Digital Camera World » Sigma

Sigma 18-35mm f/1.8: first-ever zoom lens with f/1.8 constant aperture unveiled

jmeyer — Thu, 18 Apr 2013 10:22:54 +0000

The Sigma 18-35mm f/1.8 DC HSM announced today is the first ever zoom lens to achieve a wide constant aperture of f/1.8 throughout the zoom range. Find out all the key specs of this new Sigma lens.

A Sigma 18-35mm f/1.8 price and release date were not available at the time of writing.

Sigma has revealed a new 18-35mm zoom lens with a constant aperture of f/1.8.

The new Sigma 18-35mm f/1.8 DC HSM is the first ever zoom lens to achieve a maximum aperture of f/1.8 throughout the zoom range, according to Sigma.

The previous widest aperture a zoom lens has been able to achieve throughout the zoom range has been f/2.8.

Designed for DSLRs with APS-C size sensors, the Sigma 18-35mm f/1.8 offers a focal range equivalent to 27-52.5mm in 35mm format.

Sigma says the new 18-35mm lens has been designed as a standard lens which is capable of shooting landscapes, portraits, still life photography, even studio photography.

The faster aperture throughout the zoom range will eliminate the need for photographers to keep fixed focal length lenses in their camera bags for brighter images, Sigma says.

The new Sigma 18-35mm lens also incorporates a wide glass-moulded aspheric lens and Special Low Dispersion glass, the latter which compensates for various aberrations as well as field curvature at the widest angle.

The Sigma 18-35mm f/1.8 also features Super Multi-Layer Coating to reduce flare and ghosting, and boost contrast, while a supplied petal type hood provides extra protection.

A Hyper Sonic Motor provides a silent AF function, Sigma says, while the 18-35mm f/1.8 offers a minimum focusing distance of 28cm and a maximum magnification ratio of 1:4.3.

Other features include a 9-blade rounded diaphragm, brass bayonet mount and a newly developed USB Dock that plugs into your computer and attaches to your lens, allowing you to update the lens firmware and adjust parameters such as focus.

Sigma 18-35mm f/1.8 Key Specifications

Sigma unveils ultra-light 18-250mm macro zoom for travel photography

jmeyer — Fri, 15 Jun 2012 10:21:34 +0000

Independent lens maker Sigma has announced a new DSLR zoom lens designed for travellers and backpackers, or anyone who wants an all-purpose zoom lens that’s both light and small.

The Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM is different because it’s been manufactured using a special polycarbonate material called Thermally Stable Composite (TSC).

According to Sigma, TSC enables lenses to be both smaller and lighter. The virtual elimination of internal and external barrel expansion has enabled Sigma to design a lens that’s both smaller and lighter.

For example, the non-macro 18-250mm lens without TSC weighs in at 623g, whereas the new TSC macro version tips the scales at just 470g. Physically the lens is about 1.3cm shorter and about 0.5cm smaller in diameter, and has a filter thread of just 62mm.

This new walkabout lens is designed for DSLR cameras using APS-C/DX-size sensors, and offers a 35mm equivalent focal length of 28-400mm.

Sigma’s optical stabilisation (OS) technology is also included, which should mean sharper handheld shots at lower shutter speeds. The magnification ratio of the macro function is 1:2.9 and all 13 elements that make up the lens are multi-coated to reduce flare and ghosting.

For quieter and faster autofocusing, Sigma has incorporated its Hyper Sonic Motor (HSM) mechanism, which makes it ideal for newer budget DSLRs from Nikon that don’t have focus motors built into the camera body. There’s also a rounded, seven-blade diaphragm that should produce images with a softer and more pleasing bokeh.

The new lens will be available in Sigma, Sony, Nikon, Canon and Pentax mounts, but the first to market will be the Canon version, which is expected to launch in July 2012. Pricing and the availability for other mounts have yet to be announced.

Land of the giants: the world’s largest lenses

samanthacliffe — Sat, 19 May 2012 06:00:41 +0000

Camera lenses come in many different sizes. We take a look at the unfathomably massive – the world’s largest consumer lenses.

Sigma 200-500mm f2.8 APO EX DG Telephoto Zoom

Weighing in at a hefty 34.6lbs and 726mm in length, this is not the easiest lens to carry around with you on holiday. As well as being meaty, the Sigma 200-500mm also wins some world firsts; it is the first large-aperture ultra telephoto lens to have an f/2.8 aperture at 500mm, and is the largest high-speed zoom lens available.

If you’re impressed by this and are looking for a lens that is excellent at tracking fast moving objects and you don’t mind parting with $32,000, this could be the lens for you!

Stats

Weight: 34.6lb/15.7kg
Width: 236.5mm
Length: 726mm
Focal Length: 200-500mm
Price: $32,000

DO or Di? Your lens markings explained

jmeyer — Mon, 02 Apr 2012 13:58:33 +0000

Does your lens has more letters after its name than a retired rocket scientist. What do all these lens markings mean?

You can refer to a lens simply by the name of the manufacturer, the focal length, and its maximum aperture – a Sigma 70-300mm f/4-5.6, say, or Canon 50mm f/1.4. But as lenses have often evolved from decades of development, they usually have a line of additional letters after their names, stamped on the barrel or printed on the boxes.

Some lens markings are about manufacturer branding – defining a more recent range, or a lens that’s built to higher standards than another. Others are to do with the optics themselves, and to highlight specific technologies used in the lens construction.

In the jargon-busting guide below, we’ll translate these lens markings for you.

The ultimate guide to understanding lens markings

AF Stands for autofocus. Nearly all lenses have this feature,  but there’s an increasing trend for niche lens manufacturers (such as Samyang and Carl Zeiss) to offer lenses that can only be focused manually.

AF-S Stands for autofocus-silent. This features on Nikon lenses that use a silent motor to control the autofocus.

AL Stands for aspherical lens. All camera lenses are made up of a number of individual lenses or elements. Many of these elements are spherical – as if cut from a sphere. Aspherical elements are less rounded – and are used in some types of lenses to help minimise chromatic aberration.

APO Stands for apochromatic. This features on Sigma lenses that use super-low dispersion (SLD) lens elements to reduce chromatic aberration.

AS Stands for aspherical (see AL).

Asp Stands for aspherical (see AL).

AT-X Stands for Advance Technology Extra – the branding used on all current Tokina lenses.

D A type of Tokina lens that’s compatible with full-frame SLRs.

DA Stands for Digital Auto. This features on a range of Pentax lenses that (unlike some earlier ranges) don’t have a manual aperture ring. They have a ‘Quick Shift’ mechanism that enables you to override focus manually, even when the lens is switched to autofocus.

DA* Star by name, star by nature. The premium lens range from Pentax, which combines weatherproofing with the advantages of the DA range.

DC This features on the range of Sigma lenses that are designed specifically for use with crop factor SLRs, and which can’t be used with full-frame models.

DFA This features on the range of Pentax lenses that will work with full-frame 35mm film cameras, but which are also optimised for use on crop-factor digital SLRs.

DG This refers to the Sigma lens range that’s suitable for full-frame SLRs (but that can also be used on crop-factor models).

Di Tamron’s ‘Digitally Integrated’ lenses have a full-size image circle, so they are suitable for full-frame and crop-factor SLRs.

Di II Tamron’s second-generation Digitally Integrated lenses are designed for use on popular crop-factor SLRs, and are not suitable for full-frame models.

DO Diffractive Optics is used on a handful of Canon telephoto lenses – the technology allows these long lenses to be made smaller and lighter than equivalents using conventional optical designs.

DT Sony lens with a smaller image circle, designed for use on crop-sensor cameras.

DX Tokina’s and Nikon’s way of marking lenses that are only suitable for crop-factor – or APS-C – SLRs.

ED A lens featuring Extra-low Dispersion glass in one or more of its elements, to help correct chromatic aberration. This abbreviation is used by Nikon, Panasonic, Olympus and others.

EF Standing for Electro Focus. This is the name of the lens mount that Canon introduced  on its first autofocus SLRs back in 1987. EF lenses can be used  on all Canon SLRs.

EF-S Electro Focus Short back-focus lenses were introduced by Canon in 2003. They have a small image circle so they are only suitable for use on crop-factor SLRs. A modified mount means that they can’t physically be fitted onto incompatible (ie full frame) Canon models.

EX Sigma’s designation for its premium lens range.

f/X.X The f-stop number is  the size of the lens’s maximum aperture, measured as a fraction of the focal length of the lens. On some zoom lenses there may be two apertures quoted – f/4-5.6, for example. This means that the maximum aperture gets smaller as the lens is zoomed in. The maximum aperture on the lens barrel may also be expressed as  a ratio – so 1:4-5.6.

FA Pentax lens that’s full-frame compatible, and that features an old-fashioned aperture ring.

FO Tokina’s Focus-One-touch mechanism allows you to switch quickly from autofocus to manual focus operation, and back again, by snapping the focus ring backwards and forwards.

FX A Nikon, or Nikkor, lens that’s compatible with its full-frame SLRs, as well as crop-factor ones.

G Stands for Gold – a designation found on top-class Sony lenses. It’s also used for current Panasonic Lumix compact system cameras and lenses.

HID Stands for High Index Dispersion, a type of glass used in Tamron lenses that helps to minimise chromatic aberration.

HSM Sigma’s Hyper Sonic Motor is used in some of its lenses to provide faster and quieter autofocus operation.

IF Stands for Internal Focusing, and is found on many lenses from many manufacturers. The lens is constructed so that it doesn’t change in length as the lens is focused. It also means that the front element doesn’t rotate – which can help with the use of some lens attachments, such as petal-shaped lens hoods and polarising filters.

iFn Stands for i-Function, a feature of Samsung NX cameras which allows photographers to access a number of key camera settings via a button and ring around the lens.

II This stands for second-generation – a classic lens that’s been updated in design by the original manufacturer.

III Stands for third-generation.

IS Stands for Image Stabilization – optical camera shake reduction found in a wide number of Canon lenses.

L Stands for Luxury, and is used to designate Canon’s best pro lenses, which have superior build quality and weatherproofing.

LD This features on Tamron lenses that use one or more Low Dispersion lens elements to help reduce chromatic aberration.
mm Stands for millimetres – used to measure the focal length of a lens.

OIS Optical Image Stabilisation – the system used on Panasonic lenses to reduce camera shake.

OS Optical Stabilization is  the system used on some Sigma lenses to reduce camera shake.

PC-E Stands for Perspective Control-Electronic. Used to designate Nikon’s range of tilt-shift lenses, which enable you to move the front elements on the lens to avoid or exaggerate lens distortion. They are commonly used in architectural photography to ensure vertical lines remain parallel in the picture.

PZ Stands for Power Zoom,  a servo-assisted zoom facility found on some Panasonic compact system camera lenses.

PZD Stands for Piezo Drive,  a type of ultrasonic motor used in Tamron lenses to provide  fast, quiet autofocus.

RF With Rear Focus, the group of elements nearest the camera are used to focus, providing faster autofocus. This feature is found on super telephoto lenses.

SAM Stands for Smooth Autofocus Motor – used in recent Sony Alpha lenses.

SD Super-low dispersion –  the glass used in Tokina lenses  to reduce chromatic aberration.

SDM Supersonic Drive Motor, Pentax’s fast, quiet focus motor.

SLD Super-low dispersion – lens elements in Sigma lenses that reduce chromatic aberration.

smc Stands for Super Multi Coating, a seven-layer coating used on Pentax lenses to reduce light reflected the lens itself.

SP Super Performance – a long-standing tag found on top-of-the-range Tamron lenses.

SSM Supersonic motor – used for high-speed autofocus in top-of-the-range Sony lenses.

SWM Silent Wave Motor,  the high-speed quiet AF motor used on Nikon’s AF-S lenses.

TS-E Tilt-shift Electronic – Canon’s range of perspective control lenses (see PC-E).

UD Ultralow dispersion – type of glass used in Canon lenses to reduce chromatic aberration.

USD Ultrasonic Silent Drive, Tamron’s fast, quiet AF motor.

USM Ultrasonic motor – fast, low-noise autofocus motor used by some Canon lenses.

VC Vibration Compensation – optical camera-shake reduction system on some Tamron lenses.

VR Vibration Reduction, Nikon’s image-stabilisation system.

WR Weather Resistant – found on certain Pentax lenses.

XLD Extra Low Dispersion; glass used in some Tamron lenses to reduce chromatic aberration.

XR Extra Refractive – type of glass used in Tamron lenses. It can bend light at bigger angles than normal glass, helping make the overall size of a lens smaller.

ZA Zeiss Alpha – a range of Sony lenses made by Carl Zeiss.

Fast lenses group test

dcworld — Thu, 14 Jan 2010 14:38:46 +0000

When it comes to lenses, can you get the speed you need without paying top dollar?

Fast lenses – by which we mean lenses with a wide maximum aperture that are ideal for low light – are notoriously expensive. Take the luxurious f/2.8 Canon EF-S 17-55mm and Nikon AF-S 17-55mm models we reviewed recently, both of which cost over £1,000. But with contenders from the likes of Sigma and Tamron costing half the price, you don’t have to spend such big money to get hold of fast glass.

A major bonus of fast lenses is that they allow you to use faster shutter speeds in low light, fending off the problems of both camera shake and motion blur, the latter of which can’t be fixed with any amount of optical image stabilisation. Large apertures also create a shallow depth of field, which is especially good for blurring the background in portraits.

With this in mind, a ‘standard’ 50mm focal length equates to about 75mm to 80mm with most D-SLRs, which use APS-C rather than full-frame sensors. Therefore they offer a perfect effective focal length for taking portraits. As well as offering a two-stop increase in speed at focal lengths of around 50mm, compared with most standard ‘kit’ zoom lenses, the fast zooms on test also boast constant aperture, so the maximum aperture is available throughout the zoom range.

The downside is that while zooms are unbeatable for versatility, there’s an inevitable compromise in optical quality. Go for a fast prime lens and you can generally expect a further two-stop increase in speed, with a maximum aperture of around f/1.4, negligible distortion at the fixed focal length and supreme sharpness.

Canon EF 50mm f/1.4 USM

Street price: £290

This model firmly occupies the prime lens middle ground between Canon’s rather basic 50mm f/1.8 and the massively expensive 50mm f/1.2L USM, costing nearly £1,300. It delivers a more standard f/1.4 maximum aperture and fast, near-silent USM (Ultrasonic Motor) Autofocus, complete with full-time manual override.

Rugged but fairly light in weight, it’s easy to live with. As with most Canon lenses, however, you have to pay extra for a lens hood, which will set you back £25. Optical performance proved respectable in our tests; the lens produced reasonably crisp images even under very low indoor lighting, but the drop-off in sharpness was more obvious at the maximum aperture than with some other lenses here, especially towards the corners of the frame.

Outdoors, the Canon’s resistance to flare was average but, even so, image quality is a big step up from Canon’s cheaper kit zoom lenses.

At its largest aperture, the Canon EF 50mm isn’t the sharpest tool in the box, but a major plus point of this is that the lens can give an attractive ‘dreamy’ look to your portraits. Stopped down a bit for this studio-lit shot, there’s plenty of detail throughout most of the image, but it could be a little better in the corners of the frame. Even so, there’s certainly a lot to like about this lens.

Verdict: Features **** / Build quality **** / Handling ***** / Image Quality **** / Value for Money **** Overall *****

Nikon AF-S 50mm f/1.4G

Street price: £280

Nikon’s reasonably priced 50mm f/1.8 lens only costs about £100, but is so sharp you can practically cut yourself on it. At nearly three times the price, this f/1.4 lens has its work cut out to justify the outlay, but it’s still the cheapest lens here.

As well as the slightly larger maximum aperture, the newer f/1.4G is much more of a 21st-century lens, dropping the antiquated aperture ring that is largely superfluous on D-SLRs, and adding Nikon’s Silent Wave AF-S autofocus system. As with Canon’s USM, this means you get whisper-quiet autofocus with full-time manual override, although autofocus speed isn’t as rapid as with some of Nikon’s other AF-S lenses.

At apertures of f/2.8 and smaller, sharpness proved great across the frame and, even wide open at f/1.4, it’s way above average. The quality of bokeh was also particularly pleasing, and overall the f/1.4G is worth every penny.

Every tiny nuance is captured by the razor-sharp Nikon and, when viewed at 100% magnification on a computer screen, this test shot reveals a level of detail that simply can’t be seen with the naked eye. For portraiture, it’s perhaps a little too sharp and accentuates every wrinkle and flaw in the skin. This can be easily fixed in Photoshop though, and we’d rather have too much detail to start with than not enough.

Verdict: Features ***** / Build Quality ***** / Handling ***** / Image quality ***** / Value for money ***** / Overall *****

Click through the next pages to see how the other lenses in our test fared.

Sigma 18-50mm f/2.8 EX DC Macro HSM

Street price: £315

This Sigma is the cheapest f/2.8 constant aperture lens in the group by quite some margin, yet still offers Sigma’s HSM (HyperSonic Motor) autofocus system, equivalent to Canon’s USM and Nikon’s AF-S.

The HSM is certainly fast and very quiet but, unlike the Canon and Nikon versions, doesn’t feature full-time manual override, so you have to manually switch back and forth between auto and manual focus.

Build quality feels robust, but the overall design seems like it’s cutting a couple of corners. For example, unlike the Canon, Nikon, Sony and both Tokina lenses, the focus distance scale is printed on the outside of the lens barrel rather than being stashed below a viewing window, and the finger grip on the focus ring itself is rather too small for our liking.

Optical quality is very respectable for a fast zoom lens at this price, but a bit on the soft side when shooting at the maximum aperture.

We weren’t completely convinced that the focal length of this Sigma stretches all the way to 50mm, as the flower arrangement didn’t quite fill the frame in the same way as it did with the 50mm prime lenses on test here. Image quality itself is slightly soft when shooting wide open, but sharpens up very impressively by the time you hit f/4. There’s bags of edge-to-edge detail in this shot.

Verdict: Features **** / Build quality **** / Handling **** / Image quality **** / Value for Money ***** / Overall ****

Sigma 50mm f/1.4 EX DG HSM

Street price: £359

Oddly for a third-party prime lens, the Sigma 50mm f/1.4 costs more than the competing ‘own-brand’ Canon, Nikon and Sony prime lenses on test. On the plus side, however, it also feels more sturdily built, with a chunkier design and much heftier weight that gives it a more natural balance on heavier D-SLR bodies. Like the Sigma zoom lens on test, this one features fast, quiet HSM autofocus, but this time it comes complete with full-time manual override and the focus distance scale is neatly tucked away below a viewing window.

The Sigma prime is impressively sharp even at its maximum aperture; in our tests it gave slightly better performance than the Canon f/1.4 but didn’t quite match the Nikon or Sony prime lenses. The lack of distortion and overall optical quality are noticeably better than with the Sigma 18-50mm zoom, so it’s a choice between prime lens quality versus zooming versatility.

Good attention to detail even when shooting wide open leads to even greater sharpness at f/2.8 and smaller apertures, winning out over the Canon 50mm f/1.4 in our tests. The Sigma’s street price is £70 more expensive, but at least it comes with a lens hood and soft pouch, like most Sigma lenses. This Sigma is proof, were it needed, that ‘third-party’ lenses can be a good investment.

Verdict: Features ***** / Build quality ***** / Handling ***** / Image quality ***** / Value for money **** / Overall *****

Sony 50mm f/1.4 AF

Street price: £282

Sony lenses often seem overpriced for what they actually offer, so how does this 50mm f/1.4 stand up? At first glance, it’s difficult to take the lens seriously, as it’s incredibly compact and lightweight, and minimalist in the extreme. For example, the manual focus ring seems almost like an afterthought, as it’s small and there’s no ribbed grip on it.

Maybe that’s just as well, because the ring rotates in autofocus mode as well as during manual focus, and the small size of the lens makes it difficult to hold without your fingers fouling the focus ring.

Autofocus is fairly fast, but quite noisy in operation. It’s easy to forgive any handling flaws, however, the moment you see images taken with the lens. They’re wonderfully sharp and full of contrast, even when shooting at f/1.4. Indeed, in our tests, the overall optical quality was practically as good as with the Nikon 50mm f/1.4, and better than any of the zoom lenses.

Hardly bristling with features, the Sony looks a very basic lens but optical quality is stunning. Sharpness and contrast are exemplary, even at the maximum aperture, and things get better still when you move down by a stop or two. As with the Nikon 50mm prime lens, also on test, every tiny detail in this shot of flowers is there to see in the final image. It might look humble on the outside, but the Sony has great glass.

Verdict: Features **** / Build quality **** / Handling **** / Image quality ***** / Value for money **** / Overall ****

Click through to the final page to see how the last 3 lenses in the test got on.

Tamrom 17-50mm f/2.8 XR Di II VC

Street price: £490

Fast standard zoom lenses with image stabilisation are few and far between, yet this heady combination has been combined in Tamron’s new 17-50mm f/2.8 VC (Vibration Correction) lens.

In our tests, the VC consistently gave an advantage of three to four stops, fending off camera shake and enabling the handheld use in near darkness. It’s just a shame that the high-tech VC isn’t matched in other areas of the lens’s design, which features a particularly slow and noisy autofocus motor and the lack of full-time manual focus override.

The zoom ring of our test sample was also very stiff in operation, but at least there was no hint of zoom creep. More disappointingly, the lens really lacked sharpness when shooting wide open and had to be stopped down to f/5.6 to give convincing results, even then lagging a long way behind the prime lenses. For the money, it’s not one of Tamron’s best.

There’s a lack of sharpness in this shot compared to almost all the other lenses on test, and the problem gets worse the closer you get to the maximum aperture of f/2.8. Another issue that we had was that, when shooting on a Nikon body in Manual mode, the lens consistently over-exposed images by about one or two stops, even when locking the aperture and shutter speed to the same values used with other lenses.

Verdict: Features **** / Build quality **** / Handling **** / Image quality *** / Value for money ** / Overall ***

Tokina 16-50mm f/2.8 AT-X Pro DX

Street price: £590

A sizeable and weighty affair, the Tokina 16-50mm looks more like luxury lenses such as the Canon EF-S 17-55mm and Nikon 17-55mm f/2.8 offerings, with a rugged, professional feeling build quality. Autofocus is rapid and fairly quiet, despite lacking the equivalent of USM or AF-S, and while there’s no full-time manual override, the lens features Tokina’s trademark push-pull focus ring, which enables speedy switching between auto and manual focusing.

It can be a bit too easy to switch between manual and autofocus unintentionally though. The price is as heavyweight as the lens, with street prices around £250 more than the equivalent Sigma and £100 more than the Tamron VC lens on test.

So does it have image quality to match? Distortion is fairly well-controlled considering the 16mm wide-angle ability. While sharpness is reasonable at f/2.8, however, it fails to improve much as you stop down.

Something of a curiosity, the Tokina can match most of the lenses in the group for sharpness when shooting wide open, especially in dull lighting conditions, but images don’t get any sharper when you stop down. In our tests, by the time we got to f/8 or f/11, other lenses in the group had left the Tokina a long way behind in terms of contrast and sharpness, from the centre to the corners of the frame.

Verdict: Features **** / Build Quality ***** / Handling ***** / Image quality **** / Value for money *** / Overall ****

Tokina 50-135mm f/2.8 AT-X Pro DX

Street price: £550

The big brother of the Tokina 16-50mm lens, this 50-135mm model takes over neatly where the smaller one leaves off, or at least that’s the theory. In practice, we found a few millimetres of focal length missing in the middle, the larger lens seeming more like a 55-135mm.

Weighing in at 755g, the big Tokina comes with a collar for mounting on a tripod and the solid, chunky build quality is continued from the smaller model. There’s also the same push-pull mechanism for switching between autofocus and manual focus. One notable difference, however, is that this lens has internal zooming, so the overall length of the lens stays fixed throughout the entire zoom range.

Specifically made for Canon and Nikon cameras with APS-C sensors, the effective telephoto reach of the lens is a handy 216mm or 202mm respectively, making it a relatively cheap option for a fast telephoto zoom lens.

At 50mm or thereabouts, the Tokina wasn’t quite a match for most other lenses on test, either shooting wide open or stopped down. Sharpness was still adequate for most scenarios, but not fabulous. We didn’t suffer any drop-off in quality at longer telephoto focal lengths, however, so it’s a useful lens on an APS-C camera when you need extra reach, and the f/2.8 gives a wonderfully small depth of field.

Verdict: Features **** / Build quality **** / Handling **** / Image quality **** / Value for money **** / Overall ****

Sigma 10-20mm f/4-5.6 EX DC HSM Lens review

dcworld — Tue, 13 Oct 2009 12:37:31 +0000

An ultra-wide angle lens at a cheap price, but will it deliver?

The Sigma 10-20mm f/4-5.6 is the cheapest lens in the group. The respectable 10-20mm zoom range is equivalent to 15-30mm on 1.5x crop factor cameras like Nikon and Pentax, and 16-32mm on a Canon body.

It’s available in all the same mounts as Sigma’s new, constant-aperture version of the lens, as well as in Olympus Four Thirds mount (although the effective zoom range of 20-40mm is less impressive at the ultra-wide end on Olympus cameras).

The Hypersonic Motor (HSM) autofocus system isn’t blindingly fast but proved highly accurate and whisper-quiet in our tests. The lens is also very smartly turned out, belying its modest price and featuring the texture black finish favoured by Sigma’s EX series lenses. As with other Sigma lenses, it comes complete with dedicated hood and a high-quality carrying pouch that’s worth having.

The two ELD elements of the newer Sigma 10-20mm lens on test are missing from the older version. The line-up is instead built around three SLD elements and three aspherican elements. On paper, this looks inferior but, in our tests, the lens performed as well as Sigma’s more expensive counterpart and, although sharpness was a lacking when shooting wide open, the optics sharpened up nicely at f/8.

Sigma 10-20mm f/3.5 EX DC HSM

dcworld — Tue, 13 Oct 2009 12:27:48 +0000

We put one of Sigma’s ultra-wide angle lenses through its paces.

Sigma’s newest 10-20mm lens is bigger and heavier than the other Sigma model, also tested here. It features a larger front elements that requires an 82mm filter thread, whereas most lenses in the group only need 77mm filters.

Both Sigma lenses use the company’s HyperSonic Motor (HSM) autofocus, which is practically as quiet as the equivalent Canon and Nikon systems, although it proved rather slower in our tests. Full-time manual focus override is available in all the lens’s mount options, which include Canon, Nikon, Pentax, Sigma and Sony.

The biggest bonus of the new Sigma 10-20mm lens is that it has a constant maximum aperture of f/3.5 throughout the zoom range. This is very slightly faster at 10mm and just over a stop faster at 20mm. For our money, however, this alone doesn’t warrant the additional £210 cost over Sigma’s other model, as overall image quality didn’t prove noticeably better.

There’s quite a feast of glassware inside the new Sigma 10-20mm lebs, including one Special Low Dispersion (SLD), two Extraordinary Low Dispersions (ELD) and four aspherical elements. There are also Super Multi-Layer lens coatings to reduce ghosting and flare but, overall the Sigma lacked sharpness when shooting wide open, making its reasonably fast constant aperture less of an attraction in practical terms.

Sigma DP2

dcworld — Thu, 10 Sep 2009 16:05:40 +0000

Using a fixed focal length lens and the unique Foveon X3 sensor, the DP2 is an old fashioned compact.

Megapixels alone don’t guarantee image quality. A 12MP APS-C sensor in a DSLR produces great detail and high ISO performance; the same number of pixels on the five times smaller sensor of a compact produces much less detail and far more noise, but there’s something else that affects even the big sensors in D-SLRs.

Megapixels alone don’t guarantee image quality. A 12MP APS-C sensor in a DSLR produces great detail and high ISO performance; the same number of pixels on the five times smaller sensor of a compact produces much less detail and far more noise. But there’s another dimension (literally) to this argument that affects even the big sensors in DSLRs.

All makers but one use single-layer sensors, where the red, green and blue pixels are laid out in a pattern and the colour information for each pixel is interpolated using information from its neighbours. It’s a technical bodge which we’ve grown accustomed to, but it does leave fine, pixel-level detail looking soft.

Just how soft becomes apparent when you examine images taken with the Sigma DP2. It uses Sigma’s Foveon X3 sensor, a unique triple-layer design where red, green and blue pixels are arranged in a vertical stack and each pixel in the final image has full colour information from the start. As a result, the pixel-level definition is genuinely startling.

But Sigma has a problem. The DP2 produces files of only 4.7MP, which sound tiny by today’s standards. Sigma points out that the total pixel count is actually 14.1MP which is true – it has as many red, green and blue photosites as a conventional 14MP sensor. Its output files, though, aren’t the same size.

But does it matter? You can blow the DP2′s super-sharp images up far further than you could with any conventional sensor of the same resolution. Or you could use interpolation to ‘inflate’ those 4.7MP files to 12-14 million pixels, and find that the fine detail isn’t really so very different to that of a conventional DSLR.

The DP2 can shoot JPEGs, but it really comes alive when you shoot RAW and use the dedicated Sigma Photo Pro software supplied with the camera. At low ISOs images are essentially noiseless, but at higher ISOs the quality does deteriorate faster than you’d expect with a conventional sensor. The DP2 goes right up to ISO 3200, but by this point the image quality is pretty terrible and really you probably wouldn’t want to go beyond ISO 800.

Using the DP2

The DP2′s design is straightforward, with a plain rectangular design and the minimum of external controls, all of which have a really firm, high-quality feel. These include the excellent mode dial (which is too stiff to turn by accident) and the manual focus wheel at the back of the top plate. Most routine adjustments are carried out with two quick function screens. You press the button on the back of the camera once to access the first screen (ISO, lash, metering pattern, white balance) and again to access the second (quality, file type, drive mode, picture style). It’s very fast, and very effective. The autofocus system is rather less impressive. It’s not that quick, and it’s pretty noisy, too. The manual focus dial makes up for it, though. It’s quick to use and the distance markings are clear.

The DP2′s buffer is large enough to take three RAW files or four JPEGs, but after that you have to wait several seconds for the memory to clear. This is a bit of an issue because if you’re taking lots of pictures the camera will sometimes not be ready right at the moment you need to grab the shot.

Incidentally, the ‘old’ DP1 carries on. That camera has a 28mm equivalent lens as opposed to the DP2′s 41mm equivalent. It’s not a question of which camera is newer, but which has the focal length that you need.

Sigma DP2 Review

dcworld — Thu, 10 Sep 2009 16:05:40 +0000

We put the DP2′s fixed focal length lens and unique Foveon X3 sensor to the test

Using the DP2