PhotoPlus The Canon Magazine – August 2019

The Canon Magazine 105

astro lenses

Fringing

Canon 16-35mm

Irix 15mm

Samyang 10mmSamyang 14mmSigma 14mmSigma 14-24mm

Tamron 15-30mmTokina 11-20mm

f/2.8

f/8

f/16

Lower values

represent less

fringing, and

therefore better

performance

Centre Edge Corner

2500

2000

1500

1000

500

Sharpness

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

3

6

4

5

2

1

SIGMA 14-24mm f/2.8

DG HSM | A £ 116 9 / $12 9 9

Sigma leads the way for full-frame compatible

wide-angle zooms

his Sigma gives a wider

viewing angle than any

of the other zoom lenses

on test, matching the

Samyang and Sigma 14mm

primes. Sigma also makes a

wider 12-24mm Art zoom but,

like the Canon 11-24mm, it

has a slower aperture of f/4

that’s less ideal for

astrophotography.

Exotic glass includes an

ultra-high-precision moulded

glass aspherical front element,

along with three FLD

(‘Fluorite’ Low Dispersion) and

three SLD (Special Low

Dispersion) elements. As with

the Sigma 14mm prime lens

on test, there’s a fast and quiet

ring-type ultrasonic autofocus

system with a focus distance

scale. Being a zoom rather

than prime, however, there

are no depth of field markings.

Build quality and handling

are excellent in both Sigma

lenses, but the zoom gains a

full set of weather-seals,

whereas the prime lens only

has a sealed mounting plate.

Again, the front element has a

keep-clean fluorine coating.

Both lenses are compatible

with Sigma’s optional USB

Dock for fine-tuning,

customization and applying

firmware updates.

Performance

Even when shooting at the

shortest focal length with the

widest aperture, the lens

delivers ace sharpness across

the frame, easing ahead of the

Canon 16-35mm towards the

edges and corners. Vignetting

is minimal and, in real-world

shooting rather than with

close-range test charts, barrel

distortion is negligible. All in

all, it delivers top quality and

all-round performance.

FeATUres

VerdIc T

01

A moisture- and

grease-repellent

coating is applied to

the front element.

02

The smooth-action

focus ring is at the

front, with the zoom

ring at the rear.

03

Includes three

‘Fluorite’ Low

Dispersion, three

Special Low

Dispersion and three

aspherical elements.

04

Top-quality

construction.

05

This one is

compatible with the

optional USB Dock.

FeATUres

BUIld & hAndlIng

PerFormAnce

VAlUe

oVerAll

05

01

03

T

Co LoUr FrINGING

Certain aberrations can alter the stars

ur lab tests check on the severity of

chromatic aberration. This is a form of

colour fringing that affects high-contrast

transitions at or near the edges and

corners of the image frame. So it can give bright

stars against a dark sky the appearance of red

and cyan borders. In-camera corrections for

lateral chromatic aberrations are available in

most recent DSLRs for the Canon and Sigma

lenses here, but not for other makes of lenses.

o

02

04