Sigma 24-70mm f/2.8 DG OS HSM Art

Does this stan­dard zoom suc­ceed at of­fer­ing top-level per­for­mance for to­day’s era of high­res­o­lu­tion cam­eras? Michael Topham finds out

Amateur Photographer - - 7days -

Michael Topham tests this stun­ning stan­dard zoom

Full-frame DSLR and mir­ror­less cam­era users have a tough de­ci­sion to make when choos­ing a stan­dard zoom. Opt for one that cov­ers a fo­cal length of around 24-105mm with a max­i­mum aper­ture of f/4 and you’ll find there’s a sav­ing to be made over a 24-70mm f/2.8. What you save in cost and gain in hav­ing a bit more reach at the long end you lose in terms of max­i­mum aper­ture though. If you’re after a ver­sa­tile zoom that per­forms as well in low light as it does cre­at­ing a shal­low depth of field wide open, a pro-spec 24-70mm f/2.8 is the way to go.

The Sigma 24-70mm f/2.8 DG OS HSM Art re­places the ten-year- old Sigma 24-70mm f/2.8 EX DG HSM and is a more af­ford­able al­ter­na­tive to the Canon EF 24-70mm f/2.8L II USM (£1,739), Nikon AF-S 24-70mm f/2.8E ED VR (£2,099) and Sony FE 2470mm f/2.8 G Mas­ter (£1,849). It’s a lens we’ve been in­tend­ing to re­view since its ar­rival ear­lier this year, but how good is it? And should users look­ing for one of the finest-per­form­ing stan­dard zoom lenses con­sider it?

Fea­tures

We’re look­ing at a lens that’s de­signed as a go-to for dif­fer­ent pho­to­graphic ap­pli­ca­tions. To max­imise its ap­peal with a wide range of users it has an op­ti­cal de­sign that’s op­ti­mised for DSLRs and mir­ror­less cam­eras boast­ing a res­o­lu­tion of up to 50 mil­lion pix­els. The lens con­struc­tion con­sists of 19 el­e­ments in 14 groups with 9 rounded aper­ture blades. As part of this de­sign, three spe­cial low dis­per­sion (SLD) glass el­e­ments and four as­pher­i­cal el­e­ments are used to cur­tail op­ti­cal aber­ra­tions. To keep flare and ghost­ing un­der con­trol the front el­e­ment ben­e­fits from Sigma’s Su­per Multi- Layer Coat­ing that also con­trib­utes to sharp, high- con­trast im­ages in back­lit con­di­tions. Nikon users will find that the lens also in­cor­po­rates an elec­tro­mag­netic di­aphragm mech­a­nism that al­lows it to re­ceive the ap­pro­pri­ate sig­nals from the cam­era body for a re­li­able auto- ex­po­sure per­for­mance dur­ing con­tin­u­ous shoot­ing.

Sigma has once again used its hy­per­sonic mo­tor (HSM) to keep fo­cus­ing fast and quiet, but this has been re­fined since pre­vi­ous ver­sions to de­liver 1.3x more torque and

pro­vide a more sta­ble per­for­mance across its 37cm-in­fin­ity fo­cus dis­tance range. Un­like the Canon EF 24-70mm f/2.8L II USM, this Sigma zoom fea­tures an op­ti­cal sta­biliser that al­lows you to shoot four stops slower than would oth­er­wise be pos­si­ble; how­ever this doesn’t trump an­other of its close ri­vals – the Tam­ron 24-70mm f/2.8 Di VC USD G2 (£1,249), which has the high­est vi­bra­tion com­pen­sa­tion level of its class and is ef­fec­tive to five stops. Other note­wor­thy fea­tures in­clude full-time man­ual fo­cus, which al­lows the lens to be switched to man­ual fo­cus sim­ply by ro­tat­ing the fo­cus ring, an 82mm fil­ter thread, and full com­pat­i­bil­ity with Sigma’s USB dock to up­date firmware and ad­just fo­cus­ing pa­ram­e­ters us­ing the com­pany’s Op­ti­miza­tion Pro soft­ware. As things stand the lens is avail­able in Canon, Nikon and Sigma mounts, but isn’t cur­rently avail­able in Sony E-mount. Any­one wish­ing to pair a Canon or Sigma mount ver­sion of this lens with a Sony A7-se­ries cam­era will want to use Sigma’s MC-11 adapter (£199).

Build and han­dling

The lens has a prac­ti­cal de­sign. At a glance, it could eas­ily be mis­taken for the man­u­fac­turer’s 24-105mm f/4 DG OS HSM, but in terms of size it’s frac­tion­ally thin­ner and slightly stub­bier. Some will be dis­ap­pointed to read that it’s not a weather-sealed op­tic, but the bar­rel feels strong and ro­bust which should see it stand up to the chal­leng­ing shoot­ing en­vi­ron­ments that se­ri­ous pho­tog­ra­phers en­counter. The bar­rel con­tains a large amount of metal in its con­struc­tion and ex­ter­nal mov­ing parts fea­ture ther­mally sta­ble com­pos­ite (TSC), which is re­sis­tant to ther­mal ex­pan­sion and con­trac­tion. At the rear a rub­ber ring com­presses against the cam­era mount to form an ef­fec­tive seal against dust and mois­ture. The front el­e­ment also fea­tures a wa­ter- and oil-re­pel­lent coat­ing that al­lows it to be wiped clean eas­ily.

In terms of weight it’s heav­ier than its Canon, Tam­ron and Sony ri­vals, but is 50g lighter than Nikon’s of­fer­ing. As with most lenses that weigh over 1kg, it han­dles best with cam­eras that of­fer a large, com­fort­able hand­grip and it didn’t show any sign of zoom creep, which is im­por­tant, as it doesn’t have a zoom lock. A fairly thin man­ual fo­cus ring is po­si­tioned in front of the fo­cus dis­tance win­dow. Ahead of this is the zoom ring that has its fo­cal length mark­ings printed to­wards the front. Both the zoom and fo­cus rings are rub­berised and it’s easy enough to de­ci­pher which is which from be­hind the cam­era. The feed­back of both rings on our re­view sam­ple couldn’t be bet­ter. The man­ual fo­cus ring pro­vides suf­fi­cient re­sis­tance for pre­cise fo­cus­ing ad­just­ments and the zoom ring op­er­ates con­sis­tently smoothly and needs very lit­tle ef­fort to ex­tend it to its max­i­mum reach. There are two switches on the side of the bar­rel. Set­ting the AF/MF switch to its cen­tral po­si­tion en­gages man­ual over­ride (MO) and the op­ti­cal sta­bil­i­sa­tion is sim­ply set to ei­ther on or off us­ing the switch be­low.

Image qual­ity

One of the ben­e­fits of choos­ing a stan­dard zoom with a con­stant aper­ture of f/2.8 ahead of an f/4 ver­sion is the way it per­mits the use of faster shut­ter speeds in low light. The

‘ The zoom ring op­er­ates con­sis­tently smoothly’

open­ing image to this re­view is a good ex­am­ple and by shoot­ing wide open at f/2.8 I was able to keep the sen­si­tiv­ity be­low ISO 1000 while main­tain­ing a 1/60sec shut­ter speed in or­der to keep the sub­ject sharp and the image ab­sent of hand­shake – aided by the ef­fec­tive op­ti­cal sta­bil­i­sa­tion, I should add. Our Image En­gi­neer­ing tests, which are car­ried out at each aper­ture set­ting at three fo­cal lengths, re­vealed a spike in cen­tre sharp­ness when the lens is stopped down from f/2.8 to f/4, with high sharp­ness fi gures be­ing re­turned be­tween f/5.6 and f/8. Cor­ner sharp­ness is bet­ter at wider fo­cal lengths than at the long end and im­proves grad­u­ally as it’s stopped down to f/5.6-f/8. While the sharpest re­sults are ob­tained by stop­ping down, shoot­ing at f/2.8 cre­ates some very sat­is­fy­ing im­ages. As my sam­ple im­ages that sup­port this re­view il­lus­trate, open­ing the lens to f/2.8 is use­ful when you want to em­pha­sise a sub­ject from a busy back­ground or sur­round­ings and cre­ate a pleas­ing bokeh in out- of-fo­cus ar­eas.

Vignetting is prom­i­nent at the wide end of the zoom at f/2.8, where cor­ners ap­pear ap­prox­i­mately 1.4EV darker than the cen­tre. Cor­ner shad­ing is less ob­vi­ous at f/4 and by stop­ping down to f/5.6 it van­ishes al­most com­pletely. The lens is sup­ported by Adobe so if you find your­self shoot­ing at wide aper­tures and would like to re­move vignetting later dur­ing post-pro­cess­ing you can se­lect the En­able Pro­file Cor­rec­tions op­tion from within Light­room or Pho­to­shop and it’ll au­to­mat­i­cally and ef­fec­tively cor­rect the image for you. The same can be said for cor­rect­ing dis­tor­tion. Leave the image un­touched and you’ll be aware of bar­rel dis­tor­tion at 24mm, which di­min­ishes as you zoom in to­wards 50mm. Mild pin­cush­ion dis­tor­tion also ap­pears as you en­croach 70mm. This level of dis­tor­tion isn’t a ma­jor con­cern how­ever. It’s eas­ily fixed and is com­mon with most stan­dard zoom lenses that cover a sim­i­lar fo­cal length.

An ex­am­ple of cen­tre sharp­ness wide open at the far end of the zoom Canon EOS 5DS R, 1/400sec at f/2.8, ISO 200

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