Move over, F/2.8
R. Ian Lloyd captured this Cuban street sweeper on a smoking break using a 70–200mm f/4L Canon EF IS USM on an EOS 5D Mark III. “It doesn’t intimidate my subjects like my bigger f/2.8 zoom, nor does it scream ‘professional photographer’,” says Lloyd.
For instance, Canon’s stabilized 70–200mm f/4L ($1,349, street) was significantly sharper at 200mm in our optical bench tests than was the stabilized 70–200mm f/2.8L ($2,500, street). In our distortion control, maximum subject magnification, and image-stabilization tests, results for the two lenses were very close. (Oddly, the comparable Nikon zoom pair logged the opposite results: The f/2.8 lens was sharper at 200mm, while the f/4 zoom carried the day at 70mm and 135mm.)
Another plus? Like those popular 70–200mm zooms, many f/4 lenses boast on-board image stabilization. This makes them a great favorite of still photographers, but especially of videographers. Jimmy Chin, an adventure sports photo and video shooter relies on that IS. After all, it's hard to hold a camera steady when you're dangling from a cliff. These days, he often turns to Canon’s EF 24–105mm f/4L IS USM. “That lens has incredible stabilization,” he says. “It’s great when I have to shoot handheld, especially for video.”
Many of our pros also applaud the f/4’s constant aperture. Compared with the variable-aperture zooms typically sold in kits with DSLRs and ILCs, the constant maximum aperture of f/4 means that zooming in or out has no effect on exposure. In some circumstances, such as shooting in manual mode with non-TTL studio lighting, this can be crucial because variable-aperture glass would progressively underexpose as it’s zoomed out.
Also, an f/4 zoom lets you set an exact aperture at the tele end, impossible with variable-aperture glass. “I hate when apertures change as I zoom,” says Elmakias. “Zoom settings shouldn’t change the amount of light I’m getting. It would add a whole other level of things to worry about, and I don’t really have the time for that.”
Variable-aperture shooting can also present problems in auto-exposure modes. In aperture-priority, for example, if you set a maximum aperture and then zoom longer, the aperture will become smaller and the camera will compensate by changing to a slower shutter speed—possibly too slow for your purposes.
Round Up: F/4 All Stars