Petteri's Pontifications
My musings about photography, mostly.
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Canon 90-300/4.5-5.6 USM

Canon 90-300/4.5-5.6 USM

I've never been much into tele photography. The longest lens I've regularly shot with was the 28-200 equivalent on my Minolta D7i. I did experiment a bit when I was a member of my high school camera club, but I felt that with long tele, photography becomes more of a technical than a creative exercise. However, figuring that I might be mistaken, I wanted to experiment a bit. So I went on the lookout for an inexpensive and light tele lens for the 10D. I plunked for the new Canon 90-300 USM, dubbing it the Plastic Piston (in the tradition started by Adam-T of the DPReview Canon SLR Forum). Here are my thoughts about it.

The Piston mounted on the camera

Where does it fit in?

Canon's lens line is especially strong in tele lenses, both zooms and primes. Many of them are fitted with one of Canon's best-known innovations, image stabilization (IS), while others incorporate highly advanced innovations like diffractive optics. If Nikon holds the edge in wide-angles, Canon is pretty much the undisputed leader in tele lenses. There's a lot to choose from in this ballpark. Leaving aside the bigger, heavier, much better and much more expensive professional L's and the optically heavily compromised WA-to-tele consumer superzooms, and the competing lenses from Sigma, Tamron, and Tokina, there's still a fair number of lenses comparable to the Piston:

  • Canon 75-300/4-5.6 "Bargain Bogroll" (DC and USM): the original Canon EF consumer supertelezoom, and the design on which the Piston is based. It has a bit of a bad reputation for color artifacting and poor performance at the tele end, although it appears that there's a good deal of variation between units.
  • Canon 75-300/4-5.6 IS: the focal length and aperture range are the same, but this is a totally different design. It's the first Canon consumer lens to include image stabilization. This also makes it about three times more expensive than the other Canon consumer telezooms.
  • Canon 100-300/4.5-5.6: Physically, this lens looks a lot like the 100 Macro. It's significantly better built (and more expensive) than the 75-300, but optically very similar.
  • Canon 80-200/4-5.6 "Pocket Rocket": This lens doesn't have quite the reach of the others, but I include it in the list because of its respectable optics, low price, and very compact size.

The Plastic Piston is based on the 75-300 non-IS. It shares the same barrel and very similar optics. However, the focusing performance has been improved, and it appears that Canon sacrificed 15 mm from the short end to improve performance at the tele end: from what I've seen, the 90-300 appears to be much better than a typical Bogroll, and at least as good as an exceptionally good one. It does, however, share some of its problems.

Build and handling

Let's be blunt: Canon doesn't build them any worse than this lens. The fit and finish are sloppy and loose, there are some cast seams visible, when zooming, the lens barrel extends by about 1/3, the front element rotates when focusing, and the lens mount is plastic. In other words, it feels just like what it is: an inexpensive consumer-grade zoom. If you want "L" build and feel, or intend to punish your lenses with massive use and harsh conditions, don't expect much from the Plastic Piston.

The Piston extended.

From a build features point of view, the goodies on the Piston include nothing, or USM as an option. No RT-M, no DOF scale (not that it would make much difference), not even a focus distance scale (come on, Canon!). At least the zoom functions via a ring instead of a push-pull system, but that's about it.

DC or USM?

I won't comment, but experience from other lenses suggests that micro USM may be a waste of money. It is quieter, but on other makes, it is no faster than the cheaper DC. However, Canon does state specifically about the Piston USM that it has improved AF algorithms, and the lens does feel very snappy, so in this case... who knows. If someone has a Plastic DC and wants to lend it to me to play with, I'd be happy to try a comparison.

However, despite the Spartan design and flimsy build, the lens actually handles rather well. The upside of the flimsiness is light weight: the lens is easy to point around even at full tele and the camera balances well with the lens. Indeed, the lens is so light that the plastic mount probably doesn't make much of a difference, as long as you don't swing around the camera from the lens. The zoom ring is well positioned and wide enough for good grip; the turn distance is also right to zoom through the full range easily. And where it really counts -- focusing speed and accuracy -- the lens really shines: it snaps into focus with an audible crack and sticks like a limpet.

Pigeon in flight over Saignon. The Piston can pull off this sort of thing consistently.

I don't know how well the lens will hold up in heavy use (my guess is "not very well"), but other than that and the stupid omission of a focus distance scale the build is "good enough". It's not attractive, but it gets the job done.


I've been somewhat spoiled optically by my primes. It would be stupid to expect a consumer superzoom to perform as well as Canon's best normal-range primes, and indeed the Piston doesn't. However, in general it does a respectable job: the fundamentals are OK and issues are kept mostly under control. In fact, when pushing the envelope, image quality deteriorates pretty uniformly: Canon has done a pretty good job in balancing the characteristics against each other.

Wide-open, near-infinity, maximum tele...

The bad news is, of course, that the quality deteriorates: wide-open at 300 mm and focused near infinity is definitely pushing it. With these parameters the image does develop visible artifacts: local contrast goes down pretty severely with magenta glow-type veiling around highlights, corners start to show softness, and overall contrast and sharpness suffer as well. Still, the image holds up well enough to be rescuable with some out-of-camera work... barely.

Flamingoes in Camargue (at 300 mm / 5.6).

One thing worth keeping in mind is that the Piston's performance is pretty inconsistent: in its sweet spot it performs quite respectably well, but near the edges of its envelope things start to go sour. This type of behaviour is pretty typical of consumer zooms. I've tried to map out the sweet spot to some detail, although I haven't done a thoroughly scientific investigation of it: here's a rough sketch of my view of it.

Blue represents the possible aperture-focal length combinations on the lens, green is the sweet spot. The yellow area is in the sweet spot up to middle distance but out of it for near-infinity. In a nutshell, the lens is more or less OK at f/5.6 up to about 200 mm, beyond that, it's OK at f/8 up to 300 mm and middle distance, and for 300 mm near-infinity it's OK at f/11. Of course, the lines should be fuzzy, as "OK" is very much a subjective quantity.

Within the sweet spot the pictures enlarge quite well and there are few problems that need cleaning up; it's usually enough to adjust curves or use a wide-radius USM to increase contrast a bit to give the pictures a bit of pop. Outside it, things start deteriorating. More drastic and tedious work is needed, but the pictures are still entirely usable for at least 8 x 10's, sometimes even beyond.

Sharpness and contrast

Within its sweet spot, the lens is quite sharp and reasonably contrasty (in its class). Both qualities are even across the frame at all apertures, which makes post-processing a lot easier. Opening up from f/8, sharpness and contrast fall rapidly, especially near the tele end and near infinity, although the pictures hold up to even wide-open (barely).

At 300 mm / 5.6, middle distance, unprocessed crop. Contrast has gone down the drain, and local "glows" give the picture a muddy look. However, there's a lot of detail there that judicious use of USM can dig out. Still, I really wish I had shot this at f/8 or f/11.

Here's the same crop after a few passes of USM and curves manipulation. Not perfect, but usable for most purposes... although I wouldn't want to make a poster out of this one.

At 300 mm / 11, near-infinity, unprocessed crop. The glows and softening are gone, and indeed the image looks quite sharp.

At its shorter focal lengths, the lens performs better than at maximum tele.

At 120 mm / 8, middle distance, unprocessed crop.

In other words, the lens is just fine from f/8 down, but starts to break down below that at maximum tele, and f/5.6 at medium tele.


Within its sweet spot, the lens appears pretty neutral color-wise. However, outside of it, highlight areas quickly acquire nasty magenta glows; on some pictures, this gives the picture an overall magenta cast.

Purple haze! Wide-open, near-infinity, at 300 mm: this is as bad as the lens gets.

It is possible to correct this (to a degree) in post-processing by desaturating magentas somewhat throughout the entire picture, and desaturating them heavily around highlights, for example like this:

  1. Select: Color Range - Highlights.
  2. Expand selection: 8 px.
  3. Select background layer, and new: Adjustment Layer - Hue-Saturation-Lightness, Magentas - Saturation: -100.
  4. Deselect, and Select: Color Range - Highlights.
  5. Contract selection: 2 px.
  6. Select layer mask from adjustment layer, and Fill: Black
  7. Deselect, and Gaussian Blur: 3 px.

The same picture after the de-purple-haze-ization (but with no other editing).


Bokeh on the Piston is surprisingly nice: soft and even, with no obvious shadow imaging or doubling. The color artifacts described above affect out-of-focus highlights particularly badly, though, so on pictures involving bokeh, it's doubly important to stop down. See the Pigeon picture above for an example.

Aberrations and distortions

One important area where the Piston does well is in aberrations and distortions: there are remarkably few. Pincushion distortion isn't noticeable in real-life shots, circular aberration is kept well under control (although discernible when well outside the sweet spot), and chromatic aberration is practically non-existent. (The purple hazing is not CA, although it's another type of color artifact.) Kudos, Canon.


Ouch ouch ouch. The Piston flares like a lighthouse. Canon has no excuse for not bundling a lens hood with this machine. While flare spots are unusual, the lens is particularly prone to classical veiling flare: point it towards the light, or even shoot on a bright day with incident light from the sky falling onto the front element, and you'll think you're shooting through pantyhose. Contrast goes completely down the drain, and to make it worse, the flare is often uneven across the picture, making post-processing tricky, to say the least.

Hey! Where's my contrast?

If you get this lens, a lens hood is a mandatory purchase. Even a rinky-dink little rubber one makes a world of difference, and a deep petal one helps a great deal. With a hood or your hand, you must take flare into account when shooting with this lens in bright conditions if you want to get good quality out of it. Again, come on, Canon! A few more grams of plastic can't cost that much that you can't include it with the lens. Look at the nice velvet-lined petal hood Tokina bundles with all of its lenses. Really!

The verdict: what's it good for?

I may seem to have harped on the failings of this lens a good deal on this review, and indeed they're significant enough to be worth pointing out: wide-open at maximum tele and especially near-infinity, the lens performs marginally: the pictures are rescuable and can even stand a fair amount of enlargement, but quality definitely starts to break down.

However, I'm actually pretty pleased with the lens. The weaknesses aren't showstoppers, merely limitations -- and the Piston does have some strengths that its greater siblings actually lack. It's light and highly portable, the price is right, it focuses fast and accurately, and if you get a lens hood and keep the lens at f/8 to f/11 and below (f/5.6 to f/8 and below up to 200 mm), it'll get the job done splendidly.

Moth feeding at a pelargonia in Saignon. 300 mm / 8, 1/1600, ISO 400.

I've had a lot of fun with this lens, and gotten some pictures I wouldn't have gotten otherwise. There's no way I would've lugged an "L" equivalent where I easily carried this one. With the ISO flexibility and 1.6x crop factor of the 10D, the Plastic Piston can take you well into super telephoto terrain at a bargain price. I did have to revise my opinion of super-tele photography, too -- while of course some of the pictures I've taken with it are more technical achievements than creative ones, this kind of perspective has a lot of creative mileage too.

Lavender field with swallows, from Rocher de Bellevue in Saignon. 300 mm / 11, 1/800, ISO 400.

The bottom line? If you want to experiment with super-tele photography but don't want to incur the burden (money and kilograms) of a professional quality lens, you can certainly do much worse than the Plastic Piston. Real photographers will laugh at your lens, but you will be able to get pictures with good enough technical quality not to get in the way of their photographic qualities. Just don't try to use it for indoor or nighttime sports or dusk-or-dawn wildlife work, crank up the ISO mercilessly to 400 and beyond, and you should be pretty happy with the results. I know I am. I'm going to hang on to this one for a while, at least, and maybe eventually replace or complement it with a 300 or 400 mm prime: I am somewhat spoiled by the clarity and quality of my prime lenses, and in practice I used the Piston at 300 mm almost all the time.

Swallow and moon. 300 mm / 22, 1/1000, ISO 3200.