The strong points:
- Wide zoom range (5.7×); at long focusing distance the long end's focal length really is as long as the Minolta AF Apo 400 mm 1:4.5 G's.
- Very good contrast and sharpness in a wide area around the frame's center at all focal lengths and all apertures; very low chromatic aberrations at the long and short ends, extremely low at the middle of the range.
- Fully usable with the Minolta AF 1.4× TC-II Apo at 560 mm (in manual-focus mode only, of course), only minimal loss of contrast.
- Very good mechanical build quality; there's no wobbling at all in the front barrel and no play in the focus and zoom rings.
- The focus ring has a gear reduction so when focusing manually, it will travel twice as far as the actual focus scale under the little window; focusing manually is a joy, even with a 1.4× tele converter attached.
- The focus ring doesn't rotate when auto-focusing.
- The SSM auto-focusing mechanism is silent, accurate, and responds well to fine shifts of focus distance.
- The silver finish, albeit butt-ugly, does serve a purpose, and does it well: In the sunshine the lens always is significantly cooler than the black camera body. Furthermore the surface seems fairly scratch-resistant, much unlike the notorious white paint of the Minolta apo telephoto lenses.
- Virtually no distortion at 70 mm.
- Pretty strong vignetting at full aperture at all local lengths, particularly at the short end (on full-frame format).
- Some fall-off of sharpness at the frame's edges at the short end.
- Pincushion-shaped distortion at all focal lengths except 70 mm; moderate at 100 - 135 mm, pretty strong at 200 - 400 mm (at least the distortion responds well to Photoshop's Lens Correction filter; there is no obvious wave-form component in the distorion).
- Zoom ring is very stiff (but on the other hand there is absolutely no zoom creep whatsoever, so the stiffness seems acceptable in exchange for that).
- Lens hood feels so flimsy as if it was made of card-board paper reinforced with a thin coat of synthetic resin lacquer. However Sony states that in an attempt to save weight, the hood was made from a high-tech material which allegedly is stronger than it feels. Well, how much truth is in that statement remains to be seen---indeed my hood has not cracked yet; still I don't feel too confident about its sturdiness.
Size and weight of the SAL-70400G are substantial so this definitely is no walk-around lens for casual snap-shooting ... or for airborne traveling. Still I don't consider this a bad point because wide zoom range and high performance simply don't go together with small size and light weight. The silver finish does attract some unwanted attention---but as I said, on the other hand it helps keeping the lens' temperature down in the sunshine. At times, the SSM mechanism will fail for no apparent reason which is very annoying ... until I noticed that when hand-holding the lens, the palm of the hand will sometimes unintentionally touch the lower focus-hold button which will keep the auto-focus from working. No big deal, just something to be aware of.
On an APS-C-format body this lens gets transformed to a 105-600 mm equivalent, and both vgnetting and distortion then will become basically non-issues.
-- Olaf
EDIT: See a follow-up here.
