If you're a really, really serious bird-watcher, and if (like me) you've always wanted to capture stunning images of tiny birds in action, then you surely know that the problem of finding a telephoto lens of sufficient magnification and optical quality at an affordable price is a Big Problem.  As I showed in a previous article, the most popular focal length, by far, for really hard-core bird photographers is 800mm.  Focal lengths as short as 400mm can be useful as well, especially for specific applications (such as ducks in flight), but by and large 800mm is preferred.  The question is, what is the best 800mm lens combo when image quality and price are taken into consideration?

This is precisely the question which haunted my fevered brain one year ago as I considered my options for achieving roughly this focal length in a Canon EF-mount system:

(1) Sigma 800mm f/5.6 lens
(2) Canon 600mm f/4 lens + 1.4x teleconverter = 840mm
(3) Canon 500mm f/4 lens + 1.4x teleconverter = 700mm
(4) Canon 500mm f/4 lens + 2.0x teleconverter = 1000mm

I immediately discounted the last two options, since, in the case of the Canon 500mm f/4 + 1.4x TC, the resulting focal length of 700mm seemed too short for the tiniest birds that I might find myself hunting come spring, and in the case of the 500mm + 2.0x TC, I was concerned that the use of the 2.0x TC, even Canon's expensive "EF Extender II" model, would too severely degrade image quality, since 2x converters are fairly widely maligned by those who've used them.

Thus, the options were between the 800mm Sigma prime lens and the Canon 600mm plus a 1.4x TC for an effective focal length of 840mm.  I again applied the reasoning that the use of teleconverters can only reduce image quality, and therefore decided that a prime 800mm lens was the way to go.  Since Canon didn't (at that time) offer an 800mm lens in EF mount, this left me with one option: The Sigmonster.



I was basically betting that an 800mm prime lens would be sharper than any 600mm + 1.4x TC combination, even if the 800mm lens was "third party" and the 600mm was a "name brand".  It seemed a reasonable bet at the time.

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It has now been exactly one year since I purchased the Sigmonster, and I can honestly say that this lens has made me very, very happy.  With it I have peered into the lives of countless birds, and in the process produced thousands of pleasing images.  I am indeed so fond of this lens that I have often resisted the urge to bring it with me to bed at night.  And no, I'm not joking.

Like many birding enthusiasts, however, I am always on the lookout for anything that can get me a better view of the bird.  Even if my current equipment seems ideal, I can't in good conscience dismiss the possibility that there may be an even better view that can be had with the proper equipment.  And so, as the winter months passed and the spring began to draw ever nearer, I began once again to consider my options for an upgrade.  This time around, there was only one unexplored possibility, and that was the Canon EF 600mm f/4L lens.


I only recently discovered that Amazon.com not only sells a wide variety of photographic equipment, but also offers an extremely generous 30-day return option.  This is a very useful fact!  For me it meant that I could perform a thorough comparison of the Canon 600mm lens with my Sigmonster and come to a confident conclusion.

It didn't take 30 days.

Indeed, after my first "in the field" (meaning "out my front window") session with the Canon 600, I had already practically made up my mind.  All I can say is WOW.

Let's begin, however, with the more controlled tests which I conducted inside my home (at 4:30am, no less --- sleep does not come easy to those obsessed with bird photography).  My "labratory tests" consisted of a $20 bill (obviously, I paid for the lens with a credit card...) scotch-taped to the bathroom door at the end of the hall.  I took three photos with the Sigmonster (all tripod-mounted, with mirror lock-up and remote shutter release) and then three with the Canon 600 + 1.4x TC, and chose the sharpest of the three in each case.  The image below shows these first results; the Sigmonster is on the left and the Canon 600 (with 1.4x TC attached) on the right:


As you can see, the Canon 600mm + 1.4x TC actually appears sharper than the Sigma prime lens.  When taking the shot with the Canon I moved the tripod back about 2-3 feet to account for the difference in magnification between 800mm and 840mm focal lengths.  Thus, even at a (slightly) greater distance, the Canon rig produced an image with more detail and noticeably more contrast (note the intensity of black in the image on the right, as compared with the brownish quality of the Sigmonster image on the left).

Here's another sample, with again the Sigma on the left and the Canon on the right:


This pair of images was obtained by again exercising each lens three times and taking the best of the three.  In this case the Sigmonster can be seen to be almost as sharp as the Canon, though with again significantly less contrast (i.e., observe the difference in black levels between the images).  Of course, obtaining this result required more trials, since the Sigmonster lacks image stabilization --- i.e., no matter how sharp either lens is, the image-stabilized lens will tend to show its sharpness more immediately, due to the lack of bluriness induced by camera shake.

Here's another result showing both the contrast (blackness) and detail advantage of the Canon setup:


An important caveat in all these examples is that in the case of the Canon rig, it is a Canon camera (the EOS 1D Mark III) focusing a Canon lens, as opposed to a Canon camera focusing a non-Canon lens.  It is of course conceivable that the non-Canon lens may be optically equal to the Canon lens, but may exhibit poorer image quality in practice due to the Canon camera not communicating properly with the non-Canon lens and therefore not achieving as precise a focus as with the true Canon lens.  Be that as it may, since I'm not willing to switch to a Sigma camera body, these results suggest that the Canon lens is the more useful tool of the two.

As a final example with the $20 bill, notice how the Canon image (right) reveals the hexagonal patterning in the empty space much more readily than does the Sigma image (left):


It is of course abundantly clear from these artificial tests that the Canon rig, despite the use of a teleconverter, is fully the equal of the Sigmonster, and may even be superior in terms of contrast and focusing accuracy.  I find this result very surprising, since teleconverters are well-known to degrade image quality, even if only slightly.  That the rig with the TC could perform better than the rig without is a truly remarkable testament to the inherent sharpness of the Canon 600mm lens.  It's unfortunate that I have little interest in 600mm as a focal length for general-purpose birding.

After scrutinizing these test images I have also been able to confirm a long-held suspicion of mine: that the Sigmonster produces images with an unnatural yellow cast to them.  This past year I have noticed a frequent need to reduce the level of yellow in my images, which I assumed was a common artifact of color "temperature" as produced by natural lighting scenarios.  Since the Canon does not produce such a yellow cast, I now suspect it is a by-product of the lens coatings used by Sigma on their glass surfaces.  Regardless of its origin, I must admit that I strongly prefer the color fidelity of the Canon over that of the Sigma.

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Test images of dollar bills (or even $20 bills) are only convincing up to a point.  What matters to the serious bird photographer is the performance of a system in the field.  In order to address this issue I turned to my front window.

My first willing assistant was this lovely Eastern Bluebird (Sialia sialis):


One thing you'll notice if you view the zoomed image by clicking on it is that the bokeh (i.e., the out-of-focus background) is pleasingly smooth.  Another thing you'll notice is that the image is quite sharp, with many feather details readily apparent at first glance.  Of course, the color is also quite vibrant, despite the fact that I left the saturation untouched in post-processing.

Here's a Brown-headed Cowbird (Molothrus ater) male that visited my birdbath this morning:


Again you'll note the smooth bokeh and the sharp feather detail.  These images were all shot in RAW format, with fairly minimal post-processing in Photoshop.  Based on the LCD images viewed on the camera during shooting, I could tell right away that I was getting images fully as sharp as what I was used to getting with the Sigmonster.

One thing I did notice, however, was that the Canon 600mm lens was slightly front-focusing, as you can see by looking at the in-focus region on the ground just in front of this Mourning Dove (Zenaida macroura):


Front- and back-focusing issues truly infuriate me.  They are in fact the reason I invested in the 1D Mark III camera body, since this body at present is the only one in the world (to my knowledge) which allows user-defined autofocus calibration.  Via a menu option, one can quickly dial in an AF compensation value to adjust for the front/back focusing tendencies of individual lenses.  After shooting the Mourning Dove shown above I dialed in a +5 AF adjustment (i.e., 5 units "backward", or away from the camera), which soon was modified to +7. 


After some more experimentation I quickly found that +10 produced quite nice results.  The robin pictured above and again below patiently aided me in this process.  Note that front/back-focusing can be corrected by sending the lens and camera in to Canon to have them adjusted by Canon's service technicians.  Many people send their lenses in immediately after purchase to have them calibrated, and though most of the time this appears to solve the problem, there are reports of cases in which people sent in their equipment only to have it come back in worse shape than before!

I my particular case, the front-focusing may very well be due to the fact that I'm using a 25mm extension tube to reduce the minimum focus distance from 18 feet to about 10.  The Canon literature clearly states that autofocus should not be used when an extension tube is attached, presumably because it confuses the camera.  Another possible side-effect of the use of the extension tube is some distortion around the edges of the image --- in some of the later images on this page you'll notice that the edges and corners appear not only to be out of focus (which is entirely normal, since I focused on the bird, not on the surrounding branches) but also somewhat distorted, or "stretched".  I never noticed this with the Sigma, but maybe I just never looked for it.


Despite the front-focusing issue (which appears to be corrected now by the in-camera microadjustment), the Canon rig appears to be fully as sharp as the Sigmonster, while also providing other useful perks.  According to Canon, the lens is "weathersealed", which I gather means that a bit of light rain won't harm it, though submersion in a lake obviously will.  Unlike the Sigmonster, the Canon 600 also sports a protective front glass element which protects the main objective lens from possible scratching or degradation of the lens coatings by the elements (such as salt spray at the beach).  The Canon of course sports image stabilization, which could be extremely useful on windy days.  Also, the focusing speed on the Canon is very fast, though I have to admit that the focusing speed of the Sigmonster never seemed terribly slow to me. 

My 1D body does still "rack out" the Canon 600 + 1.4x TC combo occasionally when searching for the focus, just as it did with the Sigma.  Although the Sigma has a focus-limiter switch (unlike the zoom-version of the Sigmonster, which lacks such a switch), I have rarely used it, since it tends to become an annoyance when I forget to reset it for the next shooting location.  The Canon focus-limiter switch has more settings, which in theory should be useful for specific scenarios, but I again expect to use it very, very infrequently.  I tried using it this morning on birds in my front lawn, but found that one setting worked for close birds but not for further birds, even though I have a very small lawn.

As just a brief demonstration of the value of image stabilization, here's a bluebird that I photographed with the IS turned on.  Because the IS effectively eliminated all camera shake, the image required no sharpening whatsoever during post-processing:


Keep in mind that Canon recommends that all photos taken with its digital cameras be sharpened in post-processing, since the anti-aliasing filter in front of the CMOS sensor reduces sharpness at image capture. 

With the Sigmonster I virtually never got by without applying some sharpening during post-processing.  Of course, once I had applied the sharpening to the image, the output of the Sigmonster was usually very pleasing.  But if I can get sharp images straight out of the camera with the Canon lens, then that's definitely a good thing, since it means I'll be able to spend less time fiddling with the sharpening filter in Photoshop, and more time attending to exposure and color (or, better yet, more time out in the field actually taking photos!).


I should emphasize that my Sigmonster is the non-zoom model, which some people have implied is less sharp than the zoom version.  I've never compared the two models, though the MTF charts on the Sigma web site do show some slight difference in the performance of the two models, with one model having (if I remember correctly) slightly better contrast than the other.  I suspect these MTF charts are the source of the rumor about the difference in sharpness between the two models.  If that's so, then it should be noted that MTF charts can be quite unreliable.  Indeed, Canon acknowledges that their own MTF charts are only "theoretical".  Furthermore, there can be quite a lot of variation between individual units, so that one unit may be more or less sharp than another unit of exactly the same model.  I've seen this myself with Canon teleconverters.  The point is, the apparent difference in optical quality between my copy of the Sigmonster and the Canon 600mm + 1.4x TC combo may not be representative of all Sigmonsters and all Canon 600mm lenses (especially given the wide variation in teleconverter quality, as I've already mentionted).



With that caveat aside, my brief experience with the Canon 600mm suggests that Canon's optics technology may indeed be a step ahead of the third-party brands, and this could of course manifest itself in differences between other lenses.  What's interesting is that the zoom version of the Sigmonster costs nearly as much as the Canon 600mm (and weighs nearly as much), so that the third-party lens makes little sense in terms of price difference.  However, if it is true that the zoom version of the Sigmonster is optically superior to the non-zoom (of which I am somewhat doubtful), then it may be equal to the Canon 600 + 1.4x TC combo, but with the added convenience of a 300mm-600mm zoom range, which the Canon rig lacks.  I personally have never wished I had such a zoom capability, but some users swear that it is a godsend.



One thing that I have been eager to test out on the Canon rig is its ability to produce sharp images when operated wide-open --- i.e., when the 840mm rig is used at its maximum aperture of f/5.6.  I always felt when using my Sigmonster that I needed to stop down to f/8 or f/11 in order to obtain the sharpest images.  This of course could conceivably be due to the extremely shallow depth-of-field which is induced at such a large aperture.  Nevertheless, I always had the feeling, from the few times I tried shooting at f/5.6, that the lens was simply not as sharp wide open as when stopped down.  It is in fact well-documented that most lenses do improve in sharpness when stopped down by 1 or 2 f-stops. 

Owners of the big Canon telephoto lenses --- the 500mm and 600mm f/4 lenses in particular --- often insist, however, that these lenses are tack sharp wide-open.  From the few shots I've taken with the Canon rig at f/5.6, I can't yet discount this claim.  Here's a Slate-colored Junco (Junco hyemalis) shot at very close range, at f/5.6:



You can see the effects of the very shallow depth-of-field in this photo.  While the front half of the bird is very sharp, the rear half is completely out-of-focus.  In this case I don't think that's a bad thing; for some photos that can still work well to produce an aesthetic image.  In this case I'm inclined to think that the lens is indeed quite sharp wide-open, though I'm not sure how often I'll use it at that aperture, due to the depth-of-field issue.  Note, however, that the depth-of-field does increase with distance to the subject, so that for birds at a greater distance, f/5.6 may indeed work out OK.
 


Like the Sigmonster, the Canon 600mm lens is enormous.  Although only about 1.3 lbs heavier than my (non-zoom) Sigmonster, the Canon 600 is bulkier.  It's not going to be any easier to carry around in the field, and I've already had some difficulty with that.  Although I typically do carry around the Sigmonster all day, I usually end up paying for it by being dead tired and sore when I get home. 

The Canon is well-balanced, though, and the carrying handle is quite nice.  The handle is padded underneath, and also leaves a wider gap with the lens body, so that when shooting on a tripod I'm finding it convenient to hold the handle with my left hand in order to steady it (I don't lock my tripod head when shooting, so everything is loose --- that's good for tracking birds in motion, though not-so-good for keeping the camera steady when taking the shot).



So, what don't I like about the Canon 600mm lens so far?  Not much.  The mounting "eye" for the strap is only large enough for one strap to attach at a time, which I don't like, since I prefer to attach two straps simultaneously, both to improve comfort while carrying the lens via the strap, and also as an insurance policy against one strap breaking (which has happened to me before). 

I also wish it had a much closer minimum-focusing distance.  As I noted above, I have to use a 25mm extension tube in order to reduce the close-focus distance from 18 feet to about 10, though the tube seems to induce some distortion around the edges of the image, which can be distracting when there are almost-in-focus elements at the edge of the image, such as branches and the like.  What might be a better option is to not use the extension tube at all, but to switch to my other lens (the Canon 400mm f/4 DO + 1.4x TC) for close subjects, since the latter lens has a close-focus distance of about 11 feet.  Since I always go into the field with the 800mm rig on one shoulder and the 400mm lens on the other shoulder, this is a viable solution for me.




The Canon 600mm comes with a very nice travel case --- a hardshell trunk with a soft molded interior that perfectly fits the lens.  With the hood removed, the lens actually becomes quite short, so that the case isn't all that big:




The case has a lock, so it can be checked with your other luggage during air travel.  In contrast, the Sigmonster comes with only a padded bag, which is fine for storage in the trunk of your car, but wouldn't be totally safe if chucked around by baggage handlers at the airport.

So, in summary, I think the Canon 600mm + 1.4x TC combo is an ideal birding lens, especially for small birds such as warblers, sparrows, chickadees, and the like.   Assuming you get a good copy of both the lens and the TC (without any front/back-focusing issues) and/or are able to fine-tune the autofocus performance via in-body calibration as in the Mark III, there isn't much reason to choose the Sigmonster over the Canon rig, unless zooming is important to you (it isn't to me --- but I'm pretty good at finding a little bird with a narrow field-of-view lens).  There is a modest price difference, but when you're buying such an expensive lens anyway, it makes sense to save up a few more pennies and spring for the  more expensive Canon rig, which  offers several features not found in the Sigmonster.

As of this writing, there are two other big telephoto lens options for birders which are soon to be released, and which may prove to be even better options than either the Sigmonster or the Canon 600mm + 1.4x TC rig.  The first is the new Canon EF 800mm f/5.6L IS USM lens which is due to be released in a few months.  This lens has a list price of $16,000, though the MSRP is a paltry $12,000 (!).  Canon claims that the new 800mm lens is optically superior to the 600 while weighing less, indicating that it could be an amazing birding lens for those who can afford it. 

The other new development is, coincidentally, a lens from Sigma which people are calling the SigZilla: a 500mm zoom lens with a fixed f/2.8 aperture, weighing 35 lbs, and having an MSRP of $24,999 (!).  Wow.

And if you think those are way out there, there's always the Canon 1200mm f/5.6L lens, which B&H actually has in stock as of this writing.  The price?  A mere $99,000.  Better hurry before they're gone!