Canon EOS R – Full Frame Mirrorless. Is it worth it?

by | Nov 25, 2018 | Uncategorized | 0 comments

I have used many APS-C mirrorless cameras, from the diminutive Canon EOS M100 to the medium sized Samsung NX500 to the SLR like Samsung NX1 and I have loved them all.

But the appeal of ‘full frame’ cameras is strong. After all, full frame must mean better pictures, surely? Sadly, not. No camera will make you take better pictures. Photography is an art where composition and understanding the light trump all technical advances. And virtually all cameras allow sufficient control over white balance, shutter speed and aperture to enable a good photographer to make great images.

(By full frame, I mean a sensor that is equivalent in size to a single frame of 35MM film.)

Full frame benefits

The benefits of full frame over smaller formats are usually touted as follows:

  • Better image quality
  • Better control of depth of field, especially if you want shallow DOF
  • Better low light performance
  • Bigger dynamic range
  • Higher resolution (more mega-pixels)

Not all the above are true and not all of them are true all of the time. Let’s have a look at them:

Better IQ and Low Light performance and dynamic range

A bigger sensor has bigger pixels and therefore gathers more light. This is a gross oversimplification. It is the lens that ‘funnels’ the light onto the sensor and provided the lens is putting enough light onto the sensor then the image quality will be fine with an APS-C sensor.

Full frame lenses tend to be ‘bigger’ than the equivalent APS-C lens and, therefore, adds more light. By that I mean that, as there is a ‘crop’ factor involved with APS-C cameras, you tend to use a wider lens on an APS-C camera than on a full frame.

For example, if you want a (very) wide-angle lens on a Canon APS-C then you may end up using the excellent EF-S 10-18 lens. However, on full frame the same angle of view is achieved using a 16-35MM lens. And here’s something that is often misunderstood: at the same F stop (f/2.8, f/8, etc) the 16-35MM lens gathers more light than the 10-18MM.

Why? Because:

The f-number of an optical system is the ratio of the system’s focal length to the diameter of the entrance pupil. 

f/8 on a 10MM lens is smaller in diameter than f/8 on a 16MM lens. The bigger lens, simply because of physics, lets in more light.

When there is insufficient light to be ‘collected’ by the pixels on an APS-C sensor there will be more light on a full frame sensor, provided the lens choice is as described above.

So, full frame sometimes gives better image quality but that’s due to the lens and not the sensor.

However, full frame sensor pixels (can be) bigger and so have a better signal to noise ratio, and this is a definite plus. Additionally, such sensors may have better dynamic range – they can record details from a wider range of luminance and that is a good thing.

Therefore, if the light is nice and bright and the dynamic range is not too great, an APS-C sensor will record  image that is not perceptibly lower quality than a full frame. But in low light or where the dynamic range is higher, the full frame will do better.

That said, APS-C users can compensate for much of this. HDR photography or use of neutral density graduated filters can reduce or eliminate dynamic range issues. And technology has improved APS-C’s low light capabilities and software is very good at removing noise.

There is some advantage to the full frame sensor, but nowhere near as much as you might imagine in every day shooting conditions.

Higher resolution

Full frame sensors do not always have a higher resolution than APS-C sensors. Some do. Some don’t. It is probably true that if you want the most pixels available then you need to go up to full frame or even further to medium or large format sensors. But do you really need to do that?

A 24mp sensor with 6,000 pixels across each horizontal line can, without upscaling, produce a 20 inch print and can easily be up scaled to produce a 30 inch print without discernible loss of quality.

Viewing the image on screen at 100% may well show that the full frame image is higher in quality than the APS-C one, but in normal viewing conditions the differences will be minimal or impossible to detect.

Depth of field

If you read the above carefully you’ll now see that the image sensor isn’t what gives the difference in depth of field. It is the lens, because the aperture diameter is different on equivalent lenses between APS-C and full frame.

For example, if I’m shooting portraits I’m likely to use a 135MM f/2.8 lens on full frame and an 85mm f/2.8 on APS-C. At f/2.8, the full frame will record shallower depth of field because the 135MM’s lens at f/2.8 has a larger aperture than the 85MM lens at f/2.8.

Could you compensate by using the 135MM lens on the APS-C camera? Yes, but you’d need to stand much further back and this might not suit you, or even be possible in the environment you are in.

Of course, when it comes to depth of field, a landscape photographer wants to maximise it and here, ironically, the smaller aperture size of the lens typically used on APS-C camera will give more depth of field. So, my 10MM lens at f/8 on my APS-C camera will produce more depth of field than my 16MM lens at f8 on my full frame camera.

However, the effects of diffraction will be greater on the wider lens for exactly the same reason – the aperture is smaller in size and, at a certain point, will start to distort the light. This is why you often see medium and large format photos that were taken at f/45 (etc) and yet they look so sharp. But f/45 on a medium/large format lens is much larger than it would be on an APS-C or full format equivalent lens.

Full frame costs

One thing that is not open to debate is that full frame cameras cost more financially than smaller formats. It’s easy to see why – they use more materials and the lenses tend (or need) to be bigger. More materials equals more costs. But the cost is significant…

EOS R vs EOD M50

Here’s a comparison between the EOS R and the EOS M50. Prices are in GBP and are correct as of November 2018.


EOS R: £2349.00, body only, £3269.00 including the new 24 – 105mm f/4 IS L lens

EOS M50: £399.00, body only, £509.00 including the EF-M 15-45mm f/3.5-6.3 IS Lens


EOS R: 30.3mp (6,720 x 4,480 pixels)

EOS M50: 24.1mp (6,000 x 4,000 pixels)

Just looking at these two comparisons shows just how much more expensive the full frame camera is and how little (in comparison) you get for it in final image terms. The EOS R can produce a 22 inch print at 300 dpi whereas the EOS M50 can ‘only’ do 20 inches. This is not a big deal.

Of course, the EOR R is better built, is weather sealed and so on. It is probably good value for money but it certainly isn’t over 5 times better than the M50.

(Maybe I should also mention the EOS 6D here. It is a full frame DSLR with 26.2mp and costs £1,549.00. There’s not much in it between this and either of the other cameras resolution wise and suddenly it looks really good value, although its sensor is quite old and DXO Mark has given a low rating to its dynamic range.)

There’s a trick up my sleeve…

There are a number of reasons to pick a full frame mirrorless camera to a full frame DSLR. They are smaller, (sometimes) cheaper, can have silent shutters, more autofocus points and so on. But they have one other massive advantage:

Lens design

Mirrorless cameras allow the lens to be close to the sensor because there’s no mirror getting in the way. And, from what I’ve read about lens design, this means lenses for mirrorless cameras are easier to design and can reach higher image quality. I had noticed that the diminutive pancake lenses on my Samsung mirrorless cameras produced image quality that far outweighed their size and cost. And maybe this is why – they are simply easier to design.

In any case, the lenses Canon has produced to accompany the EOS R seem truly outstanding. Then again, their prices are truly eye watering as well. I was reading Ken Rockwell’s review of the new Canon RF 24-105mm f/4L IS lens and his sample images are probably the sharpest I have ever seen from a zoom.

The downside is that these new RF lenses will not fit anything other than the EOS R, and its successors.

Additionally, if you already own a mirrorless camera with some ‘native’ lenses, such as the EF-M series, you may already have some higher quality lenses. It’s worth checking reviews to check that a lens is substantially better than your existing equipment before making a purchase.

Existing lenses

One appealing factor about the EOS R is, like the EOS M cameras, you can use your EF and EF-S lenses with it via an adaptor. Provided the adaptor is perfectly made then the image quality should be unaffected.

I’ve already pointed out how great this is for EOS M owners. And it seems brilliant for EOS R owners who already own some Canon lenses. Well it is if you own EF lenses, but it’s next to worthless for EF-S lenses. Why?

I had to search Canon’s site for this info: attach an EF-S lens to the EOS R using the adaptor and the camera switches to a cropped 11.3mp mode.

Hmmm. A fat lot of good that is. If all you own are EF-S lenses then the EOS R will be the world’s most expensive APS-C mirrorless camera! Let’s be blunt here: to use the EOS R effectively requires EF lenses or the new RF lenses.

Conclusion – should I buy one?

That depends on what you want and what you can afford.

No camera will make you a better photographer.

But if you have some EF lenses, especially the higher quality ones, and want to get a lighter full frame body then the EOS R is a good match.

If you can afford to get the EOS R with one or more of the new RF lenses then you will probably own the highest resolution optics that Canon make today. Whether or not you’ll actually see any difference in the final results (normal viewing on screen or in print) is another matter altogether.

If you already have an APS-C DSLR (or one of the EOS M cameras) with EF-S lenses and can’t afford to get EF/RF lenses then there is no point getting an EOS R.

From the price point and the fact that the EOS R and the RF lenses are weather sealed, it seems clear that the EOS R is aimed at professionals who will appreciate it being smaller and lighter than their current full frame DSLR. They won’t appreciate the much reduced battery life, however. One of the costs of mirrorless is that the sensor is always on and this chews up batteries in comparison to a DSLR.

Many reviews of the EOS R feel it is an ‘almost there’ camera in that its battery life is short*, it lacks some controls (like an autofocus joystick) and has only one card slot. Professionals will be put off by the latter in particular. Card failures are rare but a dual card slot virtually eliminates the risk of losing a priceless image.

For amateurs and semi-professional photographers, I can’t see a compelling reason to get one unless you want to use an RF lens. The EOS 6D is better value and the EOS 5DS offers far higher resolution for for very little extra (£100)…

The choice of course is yours. It’s the RF lenses that appeal to me, although they probably shouldn’t…**

*On the other hand Ken Rockwell reports getting a fair number of images from a single battery charge, especially when shooting many bursts of images. I have always found that switching the camera off whenever I’m walking around enables whatever mirrorless camera I am using to last all day. With a DSLR I can leave switched it on all day…

**In this regard I compared my Samsung NX1 and the 16-50 and 50-150 S lenses to the EOS R and the new RF 24-105 lens. My research indicates that these lenses performance is approximately the same and the NX1 has similar dynamic range to the EOS R. The EOS R has better high ISO performance, slightly higher resolution and a ton of extra features that make taking pictures easier. But I doubt it would take better landscape images, which would be my use for it. For me, I’d rather wait until Canon produce a much higher resolution mirrorless full frame camera with a better chip that yields much higher dynamic range before it’s worth making the switch…

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