Sigma 30mm f/1.4 EX DC HSM

There is really no beating a prime lens for low light photography. Even the fastest zoom lenses are never faster than F2.8 (aside from the two very impressive and very expensive Pro level zooms from Olympus that are F2.0) and such, the best bet for dim rooms and night shots is a real quick prime lens.
Obviously when you go to a prime, you give up the luxury of having multiple focal lengths at your disposal, so you must really choose carefully which focal length will most suit your needs. A fast aperture on a telephoto makes for an awesome portrait lens, but for my needs I chose to go with a normal perspective prime.
With a four-thirds body, there are not really all that many options options to choose from if you want a normal prime. The Zuiko 50mm F2.0, highly acclaimed for its sharpness and overall phenomenal performance, is 100mm equivalent on the small sensor. The 35mm F3.5 macro and 25mm F2.8 pancake, although both have their positive qualities, are too slow in my opinion to be of significant advantage over fast aperture zoom lenses like those one would upgrade to after the entry level kit lens. This leaves an Olympus or Panasonic user with 3 options, the Panasonic 25mm F1.4, the Sigma 24mm F1.8, and the Sigma 30mm F1.4.
I chose to go with the 30mm F1.4 primarily because I wanted the 1.4 aperture and the Sigma was less than half the price of the Panasonic. Also this lens features HSM focusing which neither the the 24mm F1.8 nor the Panasonic lens feature.

First and foremost, the headline feature of this lens is the exceptionally fast 1.4 aperture. Wide open you will be able to shoot with shutter speeds 4 times faster than even the quick zoom lenses with their 2.8 apertures.

The image quality is very good all things considered. Wide open you will see some softness, as to be expected with an aperture like this (and for the price) but it really sharpens up as you stop it down and will produce very crisp shots after F5 through about F11.

The 60mm equivalent is actually quite flexible. Wide enough for most social events, and makes for surprisingly good portraits when needed.

The HSM motor is indeed quick to focus when the lens has enough light and actually finds focus right away.
With the HSM comes the advantage of manual focus override at any time, although a switch for Manual or Autofocus is also provided if you want to quickly turn off the Autofocus.

The build quality I'd say is above average. It doesn't look/feel like a toy lens like kit lenses often do, or for instance Canon's 50mm F1.8.

Comes with a decent lens hood and carry case.

The price, one of these can be had for under $400 USD on eBay.

As expected, the lens is a bit soft wide open, the problem is really only apparent however towards the edges. It is however well within acceptable tolerances.

The focus on my example back focused by a few millimeters at a distance of about a foot and a half. If attempting some sort of macro work, this could prove problematic, however I've not seen any ill effects from this in any of my photography.

This lens has no macro function. The Sigma 24mm F1.8 however does, and is approximately the same cost as this lens.

Minimum aperture is F16. Again the Sigma 24mm F1.8 will be the alternative to turn to if you want a smaller aperture of F22.

The focus ring feels a bit cheap to use. Has a bit of a rough action, however I may be spoiled by the buttery smooth focus ring on the Olympus 12-60mm.

I bought this lens about 8 months ago and it is almost always on my camera. Perfect for shooting snapshots, parties, concerts, portraits, and even indoor sports. I use it to shoot basketball and you get great undergoal shots like this:

http://www.flickr.com/photos/bhobg/3804830340/

That bright f/1.4 is really fantastic.

I like this lens a lot but when I got it, Nikon had not yet released its 35mm f/1.8 AF-S. I might have sprung for that if it were available since its significantly cheaper.

Terrific sharpness, especially at f/4 down. Very good for parties in dark places with flash. Bright f/1.4 aperture allows you to shoot in some nasty light.

I've dropped this thing from a height of about 3 feet and it still works perfectly.

Backfocuses more often than I'd like, but when you nail the focus, it's brilliant. The thing is also heavy but I'm used to it.

There's also lost of barrel distortion, unlike the Nikon 50mm f/1.8 but that's to be expected.

It isn't cheap. I got mine for about US$400. But f/1.4 has never been affordable.

Nikon 50mm f/1.8, Nikon 28mm f/2.8, Nikon 85mm f/1.8

I bought this lens after looking at the Nikon 35mm 1.8 & the Sigma 30mm 1.4. I went with the Sigma due to being able to shoot at the wider aperture. I heard a lot about sigmas QC issues and this lens was one of those. It wasn't sharp at all at 1.4 until it was acceptable at 2.8 or so. It also had back focus issues, especially in backlit/low light situations.

I sent the lens off for a warranty repair, and its better now. Shooting at 1.4/1.8 is acceptable when shooting portraits, since I find the little bit of softness the lens has works well for my style of portraits. The lens still hunts on my D300 in low light/backlit situations. When using anything other than the center focus point the focusing is worse.

When the lens gets the focus the images are fantastic. I am still somewhat debating on whether to sell the lens & pick up the Nikon, but as of now I'll keep it.

1.4 aperture is handy in low light situations
Feels pretty solid

Lens hunts for focus in low light/backlit situations
Not as sharp at 1.8/1.4 as I'd wish.

Tokina 12-24
Nikon 35mm 2.8 (manual focus)

I've used Sigma's customer service a couple times, and have had mixed results with them. My TC that I sent in was fixed & returned quickly, while my 70-200 went missing for a few days.

I wantedt to comment on a couple of things that keep cropping up.
1) Focussing problems. I had a d80 and found this lens hard to focus, ended up always taking 3 shots and ususally ended up with one sharply in focus. But not always. I persisted because the results were superb. I then traded up to a D300 and the focussing problems ahve gone away, the D80 did tend to back focus which I could probably have gotten calibrated at nikon. The D300 focusses this lens very well. I never use manual focus, alwasy "spot" focussing and this lens is just fantastic.

2) Many people say this lens is a big soft wide open and best around f2 or even f3. I just don't agree with this - for the obvious reason that the DOF is so shallow, you only get one small plane of view in focus - focus on someone's eyes in a portrait, and its true to say a lot of the head will be out of focus. This is a possitive not a negative.
I find on the d300 and I almost always use it wide open, its extermely sharp.

Buy it, you'll be amazed at teh shots you can take even by candlelight, especially on tthe higher iso settings of the D300

I don't know of any at all especially at this price.

I was looking for lens with approximately the field of view of the "normal" 50mm, so I decided to bet on Sigma. Since I´ve already have a 105 Macro EX, wich I love, I thought it´s worth a try.

Very nice! I loved! Sharp, fast, beautiful lens for use even in some professionall applications.

I´ve some samples, just resized, in my Flickr album (http://flickr.com/cwpaiva)

After all, a picture is worth 1000 words!

Construction, quality of image, contrast, sharpness and bokeh

Due to great aperture, find correct focus is sometimes difficult. But this more a characteristic than a weakness.

Nikon 50mm f/1.4, Nikon 50mm/1.8 and Nikon 35mm f/2.0

Didn´t use yet.