Should I buy a 70-200 mm f/2.8 or a 70-200 mm f/4 lens?

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December 15, 2014 at 10:30 am  •  Posted in Q&A, Tips & Techniques by  •  0 Comments

Several of my friends own a 70-200 mm f/2.8 lens and I’m considering one for my EOS 7D, but there’s also an f/4 version that’s smaller, lighter and more affordable. Which one would be the best bet?
—Darren O.

The 70-200 mm f/2.8 lenses—available in virtually all brands—offer a very wide, constant maximum aperture and superb-to-superlative image quality because of their premium-grade optical elements. But as you hinted at, Darren, this type is large, heavy and not inexpensive. And yes, Canon, Nikon and Tokina also make a 70-200 mm f/4 lens with a built-in image stabilizer. In fact, Canon also makes one without the stabilizer, and it’s even more affordable (The Tokina model is not yet available in Canada.) The f/4 lenses are also premium-grade in terms of construction and high-tech optical elements.

There is certainly a substantial difference in size, and hence weight, between any brand of 70-200 mm f/2.8 vs. f/4 lens. This is one reason for the higher price of an f/2.8 model: the cost of oversized components and optical elements—especially low-dispersion glass—makes the wide-aperture lens much more expensive to manufacture. Photos courtesy of Canon Canada.

There is certainly a substantial difference in size, and hence weight, between any brand of 70-200 mm f/2.8 vs. f/4 lens. This is one reason for the higher price of an f/2.8 model: the cost of oversized components and optical elements—especially low-dispersion glass—makes the wide-aperture lens much more expensive to manufacture. Photos courtesy of Canon Canada.

In any event, here’s a quick overview of the relative benefits of the f/2.8 and f/4 zooms.

  • You can use either a 1.4x or a 2x teleconverter with an f/2.8 lens. However, an f/4 lens is not really suitable for use with a 2x device. Autofocus would either fail to operate or it would be very sluggish because of the greater loss of light to the camera’s sensor. (For more information about this topic, check out an earlier Q&A item, Should I buy a teleconverter?)
  • As reviews tend to mention, images made at f/2.8 exhibit shallower depth of field than at f/4, making it easier to blur a distracting background into a nice wash of colour. Frankly, the difference is not great enough to make this an important consideration.
  • The difference between a maximum aperture of f/2.8 and f/4 is a full stop. This is particularly relevant when shooting in low light at a fast shutter speed to freeze camera shake or subject motion. In a situation where you’d need to use ISO 6400 when shooting at f/4, you could switch to ISO 3200 for better image quality with an f/2.8 lens. (With any camera, image quality is better at a lower ISO level.)
  • All of the 70-200 mm f/2.8 zooms include a removable tripod-mounting collar, while that’s an optional, extra cost accessory for the f/4 models. This is particularly relevant to shooters who often use a tripod. Even adding the cost of the collar, the f/4 lenses are more budget-friendly.
  • Independent test reports on sites such as SLRgear.com indicate that the f/2.8 models are slightly better in terms of sharpness across the frame at a wide aperture than the f/4 models of the same brand. On the other hand, I am fully satisfied with my own 70-200 mm f/4 zoom for professional applications. The edge-to-edge sharpness and the resolution are particularly impressive in the f/5.6 to f/11 range.

Since the Canon EF f/4L IS USM zoom weighs about 700 g less than its EF f/2.8L IS USM counterpart and fits nicely into a smaller camera bag, it’s great in terms of portability. If you buy an f/4 model, you would probably want to add the A II (W) tripod-mounting collar ($175); it adds only a few grams. The decision as to which lens any photographer would prefer depends on other aspects too:  shooting style, frequency of use in low light, the desire to retain autofocus with a 2x teleconverter and the significance of the other differences discussed above.

Anyone who often photographs events in low light should certainly consider the "faster" f/2.8 lens. Shooting at f/2.8 vs. f/4 allows for making images at a lower ISO level at the shutter speed required for sharp images. (f/2.8 at 1/30 sec; ISO 3200) © 2012 Peter K. Burian

Anyone who often photographs events in low light should certainly consider the “faster” f/2.8 lens. Shooting at f/2.8 vs. f/4 allows for making images at a lower ISO level at the shutter speed required for sharp images. (f/2.8 at 1/30 sec; ISO 3200) © 2012 Peter K. Burian

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