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Saturday, 9 December 2023

Canon RF-S 10-18mm f4.5-6.3 IS STM Ultrawide zoom lens initial user review 9 December 2023

 

This is a bit unusual. We don't think to use an ultrawide lens to photograph birds. But this juvenile Australian magpie has been visiting since he was a fledgling. He is accustomed to being close and to being photographed, in this case with the camera only a few centimeters away. We can see the character of the out of focus rendition in the syzigium trees in the background. Eye detect worked well on the R10

I bought this new RF-S system ultrawide zoom as soon as it became available in Australia and have been testing it for several days.

Here is my initial review. Nobody gives me cameras to review. I buy them. I am not beholden to any entity in the camera business.

My reviews are therefore unbiassed. I go where the results take me and report my findings and experiences without pressure or influence.

By way of background, Canon has a long history of producing excellent ultrawide zooms. In the current full frame RF mount catalogue we have three UWA zoom offerings. These are the RF 15-35mm f2.8 L, 14-35mm f4 L and  15-30mm f4.5-6.3 IS STM. I have the latter and find it a very useful compact ultrawide zoom which delivers excellent results within its focal length and aperture range envelope.

Canon also has a history of making very good ultrawide zooms for its APSC crop sensor models.

In 2013 we got the EF-M 11-22mm f4-5.6 IS STM, 220 grams, length 58mm diameter 61mm, filter 55mm, 12 elements, 9 groups, max magnification 0.3x. I owned one of these when I was using the EF-M system (now discontinued)  and was very pleased with the results which it was able to deliver.

In 2014 the crop sensor DSLR system got the  EF-S 10-18mm f4.5-5.6, 240 grams, length 72mm, diameter 75mm, filter 67mm, 14 elements, 11 groups, max magnification 0.15x.

Now in 2023 we have the RF-S 10-18mm f4.5-6.3 IS STM at 150 grams, length 45mm diameter 62/69 mm, filter 49mm, 12 elements, 10 groups, 2 UD 1 asph, max mag 0.5x. The lens is made in Malaysia.

So we see this latest iteration of the crop sensor UWA zoom is the smallest and lightest yet with the bonus of the greatest maximum magnification for close-up capability.

RF-S 10-18mm on EOS R10, unlocked

Description

The RF-S 10-18mm is styled to match existing RF-S lenses. It uses an outer housing similar to but slightly different in detail from that on the 18-45mm kit lens and the optics are completely different. Both  have to be extended for use by turning the zoom ring against an initial restraint to the widest zoom position.  The lens extends most (11mm) at 10mm focal length and least (9mm) at 14mm focal length.

This continues the trend we have seen in the RF-S 18-45mm, RF 24-50mm and RF 15-30mm each of which utilises the longest physical extension at the shortest focal length.

The unlocking and zoom action on this lens feels appreciably smoother than we find on the 18-45mm kit lens.

 The rear element extends 9mm behind the face of the mount. The flangeback distance is 20mm so with space required for the shutter there is not much unoccupied space between the lens and the image sensor.

Construction is all plastic including the lens mount as is usual for Canon EF-M and RF-S crop sensor lenses.

The zoom ring turns smoothly as does the focus/control ring. A bit more drag on the front ring might be appreciated.

As usual with RF-S lenses there are no other controls on the lens barrel.

AF/MF selection is made either in a menu or on some cameras such as the R10 which I used for this test, via a rotary lever on the front of the camera body.

Note that R10 firmware 1.4.0 must be installed for correct operation of the RF-S 10-18mm lens. The camera posts a warning about this on the screen.

Stabiliser on/off is best selected in the Q Menu.

There are lugs for mounting a reversible EW-53B lens hood but this is not supplied.

All my testing was done with a 49mm Hoya HD2 clear protect filter in place.

Construction diagram


Image quality

Unfortunately Adobe has not yet (7 December 2023) released a profile for the lens so a full assessment using Raw files is not yet possible. For this initial review I have used JPGs but these usually do not reveal all that the lens has to offer.

Update 14 December 2023: The Adobe profile is now available for Camera Raw and Lightroom. 

I have  tested images with the new profile and find the corrections very good. Distortion is almost perfectly corrected. Peripheral shading is substantially corrected. Framing is just a touch wider than the JPGs. Corner sharpness is better than we see in the JPGs. Best aperture for sharpness across the frame at 10mm focal length is f5.6. Overall the converted Raw files have better sharpness, contrast, clarity and color than the JPGs.

I can say the lens is very sharp in a large central area of the frame at all focal lengths. In the JPGs there is very mild residual barrel distortion.

At 10mm focal length fine details are less sharply rendered around the periphery than in the large central area, with obvious stretching of the shape of flat subject elements due to the extreme wide view. This is most apparent on the test chart in the corners.

The corners improve at f5.6 which gives the best overall sharpness and detail rendition at 10mm.

At 12, 14, 16 and 18 mm the test chart shows very good sharpness across the frame and into the corners. Best overall result comes at f5.6 at 12 and 14mm and at f6.3 at 16 and 18mm.

Sharpness at f8 looks good but we can expect to see some softening from f11 due to diffraction if we look closely. For most photographic purposes I would use this lens at f5.0-6.3.

As with the RF-S 18-45mm kit lens we are for practical purposes quite restricted in the range of apertures which can be used for best results.  That is not necessarily a bad thing, it comes with the territory and is a limitation of which we need to be aware when using the lens.

There is massive barrel distortion at 10mm in uncorrected Raw files. Barrel distortion persists to a smaller degree right through to 18mm.

It appears the actual focal length of the lens is considerably less than 10mm at the wide end with a field of view in uncorrected Raw files much larger than the (JPG) image seen in the viewfinder.

This style of lens design is quite common in Canon RF and RF-S wide angle offerings (and those from all the other lens makers these days) with reliance on post capture processing to achieve the final output as a JPG or corrected Raw file.

Contrary to the wailings of some old-style lens reviewers, there is nothing wrong with this approach but it is something to know about and understand. I know of no sense in which computational correction of distortion is inferior to optical correction. It is certainly less expensive and enables smaller, lighter,  less expensive lenses like the one being reviewed here, to be made available to consumers.

At 10mm f5.6


I see no significant decentering in my copy of the lens.

There is mild purple color fringing in the corners at high contrast edges such as fine foliage against a hot sky. This is easily corrected in post processing.

As with all ultrawide zooms we can provoke various forms of veiling and green blob type flares with the sun just outside the frame. I tested the lens in the most unfavourable condition which is very bright hazy sun which throws light onto the lens in many different directions. Overall I find flare levels typical of modern ultrawide zooms and easy enough to avoid if we understand the conditions likely to cause it.

Out of focus backgrounds are not much of an issue with a lens like this. However when I deliberately create  out of focus backgrounds they look soft and smooth with no nasty lines.

I tested for “focus breathing”. The normal characteristic of a simple lens which focusses by moving the whole optical structure back and forth is that the effective focal length when close focussed (lens moved away from the sensor) is greater than the effective focal length when far focussed (lens closer to the sensor). So when we focus back and forth the effective field of view expands and contracts, hence the term “breathing”.  This can be undesirable especially when recording video.

The RF-S 10-18 exhibits just a tiny amount of this phenomenon, not really noticeable unless we are specifically looking for it.


MTF charts (Canon)

Performance

Autofocus for stills is fast, accurate and reliable. Autofocus in video recording is optimised for smoothness rather than outright speed. This is more appropriate to the requirements of video capture.   Face/eye detect work just fine on the R10 with stills or video.

The image stabiliser is very effective. I tested the lens on the EOS R10. With the stabiliser on I am able to get sharp shots hand held at a shutter speed about three EV steps slower on average than without the stabiliser. This is about the same result I get with most RF and RF-S lenses using my standard test method.

With careful breath control and elbows on a table I get sharp shots down to 0.8 seconds at 16mm focal length.

This ultrawide can do ultra-close-ups !   At 18mm the lens will focus on a subject almost touching the front element. I am not sure how useful this might be in the field but the capability is there if we can find a use for it.

Ultrawide view good for indoor architecture on a budget

Summary

When Canon announced the RF-S subsystem I hoped they would adapt the excellent EF-M 11-22mm lens to the new mount.

In the event they took the next step and delivered an ultrawide zoom which is even smaller and lighter than the EF-M 11-22mm with the bonus of closer focussing and negligible field of view change with focussing.

The optical capabilities are excellent across the focal length and the somewhat limited effective aperture range with just a bit of softness in the corners at 10mm, which I doubt will be noticed in most photos. Overall I think Canon’s designers have done a very good job with this lens. There are not many ultrawide zooms for any camera system which offer such pleasing optical and mechanical capability in such a remarkably compact, user-friendly package.

I think this lens is a must-buy for any photographer putting together a compact photo kit using the Canon RF-S subsystem.


Alternatives

We can fit the Canon EF-S 10-18mm with the appropriate adapter. If we already have the lens and the adapter that can provide a low cost entry to ultrawide fun in the RF-S system. But see the attached comparison photo. There is no way I would recommend buying the EF-S lens to fit on an RF-S mount camera.

There are numerous third party offerings from 7 Artisans and Laowa and others in the 10-12mm focal length range. But they are manual focus only, are primes not zooms, have no stabiliser and most have no contacts for the RF mount. There are plenty of them on the market so I have to assume they are selling well enough.

For the photo-enthusiast who likes constantly adjusting manual focus, aperture and ISO sensitivity, using one of these manual lenses might be regarded as part of the photographic experience.

But I just find them frustrating and am unable to make a case to buy one.

Another alternative is one of the  Canon RF full frame options.

The EOS R8 with RF 15-30mm f4.5-6.3 is a handy, compact ultrawide kit which delivers very good results across the focal length and aperture range.

The R8 and R10 both have 24Mpx. However  full frame pixels have advantages in clarity, color depth, dynamic range and noise over the smaller APSC pixels.

On my tests the R8 with RF 15-30mm kit delivers better sharpness, clarity, dynamic range and useful aperture range with lower noise levels at all focal length, aperture and ISO sensitivity levels than the R10 with RF-S 10-18mm kit. The difference between the two kits is more subtle than huge but it is consistent across all parameters of capability.

The crop sensor kit is smaller, lighter and less expensive.

You pays your money and makes your choice. At least some of us are fortunate enough to have a choice.

 


 

 

 

 

 

 

 

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