Sony 55-200mm f/4-5.6 DT SAM SAL-552002

SLRgear Review
July 20, 2009
by Andrew Alexander

In May 2009, Sony released four new lenses as part of a transition away from mechanically-based focusing designs. The new lenses, of which the 55-200mm ƒ/4-5.6 was one, use Sony's SAM (Smooth Autofocus Motor) system. Apart from this change, the lens design does not appear to have changed significantly from the previous 55-200mm ƒ/4-5.6 design.

The lens is designed for the APS-C sensor, meaning the lens will show some hard cropping if used on a Sony full-frame camera such as the A900 (or a Minolta film body). The lens doesn't feature a constant aperture; as the lens is zoomed out towards the telephoto end, both the maximum and minimum aperture sizes decrease. The following table shows the largest and smallest apertures at various focal lengths:

The lens is available now for approximately $230, and is also available as part of several Sony body / lens kits. The lens takes 55mm filters and ships with a circular-style lens hood.

Sharpness
The 55-200mm ƒ/4-5.6 offers excellent results for central sharpness, with some corner softening.

When used wide open at the lens' fastest aperture setting, we note a consistently excellent central sweet spot of sharp focus (~1-1.5 blur units), marred only by some corner softening (~3-4 blur units) at 100mm and wider. At 135mm and 200mm this corner softness reduces to about 2 blur units, but the central sweet spot of sharpness also reduces, to give a more even performance which is still very good.

Stopped down improves the overall sharpness of the lens. At ƒ/5.6-ƒ//8 (one stop down from maximum aperture, depending on the zoom settting) we see a marginal improvement in the center sweet spot of sharpness at 100mm and less, as well as a corresponding improvement in corner sharpness. The gain isn't as prominent at 135mm and 200mm, but it's still noteworthy. Optimal sharpness is achieved at ƒ/8-ƒ/11 (two stops down) where it isn't quite tack-sharp, but very, very good - about 1.5 blur units across the frame. This could be a case of the sensor out-resolving the lens (though I wouldn't bet the farm on that, as I'm sure the optical scientists out there reading this know much more than I on that subject).

Diffraction limiting sets in at ƒ/11, but the impact on sharpness isn't really felt until ƒ/22 - up until then, sharpness is smooth across the frame at less than 2 blur units through all focal lengths. Fully-stopped down performance is predictably not so hot - 4-5 blur units at ƒ/32-36, and 7 blur units at ƒ/45 (at 200mm).

Overall, for the price point, quite good performance when used wide open or stopped down a touch.

Chromatic Aberration
The lens is does well to reduce chromatic aberrations; we do note some purple fringing in areas of high contrast, particularly at 100mm and longer. This form of CA is exacerbated as the lens is stopped down and zoomed in, showing worst at 200mm in the corners.

Shading (''Vignetting'')
The 55-200mm ƒ/4-5.6 shows some light corner shading when used at 55mm and at its widest aperture setting; in this case, images showed corners that were a half-stop darker than the center. Stopping down by one stop essentially solves the problem, reducing light falloff below the quarter-stop level.

Distortion
Results for distortion testing were typical for this type of lens, with near-zero distortion at 55mm but quickly devolving into a complicated mix of pincushion distortion in the corners, and barrel distortion throughout the rest of the image. This level of distortion reaches its most objectionable state by 100mm, where we note -0.6% pincushion distortion in the corners, and +0.3% barrel distortion on average through the rest of the image.

Autofocus Operation
Despite using the new SAM focus system, the 55-200mm ƒ/4-5.6 isn't particularly fast to focus, going from infinity to close-focus in around 1.5 seconds. It's worth noting that the focusing ring (and thus, the front filter thread) rotates during autofocus operations, and Sony notes in the instruction manual that you shouldn't hold the ring while the lens autofocuses as it may cause damage.

Macro
Macro operation is fairly good for this lens, at 0.29x magnification (1:3.45 reproduction ratio) with a minimum close-focusing distance of 95cm (just over 3 feet).

Build Quality and Handling
The 55-200mm ƒ/4-5.6 is build entirely of plastic, with its 13 lens elements encased in a durable matte-black plastic casing. The body mount and filter threads are also plastic, leading to a very light package of just 305 grams (just over 10 ounces). The lens aperture is made up of 9 curved blades. There is no distance scale or depth-of-field scale.

The lens doesn't have much in the way of features: the only control surfaces other than the focus and zoom rings are a manual focus switch which disengages the autofocus system in the lens. The instruction manual notes that to use manual focus you must disengage autofocus on the lens, not on the body. Attempting to focus manually otherwise may damage the lens. Filter users beware: the front element rotates during autofocus operations.

The focus ring is located at the far end of the lens, a very thin 1/4-inch wide smooth rubber band that does not offer much for manual focus response. A turn of just forty degrees runs the entire focusing distance: there is not a lot of play for making minute adjustments. The overall focus travel ends in hard stops on either end of the spectrum, and there is is some additional space to focus past infinity.

The zoom ring is 1 1/4'' wide, a tough rubber ring with raised thin ribs. The ring offers about forty degrees of turning to extend the zoom through its entire range of focal lengths. The zoom ring is nicely cammed, offering a smooth turn which isn't too tight. The lens extends by 1 1/4'' by 200mm, and there is no zoom creep to speak of. To its credit, it's worth noting that the variable aperture is fairly generous, in that the lens doesn't move from f/4 to f/4.5 until just after 100mm.

The lens ships with a circular lens hood, which has a smooth matte interior finish and reverses onto the lens for storage. The lens hood adds 2 1/8'' to the overall length of the lens.

Alternatives

Unfortunately, our alternatives section is only going to be so useful for you, as we haven't yet tested any of the following lenses:

Sony 55-200mm ƒ/4-5.6 DT ~$230
The differences on paper between these two lenses are minor: the only major difference is the transition to a SAM lens motor, instead of using the body-based mechanical drive screw. While the new lens adds 10 grams of weight, everything else is the same.

Tamron 55-200mm ƒ/4-5.6 Di II LD Macro AF ~$130
Tamron has had this lens available for the Sony / Minolta lens mount for some time, and the lenses share suspiciously similar specifications. Tamron's version uses the older mechanical screw-based focusing system.

Sigma 55-200mm ƒ/4.5-5.6 DC ~$130
Sigma's version of this lens is also available in the Sony mount, and is generally the poorer cousin: less capable macro (0.22x instead of 0.29x), slower aperture (ƒ/4.5 instead of ƒ/4) and no ED glass. Also uses a mechanical focusing system.

Conclusion
The 55-200mm ƒ/4-5.6 fared well in our tests: sharpness is very good, even when used wide open, with light corner shading. CA is noticeable but light: corner shading is minor, and as is typical for this class of lens, distortion is fairly objectionable when used at the lens' longer focal lengths.

There's no immediately obvious reason why Sony decided to transition to SAM focusing with this lens, other than in the future they may elect to produce camera bodies which don't feature mechanical autofocusing screws (current Sony bodies all have this screw). The end result is a slightly more complicated manual focus operation; on the previous version of the lens, you disabled autofocus strictly from the body, where this must now be done on the lens on the current version. And while we haven't tested the previous version of the lens, we didn't note the SAM motor offering particularly fast performance (in Sony's defence though, they say the SAM motor offers smooth and precise operation, not fast).

Still, for the money, it's a light lens which offers very good performance, and makes a good camera system when paired with the 18-55mm.

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.