Canon RF 28mm f2.8 lens on EOS R7 APSC

 

Bushland scene Canon EOS R7 with RF 28mm f2.8.  6960 x 4640 pixels

I reviewed this very interesting little lens on EOS R5 full frame in August 2023. You can read that review here.

By way of a follow-up, here are some of my impressions of this lens on the Canon EOS R7, an  APSC sensor model. 

The crop factor of 1.6x on Canon APSC gives a full frame equivalent focal length of 28 x 1.6 = 44.8mm.

Pictures from the R7 have 6960 x 4640 = 32,294,400 effective pixels.

If this sensor were to be scaled up to full frame 24x36mm size with the same pixel pitch it would have about 83million pixels. The highest full frame pixel count on a consumer full frame camera model at the time of writing is around 67 million on the new Sony A7R-6. 

We quite often see in formal lens tests that very good lenses designed for typical full frame pixel counts are not as convincing when asked to resolve the very high pixel density of the R7. 

We also saw this when Fujifilm went from around 26 Mpx on APSC to 40 Mpx on the same sensor size. If scaled up this would give about 90 Mpx on full frame. Several reviewers reported that the X-100-6 with 40Mpx appeared unable to deliver any more image detail than the X-100-5 with 26Mpx. The lens used in this series was upgraded for the X100-5 but not further upgraded for the X100-6.  Apparently it is unable to resolve sufficient detail to fully utilise the sensor pixel density. 

This is a heavy crop of the top photo, originally 1647 x 1294 pixels. I enlarged it a  bit in Photoshop before publishing. Google Blogger is designed for speed of loading not fine detail so you might not be able to appreciate the actual amount of detail which this camera-lens combination can deliver.

I recently took my R7 into the bush around Sydney to test the imaging performance of the RF28mm f2.8 on this APSC body. I chose a National Park area with predominantly heath and some dry forest. For those unfamiliar, much of the bushland around Sydney is very dense and convoluted with masses of tangled native plants all competing for the same space on planet earth.

This type of subject presents a substantial challenge for any lens/sensor/processor combination especially when the foliage is backlit against hard bright sunlight. The leaves of many Australian plants are shiny so as to protect themselves from the sun’s rays. This is challenging for photography as it creates thousands of intense specular highlights in the frame. 

The R7 with RF 28mm f2.8 is only slightly larger than a Fujifilm X-100-6 especially if the Fuji is fitted with an accessory grip

The questions I wanted to answer are:

* Has the RF28mm f2.8 sufficient resolving capacity for  the R7 sensor ?

* Can it handle the specular highlights without loss of sharpness due to local flaring ?

* Are there any problems or issues which might lead to difficulty using this lens on the R7 ?

I first ran static, controlled, formal tests  photographing a test chart in even lighting with the camera on a tripod. 

This showed me that the RF28mm f2.8 is, on this test, just slightly better than my usual best lens the Sigma 18-50mm f2.8. This is most evident at f2.8 around the periphery but also slightly visible at f8.

In the bush, hand held,  the superiority of the RF28mm f2.8 is more apparent. At my usual landscape aperture of f8, my pictures with the 28 f2.8 are remarkably sharp and detailed right into the far corners, where the prime is clearly better than the zoom. There is no significant color fringing on most photos even though backlit fine foliage is a subject type generally guaranteed to elicit a bit of color fringing even on otherwise excellent lenses.

In addition the specular highlights look clean and well defined, even at 200% on screen. 

The one potential weakness of the RF28 f2.8 is flare with the sun shining directly onto the front element of the lens.  Veiling flare is easily produced with the sun just outside the frame, sometimes together with various colored circular flare patterns. I had no lens hood for my initial test so I held the camera in my right hand and shaded the lens with my left hand. Another strategy is to move the camera into the shade of a tree. Anything to keep direct sun off the front element.

R7 with RF28mm f2.8 with JJC LW-EW 55 hood mounted in front of a clear protect filter

Several lens hoods are available for the RF 28mm f2.8. Each of these is designed for use on a full frame body. 

The Canon EW-55 screw-in type maintains the low profile of the pancake lens. It is designed so a filter screws onto the front of the lens hood. The JJC LW-EW55 is a copy of the Canon one. We can, if desired, mount a filter behind the lens hood. This will cause vignetting on full frame but not on APSC.

JJC also offer the LH-EW55II which is a reversible bayonet-fit petal type hood which mounts to a screw-in adapter on the front of the lens. This is a much larger and more traditional type of filter which some users might prefer although it effectively doubles the projection of the lens/filter unit in front of the camera. 

Conclusion    The RF28mm f2.8 lens is eminently suitable for Canon APSC cameras, particularly for those with IBIS, which is just the R7 at the time of writing. It is able to transfer a remarkable amount of detailed information from subject to imaging sensor.

Just keep direct sunlight off the front element.