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How a matched tele-converter and telphoto lens can create magic
I had an older 500mm lens and began to wish for something better.
It was sharp but it was an f/4.5, which meant if I put even a 1.4x tele-converter (also called a tele-extender) on it, it became an f/6.7—which doesn’t allow enough light for my camera’s autofocus to work. And it was not image stabilized, so even on a sturdy tripod I needed to use mirror lockup and a remote shutter release for best sharpness, or else keep a very fast shutter speed. And with my full-frame Canon 5D I don’t have a magnification factor, so while 600mm f/4 sounded like the desirable upgrade, it is heavy (11.8 lb) and very expensive (about $7600).
There had to be a better way.
Enter the Canon EF 300mm f/2.8L IS. It is an incredibly sharp lens, as sharp wide open as it is stopped down according to many reviews including this one. This lens isn’t cheap at about $4,000, but that is a lot less than a 600mm. It is also lighter, at 5.6 lb. Since the 300mm is f/2.8, I would still have autofocus with either a Canon 1.4x or a 2x tele-converter. A 1.4x tele-converter costs 1 stop of light (in other words, it cuts the light intensity in half) and a 2x costs 2 stops, so the lens becomes an f/4 or an f/5.6, which is the limit of autofocus for all but the top level pro camera bodies.
In many cases a 1.4x will cause a very slight softening of the image and a 2x a more noticeable amount. But this is more the case for zoom lenses than for primes (single focal length lenses). Several online reviews indicate this lens suffers no loss in sharpness with the 1.4x, and with the 2x there is only a slight effect at the most open aperture. (That is for the matching Canon EF II tele-converters.)
With this lens I would have a 300mm, a 420mm (with the 1.4x) and a 600mm (with the 2x). Switching tele-converters isn’t as convenient as a zoom lens, but it is a price I was willing to pay for the optically superiority. And in fact, the difference between 420 and 600 isn’t huge, so I rarely use the 1.4x.
You can even stack both tele-converterson the 300mm to get 840mm, but this results in some softening, and I loose autofocus with the Canon 5D. I would have it with the 1D or 1Ds, although only with the center sensor. The amount of softening seems about equal to what I get by interpolating up in Photoshop, so I would prefer that route if I need to crop and enlarge an image.
The lens also has image stabilization, with a regular and panning mode, although there is a version without it. For me, stabilization is very important at such magnifications, even on a very sturdy tripod. I have the heavy-duty Gitzo legs without the center column (the 3530) and the Wimberley II head, which is a wonderful setup for a big lens, but I still get a big advantage from stabilization. With the freedom of movement of the gimbal head I can track a moving subject and shoot without mirror lockup as long as I keep the shutter speed fast enough. (More about how fast that is, below.)
The rather generic lens manual says to turn off stabilization on a tripod, and that would be the case if you were using mirror lockup and a remote release. But using a loose ball head, or the Wimberley head with the vertical and horizontal tension unlocked and the tripod collar loose, so you have the 3 motion axes free, you do benefit from IS. You will often see the advantages of image stabilization given in terms of the “stops” gained. IS lets you use shutter speeds 2-3 stops lower than without IS. Each stop is a halving of the shutter speed, which means you can use ¼ or 1/8 of the shutter speeds you could use without IS.
A long-standing rule of thumb is that without IS you want to keep the shutter speed at 1/focal length, or higher. So with a 100mm focal length, for example, you would want a shutter speed of 1/100 sec or higher. But with very long lenses this rule should be even more stringent. With a lens in the 400-600mm range (very approximately) if at all possible I want to keep the shutter speed at 1/focal length or higher, even with IS.
This is not an inexpensive lens but for me it is the best way to go beyond my 70-200 f/2.8 IS zoom. It is easy to feel that you can never have too much “glass”, but the longer you go the more you have to deal with camera shake and atmospheric disturbance. Because of these factors, 600mm is about my personal practical limit.
I have just ordered the new 21 megapixel Canon 5D Mark II and will now have more leeway than I did with my 12.7 megapixel 5D to crop images without sacrificing too many megapixels. That lets me achieve a magnification factor similar to that of the smaller sensor cameras, and makes my 600mm lens effectively even longer.
Options for Smaller Sensor Cameras
For those who have cameras with a smaller sensor, such as the excellent Canon 50D, its 1.6x magnification factor allows you to use the much more affordable Canon EF 300mm f/4.0L IS lens. This lens is only $1200 and is much smaller and lighter than the f/2.8. To retain autofocus you can only use the 1.4x teleconverter, but without it you have the full-frame equivalent of 480mm, and with it, 672mm, so you don’t really need the 2x.
This smaller lens is much easier to hand hold, although I can manage the f/2.8 for short periods, as you can see by the accompanying images. Hand holding is not my first choice, but in some cases it is desirable. When I was shooting these egrets I had my big Gitzo with the Wimberley II head set up, but even with all the wonderful freedom of motion it allows I was having to maneuver around a tripod leg and was unable to follow the birds if they flew almost overhead. In this case hand holding gave me more flexibility. I am only 5’ 1” and 115 lb, and not much of that is muscle. A normal-sized person could hand hold this lens easily.
Here is a hand-held shot with the 300mm lens (no teleconverter), Canon 5D at ISO 640, 1/2000 sec, f/6.7. This is the full frame image, no cropping.
And here is a 100% enlargement. No sharpening has been done other than the default in Lightroom 2. Luminance noise reduction was set at 25 in Lightroom, a very conservative amount, to effectively erase the very slight noise in the sky. Only minimal color and tonal adjustments were done.
Here is another image, this one at ISO 400, 1/2000 sec, f/8. This is the full frame, no cropping.
And here is a 100% view. As above, no sharpening has been done other than the default in Lightroom 2. Luminance noise reduction was set at 25. Only minimal color and tonal adjustments were done.
The lens has 3 focus-limit positions to minimize searching: 6.4m to infinity, 2.5m to infinity, and 2.4 to 6.5m. It has prefocus settings and a drop-in polarizer is available as an accessory. It comes in a beautifully designed and very sturdy case. For hiking, it fits beautifully in the Lowepro Lens Trekker 600 with a camera body, 2x teleconverter and lens hood attached. Although not all images are tack sharp with a small person handholding this lens, the sharpness of these two is not a fluke. The bottom line is that I absolutely love this lens!
Diane Miller is a widely exhibited freelance photographer who lives north of San Francisco, in the Wine Country, and specializes in fine-art nature photography. Her work, which can be found on her web site, www.DianeDMiller.com, has been published and exhibited throughout the Pacific Northwest. Many of her images are represented for stock by www.MonsoonImages.com.