Sony 100mm f/2.8 Macro SAL-100M28

SLRgear Review
February 17, 2009
by Andrew Alexander

Sony inherited the 100mm ƒ/2.8 macro from Minolta, whose design originated in 1986. The lens is capable of a 1:1 reproduction ratio, with focusing features that make macro work much easier.

The lens was designed to cover the entire 35mm film frame, thus it has no problem working with APS-C sized ''subframe'' digital camera bodies. On these cameras the lens will produce an effective field of view of 150mm.

The lens ships with a SH0007 lens hood, takes 55mm filters, and is available now for around $650.

Sharpness
Longstanding readers may note that this is the first lens we have tested with Sony's full-frame A900 camera, and we have spent a few extra days ensuring our results are accurate.

On the subframe A700, the Sony 100mm ƒ/2.8 macro produces impressively sharp results even wide open at ƒ/2.8, at around 1.5 blur units. Stopped down to ƒ/4, it's tack-sharp across the frame, and stays that way until ƒ/16 where diffraction limiting sets in. Performance at ƒ/22 is good, at 2.5 blur units, but at ƒ/32 things are fairly soft and slightly across the frame - at around 5 blur units.

Which brings us to the full-frame A900. At twenty-four megapixels, the camera is demanding a very high level of quality from the lens, and the 100mm macro struggles a bit at ƒ/2.8. Image sharpness is still fairly good - just under 3 blur units across the frame - but it's not as good as the results shown on the A700 at the same aperture. Performance improves as the lens is stopped down, but it isn't until ƒ/5.6 that the lens offers the same tack-sharp quality that we saw at ƒ/4 on the A700. Images stay sharp through to ƒ/16, and at ƒ/22 it's just over 2 blur units. Again, performance at ƒ/32 is slightly soft, in the case of the lens mounted on the A900, at around 4 blur units.

Chromatic Aberration
The 100mm macro showed very little chromatic aberration on either the A700 or A900 models. In both cases the best aperture setting was ƒ/4, but at any aperture the maximum CA produced was less than 3/100ths of a percent of frame height, or very good performance.

Shading (''Vignetting'')
Light falloff is essentially a non-issue for the 100mm ƒ/2.8 macro when mounted on the sub-frame A700; the only corner shading of note is found at the ƒ/2.8 setting, where the corners are a 1/4-stop darker than the center. At any other setting there is no light falloff.

Corner shading is a bit more prominent for the lens when mounted on the full-frame A900. At ƒ/2.8, the corners are almost a full stop darker than the center. This light falloff reduces dramatically when stopped down to ƒ/4 (where there is just over a quarter-stop of light falloff). At any other setting, light falloff is inconsequential.

Distortion
The Sony 100mm ƒ/2.8 macro is optimized to produce almost no distortion; the numbers are essentially zero when mounted on the A700. On the A900, there is a tiny bit of pincushion distortion in the corners (almost -0.1%) but this is a very small amount.

Autofocus Operation
The lens is not built with a speedy autofocus, the assumption being that this is not necessarily needed for a macro lens. It took about 1.5 seconds for the lens to focus its range from infinity to close-focus. There is a healthy amount of lens extension during focus operations; at closest focus, the lens is extended by almost two inches. It is also not a subtle lens while focusing, making a very audible whirring noise.

The lens is equipped with two focus-specific functions; a focus limiter switch, and a focus stop button. The focus limiter switch has three settings, one for unrestricted autofocus operation, and two settings which limit the range of autofocus movement and thus speed up the operation. The first setting limits the range to macro (between 6'' and 12'') while the second setting limits the range beyond macro (12'' to infinity). The focus stop button disables the autofocus system while it is pressed.

Macro
The lens is designed to provide the best results for macro work. Its minimum close focusing distance is 35cm, or just over one foot (this distance is measured from the focal plane, so it's a bit shorter in practical application). The autofocus controls are quite useful in macro operation; limiting the focus distance to the macro range speeds up focus point acquisition, and using the focus stop button is a handy way of making fine adjustments. Essentially you would use the autofocus to get you in the right ballpark, press the focus stop button and then move the camera back and forth in small increments until the focus is just right. Then you press the shutter button to take the photo, and focus is not affected. You could do this by switching to manual focus mode, but it's just faster and easier this way.

An important note when using this lens (and most macro lenses, for that matter) in its macro range is that as the magnification increases, the amount of light reaching the sensor decreases. By 1:2 (0.5x magnification) it's down a full stop, and by 1:1 (1x magnification) it's down two full stops. On program, aperture- or shutter-priority modes the camera will automatically compensate; otherwise, you will have to dial in some form of exposure compensation. The manual for this lens has exact values, dependent on the macro range selected.

Build Quality and Handling
The lens is plastic, with a nice black smooth finish. When shaken, there is no flexing or rattling. It's heavy - over a full pound - and very solid feeling. The lens mount is metal, and the filter threads (55mm) are plastic. The front element does not rotate during focus operations. The aperture is made up of nine rounded aperture blades.

Apart from the focus ring, the only controls on the lens are the focus limiter and focus stop button, as previously described. There is a distance scale, recessed and protected by a window, indicating distance in feet and meters. A depth of field scale is provided, though it only marks the scale with increments of ƒ/32. There is no infrared index marker. The lens barrel has a nice magnification scale on the top of the lens barrel which can be seen as the lens is focused closer to maximum magnification.

The rubber focus ring is mounted near the front of the lens with a thin ridged pattern that is easy to grip. The ring is fairly wide, 1 1/4 inches. This lens has to be the stiffest manual focus lens we have ever encountered. You really have to want to move it to get it to move. You can hear the lens moving a great deal of internal mass. The advantage of this system is that your carefully set focus point isn't going to be easily dislodged. The focus ring turns about 195 degrees, and has hard stops at either end. The lens can focus very slightly past infinity.

The SH0007 lens hood is 1 7/8 inches long, adding 1 3/4 inches to the overall length when attached. It is a bayonet-style, circular bowl-shaped hood, that reverses for storage.

Alternatives

Sony 50mm ƒ/2.8 Macro ~$450
If 100mm is too long a focal range for your macro needs and you want to stay in the Sony line, the only other macro lens in Sony's lineup is this one. Unfortunately we haven't yet reviewed a copy.

Sigma 105mm ƒ/2.8 EX DG Macro ~$380
Less expensive, the Sigma 105mm provides an almost equivalent focal length. The Sony 100mm is slightly sharper on the APS-C body, but is almost identical in other respects. The Sigma lens is slightly lighter, and also offers a focus limiter system. It's unclear what the results would be of mounting the Sigma lens on the 24 megapixel sensor of an A900.

Tamron 90mm ƒ/2.8 Di Macro 1:1 SP AF ~$450
Like the Sigma lens, the Tamron 90mm is very sharp, almost as sharp as the Sony lens at similar apertures (to be fair, both lenses are about as sharp as they can get, on APS-C sensors, by ƒ/4). The Tamron lens is lighter, but doesn't have the advanced focusing features of the Sony.

Tokina 100mm ƒ/2.8 AT-X 100 AF PRO D ~$400
Tokina produces a lens in this category, slightly less expensive than the Sony. We haven't yet tested it, but user reviews are generally positive. It's equipped with a focus limiter system.

Conclusion
When mounted on the A700, the Sony 100mm ƒ/2.8 macro provided excellent results almost across the board; the only possible objection would be that it wasn't tack-sharp at ƒ/2.8, but at 1.5 blur units, to ask for more would be very demanding. The 24-megapixel sensor of the A900 taxes the optics of the 100mm macro quite heavily, requiring some level of stopping-down to get the best results (our optimum setting being at least ƒ/5.6, if not ƒ/8 for the absolute sharpest).

Otherwise, distortion is non-existent, chromatic aberration is well handled, and there is virtually no light falloff. Focus handling options are very good, making the lens an excellent platform for macro work.

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.