Sigma 24-70mm f/2.8 EX DG DF


General

With the rapid increase in the number of digital users for the past one year, many photographers will start to appreciate lenses that come with this range. With the 1.6x FLM (Focal Length Multiplier), you effectively have 38.4-112mm. Pretty good range to compliment any other wide-angle lens you may have. Unfortunately, Canon users are left with only 2 choices that comes in this range and with a constant f2.8 aperture - Canon 24-70mm f/2.8 L and the above offering from Sigma. Being a much cheaper alternative among the two, the Sigma is often perceived to be much inferior in terms of optical quality. Heard quite abit of rumours saying that Sigma's QC during manufacturing wasn't consistent at all, with optical quality of each lens varying quite a bit. Not sure how true this rumour goes, but fortunately, the copy I owned has yet to disappoint me. Coupled with the Canon EOS D30, this lens is especially useful for portrait shooting and event coverage.




Specifications

Lens Construction (Groups / Elements) 13 / 14
Angle of view (degrees) 84.1 - 34.3
No. of blades in diaphragm 9
F-Stop Range f/2.8-32
Minimum Focusing Distance (cm/in.) 40 / 15.7
Magnification 1:3.8
Filter Size (ø mm) 82
Dimensions Diameter x length (mm / in.) 88.6x113 / 3.5x4.4
Weight (g / oz.) 700 / 24.7


Handling

Built

Overall, the lens feels quite solid in my big hands, although its a little on the weighty side (at 700g!). With the D30 and battery grip, the lens balances quite well. The distinctive matte EX finish makes it all the more pleasing to hold. Provided is also a matching petal hood that helps reduces flares quite effectively.

Zoom / Manual-Focus Ring

Switching from AF to MF requires a two-step procedure. First, you need to toggle the AF/MF switch which is located near the lens mount. Next, you need to pull the manual focus collar towards the camera body. A little troublesome but doesn't really hinders my shooting experience. The zoom ring comes a little small, making it awkward to the hand when turning. It could do with a little more dampening as well. At 70mm, the lens is most compact in size. At 24mm, the lens extends out a little more than an inch. Manual focus ring is broad, adequately rubberized and well-dampened.

Focusing

Auto-focus is very fast under ample lighting. Under poor lighting conditions, the lens does hunt a bit if the subject is not contrasty. The noisy AF doesn't help pacify your nerves either. Even the camera's built-in AF assist lamp can be quite useless, due to the huge front element (82mm) blocking off most of the light. The workaround I usually employ is to use the 420EX's AF assist lamp. The short minimum focusing distance of the lens is quite an impressive feature. At around 25cm (lens-to-subject distance) for all focal length, I can exploit interesting angles and perspectives using this lens.


Optical Quality

Below are some tests done with the Sigma 24-70mm f/2.8 EX DG DF lens mounted on a Canon EOS D30. Do note that the following test results were based solely on my own test procedures and opinions, and they do not represent the manufacturer's stand in any way.

At 1st glance, I was pleasantly surprised by the sharpness this lens produces, especially at the widest aperture. At the same time, I was equally in awe by the amount (or lack of) of Chromatic Aberrations (CA) it exhibits. Below is a example to illustrate these two attributes. Note that no post-processing was done to the images except resize.


Here are a series of cropped (unprocessed) images at 100% view to illustrate the optical quality of the lens (at 24mm) at various apertures. All images were taken in RAW format and converted to JPEGs. Sharpness was set to NORMAL.




   
f2.8 @ 24mm, centre of frame                       f2.8 @ 24mm, corner of frame

   
f3.5 @ 24mm, centre of frame                       f3.5 @ 24mm, corner of frame

   
f4.0 @ 24mm, centre of frame                       f4.0 @ 24mm, corner of frame

   
f5.6 @ 24mm, centre of frame                       f5.6 @ 24mm, corner of frame

   
f8.0 @ 24mm, centre of frame                       f8.0 @ 24mm, corner of frame

   
f11 @ 24mm, centre of frame                       f11 @ 24mm, corner of frame

   
f16 @ 24mm, centre of frame                       f16 @ 24mm, corner of frame

It appears that the lens gives very consistent quality at the center of the frame throughout the range of apertures used. Sharpness was only slightly improved when stopped down to f8 and f11, although minimal. Chromatic Aberrations were also negligible. At the corners, f2.8 appears slightly soft only. And once again, consistency is maintained across the remaining aperture values.

Next, lets take a look at how the lens performs at the 70mm end.




   
f2.8 @ 70mm, centre of frame                       f2.8 @ 70mm, corner of frame

   
f3.5 @ 70mm, centre of frame                       f3.5 @ 70mm, corner of frame

   
f4.0 @ 70mm, centre of frame                       f4.0 @ 70mm, corner of frame

   
f5.6 @ 70mm, centre of frame                       f5.6 @ 70mm, corner of frame

   
f8.0 @ 70mm, centre of frame                       f8.0 @ 70mm, corner of frame

   
f11 @ 70mm, centre of frame                       f11 @ 70mm, corner of frame

   
f16 @ 70mm, centre of frame                       f16 @ 70mm, corner of frame

At the longest end, the lens does exhibit some softness around the centre at the widest aperture. The sharpness improves significantly from f5.6 to f11. At the corners, the lens performs similarly, with softness at apertures below f5.6. CA is very well controlled.


Samples

Different types of subjects were used in this section to illustrate how the lens fare when used for various types of photography.
 
 
 
 


Conclusion

In general, this lens performs very well in most aspects. It is the only lens that directly competes with the Canon's equivalent in terms of focal length and aperture. But being much cheaper in cost and lighter in weight, the Sigma is a worthy consideration for photographers with a tighter budget. Personally speaking, this is one lens that I instend to keep for a long time.

Pros


Cons










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