PhotoPlus The Canon Magazine – August 2019

100 http://www.digitalcameraworld.com

SUPERTEST

Centre Edge Corner

2500

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Sharpness

f/1/8f/2.8 f/4 f/5.6 f/8 f/11 f/16f/22

CANoN EF 16-35mm

f/2.8L USM III £18 49 / $1899

Launched nearly three years ago, this Mk III zoom

received a major overhaul

anon’s most ideal zoom

lens for full-frame

astrophotography, this

one isn’t as wide-angle

as the EF 11-24mm f/4L USM,

but is an all-important f-stop

faster. The maximum viewing

angle is slightly less than the

14mm and 15mm full-frame

lenses on test, equating to 108

degrees compared with 114 or

110 degrees.

This lens gains a large and

complex double-surface GMO

(Glass Moulded) aspherical

element at the front, adding to

two UD (Ultra-low Dispersion)

elements and a ground

aspherical element at the rear.

Upgraded, high-tech coatings

include both SWC

(SubWavelength Coating) and

ASC (Air Sphere Coating) for

greater resistance to ghosting

and flare. Weather-resistant

attributes are extended to

include moisture- and grease-

repellent fluorine coatings on

the front and rear elements.

The lens is quite long at

128mm, considering that it

doesn’t have a built-in fixed

hood. Unlike with most lenses

here, the separate bayonet-fit

hood enables the easy

attachment of filters, via an

82mm thread. Build quality

is up to Canon’s usual robust

L-series standards.

Performance

Sharpness and contrast are

impressive across the zoom.

The Mk III has much improved

corner-sharpness compared

with the previous edition, but

still lags behind the competing

Sigma 14-24mm zoom on test.

There’s very little spherical

aberration at f/2.8, but coma

and astigmatism can be quite

visible near the extreme

corners of the frame.

FeATUres

VerdIc T

01

There’s a filter

attachment thread

and separate hood.

02

Fluorine coatings are

applied to the front

and rear elements.

03

The inner barrel

extends during

zooming but the

overall length

remains fixed.

04

Rotational travel

of the focus ring

is short.

05

Fast autofocus

speeds are enabled

by a new and more

powerful central

processor unit.

FeATUres

BUIld & hAndlIng

PerFormAnce

VAlUe

oVerAll

01

04

02

03

C

n addition to our usual range of real-world and lab-based

testing, we focused on aberrations that affect the

performance of lenses for astrophotography at their

widest apertures. Towards the corners of the image frame, these

include vignetting, ‘coma’ which gives stars and other celestial

bodies the appearance of having a comet-like tail and

‘astigmatism’, which turns dots of light into lines.

Spherical aberration can occur throughout the entire

image frame, giving points of light a soft halo effect. All of these

aberrations tend to be reduced when narrowing the aperture by

an f-stop from its widest setting. For zoom lenses, the results of

lab tests shown on the following pages highlight performance at

their shortest focal length. This is generally their preferred zoom

setting for astrophotography, and the closest equivalent to the

focal lengths of the prime lenses on test.

How wE TEST

We’re paid particular attention to lens

aberrations that are problematic when

shooting the night sky

I

05