Zeiss 21mm/2.8 vs. Olympus 21mm/2.0 vs. Nikkor 20mm/2.8 AIS on Canon Crop Camera

<p>Cost considerations aside, how do these three lenses rank on sharpness at f/2.8? I would be using them on a Canon 30D or 40D. Considering that I would be using them on a crop camera, would I really see any advantage that the Zeiss lens is renowned for in the corners? Is the Olympus lens usable at f/2.0? I would buy an appropriate focus confirmation adapter for whichever I choose. BTW, which brand of adapter do you recommend for $50-100?<br>

The things I would be using these lenses for would be daytime casual shooting (I like the 32 - 35mm perspective that these lenses will give better than a 'normal' 50mm perspective), daytime landscapes, low-light environmental portraits (where f/2.0 would really help), and most important, wide-field astrophotography (where the Olympus f/2.0 would also be great if usable at that aperture). I am still interested in differences at smaller apertures for daytime casual and landscape shooting, but the wide apertures are of key interest to me.<br>

As you may know, astrophotography will be the greatest test of these lenses' sharpness (light fall-off will also be very important here), particularly in the corners. Astigmatism in the corners ruins the sharpness of some supposedly sharp lenses--it turns pinpoint stars into seagulls.<br>

So considering these lenses will be used on a crop camera, which would you recommend? Has anyone tried all three, especially by any chance with astrophotography? Thanks.</p>

<p>These lenses have been extensively reviewed on at:<br>

http://www.fredmiranda.com/forum/board/55<br>

From what I've seen there is no doubt the zeiss has the highest resolution/contrast corner to corner. The only negatives with regards to zeiss are:<br>

price,size,mustache distortion. I owned the zeiss briefly and it was a very fine lens but the size annoyed me (my walk around kit was 28f2.8, 50f1.4, 100f3.4) and this lens was more or less as large as those three combined.<br>

You can buy the zeiss in native canon or nikon mount (I believe the new lens is suppose to be on par with the old one but I've not read much about it and I think they had to change the material used in the glass).<br>

No comments on the other two lenses but I've never been a huge fan of the olympus. The 21f3.5 is nice (cheap and small with high contrast but vignets until f8 or so and absolute resolution is not that high). Still, for my usage I would pick the 21f3.5 over the zeiss 21f2.8 ('cept that I hate adapters).</p>

 

<p>Thanks Alan. I guess I didn't really realize how big the Zeiss is. Also, I looked and searched that forum on fredmiranda.com, but the threads that turned up with the keywords "Zeiss 21" were mostly about buying or selling the lens. I didn't see any comparisons, but then I do not know the best way to search on that forum.<br>

The comment you made that I am most interested in was the "mustache distortion" on the Zeiss. That sounds like the astigmatism turning pinpoint stars into seagulls comment that I made in my original question. Are you saying that the Zeiss suffers from this in the corners? If so, why does the lens have such a great reputation for being sharp all the way into the corners? So, do you have a 20/21mm lens now? If so, which one?</p>

<p>I don't understand why you're worried about these lenses edge sharpness when you're going to be using them on an APS cropped sensor. Either of them should be more than Adequate for that purpose. It would be worth looking for an M42 or Exakta mount Zeiss Jena 20mm Flektogon. Should be cheaper than either of these lenses.</p>

<p>Russ, that's the point. I don't know if I need to be worried about edge sharpness on a crop camera. That's part of my question. Do these lenses show any difference on a smaller sensor or are any of the three good enough?</p>

<p>I decided to buy one of the Nikkors and try it out. After I get it and do some astrophotography, I will report back how well it works for this. -- Larry</p>