Some days ago I got a first sample of the new Sony AL 2.8/28-75mm SAM. The lens, sold as a kit lens with the 24MP full frame Alpha 850, is based on the well known Minolta/Tamron 2.8/28-75mm. The optics seem to be identical - 16 elements, four of them being aspherical, three low dispersion, and two elements with a high refractive index.

The new Sony 2.8/28-75mm fits nicely between the slightly outdated Minolta/Sony 4/24-105mm and the big, heavy Zeiss 2.8/24-70mm. On the A900, the Sony 2.8/28-75mm feels much more balanced than the Zeiss - clearly a plus. In my opinion the Zeiss - especially in its 70mm position, is too big for a simple "2.8/70mm" lens. The overall "quality feeling" of the Zeiss, however, is clearly superior. While the Sony mainly relies on high-quality plastics, the main Zeiss components are made from metal. Manual focus is much smoother and more precise on the Zeiss, and so is zooming.

Sony (or probably Tamron) has dropped the screw-driver AF in favour of a built-in micromotor. In my opinion this is a step backwards. Using the new lens on the camera, one can't rely on the handy AF/MF toggle button any more. For MF operation one has to switch the AF/MF switch on the lens - the two camera switches won't work properly (they will de-activate the AF, but you still can't use MF).

The AF itself is rather fast, and slightly less noisy than the internal Alpha 900 AF motor. The micromotor of the Sony seems to be less precise than the SSM of the corresponding Zeiss Vario-Sonnar 2.8/24-70mm: when adjusting the Micro-AF in small steps (2-3 units), the Zeiss was always reacting and re-adjusting its focus. The Sony, however, did so only after changing micro-AF in major increments (about 10 units).

Bokeh - checked at f=70mm and wide open, is a bit "noisy" for both the Zeiss 2.8/24-70mm and the Sony 2.8/28-75mm. The same is valid for the 24-105mm and the 4/35-70mm (results not shown here). The only lens with a good, calm bokeh at f=70mm is the Minolta AF 4-4.5/28-135mm. Even though the 28-135mm is only f4, the background of 28-135mm images taken at 70mm/f4 looks as blurred as the background of 24-70 images taken at 70mm/f2.8!

Now let's look at the results. All images were taken with my Sony Alpha 900 24 MP DSLR, using a Manfrotto 055CB tripod with Manfrotto 410 three-way head, and 2s Mirror Lock Up (MLU) to reduce vibrations. Image stabilizer was "Off", ISO set to 100, and RAW files were converted using Photoshop (sharpening 50, radius 0.5 pixels, detail 50). Neither vignetting nor CAs were corrected (bear in mind that e. g. the Nikon D3, the D3x and the D300 apply such corrections automatically to their JPGs and to NEFs).

The village shown here is Morcote, a well known touristic spot on the Lago Maggiore in Southern Switzerland.

The first 100% crops are from images at f=28mm, and wide open (scroll down for results at f=70mm):

	Excellent in the center, not really satisfying in the corners: the Zeiss Vario-Sonnar T* 2.8/24-70mm @ 28mm f2.8
	Slightly less resolution in the center, but clearly better corners than the Zeiss (at least at f=28mm): The Sony AL 2.8/28-75mm SAM (obviously a clone of the Tamron / Minolta 2.8/28-75mm)
	Low contrast, but detail resolution not bad at all - a quite even performance over the entire full frame: The Minolta AF 2.8-4/17-35mm wide open.
	At f4 about the same corner resolution as the Zeiss 2.8/24-70mm at f2.8 - but much more vignetting: the small and lightweight Minolta / Sony AL 3.5-4/24-105mm
	Very good in the center, better than the Zeiss in the corners: The Minolta AF 4-4.5/28-135mm wide open.
	A veteran from the first series of AF lenses: the Minolta AF 3.5-4.5/28-85mm

The following 100% crops are from 28mm/f5.6 images:

	At f5.6 the Zeiss still has remarkable problems in the corners, even though this is not the wides angle of the lens.
	The Sony/Tamron/Minolta 2.8/28-75 now has a clearly better performance than the Zeiss: The center is comparable, but te corners are better.
	Less contrast compared to the 2.8/28-75mm, but still better than the Zeiss 2.8/24-70mm (remember, we ar talking about f=28mm only!): the Minolta 2.8-4/17-35mm (D)
	At f5.6 similar permormance as the Zeiss 2.8/24-70mm: a remarkable result for the Sony 3.5-4.5/24-105mm

The following 100% crops are from 28mm/f11 images:

	Finally the Corners are very good as well - Zeiss at 28mm/f11
	Still slightly better than the Zeiss, but the differences are neglectible - Sony AL 2.8/28-75mm SAM
	Probabla the best overall result: Best detail resolution, slightly inferior contrast, and much less vignetting - The Minolta AF 2.8-4/17-35mm (D) @ 28mm/f11
	Surprise: the Sony 24-105mm again on par with the Zeiss
	At ist wide end slighty inferior to the Zeiss - but check the results at f=70mm before you draw your conclusions about the 28-135mm ;)
	Decent results for 25 year old mid-class zoom: some CAs, but otherwise very useable: the Minolta AF 3.5-4.5/28-85mm. Again: Check the results at f=70mm before buying it secondhand ...

Now at 70mm, first the overview:

	Again perfect in the center, but some problems in the corners: The Zeiss wide open at f=70mm These problems mainly arise from field curvature - and since bokeh isn't that good at 70mm near infinity, the corners look slightly weird.
	The Sony AL 2.8/28-75mm wide open: now the Zeiss is better ...
	Softer center than the Zeiss, but comparable corners: the 24-105mm at 70mm/f4
	1.5 stops slower than the Zeiss, but comparable performance wide open: The Minolta 3.5-4.5/28-85mm
	At 70mm the winner is clearly the good old Minolta 4-4.5/28-135mm. At f4 it performs clearly better than the Zeiss at f5.6. But: It is sensitive to flares,and its closest focusing distance is 1.5m (instad of 0.33m using the Zeiss).

At 70mm and f5.6:

	Still not brilliant: the Zeiss 2.8/24-70mm at f5.6. Now the strange shape of the "unsharpness" in the corners become even more obvious. While the center is perfect, all four corners have a distinct difference in resolution between sagittal (high resolution) and radial structures (low resolution).
	Not much improvement compared to f4.5, but still better than the Zeiss ...
	Again: clearly the best image quality - Minolta AF 4-4.5/28-135mm

Finally at 70mm and f11:

	The Zeiss is now good in the corners as well - but even at f11 it still isn't as good as the Minolta AF 28-135mm at f4. Why didn't the Zeiss people look at the Minolta before starting their work ...?
	Comparable to the Zeiss
	Oops - better than the Zeiss, and better than the Sony 2.8/28-75mm ... On 24 MP full frame DSLRs, the 24-105mm cleary needs to be stopped down to f11, but then - as a landscape & travelling lens - it delivers surprisingly good results!
	Even at f11 not much better than at wide open - not the best zoom lens for the A900 (but probably still better than many other)
	Diffraction comes in: The center has slightly less details than at f5.6. Slightly better than the 24-105mm, but not much ...