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Canon EF 100/2.8 Macro USM Lens Review

by Philip Greenspun, February 2008

A 100mm macro lens has long been the standard for photographers using full-frame cameras. The magnification of the 100mm lens provides sufficient working distance from most subjects and does not add a lot of weight or bulk compared to shorter macro lenses.

This is an extremely sharp portrait lens that focuses down to 1:1, i.e., you can photograph an object as small as the 24x36mm sensor in a full-frame camera or the 15x23mm sensor in a Digital Rebel. The front element of the lens will be about six inches from the subject when focussed down to 1:1.

The Canon 100/2.8 Macro USM is available from amazon.com, (buy from Amazon).


The lens design is of medium complexity, with 12 elements of glass arranged in 8 groups. The same arrangement of glass that produces sharp images at infinity will not produce optimum results focussed close. Consequently, three of the 12 elements are in a "floating group" that moves as the focus is adjusted, i.e., the optical formula of the lens changes as the lens is focussed from infinity down to 1:1.


Focus is via an ultrasonic motor, which provides for very fast autofocus and full-time manual focus. The lens includes a switch to limit the autofocus range to 0.5 meters so as to avoid slow back-and-forth hunting with non-macro scenes. More unusually, the focus mechanism is entirely internal. The front filter does not rotate and the lens does not extend, even when going from infinity all the way out to 1:1.

The lens takes 58mm filters and a very deep ET-67 circular hood that bayonets on to the outside. For easy removal and reinstallation of the lens cap with the hood in place, it is best to get a lens cap with center releases, such as the Tamron (available from B&H Photo). A tripod collar, denoted "Tripod Mount Ring B", is sold separately, but should not be necessary with the beefier Canon bodies.

Weight is 21 oz. or 600g.

f/8 and be... out of focus

The young photographer asks the veteran for advice on how to take pictures. "f/8 and be there," is the standard answer, but it isn't a very good one for a 100mm macro lens. Depth of field at 1:1 magnification at f/8 is about 1mm, i.e., not sufficient unless the subject is flat and the lens is precisely orthogonal to the subject plane.

Image at left: f/8

Image at right: f/16

For most practical macro purposes, life starts at f/11 and gets smaller from there. Here is the same subject at f/11, f/22, and f/32. Notice how the tail and wingtips of the airplane come into progressively sharper focus. Depth of field at f/32 should be approximately 4mm, still not much, but viewers of macro images are accustomed to selective focus.

f/32 and be unsharp

If good depth of field is the goal, why not set the lens to its minimum aperture of f/32, use a big strobe or tripod and long exposure time, and get as much depth of field as possible? Diffraction. Photographing objects through a tiny hole, such as a lens's minimum aperture, creates a somewhat fuzzy image due to diffraction.

Why mention diffraction in a review of this specific lens? Diffraction is a more serious problem with macro photography than with general purpose photography. With macro, one is more likely to require very small apertures to obtain sufficient depth of field. What's worse, at high magnifications, the effective aperture becomes ever smaller. For example, at 1:1, the 100/2.8 Macro USM might be set to f/32 but in terms of the amount of light transmitted and the diffraction, it is functioning as though it were set two f-stops smaller, i.e., f/64.

What's wrong with f/64? A lot of 8x10" view camera photographers use f/64! Keep in mind that the 8x10" view camera photographer is likely using a 300mm lens and that f-stops are ratios. An f/64 aperture on a 300mm is much wider than an f/64 aperture on a 100mm lens.

Here is some printed text at f/11, f/16, f/22, and f/32. The magnification was 1:1 and light was from a Canon MR-14EX ring light. Click to get larger versions so that you can see how the text becomes fuzzier and lower contrast at f/32.

Good for eBay?

Sure. Get a light tent from www.ezcube.com, a couple of EX strobes and a wireless controller, and you're all set. Here are a couple of examples taken with just a simple Canon macro flash:

Good for portraits?

A 100mm lens set to f/2.8 sounds more or less ideal for portraits. Does that make the 100/2.8 Macro USM a great portrait lens? Not quite. For its popular portrait lenses, e.g., the 85/1.2, 85/1.8, 100/2, and 135/2, Canon puts a lot of effort into making the background blur ("bokeh") pleasing. This lens is not going to render out-of-focus highlights as smoothly as a lens specifically designed for portraits. Nor is the extra sharpness of this optic necessarily welcome by subjects, unless the goal is a reference image prior to dermatological surgery.

How does it work on a small sensor body?

On a small sensor body, such as a Canon EOS 40D, (buy from Amazon) (review), this lens works the same as a 160/2.8 macro lens would on a full-frame camera, with the exception of more depth of field for any given aperture (explanation). For taking photographs of skittish insects, this would be an excellent choice on a small sensor body.

Killer Accessory

The most useful accessory for this lens is a Canon macro flash.


The superb Canon EF-S 60mm f/2.8 Macro USM, (buy from Amazon) (review) on a small sensor body, such as one from the Digital Rebel series, produces the same working distance and magnification as the 100/2.8 on a full frame body.

On a full-frame body, here are the main alternatives:

Sigma, Tamron, and Tokina all make fixed focal length macro lenses in the 90-105mm range. Optically these are very high quality, but they lack the ultrasonic motor and internal focus of the Canon. Moreover, the third-party lenses are not significantly cheaper.


Canon delivers everything that a photographer could want in a 100mm macro lens: ultrasonic focus motor, internal focus mechanism, non-rotating front element, floating optical group for consistent image quality at different magnifications, rugged construction, and reasonable price.

Where to Buy

You can get the Canon 100/2.8 Macro USM overnight from amazon.com, (buy from Amazon).



Two sides of a medal depicting some of the buildings of Rome. The medal is 2.75" in diameter. View the 100 percent JPEG (3786x5651 pixels) to see the detail. Both images exposed at f/11 with the Canon MT-24EX Macro Twin Lite Flash, (buy from Amazon) (review).

Text and pictures copyright 2008 Philip Greenspun. Unless otherwise noted, all images on this page were taken with a full-frame Canon EOS 1Ds Mark III, (buy from Amazon) (review).

Article created February 2008

Readers' Comments

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Peter Norvig , February 13, 2008; 01:23 A.M.

If you're interested in longer working distance, don't forget that Sigma makes a 150mm f2.8 and both Sigma and Tamron a 180mm f3.5; all good quality and cheaper than Canon's 180mm.

Image Attachment: spider 2701.jpg

Janne Sinkkonen , February 25, 2008; 10:18 A.M.

The drawback of internal focusing is changing focal length. At 1:1 it is much shorter than 100mm. This may or may not be a drawback, but working distance is reduced.

JDM von Weinberg , February 25, 2008; 12:20 P.M.

Nice review. Very useful. Thanks

For additional opinions on many macros, I also like


It and this site are the best of all the reviews on the internet, IMHO.

For those who revel in minute technical details, the Photozone reviews have lots of charts and graphs.

Asterios Moutsokapas , February 26, 2008; 05:42 A.M.

Is the bokeh unpleasant only for distant subjects such as portraits? The out of focus areas in the sample images in the macro range seemed fine to me and certainly not splotchy as is the case with some other lenses. Also, for me personally, pore-resolving sharpness is just fine as I have the option of deciding whether to keep it or not which you don't have with softer lenses.

Jeff Evans , February 26, 2008; 02:43 P.M.

using the 100/f2.8 usm macro

I have been using this lens for a year and a half on my Rebel XTi and have found it to be a great tool that I reach for frequently. I highly recommend it. When paired with the Kenko extension tube set it delivers great additional magnification, too.

In response to the bokeh question, you can judge for yourself. Here are two portraits shot with this lens:

On Horseback Kate

and here are a few macros photographed with it in combination with the MT-24EX twin flash:

Delicious! CaterpillarSphinx Moth at Milkweed

Depth of field and working distance are munite and at high magnification. Paried with all 3 extension tubes in the Kenko set stacked together (12mm + 20mm + 36mm = 68mm) on my Rebel XTi gives about 2x magnification by my figuring, but focusing is very tempermental. This was taken with that setup on a tripod. I should have used the mirror lock feature to reduce camera shake. The focal plane is just a bit shy of the subject.

Fungus Fly

I do wish it came with a hood for non-macro shooting (it would get in the way when working close to a small subject). Otherwise it's been fantastic and is super sharp. There are more photos shot with this lens in my photo.net gallery.


Apollo san , July 04, 2011; 05:18 A.M.

This is a great tip , thank you for sharing, Im sure to use this on my photograph sessions. i just love this site, specially that im using canon myself. 

Like this part "I have been using this lens for a year and a half on my Rebel XTi and have found it to be a great tool that I reach for frequently. I highly recommend it. When paired with the Kenko extension tube set it delivers great additional magnification, too. "



carla kim , March 05, 2012; 04:22 P.M.

I admire what you have done here. I like the part where you say you are doing this to give back but I would assume by all the reviews that this is working for you as well. 

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