Hands-On with the Sigma 50-500 F4.5-6.3 APO DG OS

Article and images by P3's Melanie Beus 
The lens used for this review was with a Pentax mount, and used on a Pentax K-7 camera. Although it will, by necessesity, be somewhat skewed toward the peculiarities of the Pentax DSLR system, many portions of this review will be applicable across all camera systems.

The latest version of Sigma's super zoom, the 50-500mm, AKA "Bigma", come equipped with their proprietary HSM (hyper-sonic motor) focusing system. This is but one of the changes from the previous iteration.


"Let's not kid ourselves. This lens is a beast. And it's made even more beastly when zooming out to 500mm. It is fairly unreasonable to expect to be able to produce perfect images with this lens in the first few snaps of the shutter."

Specifications

Lens Construction - 22 Elements in 6 Groups

APO Tele Converter - 1.4X MF, 2X MF

Angle of View - 46.8-5.0

Number of Diaphragm Blades - 9

Mininum Aperture - f22

Minimum Focusing Distance - 50-180 cm / 19.7-70.9 in

Filter Size (mm) - 95

Maximum Magnifications - 1:3.1

Dimensions(Diameter x Length) - 104.4x219 mm/4.1x8.6 in

Weight - 1970g / 69.5oz.

These are the basics. There are a few peculiarities with this lens and the use of teleconverters for various mounts and the use of various filters. The details of these issues can be found on the Sigma web page for this lens: http://www.sigmaphoto.com/shop/50-500mm-f45-63-apo-dg-os-hsm-sigma#photouploadspot

What's in the Box

Well quite a bit actually. The lens obviously, along with front and rear caps, tripod mount, and a carrying strap to attach to the lens. The front cap is a pinch-style cap that is not interfered with by the lens hood, nor prone to popping off the end of the lens with the accidental bump from protruding side buttons. The lens hood is a double-hood system. The main, petal shaped hood for general use, and a straight hood adapter that attaches to the lens front, with the petal hood attaching to the end of that, creating a longer shade for use with APS-C sensors. A step-down ring is also provide for use with the APS-C sensors, enabling the use of an 86mm filter as opposed to the 95mm filter size required by the front of the actual lens. A case with carrying strap is included with two bottom padded removable inserts (the need for which one or both being dependant upon the attachment or not of the lens hood adapter). And of course an instruction manual.

Whats In The Box

Use, Handling, and Size

Let's not kid ourselves. This lens is a beast. And it's made even more beastly when zooming out to 500mm. It is fairly unreasonable to expect to be able to produce perfect images with this lens in the first few snaps of the shutter. It requires some practice to became accustomed to using a lens of this size. The two part lens hood (if shooting it with an APS-C camera only extends the length (but does not really add much to the weight). Unless one is well practiced in shooting a lens of this weight and size, it does take some practice to really master.

Lens, Lens with Shade, Lens with Shade and Shade Adapter

To get an idea of it's relative size, below is a side by side size comparison of the Sigma 50-500 with the Sigma 70-200/2.8 (the previous, non-OS version). The 50-500 is zoomed all the way back to 50mm. The 70-200 does not change length with zooming.

Image Quality

Chromatic Aberation

Some degree of fringing occurs in the usual situations where one would expect to get fringing. Below is an example of what is obtained, bright sunlight, out of focus area, 100% crop. Green and magenta fringing is apparent on either edge of the bright, blown out portion of the horizontal branch.

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Sharpness

The lens is decently sharp at the shorter end and middle ranges of the lens. However, the sharpness does drop off at the longer ends. There are also a discernable lack of sharpness of images when focusing over a larger distance. The image of the child below was taken at 170mm and the the image of the bird was taken at 500mm. Both were shot from within 10 feet or so. The image of the squirrel on the tree was at near infinity and there is a definite loss of sharpness exhibited. In spite of these observations, the lens is still a great tool for wildlife and birding, and even general use as exhibited by the portrait detail.

Comparison of optical stabilization systems

This latest version of the 'Bigma' comes with in-lens optical stabilization. There are two modes available: Mode 1 is a standard stabilization function, while mode 2, according to the documentation, is to "detect the vertical camera shake and overcome blurring." This statement is being interpreted as meaning that it is to be used while panning. Both Sony and Pentax DSLRs come with in-body image stabilization. The use of either one system or the other is recommended for best image quality.

The in-lens stabilization was compared with the in-body stabilization. Although individual shooting styles and ability will produce varying results, the general impression for this particular review has yielded a result of the in-lens system having a slight edge over the in-body system. This applies to the Pentax K-7 only as results with other bodies may vary. The images below show both systems in use, at 50mm, 200mm and 500mm. The top row is using the in-lens system and the bottom row using the in-body system.

In-lens Optical Stabilization
	50mm	200mm	500mm
In-Body Shake Reduction
	50mm	200mm	500mm

One particular advantage to use the in-lens OS over the in-body SR, is the ability to quickly adjust the OS system for panning. It can be changed over with the mere flip of a switch, rather than having to go into the camera and turn off the SR, then turn on the lens OS.

Exposure and Color

Over exposure when any of the auto-exposure modes seems occuring. AV exposure was compared to the Pentax DA 55-300 at 100mm. This lens was chosen because it's maximum aperture values match the Sigma 50-500. Both lenses were shot AV mode, matrix metering, wide open, at 100 ISO. With no exposure compensation applied, the camera chose a shutter speed of 1/100 sec for the Sigma, and 1/250 for the Pentax. While Pentax does have a reputation for under exposing, the image with the Sigma lens does appear to be over exposed. The following images are both lenses at no EV, -1 EV and -2 EV.

Sigma 50-500	-1 EV	-2 EV
Pentax 55-300	-1 EV	-2 EV

A cursory examination of SV, TV and TAV modes, where the camera is making a decision on proper exposure, yielded images that were somewhat over expsosed as well. It must be noted, however, that this is with this particular camera, the Pentax K-7. And it seems to be limited to bright sunny lighting situations. With other models and other makes of camera, the results may vary.

Color is pleasant and quite true to life.

Bokeh

With 9 apeture blades, the out of focus areas of images produced by this lens quite pleasant for the most part. In the image below, the gradation of the blur can be seen as the ground recedes.

F/8, 410mm

Conclusions

This lens does a lot. It covers a huge range of focal lengths, and has the ability to serve for both general purpose and for specialty situations such as sport and wildlife. The image quality is generally quite acceptable for most situations, although it is better at the shorter lengths and closer range than longer and farther. Overall the versitility and quality make it an excellent value.