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Sigma 30mm F1.4 EX DC HSM

Review Date: Dec 11, 2008 Recommend? no | Price paid: Not Indicated | Rating: 8 

Pros: center sharpness even wide open, nice focal length for indoors
1.4 is not really 1.4, limited use, too expensive for what it does

I just returned my Sigma 30/1.4 today. I had it for a little longer than a week, but I have reasons to return it.

First I must say, it is a great lens. The focal length is really nice indoors in normal-sized rooms, the perspective you get is really about "standard" (what you see with your eyes). I took some shots of a little boy i took care of (18 months) and they make great photo album pics. But then, this is also a limitation of the lens. "Real" photographers will tell me that it is good to run around for half an hour in order to find the "right angle" for your shot - that's not for me. I just love the versatility of a zoom lens. With the 30/1.4 you constantly move around to frame your picture. Outdoors or in big rooms it's worse - you just can't make a good shot unnoticed.

A big plus is the fact that because of the short focal length, 1.4 is not as shallow DOF as you might think. In fact, it is pretty usable if you are about or more than 1m away from your subject. I had the KM 50/1.7 before, and it was really "worse" in terms of DOF - meaning you could hardly use 1.7 because it was really really hard to get a face in focus so it wouldn't look strange. With the 30mm it's not that bad, even at 1.4 you can make a portrait that looks not too blurred all around.

Many people report focus problems, like front or rear focus or hunting/focus misses. I did not have any problems, and this is amazing because the A100 is not the best when it comes to focus accuracy (I have troubles with my Tamron 17-50/2.8 all the time...). Maybe I just got a good sample.

Anyway, I already wrote about the limited use (for me, at least), but that alone wouldn't have been a reason to return it (although I hesitated to pay almost 400 euro for a single-purpose lens). Much worse was when one eveing I sat in my room and took some comparison shots with it, I realized that the f/1.4 apparently is not really f/1.4. I did a simple test: my room, evenly lit by a light bulb, manual exposure.
- all on ISO 1600 (not that it would matter)
- [email protected]/2.8: shutter 1/25 - good exposure
- [email protected]/2.8: shutter 1/25 - good exposure
- [email protected]/2.0: shutter 1/50 - good exposure
- [email protected]/1.4: shutter - what would you think? Right, you would think shutter speed has to be 1/100 for the same exposure as the other two. WRONG! At 1/100 the image was visibly underexposed, even more visible in the histogram. Only at 1/60 shutter the image was about equally bright as the other two! WOW, what a fake I say! After that, I searched specifically for exposure problem with the Sigma, and behold, many people report problem. For most of them, wide open (1.4) is good, but the stopping down the picture is too bright. Now, that happens when wide open is not 1.4 but slower in reality, because the camera THINKS it measures exposure through a 1.4 lens, but really the Sigma gives you about 1.8 I'd say.

That was a real reason to give it back - I wanted the lens for two stops faster than the Tamron, but I got only a bit more than 1 stop.

If you disagree with my findings, test the lens for yourself (unchanged lighting, manual exposure) and report back. I can't imagine this is by chance - it's marketing and nothing more to me.