Sigma 50-500/4.5-6.3 DG OS Lens Review
While the Sigma 50-500/4.5-6.3 HSM has been around for a while now, a new OS (Optically Stabilized) version has just been released by Sigma. For a lens as long as 500mm, which is intended to be used handheld, stabilization is a big plus, especially with a relatively modest f/6.3 maximum aperture. Sigma suggest that their OS system can provide up to 4 stops of stabilization which is very useful.
The lens has a “semi-matte” and “sparkle” finish, unlike any other manufacturer’s lenses. I don’t know if the finish will stand up as well as regular paint (or plastic), but it looks nice.
Build quality of the lens seems good. Focus and zoom controls were smooth and there’s a lock at 50mm available to keep the lens compact when traveling and prevent accidental extension.
The lens is supplied with a nice carrying case, a lens hood and a filter adapter to allow the use of 86mm filters for crop sensor camera use, rather than the 95mm filters which are required when the lens is used on a full frame camera. The lens does have full frame coverage and so can be used on any DSLR. It’s available in mounts for Sigma, Canon, Nikon, Pentax and Sony/Minolta bodies.
The lens is well balanced for handholding and the tripod foot can be removed if desired. It’s actually very useful for carrying the lens when attached to the camera, so I left it on, even when I wasn’t using a tripod.
Sigma 50-500/4.5-6.3 OS HSM Specifications
Lens Construction 22 Elements in 6 Groups Angle of View 46.8-5.0 Number of Diaphragm Blades 9 Miminum 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)
104.4×219 mm/4.1×8.6 in Weight 1970g / 69.5oz.
I’d rate the center image quality of the 50-500/4.5-6.3 OS HSM as very good at all focal lengths in the center of the frame. Image quality does fall as you move out towards the edges and corners of the frame, especially when shooting with full frame cameras.
Even at 500mm center quality is very good wide open at f/6.3 as long as you get good focus (more on focus issues later). In fact it approaches (but doesn’t quite equal) the image quality of my Canon EF 500/4.5L at f/6.3. The difference comes when looking at the outer parts of the image where there is some softening and chromatic aberration, even in crop sensor camera images.
At shorter focal lengths sharpness is also very good and even at the edges of a full frame image they hold up well. There is some chromatic aberration throughout the focal length range, but it’s most noticeable at the telephoto end of the zoom range.
Though the Sigma 50-500 OS isn’t a macro lens, it nevertheless provides a pretty useful maximum magnification of about 0.32x at the 200mm setting and a focus distance of around 0.6m (subject to sensor plane). At the nominal 500mm zoom settings the lens provides around 0.22 at a focus distance of around 1.8m.
The lens barrel has markings corresponding to various focal length settings which give the maximum magnification and minimum focus distance at that focal length (see the illustration on the right).
The 50-500 uses a humongous 95mm front filter (there’s no provision for a rear mounted filter). Although you probably can find UV, ND and polarizers in a 95mm size (and those are the three filters most used with digital), they aren’t going to be cheap if you go with a quality brand. A 95mm B+W Kaesemann circular polarizer is $240 for example. There is an adapter included, which allows the use of slightly smaller 86mm filters when the lens is used on a crop sensor camera (on full frame you would get additional vignetting), but even 86mm filters aren’t cheap (an 86mm B+W Kaesemann circular polarizer is around $170) and you’re unlikely to already own any since they fit few lenses.
Sigma cautions against using a polarizer with this adapter for fear it will become stuck. I’m not quite sure why they single out a polarizer, but perhaps because it’s somewhat more difficult to remove a stuck polarizer due the the front being able to rotate. There’s less to grab onto than on a UV filter. The adapter ring is plastic and if it’s used you have to buy an 86mm lens cap (only a 95mm lens cap is provided).
The Sigma 50-500/4.5-6.3 OS HSM shows vignetting when shot wide open, as do all zooms. The effect is, of course, more pronounced when the lens is used on a full frame camera then when it’s used with a crop sensor camera. Least vignetting is seen at around 100mm and most is seen at the focal length extremes of 50mm and 500mm. The images on the right are full frame shots using an EOS 5D DSLR.
Stopping down by one stop pretty much eliminates vignetting with crop sensor cameras and stopping down 2 stops pretty much eliminates vignetting on full frame cameras.
Sigma’s optical stabilization (OS) system works well. I compared the handholdability of the SIgma 50-500 OS HSM with that of the Canon EF 70-300 IS USM at a focal length setting of 300mm and found the stabilization offered by the Sigma lens was at least as good as that offered by the Canon, around 3 stops. Even at 500mm the OS was very effective. I did notice a bit of a tendency for the OS system to “fight” against operator movement of the lens. By that I mean that it was quite difficult to get the focus point exactly over the part of the subject I wanted. If it was off to the left and I moved the lens to bring it back to center, the OS system would kick in, shift the image and I’d overshoot back and forth! It’s only an issue at longer focal lengths, but the Canon system seemed a little “smoother”. No big deal, just something I noticed.
The OS system has two modes (I and II). Mode I gives dual axis stabilization while mode II provides single axis stabilization, which is more useful when panning with a moving subject.
I did notice some contrast loss due to flare when shooting towards a light source at longer focal lengths. Unfortunately, like all high ratio zooms, the supplied lens hood doesn’t help a lot. A lens hood for a zoom has to be wide enough not to cause vignetting at the widest focal length settings, so the hood for the 50-500 is effectively a hood designed for a 50mm lens and full frame use. At 500mm it’s not very effective. but as I mentioned, this a a problem inherent in the design of wide range zooms. You could fabricate a much more efficient lens hood for 500mm use on crop sensor cameras—you’d just have to remember to remove it at shorter focal lengths or if you were shooting full frame!
If 500mm isn’t enough for you, there’s the option of adding a 1.4x or 2x TC. The Canon TCs won’t fit on the Sigma 50-500 OS HSM because the aperture at the back of the lens isn’t large enough to accommodate the protruding front element of the Canon TCs. However, the Sigma TCs will fit okay and the Tamron 1.4x TC, which I have also fits on the 50-500.
Since a 1.4x takes the aperture to f/9 and a 2x takes it to f/13, focusing is an issue since AF will fail or at least be unreliable. I could (much to my surprise) actually get the lens to AF with the Tamron 1.4x attached, though only on very high contrast subjects in good light. Image quality wasn’t too bad either (at 500mm). More detail was recorded using the 1.4x TC than could be seen in an upsized image shot at 500mm, just don’t expect razor sharpness. I also saw some additional vignetting with the Tamron 1.4x TC and the lens set to 500mm when shooting with a full frame camera.
The Sigma 50-500/4.5-6.3 OS HSM is obviously a variable aperture lens, f4.5 at 50mm and f/6.3 at 500mm, but there’s no information in the lens name that tells you just how the maximum aperture varies with focal length. Here are my measurements which are based on EXIF data of images shot at the points when the maximum aperture dropped by 1/3 stop steps.
- f/4.5 @ 50-55mm
- f/5.0 @ 56-112mm
- f/5.6 @ 113-243mm
- f/6.3 @ 244-500mm
The focal length of a lens is defined by its optical properties when focused at infinity. While testing the Sigma 50-500 against a few other lenses (notably the Canon 500/4.5L and Canon 300/4L) I noticed that the subject scale was slightly smaller with the Sigma lens, particularly when focus was closer than infinity. I had previously measured the focal length of the Canon lenses and found them to be very close to their nominal values. So using the Canon 500mm lens as a standard I measured the relative magnification of the Sigma 50-500 at various focus distances and calculated what the effective focal length was at the 500mm setting. These are the results, assuming the Canon lens stays at 500mm.
- At infinity Canon 500mm, Sigma 485mm
- At 25m focus, Canon 500mm, Sigma 465mm
- At 7m focus, Canon 500mm, Sigma 435mm
At 2.5m I compared with Canon 300/4L and 1.4TC with the Sigma at 500mm. Assuming the Canon holds its focal length I found:
- At 2.5m, Canon 420mm, Sigma 385mm.
That means that I saw more magnification with the 420mm Canon combination than I did with the Sigma 50-500 set to 500mm.
So what do these numbers mean? Well, like just about every close focusing telephoto zoom, the Sigma 50-500 reduces its focal length as it focuses closer. It’s a very common technique and yields a smaller lens capable of closer focusing and higher magnification. However, it does mean that at any given distance you don’t get quite as much magnification as you might expect from the stated focal length.
As long as you can get closer to your subject (e.g. when taking pictures of flowers), then the reduction in effective focal length (or to put it another way, the lower magnification at any given distance) doesn’t matter. You just take another step closer.
Where it can make a difference is if you can’t get closer to your subject. For example, if you’re photographing wildlife from a blind, you can’t move closer. You have to shoot from a fixed distance and if that distance is short, you may get lower magnification with a 500mm zoom set to 500mm than with a 500mm prime lens.
This isn’t a huge deal, lots of lenses do it, but it’s something many users don’t expect and are surprised when they accidentally discover it. It’s not something that the lens makers, be they Canon, Nikon or Sigma, usually talk about.
In general, focus was pretty fast, pretty quite and pretty accurate. Maybe not quite as fast as the best Canon USM lenses, but still pretty good. Focus can be manually “touched up” without switching into manual mode (the same as Canon’s F-TM or full time manual focus). Focus can be switched to fully manual if desired.
Looking at images shot at 500mm I noticed that some of the images seemed sharper than others. I first noticed this when taking shots of the moon. The lens was on a tripod, there’s no possibility of focusing on anything but the moon (no confusing background!) and I was using a remote release.
Shots taken using manual focus with the camera using Live View and a 10x magnified display were all sharp, so I’m assuming my technique was good.
I also noticed missed focus on a few “normal” shots. Not all of them, not most of them, but some of them (maybe 1 in 10 or 1 in 20?).
Is this significant? Well, Canon’s spec for focus accuracy is “within the depth of field” for lenses between f/2.8 and f/5.6, which isn’t a very tight spec. Cameras with high precision sensors have a focus accuracy spec of "within 1/3 the depth of field) for lenses which are f/2.8 and faster. Normally lenses do better than that of course.
Canon also specifies that lenses must be f/5.6 or faster to meet that spec, indeed, for their crop sensor DSLRs Canon cut off AF for slower lenses (e.g. f/5.6 lenses with a 1.4x TC attached). Canon do not produce any lenses slower than f/5.6. Sigma has devised a system, which reports the correct aperture to the camera (f/6.3) but which does not trigger Canon’s block on AF with f/6.3 lenses. I don’t know how they do it, but they have figured out a way. This certainly raises the question of whether the AF system can achieve its best performance with such slower lenses. If the lens optics weren’t capable of sharp images, you might never notice small focus errors, but with a sharp lens (and this lens can be sharp in the center of the field, even at 500mm), they can be seen. Perhaps results would be different with a 1 series Canon DSLR, which has a central AF sensor capable of reliable operation with lenses as slow as f/8, but unfortunately at the time of these tests I did not have such a body available to me.
I saw the effect at 500mm and 400mm, but at 300mm and below I didn’t notice any significant focus accuracy issues. I still don’t really know if it’s a camera issue, a lens issue or I’m just both unlucky and unusually picky! I’m hesitant to mention this for fear readers will misquote me any say “the lens doesn’t focus properly”. That’s not really what I’m saying. I was pretty happy with focus most of the time, but there were some soft shots that I couldn’t really attribute to bad technique.
The Sigma 50-500 OS HSM is quite a remarkable lens. It’s the widest range long telephoto zoom made by any manufacturer. Canon’s closest competitor would be the EF 100-400/4.5-5.6L IS USM and Nikon’s would be the Nikon 80-400mm f/4.5-5.6D ED VR. Tamron has the Tamron SP AF200-500MM f/5-6.3 Di LD (IF) but it lacks image stabilization and has an even smaller zoom range.
Considering its range and price, the Sigma is unique and overall provides fairly impressive performance. Center sharpness is generally very good and comes close to that of some very good Canon lenses (the EF 300/4 and EF 500/4.5L). Away from the center and particularly at the edges and corners – and particularly on full frame cameras—the primes do better of course. However, in practical terms, most people using a long telephoto will put their main subject in the center of the frame, and the edges and corners will likely be of lesser importance.
There are few concerns about the Sigma 50-500 OS though. Vignetting is pretty noticeable, especially at 500mm on a full frame camera. However, vignetting can be digitally corrected with the right software (though that doesn’t include Canon’s DPP RAW processor which only corrects for distortion, CA and vignetting with Canon brand lenses).
Then there’s the reduction in focal length as the lens is close focused. At infinity the focal length extends out to somewhere around 480-485mm, which is within the normal ±5% range considered acceptable. However, focused down to around 7m the focal length drops to around 435mm and focused down to 2.5m the focal length drops down to around 385mm. This is nothing unusual for an internal focus telephoto zoom with close focusing ability, but it does take some people by surprise. The Sigma 50-500 is capable of much higher magnification than, say, a Canon 500/4L IS because it can focus so much closer. At the nominal 500mm setting the Sigma gets to at while the Canon only gets to 0.12x at 4.5m, so if you can get closer, you can get more magnification with the Sigma 50-500 OS. However if you’re at a fixed distance (say in a blind 7m from a bird feeder, a 500mm prime like the Canon will give you an image of your subject that’s about 15% larger.
The Sigma 50-500 is also rather slow at f/6.3. This is an issue because the f/6.3 aperture comes in at around 245mm, so it makes the lens a 300/6.3 and a 400/6.3 as well as a 500/6.3. With the ever increasing performance of DSLRs at higher and higher ISO settings, a slow lens isn’t as problematic as it was back in the days when you had to shoot ISO 50 slide film for maximum image quality, though it’s possible (but by no means proven) that an f/6.3 aperture may at times result in some AF issues, which brings us to…
AF issues. I felt from extensive testing that the Sigma 50-500 OS wasn’t always delivering the image quality that it was capable of when using AF at longer focal lengths. I had the feeling that the optics may be better than the AF precision that the lens can consistently deliver, at least at the long end of the zoom range. Don’t get me wrong, most of the shots were sharp—but a few were unexpectedly off focus.
All performance issues have to be weighed against the fact that the Sigma 50-500 OS sells for about1/3 the cost of a 500mm prime lens, but it also covers 50-499mm too! That’s a huge leap in convenience and versatility. A more appropriate comparison would be with the Canon 100-400IS and Nikon 80-400VR lenses, both of which are priced around $1600, about the same as the Sigma 50-500 OS is selling for. The decision on which lens to buy is much easier for Sony, Pentax and Sigma camera owners, since there’s really no competition with a similar focal length range to choose from! Sigma does make a 150-500/5.6-6.3 OS HSM lens for about 2/3 the cost of the 50-500. I suspect many photographers would buy the 50-500 for use as a long telephoto and so probably wouldn’t use the 50-150 range all that much, in that case the 150-500 OS might also be a lens worth considering, especially if you also have a lens like a 70-200 in your kit.
The bottom line is that I enjoyed using the Sigma 50-500 OS HSM and I got some great (and sharp) shots with it that I probably wouldn’t have gotten with any other lens I own. I wouldn’t have walked around carrying my 500mm prime because it’s too big and heavy, and even if I had had it with me mine doesn’t have IS so handholding it would have been difficult and it doesn’t focus as close as the Sigma so I wouldn’t have had the magnification the Sigma gave me! See the first sample image (Swift) for an example of a shot I captured with the Sigma lens at 500mm that I wouldn’t have otherwise got.
Sigma 50-500/4.5-6.3 OS HSM Image Samples
||Canon T2i, Sigma 50-500 OS HSM, 500mm, f/11, ISO 3200. This is a slight crop from a close focused image (about 3m from the subject). Nothing wrong with this image! Focus is good and the T2i turns in remarkably high image quality for ISO3200. This shot was handheld at 1/500s with the OS (optical stabilization) on.|
||This is a shot taken with the Sigma 50-500 OS HSM at 500mm on a full frame DSLR (EOS 5D). Vignetting is pretty apparent in this shot. It could be corrected in an image editor, but not Canon’s DPP which only allows corrections of RAW images taken with Canon lenses.|
||The wide zoom range of the Sigma 50-500 OS HSM is shown in these two images. The upper image was shot at the 50mm setting while the lower shot was taken at the 500mm setting.|
||The zoom capability of the 50-500 OS HSM was used to frame this shot. Zoom setting was 332mm and with OS turned on the image is sharp, even with the lens handheld at a shutter speed of 1/60s.|
||The close focus ability of the Sigma 50-500 OS HSM is quite useful. This shot was taken at about 1/3 life size at around 330mm. Though not due to the lens, this shot from the Digital Rebel T2i is remarkably noise free despite being shot at ISO 6400 (some additional noise reduction was applied, but even so it’s pretty good).|