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  Reviews by: David C Palmer  

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Sigma 30mm F1.4 EX DC HSM

Review Date: Jul 22, 2007 Recommend? | Price paid: Not Indicated

Pros: Relatively-small, lightweight, convenient focal length
Beware possible quality control problems. Potential front-focus problems (at all apertures) on Canon cameras. Corner quality is poor. Bad "bokeh" (triangular highlights) resulting from misaligned diaghram blades on some models.

In response to a previous reviewer, any "fast" lens requires some degree of care with focussing because of shallow depth of field. That's exactly when many of us are attracted to these lenses. The main problem with this Sigma lens, however, is nothing to do with depth of field. It is to do with quality control, and "broken" auto focus (with the lens stopped down!) for distant subjects.

I regularly shoot at f/1.4 - using, e.g., the Canon 35mm f/1.4 L and 50mm f/1.4 lenses, using both a Canon EOS 20D and 5D. I love the control this gives me to isolate my subject and control background blur. I also like using longer lenses at wide apertures (e.g., 85mm f/1.8 and 135mm f/2 L). Again, one gets shallow depth of field, with pleasing results. I know how to handle these effects and use them regularly.

Wanting to have a convenient "50mm-like" focal length for my 20D camera, I went ahead and purchased the Sigma 30mm f/1.4 lens. I had read some rave reviews, but was completely unprepared for some many problems:-

1. Close-ups were great - at the centre of the field - but the corner quality isn't so good - quality drops off dramatically away from the centre. Check out the Sigma MTF charts and you'll see what I mean.

2. Out-of-focus specular highlights can show ugly triangular patterns - this may well vary from sample to sample. However, close inspection of the stopped down apertures on three different lenses - yes, THREE lenses - showed that the aperture blades aren't aligned correctly, giving a very distorted, almost triangular shape when stopped down, instead of an octagon. This has been well-documented by other users on the web (e.g., see the Canon lens forum on

3. My biggest shock came when I took the lens outside and tried photographing distant subjects. All out of focus! This is nothing to do with shallow depth of field! I was using f/8 and upwards to f/16. Distant subjects - e.g, 10m to infinity - were, quite plain and simply out of focus. I returned the lens, but the second copy had the same problem. I returned the second copy to Sigma UK who also borrowed my camera so that they could "calibrate the lens to match the camera". I supplied some example photos and they _agreed_ with me that the lens was at fault. They could not fix the lens. Instead they sent me a copy from a newer batch. This did fix the focus-at-infinity issue, but had problems of its own...

4. Uneven image quality across the frame. The right-hand side of the images taken with copy #3 of this lens were fuzzier than the left- and central portions.

I am sure that there may be copies of this lens that are fine (apart from at the edges), but I would strongly warn potential customers to beware of Sigma's quality control. In particular, if you are a Canon user, you should be aware that Sigma reverse-engineers the Canon auto focus mechanism, and clearly _some_ Sigma lenses are not compatible with the auto-focus tolerance of _some_ Canon cameras.

If you're looking for a good lens in this focal length for a Canon camera, I'd strongly recommend giving the cheap Canon EF 35mm f/2 lens a go. It's not very-well built, but in my experience it provides fantastic image quality for the price and proved far more satisfactory than the more expensive Sigma lens.

Sigma 30mm F1.4 EX DC HSM

Review Date: Jul 20, 2007 Recommend? no | Price paid: Not Indicated | Rating: 3 

Pros: Small(ish), light(ish), max. aperture, build quality
Severe front focus problems on Canon cameras, dire corner performance, uneven image quality

I really wanted to like this lens, but after 3 copies, including a factory calibration of the lens + camera, I had to give up.

I used this lens on a Canon EOS 20 D camera. The first two copies gave excellent quality for close ups, but dire results for distant shots. The problem turned out to be severe front focussing. Anything further than about 10 m away was out of focus.

My second copy of the lens went back to Sigma UK, together with my camera. They couldn't fix the problem, but sent me a new lens, which they tested on my camera. The front focus problem was fixed, but other problems emerged: as the MTF charts show, whilst the lens is sharp in the centre, its corner quality is lousy. Furthermore, I found that the image quality dropped off towards the right-hand side of the image.

After three copies, I gave up. The el-cheapo Canon 35mm f/2 lens is SO much better (and cheaper).

I've now moved to full-frame and am happily using all-Canon products. No more Sigma for me!