snaggs said:
Ok, sold on the 85mm, but still not on the Sigma 12-24.
Hey, don't feel compelled to get "sold"! I'm just sharing like you asked, if you disagree fair enough.
With 1.5 crop it is only shooting out of the middle of the lens, the best part.
All things being equal, then yes. But in theory DX lenses are also designed for the smaller sensor which means they *can* have higher resolving powers than their 35mm counterparts, like their 35mm counterparts generally have higher resolving power than MF and LF lenses.
Lets do a small comparison;
Based on that thread I'm inclined to agree with you on the optical quality. Which surprises me because the Nikkor should be optimised for the smaller sensor.
The one thing to note is that different lenses behave differently on different digital cameras. It's a strangely weird one. But my Tamron 14 for instance is brilliant on my F5, rubbish on my D1x (as in like seriously, is it out of alignment kind of rubbish), but brilliant on the 14n.
I haven't used the Sigma, and have only limited experience with the 12-24 DX lens myself. I have no quality issues with the Nikkor from my pictures with it. Personally I'm confident enough in the Nikon brand to trust it to give me results that meet my needs, so I'm not fussed if the Sigma *is* optically better. But I do have general issues with Sigma in general that might or might not apply to the 12-24. Specifically build quality (I think their 120-300, 70-200, and 300 lenses - all the f2.8 versions - are poorly put together) and they also hunt in focusing; quite probably not such an issue for a superwide zoom. They also do not have full time manual focusing (more of an issue for a superwide), and also are overally slower to achieve focus than their comparable Nikkors.
Given the sharpness and better CA of the Sigma, is the speed of the Nikkor worth so much ?
If you need it, yes. Speed is always disproportionately expensive. Witness say a 70-200/4 compared to a 70-200/4.5-5.6.
In terms of worth the optical tradeoff... again it depends. If it does a good enough job then I'd take the Nikkor even if the Sigma were better. But if the Nikkor didn't even do a satisfactory job, then there's no decision to be made, Sigma it is.
Currently the Nikkors resale is better, but then Sigma is a different company than of old. Since they've gone CAD with raytracing, they are making some top quality lenses. I think resale prices will change for two main reasons;
Depends. I assume these top quality lenses refers to their EX line. I've seen very very dubious results from two of their EX lenses, being the only two I've actually seen test results for. But subject to the proviso of the last point below.
As for resale prices changing, think again. Resale prices are driven by how much people will pay for the items. Which in turn is related majorly to reputation and build quality (affecting depreciation/residual value). Reputation is a pain to change and takes a long time, and Sigma have never really had a problem with optics reputation wise, it was their build quality that people had nightmares about (can you say, metallic tape?). Their build quality while better than before, is still, IMO, a long way short of top stuff from Canon or Nikon. But again, like I say above about optical quality, if the build quality is good enough for you then go for it.
(1) Back in the old days, where everything was hand-designed, Lens design was an art, and Nikon had the best scientists and engineers. Now that everything has been quantified, and theirs enough CPU power in computers, everyone can achieve optimal designs.
Quite possibly true, but like I said above, I've dismissed Sigmas for reasons other than optical quality; reasons which you might have lend no importance to. And I have also seen Sigma optics that apparently (again subject to tests being accurate, see below) are very, very poor compared to the equivalent Tamron and Canons.
(2) Pre-internet, reputation was sometimes all you had to go on for performance. Now everyone can find a wealth of information on lenses prior to purchasing.
Yes but be careful about duff information too, which unfortunately the Internet is sometimes rife with. The one curious thing about that test is to be careful that it's carried out proper skill and by someone who knows what they're doing. On the surface the test seems legit, but in the comparison shot with the lenses on display (with lemons and the Canon logo), something doesn't seem right. The Nikkor doesn't even seem sharp as a 640 x 480 image (crop). That isn't right at all. Frankly I would struggle to distinguish any of my stable of lenses with say a 28-200 zoom at 640x480.
I saw another post on dpreview where a guy compared a D70 and D100. His comparison shots were great except in one comparison the D70 was in focus and the D100 out of focus, resulting in the D100 looking soft (as is its reputation) and the D70 sharp. But in the next comparison shot the reverse was true, and things like this make you wonder how accurate the tests really are.
Good luck!