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Nikon's classic 28mm f/2.8 Ai-S goes head to head with the Minolta MC W.Rokkor-SI f/2.5

The Nikon Nikkor 28mm f/2.8 Ai-S was first on the market in 1981 and has eight elements in eight groups and seven aperture blades, 52mm filter size. The Minolta MC W.Rokkor-SI f/2.5 came on the market in 1979 and has nine elements in seven groups with six aperture blades, 55mm filter size. At the time it was the fastest 28mm SLR lens available. Why for decades was Nikon the only one to get it with seven aperture blades for nice looking point light source stars? First we'll take a look at infinity in full sunlight. Shot with the Sony A7 on a tripod with high enough shutter speeds to rule out movement. Focus was done in the center wide open with no adjustments for focus shift. White balance set to sunlight in the first image, showing the yellowing of the radioactive element in the Minolta 28mm f/2.5. Later images are corrected to better match the Nikkor as that's something we do with raw images every day. Mouse over images for the swap.

Despite the faster aperture the Minolta here is at 1/4000 f/2.5 while the Nikon is at 1/6400 f/2.8. White balance and vignetting oh my!

After two weeks of UV treatment the Minolta has improved both in white balance and light transmission, here it is at 1/6400 with the Nikon.

After adjusting white balance the Minolta is shockingly similar to the Nikon.

In the corners the Nikon 28mm f/2.8 Ai-S is superior.

Vignetting on the Minolta 28mm f/2.5 dramatically improves at f/4 but it's still behind the Nikon 28mm f/2 and 28mm f/2.8 Ai-S

Both look great in the center at f/4, no difference that will be noticed in real world use. The shadows make the largest difference here.

The 28mm f/2.8 AIS is still ahead in the corners.

Nothing has changed in the overall shot except vignetting is suddenly gone for the Minolta at f/5.6, so I'm skipping the overall shot. It's still 2/3 stop behind the Nikon 28mm.

Both improve at 5.6 in the corners but the 2.8 AIS says ahead, yet I'd say the Minolta is better than the well known (and much more expensive) Nikkor 28mm f/2

I'd go so far as to say the $65 Minolta is besting the $1,200 Sony Zeiss 24-70mm f/4 FE in all but the very extreme corner.

No vignetting at f/8 for any of the primes; center crops

Both improve a little but the very extreme corner isn't quite there. They both got some help from the automatic chromatic aberration fix in photoshop, although the Minolta needs less help.

Diffraction takes a toll at f/11 and they all look the same in the center. Both have resolution to the corner.

As for the Sony Zeiss 24-70mm f/4 FE it's rather embarrassing.

How close can they focus? Minimum focus distance wide open with the Minolta Rokkor SI 28mm f/2.5

Minimum focus distance wide open with the 28mm f/2.8 AIS.

There is a lot more to a lens than sharpness, yet the Minolta MC W.Rokkor-SI f/2.5 really puts in a convincing performance for a lens that tends to sell around $50-100 on the used market while the Nikon 28mm f/2.8 AI-S appears better in all regards, it's also triple the cost without triple the performance. Yet isn't diminishing returns the story of photography equipment?

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