Canon 50mm f/1.8: the evolution of an icon

Anyone interested in photography will surely have heard of the “nifty fifty” – the 50mm standard SLR lens. Almost every single SLR manufacturer had a 50mm lens with and f/1.7, f/1.8 or f/2.0 aperture that was sold as the “kit lens”, and Canon was no exception. These days, “kit lens” has become a dirty word for a cheap, flimsy and poor quality zoom lens, but in the heyday of manual focus photography 50mm kit lenses were among the sharpest, fastest, smallest and lightest lenses available in the whole range, only surpassed in quality by their faster and spendier 50mm f/1.2 and f/1.4 cousins.

Canon is no exception, and over the nearly-60 years since they introduced their first SLR I’d be willing to bet that that combined sales of their 50mm f/1.8 models outnumber every other SLR lens sold, ever. I decided to check out every model Canon has churned out and explore the technologies introduced with each revision. To date, Canon has released fourteen versions of its 50mm f/1.8 since 1959 and while some have been minor revisions, others have been leaps in technology – but all with a shared heritage.

Every single one of these 50mm lenses (except one) has the same optical formula of six elements in four groups – the classic double Gauss arrangement which was first invented in 1888 and is still used to this day.

Lenses

Some of these lenses are directly marked I, II, etc on the lens itself to denote the revision. However some are not marked with the revision, so in these cases the revision is in brackets.

R mount

R 50mm f/1.8 (I) (1959)

Canon launched its first SLR, the Canonflex, in 1959 with just two interchangeable lenses using a new mount, the R mount. Canon’s R lenses were the first to use a breech-lock mounting system – all their previous lenses were equipped with a screw mount for use on rangefinders. The breech mount was superior to the screw mount as no wear occurred on the distance-critical mounting surfaces. It was a bit slower to use though, and some photographers felt that it was difficult to change breech mount lenses with one hand. Nonetheless, the breech mount stayed with the R mount and its successors for two decades.

The R 50mm f/1.8 has two aperture rings which makes it looks like a preset lens, however it is actually an automatic lens. One aperture ring sets the desired aperture that will be used when the photo is taken (although the aperture stays wide open until that point) while the other ring is effectively a depth-of-field control. The lens mount has two levers lever which the camera activates when the photo is taken (to ensure the lens stops down to the desired aperture at that moment, before springing open again) and when the film is advanced. The camera has no way of knowing what aperture the lens is set to, nor does it need to – as the Canonflex cameras had no TTL metering.

The R mount 50mm lenses were officially known as R 50mm f/1.8 but they all carried the designation Super-Canomatic Lens which is probably the coolest name of any camera lens.

R 50mm f/1.8 (II) (1960)

A mark II and III quickly followed the first version with only cosmetic differences.I have the II in my collection.

 

 

It has a larger knurled focus ring but the two aperture rings are closer together. In my opinion this makes them a bit fiddly to use…

R 50mm f/1.8 (III) (1963)

…and apparently someone in 1960 agreed with me because the mark III moved them further apart again.

FL mount

FL 50mm f/1.8 I (1964)

The FL mount replaced the R mount when it was launched with the Canon FX camera in 1964. It shares the same physical lens mount but uses a simplified single-lever system. R and FL lenses and cameras are compatible with each other.

 

 

The design of the lenses was smartened up, too. FL lenses are smaller and lighter than their R-mount predecessors. They scrapped the second aperture ring and instead had a switch which could be set to A (auto) or M (manual). In A, the aperture always remained wide open until the moment of exposure, but in M the aperture stopped down to the value set on the ring.

FL series cameras allowed TTL metering for the first time with stop-down metering. The photographer would keep the aperture wide open for composing and focusing (A mode), but would stop the aperture down in order to get a light meter reading at the correct aperture (M mode, or by using the stop-down lever).

FL 50mm f/1.8 II (1968)

Unlike most mark II lenses from Canon which are minor revisions, the FL 50mm f/1.8 II was a complete optical redesign, and is one of the few that carries the II designation on the lens itself. It was still fundamentally based on the double Gauss formula but had various improvements, including the elimination of astigmatism, reduced aberration and a new magenta/purple lens coating.

FD mount

FD 50mm f/1.8 (I) (1971)

The introduction of the FD mount in 1971 was a gamechanger. It had extra levers and pins on the mount so the camera could tell what the maximum aperture of the lens was, and perform TTL metering with the aperture fully open. This paved the way for full automatic exposure, although the first generation of FD cameras didn’t support that, and were controlled effectively as fully manual cameras with match-needle metering.

 

 

The FD mount also did away with the concept of preset lenses and A/M switches by having an aperture that could be controlled by the body. Setting the aperture ring did not have any effect until the camera commanded the lens to stop down at the moment of exposure.

This generation of lenses (and the mark II that followed it) are known as “chrome nose” lenses, because the filter thread and lens hood bayonet at the front is made from chromed metal.

FD 50mm f/1.8 (II) (1971)

I’ll be honest, I can’t work out the difference between the mark I and the mark II, which was released in the same year. However it is clear that the two “chrome nose” models were only in production for a fairly short time before being replaced, which contributes to their relative scarcity today, compared with the later models.

FD 50mm f/1.8 S.C. (I) (1973)

This lens is the first one to carry the SC designation. SC stands for Spectra Coating which is Canon’s trademark for their multicoating process. Some previous lenses also had the same coating but this was the first version use it as a selling point. There was also a superior SSC (Super Spectra Coating) but this was not used on the lower-range lenses such as the 50mm f/1.8.

The first SC lens is somewhat smaller and lighter than its chrome nose predecessor but otherwise is styled pretty much identically, with the exception that the filter ring and lens bayonet are now made from black plastic.

FD 50mm f/1.8 S.C. (II) (1976)

The mark II is slightly smaller and lighter again than its predecessor, but the most notable difference is that the number of aperture blades has been reduced from six to five. This trend continued with the rest of Canon’s 50mm lenses.

 

 

New FD 50mm f/1.8 (1979)

After 20 years of breech-mount lenses, Canon redesigned the physical latching mechanism and replaced the breech mount with a rotating bayonet mount, known as New FD (sometimes written as FDn). It was fully compatible with the original FD mount.

 

 

At the same time, Canon gave all the New FD lenses a makeover, styling them in black, making them slimmer and using plastic instead of metal. Overall, this means the New FD version is much lighter.

The New FD lenses all have better Super Spectra Coatings (SSC) – except for the New FD 50mm f/1.8 which retains the Spectra Coatings (SC) of the original FD series. The SC and SSC designations were dropped. The optical formula also remains unchanged, however this is the first of Canon’s 50mm f/1.8 lenses to stop down to f/22 instead of f/16. This may be a reflection of the faster films that were becoming available throughout the 1970s.

AC 50mm f/1.8 (1985)

The uncommon AC 50mm f/1.8 was an attempt at retrofitting autofocus capability to the manual focus FD mount. It was only compatible with the Canon T80 camera (although the T80 could use any FD lens). The physical mount was unchanged but the lens also had some electrical contacts alongside the physical linkages to control the autofocus and aperture. It is still possible to focus manually with this lens, but it clearly isn’t what Canon had in mind as the manual focus ring is only accessible with the fingertips through two slots that have been cut on the sides of the lens barrel.

 

 

While this solution “worked”, it wasn’t very good. The autofocus was too slow and inaccurate to be useful, and ultimately Canon decided to throw it all out and start over with the incompatible but autofocus-from-the-ground-up EOS system, which used EF lenses. However the concept was proven and Canon’s engineers continued developing the technology.

This lens is based on the New FD 50mm f/1.8 but differs from it optically in that it can focus down to 50cm – the first of Canon’s 50mm f/1.8 lenses to focus closer than 60cm.

EF mount

EF 50mm f/1.8 (1987)

The EF mount was a radical departure from the R/FL/FD line, and wholly incompatible with it. EF lenses have a different physical mount and no physical linkages – all communication is done electronically. All EF lenses support autofocus and contain motors and circuitry, so they tend to be a bit bulkier than their FD counterparts, although often lighter too, through extensive use of plastics. However, the styling is unrecognisable. With autofocus replacing the prominent focus ring and electronic aperture control from the camera body removing the need for an aperture ring, EF lenses had a much smoother barrel and no need to touch any controls on it during normal use.

The EF 50mm f/1.8 shares the a related optical formula as the New FD 50mm f/1.8 with the same six elements, but splits them into 5 groups rather than 4. In reality this means a group which used to be two elements cemented together is now two elements with an air gap.

EF 50mm f/1.8 II (1990)

The later EF 50mm f/1.8 II is optically identical to the mark I but seems to be an exercise in cost and weight saving. The mount flange is plastic rather than metal (a first for Canon) and the focus ring (which isn’t supposed to be used much, as this is an autofocus lens) is small and fiddly to use.

 

 

The EF 50mm f/1.8 II is the longest-lived of all Canon’s 50mm f/1.8 lenses, making it a whopping 25 years before being replaced. During this time, digital cameras were introduced but in Canon’s case, they used the same EF mount so no modifications were necessary and the same lens continued to be sold.

EF 50mm f/1.8 STM (2015)

As the predecessor of the STM model lasted a quarter of a century, you might wonder what was wrong with it. The EF 50mm f/1.8 STM is optically identical to the I and II EF models, so what changed? In the 2010s, DSLRs with video became the norm, but lenses like the EF 50mm f/1.8 II suffered from noisy and jerky autofocusing which ruined the video. The more expensive lenses boasted a USM designation (ultrasonic motor) and were almost silent during focusing, but for the cheap end of the range, Canon came up with STM (stepper motor) technology for silent autofocusing when shooting video.

The EF 50mm f/1.8 STM also has 7 curved aperture blades – the first Canon 50mm f/1.8 to have more than 6, and presumably designed with video in mind.

Timeline

Some people find it easier to visualise information in graphical form, so I knocked up a timeline showing all the 50mm f/1.8 lenses. For those of you reading in the future, I have assumed that the production of the STM version ceased at the end of 2018 (it probably won’t/didn’t!)

Canon 50mm timeline
Canon 50mm timeline

Specifications

Lens Launched Groups / Elements Aperture blades Minimum aperture Closest focus distance (m) Maximum magnification (x) Filter diameter (mm) Max diameter × length (mm) Weight (g)
R 50mm f/1.8 (I) 1959 4/6 6 16 0.6 58 65×48 295
R 50mm f/1.8 (II) 1960 4/6 6 16 0.6 58 65×48 305
R 50mm f/1.8 (III) 1963 4/6 6 16 0.6 58 65×48 305
FL 50mm f/1.8 I 1964 4/6 6 16 0.6 0.104 48 61×40 228
FL 50mm f/1.8 II 1968 4/6 6 16 0.6 0.103 48 62×43 280
FD 50mm f/1.8 (I) 1971 4/6 6 16 0.6 0.103 55 65×45 305
FD 50mm f/1.8 (II) 1971 4/6 6 16 0.6 0.103 55 65×45 305
FD 50mm f/1.8 S.C. (I) 1973 4/6 6 16 0.6 0.103 55 64×45 255
FD 50mm f/1.8 S.C. (II) 1976 4/6 5 16 0.6 0.103 55 63×39 200
New FD 50mm f/1.8 1979 4/6 5 22 0.6 0.100 52 63×35 170
AC 50mm f/1.8 1985 4/6 5 22 0.5 0.150 52 74×48 210
EF 50mm f/1.8 1987 5/6 5 22 0.45 0.150 52 67×43 190
EF 50mm f/1.8 II 1990 5/6 5 22 0.45 0.150 52 68×41 130
EF 50mm f/1.8 STM 2015 5/6 7 22 0.35 0.21 49 69×39 160

Test pictures

Facts and figures only tell you so much, but some test pictures are worth a thousand rambling words. The only camera I have that can use all of these lenses without resorting to an adapter with corrective optics is my Canon EOS M mirrorless, which can take R/FL/FD lenses via a dumb adapter that is basically an extension tube, and EF lenses via an adapter with electronics (since the EF-M mount used on the EOS M series is electronically compatible with the “classic” EF mount). For R/FL/FD lenses, the EOS M can’t communicate with the lens so it effectively operates in aperture priority mode with stop-down metering. EF lenses work natively.

When I started setting up the test shots, I realised that the R and FL lenses wouldn’t mount on my adapter properly. I noticed that the lenses have a wedge-shaped lump around part of the rear element which fouls the stop-down signal pin of the adapter. As I planned to take all the test images at full aperture, f/1.8, it was easier to simply remove the signal pin, which is just a long screw which sticks in from the outside.

EOS M to FD adapter
EOS M to FD adapter

Now I have the ability to test all of my lenses, but annoyingly I found that my R 50mm f/1.8 II has got a stuck aperture and I wasn’t able to open it up to f/1.8. It’ll need servicing before I can test it, so I omitted it for now.

All of these test shots were taken with the EOS M in aperture priority at f/1.8, fixed white balance (cloudy), ISO 100. The only variable that the camera could change was the shutter speed. The shots were all taken from a tripod, although I do appear to have knocked the alignment a little when changing lenses repeatedly.

The first set of pictures I took was a straight shot of my back garden. In itself, it’s not particularly interesting, but it does give a feel for how each lens looks.

 

There isn’t much to choose between these lenses, so it’s a bit more interesting if we take a 100% crop of the centre, specifically looking at the sharpness. I used the screws in the hinge as a target for manual focus using 10× magnification on the EOS M, but there is still some scope for focus errors at f/1.8. Some evidence of varying colour rendition is also visible.

 

Even more telling, I took a 100% crop from the top-left corner where there was bright sky, which should be a challenge for any lens. I am expecting the older lenses to show flare or loss of contrast. It is worth noting that the EOS M is an APS-C crop-sensor camera, so the corner of the digital frame is not the corner of the frame as it would appear on a 35mm camera.

 

I tested for light fall-off in the corners by shooting an image of the rendered wall of my house. All of the lenses show some evidence of light fall-off but it is significantly better in the EF lens. Notably, this is the only lens in the test sample with the newer “6 elements in 5 groups” optical layout, as opposed to the “6 elements in 4 groups” layout seen in earlier lenses.

 

The centre crop of these thrilling wall pictures was not very interesting, but the corner crop shows up some aberrations. Once again, bear in mind that the EOS M is a crop-sensor camera and the “true” image goes beyond what the EOS M’s sensor can “see”.

 

The FL lens shows significant coma, which we expected, as the FL II’s selling point was better aberration control.

Summary

We’ve taken a look at Canon’s 50mm f/1.8 SLR lenses since 1959 and we’ve had the chance to test a representative selection of them. It is clear that the technology has improved with each generation, enabling new ways of using the lens and improving image quality.

There’s no point in saying which is the “best” but I will say that I have a soft spot for the FL lens. It has a characterful rendition and is small and light. It has nice controls and handles well on a 35mm SLR  and on a mirrorless digital.

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