I like to try and stay fit, and do a number of different sports with this goal in mind. One is sea-kayaking, and it is also the only one that combines well with bird watching and -photography.
In the kayak I can easily carry my camera between my legs – as long as I’m happy to leave the big 500mm behind (or stowed in a sealed compartment). This means I use the 300mm f4 lens, and since I am shooting full-frame I also generally have the 1.4TC mkii mounted. Still, that gives just 420mm effective focal length, and that is often too short. So on this trip I tried a new approach, mounting a Kenko Pro teleconverter behind the Canon-combo described above. This gives a 588mm f8 lens, and in the following we’ll be looking at how this setup performs, image-quality wise.
I ran into a very accommodating reed warbler. Here’s an entirely unprocessed shot of the bird – click on it to enlarge:
One more of the same bird, and the same lens combo. In both instances the depth-of-field is crazy shallow; this is due to the very short distance between the focal plane and the bird, as both shots are just about straight off the sensor with no cropping applied.
What I encourage you to look at is the sharpness of the image in those parts that are in fact in focus; I must admit I am more than a little pleased with the image quality of these, something that is particularly interesting for a number of reasons:
- The 300mm f4 costs around 1/8 of the 500mm f4 lens
- The former is fully hand-holdable and can be carried around for days (on a normal-sized camera housing) without becoming a nuisance
- The 500mm is not suitable for use in, say, a kayak, or any other small vessel/vehicle
- Travelling on commercial flights with the 500mm lens is a pain in the arse – the 300mm fits in my normal camera backpack (Lowepro 300)
Note that there is still a place in a nature-photographers kit bag for the big lens, if you can afford it and find that the low-light benefits justify the investment, but the other option is great to have in a pinch, and can leave you with absolutely acceptable results as long as there’s plenty of light available.
Regarding autofocus, on my 1Ds mkiii and 5D mkii it worked great – best on the latter, which is slightly newer. As far as I have been able to learn, the Kenko converter doesn’t tell the camera that there is a Canon tc in front of it, so even if your camera normally won’t autofocus with anything darker than f5.6 it may still work.
The images above are unprocessed in Photoshop – only RAW-converted in Canon DPP and reduced in size in Photoshop – no sharpening applied. Here below is the first image, with one click on the USM function – again, click on the image to see the full size, and hopefully you’ll agree that this is better than one would expect from two tc’s stacked: