Four 100-400 tele zooms compared

Sigma 150-500, Sigma 120-400, Canon 100-400, Sigma 50-500. Click here to enlarge.
 
Tele zooms are very popular lenses, both for professional and amateurs: they offer good reach at an affordable price, and they can be a good "lightweight alternative" for handheld shots, or for long trips where you can carry heavy big lenses.  
 
In this test, I have compared the Canon 100-400 (a very old lens, announced in 1997, but still one of the best tele zoom on the market) with the mythical Sigma "Bigma" 50-500 and with the new Sigma 120-400 OS and 150-500 OS, two new interesting teles with both image stabilization and ultrasonic autofocus.
 
 

Specifications

 
 

Built quality, stabilization and autofocus

The built quality of these four lenses is very similar: they all feel solid and professional; they have metal barrel and a nice finish. Sadly, none of these lenses has weather sealing. In terms of size, the 150-500 is clearly bigger than the other three lenses; the Canon 100-400 is the smallest and the lightest of the group.

Sigma 150-500, Sigma 50-500, Sigma 120-400 and Canon 100-400. Click here to enlarge.
 
For handheld shooting, the image stabilized lenses have a clear advantage in comparison with the 50-500; I'd say that the Sigma OS is about on par with the 2 stops image stabilization of the Canon 100-400. All these four lenses have ultrasonic AF, and the AF speed is similar - it is quite fast, much faster than non-USM lenses, even though it is not as fast as the autofocus of top pro superteles. If can improve the AF speed using the focus limiter; other than that, all these lenses support full time manual focus (you can manually tweack the focus even during AF operation).
 
 

Image quality comparison

I have tested the lenses on my Canon 1DsIII (21 megapixel, FF). The lenses was mounted on tripod; I have used mirror lock up and self timer. The following images are 100% crop from the unprocessed RAW file. (note: s120 is Sigma 120-400, c100 is Canon 100-400, s50 is Sigma 50-500 and s150 is Sigma 150-500).  
 
 
 
150mm:

Wide open, the Sigma 50-500 and the Canon 100-400 are clearly the best; both the 120-400 and the 150-500 produce similar image quality and they shot less contrast than the other two lenses. At f/8, all the four teles gives identical image quality.  
 
 
 
300mm:

Wide open, the Canon 100-400 is slightly better than the other lenses, but there is not a big difference (the sharpness is about the same, but the Canon shows a little more contrast). At f/8, all the lenses improves in contrast and sharpness and the results are nearly identical for all four lenses; the 150-500 is an hair less sharp than the others, but in the field I doubt that you would see any difference at f/8.  
 
 
 
400mm:

At 400mm, all the four teles show a loss of contrast; wide open the Canon 100-400 is still an hair sharper, while at f/8 all lenses show an improvement and it is very difficult to see a difference in the image quality.  
 
 
 
500mm:

The only two lenses that reach 500mm are the 50-500 and the 150-500; the image quality is similar, even though, surprisingly, the 50-500 is a little shaper.
 
 

Conclusions

The big surprise in this test has been the Sigma 50-500: it is a 10x zoom, but it is about on par with the more expensive, 4x Canon 100-400 IS! The zoom range is truly amazing, it allows to take photos of a wide range of subjects and it has a good AF, that helps for wildlife photography. Considering the price, I recommend this lens, if you don't mind using it almost always on tripod - if you want a lens for handheld photos, I'd suggest to choose one of the stabilized zooms.  
 
The Canon 100-400 L IS gives very good image quality at every focal lenght; it has fast autofocus and good image stabilization: if you don't need the extreme versatility of a 50-500 zoom and the higher price is not an issue, I recommend the Canon.  
 
In terms of value for money, the Sigma 150-500 and the 120-400 are the winner of the test; they are much cheaper than the Canon 100-400 and they offers good image quality. The 50-500 is a little shaper in the studio tests, but in the field I think that the image stabilization of the 150-500 and 120-400 will compensate for the slightly lower sharpness. At $800, the 150-500 it is the cheapest 500mm that I know, and it has both stabilization and ultrasonic autofocus! If you want a lot of reach and you have a tight budget I recommend this lens.  
 
The 120-400 performance is very similar to the 150-500, and it is even cheaper. If you compare it to the Canon 100-400, it is almost 50% less expensive, and it offers the same reach! In terms of image quality, the Canon is slightly better, but if you have a limited budget the Sigma is a bargain at its price.