Last year I sold all my full frame gear in favour of the
Canon EOS R7, a crop sensor mirrorless interchangeable lens model with 32
megapixels.
My preference and practice is to work with zooms, many of
which offer excellent sharpness with good optical characteristics and great
versatility.
But I started to wonder if maybe I could tease out even more
image detail from the R7 with one of the prime lenses which are now available
for Canon APSC cameras.
So I ran a series of tests using my usual test chart with
the camera on tripod and some complex and highly detailed landscape subjects,
mostly shot hand held.
I chose two primes, the Canon RF 24mm f1.8 IS Macro which
can cover full frame if desired and the
Sigma 23mm f1.4 DC DN which only covers the smaller APSC sized sensor.
The zooms are the Canon RF-S 18-150mm f3.5-6.3 IS STM and
the Sigma C 18-50mm f2.8 (constant) DC DN.
I made many photos with the lenses covering the full range
of apertures and focal lengths with a final round of tests at 23/24mm and f2.8
(not available for the RF-S 18-150mm), f4 and f5.6 for close comparison.
The Sigmas do not have an image stabiliser, the Canons do.
The actual tests are boring so I will just offer my
conclusions, but before doing so I need to make some observations on sample
variation in lenses and testing variation in the hands of various photographers
using different methods.
The effect of all these variations is that we can find one
reviewer stating lens A is better than lens B and another reviewer saying the
opposite. I believe it is not necessary to invoke fault or fraud to explain the
range of opinions about any lens model but to acknowledge that there is more
sample variation in making lenses than camera bodies and more variation in lens
test procedures than in measuring camera parameters such as digital noise or
dynamic range.
The main aim of my tests is to discover which lens gives me
the sharpest rendition of fine subject details but I also looked at other lens
characteristics along the way.
| Image may be NSFW. Clik here to view.  |
Canon EOS R7 with Sigma 18-50mm f2.8 at f9. Extremely complex bush scene with difficult backlighting rendered nicely here. |
Results:
My copy of each lens is well centered with no significant
difference in sharpness between the left and right sides of the frame. Each
lens focusses accurately and quickly on the R7.
Each of the lenses is equally very sharp in a large central
area of the frame and toward the edges on the long side of the frame. In this
area I could not pick which lens made which test frame without the exif data.
Most of the differences between the lenses are on the short
side of the frame and in the corners.
Files from the RF-S 18-150mm have slightly lower contrast
and acutance than the Sigmas but contain the same amount of actual visual
information which responds to a touch more contrast and sharpening in Adobe
Camera Raw.
The least satisfactory lens of the group is the Canon RF
24mm f1.8 Macro IS STM. This delivers the softest edges and corners. When the test files are viewed side by side
the RF 24mm is obviously worse than the other three lenses.
I cannot recommend this lens for Canon APSC cameras. I have
also used and tested it on full frame with the same disappointing results.
Next comes the Sigma 23mm f1.4 DC DN. From f2.8 the 23mm offers no better
sharpness across the frame than the 18-50mm f2.8 zoom.
I can recommend this lens only if our use case absolutely
requires an aperture of f1.4-f2. Interiors,
low light situations, stage performances and the like spring to mind. I
find that most of the time, even indoors in low light, f2.8 is quite good and
these days with Adobe Denoise AI and other denoise software available, high ISO
settings are not the problem they once were.
The Sigma 18-50mm f2.8 DC DN is a welcome addition to the catalogue of good
quality zooms now available for Canon RF mount crop sensor cameras. At the time
of writing it is best used on the R7 which has an in body image stabiliser as
the lens does not have an optical stabiliser. It is very compact for a constant
f2.8 zoom, delivers good to very good sharpness across the frame at all focal
lengths and apertures down to about f11 when diffraction at the aperture
diaphragm starts to degrade image quality.
This is, in April 2025, my choice for low light and indoor
work with the Canon R7. It is also good for landscape, street and documentary.
The Canon RF-S 18-150mm IS STM has three times the zoom
range of the Sigma, an optical stabiliser, the best close-up capability of the
four lenses tested here and good to very good image quality across the frame at
all focal lengths and apertures up to about f11. My copy of this lens is a bit
better than the Sigma at 18mm and just as good from 23-50mm, bearing in mind my
comments about contrast and acutance above.
This is the most versatile of the four lenses and the best
for any outdoor work and travel. The extra reach of the 18-150mm is very
welcome in many situations. This lens is
also good indoors at the wide end of the zoom with f3.5 being only 2/3 stop
smaller than the Sigma zoom.
| Image may be NSFW. Clik here to view.  |
Canon EOS R7 with RF-S 18-150mm f3.5-6.3. A good combination for street and lifestyle documentary work |
Summary
My three lens kit for the Canon R7 consists of:
* Ultrawide:
Sigma C 10-18mm f2.8 DC DN
(Full frame equivalent 16-29mm)
* Standard:
Canon RF-S 18-150mm f3.5-6.3 IS STM (Full frame equivalent
29-240mm) or
Sigma C 18-50mm f2.8 DC DN. (Full frame equivalent 29-80mm)
*
Telephoto/sport/action/wildlife:
The Sigma 18-50mm can
be complemented by the very compact Canon RF-S 55-210mm f5-7.1 IS USM. (Full
frame equivalent 88-336mm) Lens test specialists usually ignore or denigrate
this modest little lens but I find it delivers very good image quality over a
useful range of focal lengths.
If our standard lens is the Canon RF-S 18-150mm, then the Canon
RF 100-400mm f5.6-8 IS USM. (Full frame equivalent 160-640mm) is the ideal
telephoto for our kit. This is a full frame lens which gives very good results
on either full frame or crop sensor bodies.
For greater reach I also use the Canon RF 100-500mm f4.5-7.1
L IS USM however this lens is much larger and more expensive than the others
mentioned here.
My preferred lenses are all zooms. I have nothing against
prime lenses having used them exclusively for many years. But zooms have become
smaller, lighter and much better optically than they were a few years ago. The
main advantage of current model primes is their greater maximum aperture which
may be desirable in some low light situations and when visual separation
between subject and background is desired.
Footnote: The sharpest Canon APSC lens I have ever
tested is the EF-M 32mm f1.4.STM which delivers excellent to outstanding
sharpness right from f1.4 on a Canon M6.2 camera body. Unfortunately it lacks
an image stabiliser and autofocus on the M6.2 is slow and jerky. If Canon
introduced an updated version of this with better AF for the RF-S system I
think it would be well received.
Another EF-M lens I would like to see with the RF mount is
the 22mm f2 STM. The selling point of this little lens is its very compact size
together with good sharpness across the frame. When mounted it hardly protrudes
beyond the front of the camera handle.