Previous page Next page

Studio Tests (Full frame format)

Examine the 100mm F2.8 L IS USM Macro on its native full-frame format, and the results are nothing short of exceptional. It sets a new benchmark in our studio tests, handily outperforming the Olympus Zuiko Digital 50mm F2 Macro. Again it surpasses the EF 100mm F2.8 USM Macro (which itself is excellent); it's sharper and has even lower distortion, at the price of a tiny amount of chromatic aberration and a third of a stop more falloff. Very, very impressive indeed.

Sharpness Sharpness is exceptional in the center even at F2.8, dropping to merely excellent in the corners. Stop down and things only get better; at the very sharpest apertures (around F6.3) we see results which are nothing short of superb right to the extreme corners. Stop down further and diffraction progressively softens the image, but apertures down to at least F16 are still perfectly usable; smaller apertures should probably only be used if depth of field is paramount.
Chromatic Aberration Chromatic aberration is exceptionally low; there's a tiny amount of red-cyan fringing detectable, but it's of little practical significance.
Falloff We consider falloff to start becoming noticeable when the corner illumination falls to more than 1 stop below the center. There's about 1.7 stops falloff at F2.8, which disappears by F4, and shows a slight asymmetry towards the bottom of the frame (suggesting some physical vignetting by the 5D Mark II's mirror box). Overall not much to worry about.
Distortion The 100mm macro maintains its excellent distortion characteristics on full frame, with just a trivial amount of pincushion distortion detectable.

Full-frame compared to APS-C

Eagle-eyed viewers will no doubt have noticed that the MTF50 sharpness data at any particular focal length/aperture combination is distinctly higher on full-frame when compared to APS-C. This may at first sight appear unexpected, but in fact is an inevitable consequence of our presentation of the sharpness data in terms of line pairs per picture height (and thus independent of format size).

Quite simply, at any given focal length and aperture, the lens will have a fixed MTF50 profile when expressed in terms of line pairs per millimeter. In order to convert to lp/ph, we have to multiply by the sensor height (in mm); as the full-frame sensor is 1.6x larger, MTF50 should therefore be 1.6x higher.

In practice this is an oversimplification; our tests measure system MTF rather than purely lens MTF, and at higher frequencies the camera's anti-aliasing filter will have a significant effect in attenuating the measured MTF50. In addition, our testing procedure involves shooting a chart of fixed size, which therefore requires a closer shooting distance on full frame, and this will also have some influence on the MTF50 data.

Macro Focus

The 100mm, as expected, retains its excellent closeup abilities on full frame. Again the measured closest focus is 29cm, giving a 13cm working distance from the front of the lens to the subject.

Central sharpness is extremely high even at F2.8, so much so that stopping down to F8 gives no visible improvement. Corners are slightly softer at F2.8, but by F5.6 reach the same exceptional level as the center. The image starts to soften visibly at F16; at F32 it's very soft and low in contrast, so best avoided.

(Click here for macro test chart shots at F2.8 and F32 - WARNING the latter is not pretty.)
Macro -36 x 24 mm coverage
Distortion: None
Corner softness: Very low
Focal length: 100mm

Bellows factor

One characteristic of macro lenses not widely appreciated outside of enthusiast circles is the fact that, at large magnifications, the apparent aperture of the lens changes significantly. This means that you need to use longer shutter speeds than you might think (and would be indicated by an external meter) when shooting at macro distances. Of course the camera's metering system will deal with this automatically in normal use.

We've tested this effect by pointing the camera at an evenly illuminated surface and seeing how the exposure changes on focusing closer. Here we're comparing the 100mm F2.8 L IS USM Macro with the older, non-IS version and two other recent internal focus macro lenses, one for APS-C and the other for Micro Four Thirds.

 
1:2
1:1
Canon 100mm F2.8 L IS USM Macro
-1.3 stops
-2 stops
Canon 100mm F2.8 USM Macro
-1.3 stops
-2 stops
Tamron 60mm F2 Macro
-1 stop
-2 stops
Panasonic 45mm F2.8 Macro OIS
-1 stop
-2 stops

All of these lenses behave in pretty much the same way, losing about a stop of light (and therefore requiring a stop slower shutter speed for correct exposure) at 1:2 magnification, increasing to 2 stops at 1:1.

Optical Image Stabilization

The EF 100mm F2.8 L IS USM's party trick is its new Hybrid Image Stabilization, which Canon claims to be the first system that is genuinely effective at macro distances. Despite this the company only claims a benefit of 2 stops at 1:1 macro, as opposed to 4 stops at more 'normal' distances.

In use the stabilizer is near-silent, locking rapidly to give a viewfinder image that, for longer subject distances at least, is rock-steady. At distances shorter than about 1m, the stabilization starts to become visibly less effective.

'Normal' range test

We've generally found the stabilization units in SLR lenses to be pretty effective in real-world use, and to quantify this, we subjected the lens to our studio image stabilization test. With its 100mm focal length, we'd normally expect to be able to get good results handheld at 1/125 sec. The camera used was the Canon EOS 5D Mark II, and subject distance approximately 3m.

We take 10 shots at each shutter speed and visually rate them for sharpness. Shots considered 'sharp' have no visible blur at the pixel level, and are therefore suitable for viewing or printing at the largest sizes, whereas files with 'mild blur' are only slightly soft, and perfectly usable for all but the most critical applications.

IS OFF IS ON

Canon has been making image-stabilized SLR lenses for almost 15 years, and that experience shows. In a hugely impressive result, we see a full 4 stops of stabilization, with similar similar levels of sharpness obtained a 1/8 sec with IS on as at 1/125sec with IS off. This is pretty well state of the art at the time of writing.

Close range test

To see how effective Canon's new Hybrid IS actually is at dealing with shake during macro shooting, we repeated our test at a much closer distance, with an image magnification of approximately 1:1 (very much the worst-case scenario). In this test we also have to take special steps to keep the chart consistently in focus, using a small aperture combined with AI Servo focusing.

IS OFF IS ON

The Hybrid IS is clearly having some positive effect even at 1:1 magnification, but in truth the benefit isn't huge (closer to 1 stop in this test as opposed to Canon's claimed 2 stops), and we struggled to get many really sharp shots which truly reflected the lens's exceptional resolution. It's worth noting here that the 1/focal length rule of thumb for estimating the lowest 'safe' hand-holding shutter speed has clearly broken down, which tends to be the case when shooting at macro distances - you need to use even faster shutter speeds than usual.

The Third Dimension (or, where Hybrid IS still breaks down)

In its publicity material describing Hybrid IS, Canon helpfully provides a diagram explaining how its new technology corrects for slight vertical and horizontal shifts in the camera's position, as well as the usual tilts. What it fails to mention, though, is a third dimension of shift, namely back and forward movements of the photographer (and camera) relative to the subject. This has the effect of throwing the subject out of focus, and becomes highly problematic at macro distances for which depth of field is measured in millimeters or less.

The problem with this kind of movement, and the focus shift it creates, is that even the new Hybrid IS system doesn't attempt to correct for it. All you can do is set the camera to continuous autofocus, and hope for the best. This of course assumes you can place an AF point precisely where you want to on the subject, which often isn't possible.

In practical shooting with the 100mm macro, this effect frequently negates any potential benefits offered by the  Hybrid IS, as there's little point in getting a picture which is unaffected by shake but not in correct focus. So until designers work out a way to continuously correct focus in a similar manner to shake, even Hybrid IS is only a very partial solution.

Previous page Next page
868
I own it
228
I want it
63
I had it
Discuss in the forums

Comments

Canon40Dman
By Canon40Dman (2 months ago)

I love my Macro Photography, l had the Tamron 90mm superb lens for macro and portrait photography, but when l bought the new Canon 100 mm macro with the new hybrid IS. This lens is just superb. If you like your Macro photography and you have the cash buy one.

0 upvotes