Canon EF 70-300mm IS DO USM: Just DO it!?

Author's Rating:

Pros: Image stabilization, far-field performance, compact length, internal focus, panning IS, accessories included

Cons: Expensive, relatively "slow", somewhat disappointing in the near-field, large diameter

The Bottom Line: 
An excellent lens for a premium price, but slightly less versatile than the hype suggests.

Author's Review
So you just got that amazing entry level professional dSLR (EOS 20D) and finally grew out of the kit lens. You even upgraded to a more versatile universal zoom lens and a dedicated portrait / macro lens. Now may be the time to discover that you need more to go 'farther' -- literally. Or to be more exact, to bring far objects closer. A 70-300mm telephoto lens is the perfect companion for the Canon EF-S 17-85mm IS USM f4/5.6 regarding covered field of view, and applying the 1.6x lens factor of the EOS 20D or Digital Rebel alike, the 300mm actually are more like 480mm in 35mm terms. Now that's already a serious telephoto lens!

I just upgraded from a (optically not bad) "Sigma 70-300mm Super II Macro APO", and the reasons for spending the extra $$$ read basically like the main features of the Canon lens:

- Diffractive Optics = more compact
- Image Stabilization = extended usability
- Ultrasonic Drive = quiet & fast
- Internal Focus = better handling

So let's see if these were all the right reasons to spend the money ...


DIFFRACTIVE OPTICS

Digital is everywhere and even lenses get tagged with some form of label containing 'D' for better marketability. Whether it's "Di", "DC" or "DG", it typically refers to the AR coating, which is vital for digital cameras due to their reflective sensors. Often, it also describes the smaller picture area in the focal plane. Nevertheless, Canon's "DO" is a far cry from that. "Diffractive Optics" is supposedly the next best thing since the proverbial "sliced bread", at least from a photographer's perspective. Marked with a green ring, the 70-300mm is only the second lens by Canon to sport this kind of optics, and the first zoom of the two. Sounds new and fancy? Well, you may be surprised to be very likely already accustomed with it, at least if you've ever used overhead projectors. That's right, the same technology is used there to keep the main lens thin. However, the design for a zoom lens is significantly more complex.

Diffractive Optics reduce the overall depth (length) of a lens, but the first contact with the EF 70-300mm IS DO USM makes clear that this is no dwarf either. While slightly shorter than the Sigma 70-300mm APO Macro Super II, it's almost the same amount bigger in diameter. In other words, quite a 'fat' lens. Comparison to the Canon EF-S 17-85mm IS USM f4/5.6 reveals virtually the same length (5mm difference at minumum), but again a significantly bigger diameter. Strap this baby on your SLR and people know you mean business. However, compared to Canon's "L" series, this lens is small. ;-)

Based on those dimensions, size may appear to some like a phishy argument for Diffractive Optics, but Canon claims to also achieve picture quality comparable to a 'L' grade lens (low distortion). Reviewing the MFT chart and comparing it to the Sigma doesn't support such claim and taking a few pictures on a tripod (disabled IS) revealed that the APO is slightly superior in contrast (resolution) but slightly inferior regarding chromatic aberration (color fringing) in the near-field. Taking the same experiment to the far-field clearly brought the Canon lens out on top. The following list and ranking is subjective and the rating comparitive ...

Sharpness ranking (tripod): f~70mm / d=1.5m / a=f8
1. Canon EF-S 60mm f2.8 USM (*****)
2. Sigma 70-300mm f4/5.6 APO Macro Super II (****-)
3. Canon EF 70-300mm f4.5/f5.6 IS DO USM (***--)
4. Canon EF-S 17-85mm f4/5.6 IS USM (***--)
5. [Canon EF-S 18-55mm f3.5-f5.6 (**---)]

Sharpness ranking (handheld): f=300mm / d=200m / a=f8
1. Canon EF 70-300mm f4.5/f5.6 IS DO USM (****-)
2. Sigma 70-300mm f4/5.6 APO Macro Super II (**---)

Chromatic Aberration ranking: f~70mm / d=1.5m / a=f8
1. Canon EF-S 60mm f2.8 USM (*****)
2. Canon EF 70-300mm f4.5/f5.6 IS DO USM (****-)
3. Sigma 70-300mm f4/5.6 APO Macro Super II (***--)
4. Canon EF-S 17-85mm f4/5.6 IS USM (**---)
5. [Canon EF-S 18-55mm f3.5-f5.6 (*----)]

Chromatic Aberration ranking: f=300mm / d=200m / a=f8
1. Canon EF 70-300mm f4.5/f5.6 IS DO USM (*****)
2. Sigma 70-300mm f4/5.6 APO Macro Super II (***--)

f ... focal length
d ... distance
a ... aperture

Apparently size isn't such a good argument for this lens and sharpness (near-field) isn't either even on a tripod with disabled IS. The advantage of the only fixed lens in this test isn't all that surprising, but the better up-close performance of the Sigma over the much more expensive Canon EF 70-300mm f4.5/f5.6 IS DO USM sure is. This is most likely attributable to the macro function (below 2 meters) of the Canon telephoto lens. In the end the most expensive lens (DO) justifies its existence with significantly better far-field results (focal length = 300mm, distance > 2 meters) due to better chromatic aberration and mostly the Image Stabilization. So let's take a closer look at that (IS) ...

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IMAGE STABILIZATION

IS (Image Stabilization) compensates motion of the camera only (mostly for hand-held shooting) and does not affect moving objects in any way. It extends the usability of this lens for critical low light conditions and especially for a telephoto over and above 200mm.

While a standard zoom doesn't see significant benefit from IS when enough light is available, it becomes more important for long focal lengths like 300mm, since it gets harder under normal conditions to allow shutter speeds faster than at least the reciprocal of the used focal length. (Rule of thumb: Shutter Speed = 1 / Focal Length) For instance, using the 300mm setting, the shutter speed should be faster than 1/300 second. This is especially true for 'slow' lenses with rating equivalent to apertures smaller than f4 (f4, f4.5, f5.6 ...).

The EF 70-300mm DO IS USM lens is designed to be effective for up to 3 stops beyond the optical rating. Using the example above, the 300mm focal length now allows a slower shutter speed of up to 1/40 second with similar results as far as camera motion induced blur. That's is well worth the consideration for nature photography -- especially at dusk or dawn! A faster lens like a f2, on the other hand, would allow to shoot at 1/300 sec and be better suited for action photography -- if not stopped down.

Applying the lens factor to dSLRs like the Canon EOS 20D (1.6x), it becomes very hard to hold the camera steady enough for a sharp picture. (Now you need at least 1/480 sec shutter speed, since the smaller 'negative' also uses smaller photo receptors for the same output resolution. (Photo cells are 6.4 micron in the case of the 20D, or 1/20 of a human hair.)

Be advised that IS is an active system and typically only "works" with the trigger pushed half down and during the actual shutter action. It's designed to take the 'jitter' out of hand-held shots at slow shutter speeds, but works slightly against you on tripods. In those cases it's better to turn IS off to prevent the mechanism from slightly moving in it's resonance frequency and ultimately causing a slight blur. Further, the power consumption of the IS reduces battery life in a EOS 20D to 80% under normal use (up to 10 sec focus time per shot). However, frequent focussing without actually taking a shot will reduce battery life to less than 80%. (I found that during the intitial play time, battery time was reduced to as little as 30%.)

Anyway, Image Stabilization works well within the scope, and is especially useful for the far end of the zoom range where a big aperture (i.e. f2) would give extremely shallow DOF. (The focal length of 300mm translates into 8 degree of horizontal viewing angle. For the EOS 20D that's divided into 3500 pixels, and even minute motion (less than 0.0025 degree) causes approximation over 2 pixels ... a.k.a. blur.) Of course all this holds only true for static subjects relative to the shutter speed.

As other professional lenses with IS, the EF 70-300mm IS DO USM allows basically two IS modes with one active in both axis' and the other one to allow panning while stabilizing only the vertical axis. This is especially interesting as it works both in portrait and landscape. The camera body determines the orientation and tells the lens which is the vertical axis to be compensated and only leave the horizontal untouched for panning. (Note: The Canon EF-S 17-85mm IS USM f4/5.6 doesn't provide the panning mode.)

Overall, Image Stabilization performs well and certainly scores points for this lens. Let's see if the final major argument (USM drive) can do the same ...

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ULTRASONIC MOTOR DRIVE

The extremely fine near-field focus range of the Canon EF-S 60mm f2.8 USM may not be a good example for a speedy AF of a USM drive, but putting the EF 70-300mm IS DO USM into comparison to the traditional "Sigma 70-300mm" drive, makes clear that USM has an edge and is much (!) quieter while performing significantly faster. Overall speed feels very similar to the Canon EF-S 17-85mm f4/5.6 IS USM lens. A nice side effect of Canon's USM drive is that using the manual focus ring during autofocus does not harm the drive. Your investment in this lens is safe in the long-run, good to know at a similar price as the EOS 20D body itself.

Cameras supporting E-TTL II (like the EOS 20D) require an USM drive for distance feedback. Hence by using the enhanced flash in the Rebel XT or EOS 20D, this lens might even help your flash pictures -- provided you're close enough. However, given the scope of a telephoto lens, this may not be significant since your subject may be well out of reach for even the most powerful external flash.

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OTHER FEATURES

The internal focus is the same principle as many recent Canon lenses, but still is a great feature for everybody who cannot live with a moving or rotating lens end while focussing. (Applications that need Circular Polarizers or Graduated NDs are the most common cases where internal focus is really helpful. Disturbance during close-up (macro) photography is really no issue with a lens like the EF 70-300mm IS DO USM since it won't let you get much closer than 1 meter anyway. Besides, a macro lens like the Canon EF-S 60mm f2.8 USM is much better suited for that anyway.

The included lens pouch (LP1116, $30 value) is a nice touch, though it really should be a standard. Both the Canon EF-S 60mm f2.8 USM and the Canon EF-S 17-85mm f4/5.6 IS USM didn't have a pouch included despite the relatively high price. The same is true for the included hood ($25 value), which neither of the other two lenses had either.

The EF 70-300mm IS DO USM sports a lock switch which keeps the lens in the 70mm position (only) to prevent damage due to accidentally extending the front barrel and hitting an obstruction while hanging off the neck strap. This is also important for storing since the weight of the lens body (700g) pulls the telescope out easily when grabbing the lens by the hood (which fits on reversed for storage). The internal focus is independent from that lock and should you 'forget' to release it, all that happened is that your lens just got turned into a quasi-fixed 70mm lens. Under normal use, however, the lens doesn't creep out of zoom, but pointing vertically up or down will move the lens with very little shock impact and sometimes even without. This is especially cumbersome since the zoom adjustment ring sits very close to the camera body and not necessarily in a natural position when taking pictures.

The macro mode is seamless and works across the whole zoom range (unlike the Sigma lens). It does't require a mechanical switch as seen in the Sigma 70-300mm Super II APO. However, it's no replacement for a dedicated macro lens either and this may be rather insignificant.

The EF mount makes this investment future-proof as it fits both Canon's smaller dSLRs and traditional film cameras as well as professional full-frame dSLRs. So even if you upgrade from the entry level professional dSLR (EOS 20D) to a full frame or 35mm camera, this lens is designed to stay with you. The same may not be true for the more specialized EF-S mount as found in the Canon EF-S 17-85mm IS f4/5.6 USM and
Canon EF-S 60mm f2.8 USM.

Somewhat odd is the Field of View (FOV) in direct comparison to the similar Sigma lens. While virtually identical in the far-field (focus near infinity), at below 2 meter distance (macro) the Canon lens' 300 mm focal length feels more like the 200 mm of the Sigma lens.

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SUMMARY

The EF 70-300mm IS DO USM is a tempting mix of modern technology and overall useful features: Three diffractive optics keep size relatively small. Image stabilization turns the relatively slow lens into a near f2.8 lens. Chromatic aberration is low (long distance) and similar to more expensive 'L' lenses (low dispersion) from Canon. The ultrasonic drive moves the internal focus rather quickly and without much noise. The distance readout for E-TTL II may be less of importance since your target may be well outside the reach of any flash anyway.

If it was just for picture sharpness (contrast) while using a tripod, the EF 70-300mm IS DO USM appears too expensive compared to the "Sigma APO" while gaining almost similar picture quality -- on average. The scale tilts in favor of the Canon lens when attempting handheld shots and quick focus is essential. For moving objects, (i.e. sports photography) both lenses are at a disadvantage to a speedier lens (f2.8 or better) -- especially in low light conditions. However, looking at a "f2.8 L" zoom lens brings cost and size up significantly. The next best thing might as well be the EF 70-300mm IS DO USM.

In applications where more depth of field is needed, a faster lens typically is stopped down to a slow aperture (i.e. f8) anyway and looses all of it's advantage. (A big aperture rating like f1.4 or f2 produces very shallow depth of field in telephoto lenses.) This is exactly the point where Image Stabilization has no match since it still allows to shoot at f8 while following the shutter speed rules of roughly f4.

The EF 70-300mm IS DO USM has a purpose and if you remember my intentions for this lens, this is exactly what I got out of it. A great telephoto lens with excellent far-field performance! For everything else, well I still have the other lenses which may be better fits in certain applications. (i.e. macro and portrait are better left to the Canon EF-S 60mm f2.8 USM lens.

Overall, I can absolutely recommend the EF 70-300mm IS DO USM but before you spend the money, it may be worth to look at the Sigma 70-300mm APO Super II. It saves you almost $1000.- and produces similar results regarding sharpness (contrast) with sufficient light available or a tripod. However, if you need IS and excellent (minimal) chromatic aberration, the EF 70-300mm IS DO USM is a prime candidate near the $1000.

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© 2005, theuerkorn


FURTHER READING

Canon EOS 20D dSLR camera
Canon EF-S 17-85mm IS f4/5.6 USM zoom lens
Canon EF-S 60mm f2.8 USM macro lens
Canon Speedlite 420EX external flash
Canon EF12-II extension ring


* ... Chromatic Aberration: White light is "formed" by a wide range of different light wavelengths. Each wavelength has a slightly different focal point in the same lens. Advanced designs try to compensate for this effect with optics that negate physics (aspherical lens). In less sophisticated designs, this is very obvious near the picture border when photographing an intense white object (i.e. picket fence in bright daylight) in front of a high contrast background. Often you find a blue "halo" on one side and a red one on the other of the white object. This is mostly due to a standard lens design that doesn't compensate for the physical effect called "Chomatic Aberration". However, even the most advanced designs are not completely free of this effect, especially in the very corners.

More detail on chromatic aberration ...
http://www.dpreview.com/learn/?/Glossary/Optical/Chromatic_Aberrations_01.htm

Another online review (w/ pictures) ...
http://www.wlcastleman.com/equip/reviews/70_300/