Canon 70-300 DO Lens: Good Concept, Shame about the Contradiction

A recent review of the Canon 70-300 DO lens in Popular Photography has prompted me to report my own experience with this much-maligned lens.

A portable telephoto is pretty much an oxymoron: an inevitable compromise between two contradictory concepts. For moving about, typically smaller and lighter are better. For image quality in a 300 mm lens, usually larger is better, with more glass correlating with better light gathering ability.

Enter Canon’s DO lenses. The DO stands for diffractive optics, and these are the first lenses from any manufacturer (and at this stage there are only two: the 400 f4 DO IS USM and the 70-300 f4.5-5.6 DO IS USM) to employ a grate in the lens elements that bends the incoming light to a greater extent than normal refractive lens elements, thereby allowing the lens to be smaller and largely free of the chromatic aberrations that plague digital photography (usually seen as purple fringing along high contrast edges).

First introduced in 2004, the Canon 70-300 DO IS USM lens (with a street price of around $1200 USD) promised to deliver the Holy Grail in the world of the portable telephoto zoom: a small, compact lens that could produce stellar image quality. Not only that, Canon threw in the very latest image stabilization technology (supposedly making you at least three stops steadier than you would otherwise be handheld), meaning that you could leave the tripod at home. It all seemed far too good to be true – and, in essence, it was.

Initial reviews were not favorable. The lens got slammed by users, if not reviewers, because it wasn’t particularly sharp, especially at the long end. What it lacked in contrast, it compensated for by being spectacularly prone to flare anytime there was a bright light source anywhere near the frame. It could also produce a curious halo effect around some subjects and specular highlights could be rendered in strange ways, making for a distasteful bokeh. And, if those were not sins enough for the Canonatics, the lens was especially dissed because in 2005 Canon produced a conventional 70-300 lens at half the price that had IS, better image quality (according to some), and was not much bigger while actually being lighter than the DO lens.

The Canon 70-300 DO proved handy for capturing this Columbian ground squirrel (300 mm, ISO 200, f7.1, 1/400)

100% crop of ground squirrel, no sharpening applied: sharpish rather than bleeding edge

Still, the 70-300 DO made my mouth water and my bank manager quake: what I’d give for a lens that small and blessed with the ability to go sans tripod. It enticed the travel photographer in me and the mobile wildlife photographer in me as surely as if it had been Penelope Cruz in her underwear.

I think that most of us buy camera gear in the same way that we go flying: we are very aware of the nasty outcomes that are possible but we proceed on the basis that we don’t believe they are going to happen to us.

My reaction to the 70-300 DO was initially very positive. It is squat (only 10 cm in length), unexpectedly heavy (720 g) and well-built. Canon reserves the red line around the distal end of its lenses for those that get the professional “L” classification. For lenses based upon DO technology, Canon uses a green line. While the 70-300 DO dresses in green, there seems little doubt that it is built to L-lens standards.

The excitement I felt lasted only until I attached the lens to a camera. The results were awful. Drab. And, most disappointing of all, soft as a sponge. It had instantly claimed the title as My Least-sharp Lens. Even my old EF 100-300 f4.5-5.6, which if it were a knife would have difficulty slicing through butter, was sharper and had way better contrast.

After trying all sorts of tricks and different post-processing, all without joy, I was about to relegate the lens to the drawer I have reserved for “Life’s Mistakes” (I won’t tell you what else resides there, except, suffice to say, it is rather full), when I decided to send the lens to Canon to see whether there was anything they could do to resuscitate it.

To cut a long and convoluted story short, Canon agreed my copy was substandard, ordered a part from Japan that took months to materialize, and eventually returned my lens to me in substantially better health.

It is still not crisp, like my 70-200 f2.8 L, and my 300 f4 L kills it – but it is now acceptably sharp, even at 300 mm. There is a nice evenness to the images it produces that extends across most of the frame, with just the corners being a bit blurry when the lens is wide open (but given that it is a rather slow lens, with the aperture topping out at f5.6 at the long end, that means most of the time).

I can deal with the lack of contrast in post-processing, even though I’d rather not have to do that. What I cannot deal with – and it is hard to anticipate when they will rear their ugly heads – are the weird halos that are sometimes apparent. Chromatic aberration may be absent, but what use is that when the cure is worse than the symptom?

100% crop showing halo effect along edges of a rose (300 mm, ISO 200, f5.6, 1/1000)

The results from PopPhoto’s tests indicate that the lens turns in pretty decent image quality. And there is no doubt that you can get by with the 70-300 DO if producing prints in the 10x8 range. I often want larger and, as a consequence, I must admit that I seldom take the lens with me. If I want to travel light these days I take an Olympus Zuiko ED 40-150 f4-5.6 (which, with the 2x factor of the four-thirds system translates to an 80-300 full-frame equivalent): it weighs only 220 g and, while it is not nearly as robust, its image quality eats the 70-300 DO for lunch.

In conclusion, then, I find it hard to recommend the 70-300 DO. If you already have one and are not satisfied, then I’d suggest that you send it to Canon for calibration. But keep your expectations in check: this lens is not so much Penelope Cruz in underwear as it is Danny DeVito in drag – and, personally, I find other alternatives more attractive.