The new Sigma 30 mm lens is a well balanced addition for mFT bodies. It is no pancake but its 39 mm length keeps your camera compact. Also its weight is mere 135g. The balance is good for instance with E-P3 body above. All comments in this blog are based on this combination.
A 30 mm mFT lens corresponds to 60 mm angle of view in full format 35mm. This is a rare angle of view in prime lenses, but on the other hand it would fix the gap for me between 20 mm Lumix and 45 mm M.Zuiko lenses. Physical size would be similar, too. This lens is also available for APS-C size mirrorless cameras. There actual angle of view corresponds to normal focal length. Sigma 30 mm lens has a telecentric optical construction with 7 glass lenses in 5 groups. Two of these lenses are moulded aspherical and one of these has aspherical surface on both sides. The closest focusing distance is 30 cm.
This lens is sold in Europe for under 200 euros, which did not make me to expect for top quality mechanically or optically. My test sample showed some rattling when shaken, which comes (obviously?) from diaphragm blades. This is normal for this lens as I have heard similar comments from others. Diaphragm rattles also while metering light in some circumstances. I did not notice any adverse side effect (like inconsistence in exposures) from these phenomena in images. Internal autofocusing is fast, markedly faster than, say, Lumix 20 mm f/1.7 lens AF. It is not as fast as latest M.Zuikos, though. Focusing is quiet, if not totally silent. This lens has a linear AF motor just like other latest internally focusing mFT lenses. Linear motor needs less moving parts and helps in quietness. Mechanically the most negative thing for me is focusing ring which jerks when you try to make small focusing adjustments. Focusing ring turns okay in constant move but starting without a jerk is difficult or impossible. Focusing ring is also obviously too thin as pressing fingers makes it lock up. In my opinion this lens should be taken as an AF only lens. During AF operation focusing ring is switched off and has no effect.
Sigma´s 30 mm lens communicates slowly with camera body when turning camera power on. It takes longer to get camera ready for the first shot than normally with mFT lenses.
I shot my standard test target at apertures from F2.8 to F8. The results were a very positive surprise!
Image center is very good already wide open at F2.8 and reaches its top at F5.6. Edges lag behind at every f-stop, but differencies are not too big to show in normal images except for maybe F2.8 which is not actually bad. I have used Lightroom 4 automatic feature to correct chromatic aberration from these test shots, just like I would do in normal images. Chromatic aberration is not strong and it is removed effectively.
Image Samples and Conclusion
Images below were shot as RAW files with Olympus E-P3 and they were opened into Lightroom 4 and saved as sRGB JPEGs from there. I have done my standard procedure: removed chromatic aberration with LR4 automatic feature, checked and adjusted white balance and tonal range in LR4 Basic window and added slight sharpening in LR4 Detail window. Crops are all 100%.
I think Sigma has produced here a lens, which is optically significantly better than I expected. It gives much compared to its price and is definitely worth considering if this focal lenght is otherwise interesting.
F2.8 @ ISO 200, 1/1000s. Nice image quality already wide open. Slight coloring in strong contrast edges might be as much from Lightroom as from lens.
F2.8 @ ISO 320, 1/80s. Hair detail should be examined while remembering how flat this light is.
F2.8 @ ISO 400, 1/60s.
F2.8 @ ISO 1250, 1/80s.
F2.8. Bokeh - rendering of out of focus areas - depends on contrast of lighting and relative distances between focusing point and background. Diaphgram has seven curved blades, which gives beautiful, almost round out of focus spheres.
F5.6 @ ISO 200, 1/125s. This lens tolerates back light quite well. You can get flare and reddish edges like here, if sky is lighter than everything else by several stops. Generally bright spots are no problem.
F5.6 @ ISO 200, 1/60s.
F5.0 @ IS0 200, 1/500s.