Sigma 12-24 test shot page up...

Started Dec 20, 2003 | Discussions thread
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Petteri Sulonen Forum Pro • Posts: 24,585
Sigma 12-24 test shot page up...

I put together a page of today's test shots from the Sigma 12-24. You can find it here: [ http://www.seittipaja.fi/index/galleries/s12-24/ ] (Note: clicking on the pics will get you an error 404; the "thumbnails" are actually 100% crops, so I left out the slideshow to save server space). See for yourself and draw your own conclusions.

Here are my observations.

First off, the thing I was most concerned about is consistency across the frame. A 20 mm prime lens isn't guaranteed to be even across the frame on full-frame, so a 12-24 even with the 1.6x crop factor is far from obvious, either. Also, typically for December in Finland, today was overcast and pretty dimly lit; I had to go to ISO800 for some of my f/11 test shots (I did these hand-held; sorry guys but I'm not freezing my fingers off on a tripod just out of love for dpreview.) So, I didn't really have a good shot at testing for flare. Contrast and color are also tough to judge, as I didn't do any comparison shots against a reference lens (I plan to use my 35/2 for that one of these days).

So, take these conclusions as still tentative and subject to change. And, of course, I haven't shot any film with the lens yet, so I've no idea how the corners outside the 10D sensor look: I've been surprised by lenses before in this respect, both positively and negatively, so I won't even venture to guess.

OK, enough disclaimers.

1. Sharpness

Center sharpness is impeccable at all apertures and focal lengths: the lens easily outresolves the sensor. Sharpness fall-off towards the corners is discernible until approximately two stops down from wide-open, but IMO the fall-off is pretty negligible: less than I had expected for a lens this wide. An exceptional 20 mm prime on full-frame would do somewhat better, but not by much. A very good 35 mm prime on full-frame would clearly beat the 12-24 at 24 mm, but that's would be a hard game to beat: some 35's are legendary.

Two stops down, the lens is very sharp. I'm going to absolutely love shooting off-the-tripod landscapes with it.

Interestingly, the lens maintains its characteristics very constant through the focal length range: the sharpness fall-off is very similar at 12 and at 24 mm.

2. Chromatic aberration

Very positive surprise here: for CA, the lens is just about as good as any zoom I've seen, and better than some primes. I did catch one pretty clear instance of transverse CA (shiny object on a dark background near the edge of the frame), but in my CA test shots of branches against the sky, I had to blow up the picture to 200% actual pixels to be able to easily see the CA. This problem is kept well under control.

3. Halation

The mystery of the "soft corners" explained: the lens is prone to a certain amount of halation wide-open near the edges. If you get a dark, sharp edge near the edge of the frame, you will get a noticeable "light spillover" that will decrease contrast and give an appearance of softness. Most lenses do this wide-open, and this one isn't particularly bad (e.g. the 50/1.4 does this noticeably more; of course, this is long gone by the time it hits f/4.5, though).

4. Vignetting

Vignetting is noticeable if you have large, evenly lit areas in wide-open shots. However, it's nowhere near objectionable enough to make you want to use radial ND filters (good thing too, since there's no filter threads; I've no idea if you could make a gel filter like this either). In a more "chaotic" picture, the vignetting is completely unnoticeable, as it's overwhelmed by the lightness differences in the scene.

5. Distortion

I'm quite impressed by this characteristic: there's barely any distortion to be seen. Yeah, you can see it if you go through the trouble of shooting a rectangular object exactly at right angles and then using a straight reference to measure it, but at least I didn't notice it without jumping through these kinds of hoops. Distortion is well below my "noticing threshold" at all focal lengths.

6. Flare

I'll reserve my judgment about this for now. None of my test shots had major problems with flare, but the lighting conditions were very easy in that respect. We'll see later.

Conclusion:

The image holds together respectably well at all apertures and focal lengths. You can detect all kinds of interesting gremlins if you magnify to 200% and really look for them, but they're kept pretty nicely in their cages: nothing in particular jumps out at you. Some softening towards the corners is discernible at all focal lengths less than two stops from wide-open, but less than I had feared. There's very little CA for this type of lens, and extremely little distortion.

What's it good for? Well, I'll wager this lens absolutely shines at off-the-tripod architecture and landscape shots: stop it down to f/11, and even the most critical photographers should be happy with the results. IMO corner sharpness wide-open is more than sufficient for hand-held shooting. However, the lens is less than ideal for situational photography, because it is rather dark: with the 10D cranked to 800, it's OK in good indoor lighting, but marginal in poor indoor lighting. The 20/1.8 would make a very nice companion for it.

Anyway, given the extreme characteristics of the lens, I think it's doing a damn fine job. Perfect it isn't, but I get a feeling that Sigma didn't cut any corners: they did as good a job as they were able. Whether it's good enough for your standards, only you can judge: look at the pictures, try to find a copy to test-shoot, and draw your own conclusions. I can only say that it's good enough for mine.

Petteri
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Portfolio: [ http://www.seittipaja.fi/index/ ]
Pontification: [ http://www.seittipaja.fi/ ]

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