While Full Frame DSLRs are not as unusual as they used to be five years ago, most "serious" DSLR users still invest only in APS-C cameras - inspite of the fact, that they usually own quite a lot of full frame legacy lenses. Sony has shown that a 24MP Full Frame DSLR doesn't have to be much more expensive than a "prosumer" 12MP or 18MP APS-C-DSLR. However, many potential buyers of a semi-pro DSLR still are convinced that a 24MP Full Frame DSLR requires extremely expensive (and thus unaffordable) lenses. They are wrong. Using 25 years old Minolta AF primes and zooms on a 24MP sensor will result in much better detail resolution than using modern "digitally optimized" lenses on 12MP APS-C DSLRs.

I have run a small comparison between the Sony A900 with Minolta AF 2.8/20mm and the Sony A700 as well as the konica Minolta Dynax 7D with Sony (Tamron) 4.5-5.6/11-18mm. I think that these results may be of some interest for Nikon users as well, since the 24MP Sensor of the A900 can be found in Nikon's D3x, the 12MP Sensor of the A700 was used in Nikon's D300, and the 6MP Sensor of the Dynax 7D is working inside the D100.

The Minolta AF 2.8/20mm from 1987 is a small superwide lens with fast AF and 72mm filter thread. Even though the lens is light (285g) it's an all-metal construction. Since I bought it back in 1988 I have used it extensively on my film SLRs. While it used to have a fairly low contrast and visible vignetting wide open, it was good from f5.6 on and perfect at f8 or f11. Many APS-C DSLR users still have it somewhere in a cupboard, but the lens is not much fun on the APS-C sensor.Thus it can be bought here in Switzerland for about 300 CHF / USD. For my first Minolta DSLR, the Dynax 7D (6MP APS-C), I had to buy the Konica-Minolta AF 4.5-5.6/11-18mm, a Tamron clone. Later I changed to the Sony AL 4.5-5.6/11-18mm version, and used it on my Alpha 700 (12 MP APS-C). Center resolution is excellent even wide open, but the corners suffer, and they never become excellent - even when stopping down to f11.

I have shot the same image with the following combinations:

1) Konica Minolta Dynax 7D, Sony 4.5-5.6/11-18mm @ 13mm f5.6
2) Sony Alpha 700, Sony 4.5-5.6/11-18mm @ 13mm f5.6
3) Sony Alpha 900, Minolta AF 2.8/20mm @ f5.6

The photos were taken using a professional Manfrotto MTL 8351B carbon tripod equipped with a Manfrotto 410 three-way-head. The cameras were set to 2s mirror lock up, antishake was turned off, and focus was checked using full magnification on the DSLR screen. All cameras were set to ISO 100 and manual white balance (6500K). Later the raw data were developed to 24MP and 12MP size using Photoshop CS4. Sharpening was set to 55, radius to 0.5, and shadow recovery to +15. Vignetting correction was +15, but no other lens correction (and particulary no CA correction!) was applied. The other values were "standard" and kept constant for all converisons.

First the 24 MP files, needed for a 30x40cm (A3) offset print at 300 dpi:

100% crops from the center of the 24MP images There's no question - the 24MP full frame DSLR delivers more detail than the 12MP APS-C. Stopping down to f11 (not shown here) doesn't change much; the resolution decreases slightly, but this is hardly visible unless one can directly compare the images by clicking through layers.

100% crops from the corner of the 24MP images. - While f5.6 is certainly not the optimal aperture for the old Minolta 20mm prime, it gives much better corner results than the "digitally optimized" Tamron/Sony 11-18mm ... At f11 (results not shown here) the corner resolution is improving on all three camera/lens combinations, but again FF cleraly delivers the best results. Interesting: The CCD of the Dynax 7D seems to have less problems with the low-contrast corners of the 11-18mm than the CMOS from the A700!

Next the 12 MP files, for a 20x30cm (A4) offset print (300 dpi):

	Many users will rarely print larger than 20x30 cm, and they think that 12MP are by far enough. Downsized to 12MP (without any additional sharpening applied!!) the 24MP files of the A900 still have more detail than the native 12MP files of the a700. In the center of the frame the difference is not overwhelming, though.
	Downsizing A900 ful frame images to 12 MP however results in much better corner resolution compared to the native 12MP files from the A700. Obvioulsy even 20x30 cm prints will benefit from the full frame ...

While I had run several previous test runs using extremely cheap kit lenses on the A900 and expensive Zeiss glass on the A700 (the A900 in most cases was better), this is my first one using "middle class" glass on both cameras. The result is unambiguous:

1) Old Minolta legacy primes on a 24MP FF sensor give much more detail than modern "digitally optimized" zoom lenses on an 12 MP APS-C sensor.

2) This is true even for the 20mm superwide (usually old superwides are considered to be problematic on high-resolution FF DSLRs)

3) While I have shown here only the 24MP results of the 2.8/20mm, at f5.6 similar results can be obtained with the Minolta AF 2.8/24mm, the 2.0/28mm, 2.8/28mm, and the 1.4/35mm G. Other lenses such as the 2.0/35mm, the 1.4/50mm, the 1.7/50mm, the 2.8/50mm Macro, the 2.8/100mm Macro and the 2.8/135mm will deliver even better corners, and the Minolta gems such as the AF 1.4/85mm, the 2.0/100mm, the 2.8/135mm STF, and the 2.8/200mm APO are much better than the 2.8/20mm shown here.