018 The Canon RF mount

Considering that I’m writing this before any public displays of the RF mount or EOS-R I should note that this is a preliminary discussion ;-) All our EOS R info and updates is on the EOS-R page

There are to be 4 RF lenses at launch, three of which are in the premium ‘L’ category

RF 28 – 70 mm F 2 L USM
  • Lens composition: 13 groups 19 elements | mfd: 39 cm
  • Filter diameter: 95 mm | Size: 103.8 × 139.8 mm | Weight: 1430 g
RF 50 mm F 1.2 L USM
  • Lens construction: 9 groups of 15 elements | mfd: 40 cm
  • Filter diameter: 77 mm | Size: 89.8 x 108.0 mm | Weight: 950 g
RF 35 mm F 1.8 Macro IS STM
  • Lens construction: 9 groups 9 elements | mfd: 17 cm
  • Filter diameter: 52 mm | Size: 74.4 × 62.8 mm | Weight: 305 g
RF 24 – 105 mm F 4 L IS USM
  • Lens construction: 14 groups 18 elements | mfd: 45 cm
  • Filter diameter: 77 mm | Size: 83.5 × 107.3 mm | Weight: 700 g

Three lens adapters are available – a basic EF->RF one which you’ll need to be able to use EF lenses.

control ring adapteref to rf adapteradapter with filter holder

The two others EF->RF adapters give some thought to where the EOS-R range is heading.

One with a control ring. since RF lenses have a control ring that can be used to control the camera (as well as focus and zoom rings)https://1.img-dpreview.com/files/p/TS1800x1200~sample_galleries/8971548551/1796701195.jpg

One with a drop in filter slot – aimed primarily at video I’d suggest.

The new mount is compared to EF/EF-S  in this diagram – from Canon’s EOS-R system white paper, which also discusses some of the reasons for the new mount and how it affects lens design.

RF mount design

The adapter problem

No-one uses adapters by choice, they solve a physical/electrical interface problem.  In general it’s a sub-optimal choice since it makes for more kit to carry round, more points of failure, slower to work with and is just hassle you could do without. That said, sometimes they are just useful, such as when I use Mamiya MF lenses on an EF shift adapter

At a practical level, the 18mm EF-M flange distance vs. the 20mm for RF means that you won’t be able to use your EF-M lenses on an RF body – a simple adapter is probably not possible in the same way as you couldn’t simply fit the old Canon FD lenses to the EF mount (I say ‘probably’ since I’ve not got any EF-M lenses or an RF body to check from a mechanical POV).

Canon got a lot of flack in the 80’s for the FD->EF switch, and that was without the echo chamber of the internet – you found out about this reading about trade shows in your (print) photography magazine. In some ways, Canon’s FD to EF migration was a clean break – it was a pain for some pro users, left a lot of people with a big cut to the used value of their kit, but set Canon free from the constraints of a mechanical lens-camera link – something I’d suggest has caused difficulties for Nikon over the years with the evolving F mount.

Nikon has an easier job with the Z series in this respect – it’s the same big break that Canon had in 1987 and frees them from the F mount.

Both Canon and Nikon will have debated long and hard about the merits of a mount change and how it fits with their estimates of camera sales in different regions and user types.

Update note: Canon have confirmed that the RF mount will be proprietary – so no licensing (actually the same as all their previous mounts, so hardly a surprise). Expect a delay whilst third parties see if they can reverse engineer it.

Cameras and their markets

At the moment the first EOS-R seems pitched at around the EOS 6D Mk2 level, aimed at the advanced amateur/prosumer market. You could argue it’s a bit more 5D oriented, but we’re splitting hairs…

The initial RF lenses are all quality lenses aimed at making a firm marketing statement that Canon is serious about the mount. The choice of ‘L’ designations is deliberate.

There are no ‘L’ EF-S or EF-M lenses. If you want APS-C  and ‘L’, such as my TS-E24mm F3.5 L Mk2, then you buy EF and use a crop sensor EF-S camera or an EOS-M and the EF->EF-M adapter.

The current range of EF-M lenses suggests to me that the EOS-M range is destined to be at the XXXD/XXD level – most will never even see their lens changed and people will be happy with them. Anyone who’s assiduously built up a collection of EF-M lenses in the hope that something better would come along has seriously mis-read their Canon tealeaves.

I’m much more interested in where the EOS-R line goes, both upwards to 5D/1D levels and how they handle the 7D question.

The 7D question

What place is there for a high spec APS-C camera in Canon’s range. It’s a similar question to the place of the D500 with respect to Nikon’s Z series.

The 7D mk3 (info/rumours) is by some measures, well overdue. An update for the 7D (launched 2014) could well be Canon’s first APS-C EOS-R, with really advanced performance and setting out the stall for a major shift to mirrorless. Follow that with a super high res full frame version and something to match the 1D X mk3 and Canon has a range that says EOS-R is the future for high end imaging. Of course just how soon Canon decide to really push the move to EOS R, and how many more DSLR models we see as updates is unknown, and I’d expect a lot of flexibility in the timing of Canon’s plans at the moment.

Where does this leave EF-M?  I don’t know, but watching over the last few years I’ve just never seen it as any more than Canon dipping their toes into the mirrorless market, and whilst the lenses were nice they were never going to be classics in 20 years time.

Update: The announcement of an EF-M 32/1.4 fast ‘standard’ prime certainly looks like a definite positive statement towards EF-M and the small camera market.

I believe that there is far too much read into some spurious ‘upgrade path’ from basic Rebel, through xxD and on to the dizzy heights of the 5 and 1 series.

If you buy a ‘Rebel’ level (xxxD here) Canon DSLR are you really going to hold on to some of those cheap EF-S lenses as you ‘move up’? I think not, and I suspects Canon’s business intelligence tells them that too, despite what the internet says.

I suspect I’ll move to mirrorless in a few years, just because of the features of a particular camera body – yes, I’ll use adapters for some of my lenses, but I’ll get RF lenses too – if they are better and what I need for the job ;-)

Beware the internet noise

Like many others I’m looking forward to Canon’s next step in their lens journey.

What I’ve written here are just my own opinions based on my own photography. Over the next few month expect an awful lot of froth and drivel over how Canon/Nikon/Sony have completely messed thing up – just don’t forget to go out and take some photos with what you’ve got ;-)

Other EOS R and RF info here

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