[VoiceOfReason]

I do alot of shooting at anime conventions in low light, and I've noticed on both my Pentax 18-55 DA L and my newer Sigma 18-50mm F2.8-4.5 DC OS HSM I really stick around the 18-22 mm range almost the whole time. So, what I want is a good prime, and one that is fast for the crappy and low light at anime conventions. I work as a dealer, so am in the dealer hall all day, which is where I get most of my pictures. I also get some later after dinner, so generally 8-12 at night, again in really crappy lighting.

So, from what I have heard, and I don't know if this is true, most lenses you have to do a 1.5 conversion on to get the true length on an ASP-C camera like my Kx, and from what I read the Sigma 30 mm doesn't need that conversion, so, while I am not sure if that is the case I'm asking for advice here. Which one of these, Sigma 30mm F1.4 EX DC HSM or Sigma 20mm F1.8 EX DG ASP RF, would be best? Also, would you have an even better recommendation? Thanks!

[Zav]

Focal length is focal length, period.

The Sigma 30 is an APS-C lens only while the 20 can be used on film camera. If most of the time, you are between 18 and 22mm, you won't be happy with the 30mm.

The Sigma 20 f1.8 is probably the only ultra fast AF lens at this focal length. Yet, I would search for users feedback and samples as this lens has the reputation of being soft on the corners.

[hcc]

An outstanding prime is the Pentax FA31mm f1.8 Ltd. There is a lot of discussion about this lens because it is not cheap but it is truly outstanding. In low light, it is fast , and it excels in any lighting.

Food for thoughts...

[pop4]

Or, as an alternative, are you allowed to use flash? If so, you could get a flash instead and take control of the lighting.

[pinholecam]

I am surprised that you'd not have significant distortions for the anime characters (I assume that is the subjects you are taking) using a 20mm.

If the bkgnd isn't that important, why not try a strobist setup in the stand/stall you are manning.
Whats a dealer btw?
A single umbrella on light stand is all you need, and a cheap ebay wireless flash trigger of course. It will free you from the frustrations of poor lighting as well.

[reeftool]

If you're shooting at 18-22 with your kit lens, the 30mm is going to be much longer than you are using now. Whether the lens is made for FF or APS-c, 30mm is going to have the same view so I would recommend you take a round of shots at 30mm with your current zoom as the frames will look the same with the Sigma or any other 30mm. For your uses, look at the Sigma 20/1.8 or the 24/1.8. The depth of field is going to be much smaller with the faster lenses wide open and that is something to consider when shooting people in a convention or crowd. As some other comments have suggested, you may get some better results by investing in some good flash gear.

[VoiceOfReason]

I have no way to get any flash gear into my booth. In answer to what a dealer is, it's pretty much what it sounds like. In my booth we sell anime DVDs, and pretty much everyone I get my shots of are on the other side of the tables we have all of our stuff set up on. It pretty much forces me into a point and shoot type of situation where I can't really use the built in flash (lens shadow anyone?). The only things I have control over due to the speed at which I have to take the pictures is the zoom on my lens, shutter speed, and aperture.

I do have to say thanks for clearing that up about the 30. It would be too long for me. The FA31 would be too long too.

All I really care about is the subject in the middle of my shots, so any softness in the background or the edges really doesn't bother me. The subject being someone who is dressed as an anime or game character.

Here are 2 examples of what conditions I have to deal with from the last convention, and the third one is one of the guys sitting inside the booth, so you can see an example of what I am taking my pictures across. Ohh, and the area is normally VERY crowded, but for a quick shot I can normally get people to open a space for me as long as it does not take very long to get the shot.







So now you can see what I have to work with.

Again, pretty much everything is taken at the 18-22 mm range, and a flash is pretty much a no-go sicne I have to grab the camera right away between taking money and handing DVDs over.

So, does that mean the Sigma 20mm f/1.8 is the best one for me? All I care about is my subject, forget the background. If I can ever get out and away to do outdoors photography during the con it may be a different story.

[Nick Siebers]

Sigma 20/1.8 will probably help. Flash gear would be better.

[reeftool]

The Sigma 20/1.8 would most likely work for you. Just be aware that your focus will have to be right on because DOF is very narrow. I have used the DA 15 and DA 10-17 in close quarters and both performed quite well. They aren't as fast but both are very sharp. This is with the DA 10-17 last winter in a crowded barn where bird handlers were putting on a show.

[pinholecam]

I have no way to get any flash gear into my booth.


.

Actually its really doable. Seems like placing one to the back left or right to where you are seated will really do pretty well in fact.
A light stand takes up no more standing space than a 1ftx1ft.
Might be an added attraction to business too


Here are some taken at a local cosplay event using a white wall as back drop and a DA18-135mm.

[kenafein]

What about a table top tripod and a sigma 10-20mm 3.5? Flash solution would certainly be the cheapest. What about a swivel flash on your camera and you can bounce the light or use a diffuser so you don't get the shadow?

Amazon.com: Joby GP1-E1EN Gorillapod Flexible Tripod (Grey): Camera & Photo

Looks like you can even get diffusers for your popup flash.

http://www.amazon.com/Gary-Fong-Puffer-Flash-Diffuser/dp/B0011000R6/ref=sr_1...8238733&sr=1-4

[Pentaxor]

I would suggest using a flash with diffuser. there are small diffusers that you could put on your pop-up flash. if not, but the smallest and cheapest external flash you could ever find and put a diffuser on it.

[Biro]

If you went with the flash solution you might get away with keeping your kit lens and Sigma 18-50. But if you decided you wanted better sharpness and contrast (at least better than the kit lens - I haven't used the Sigma) along with the flash, then there are a number of lenses available to you because they don't have to be ultra fast. Two Pentax lenses I can recommend are the DA 21mm f/3.2 Limited prime and the DA 12-24 f/4 zoom. If the 12-24 is too expensive, then you can go with Sigma's 10-20 zoom for less money as has already been suggested (although distortion is a bit higher than with the Pentax 12-24). That DA 21 is awfully light, small and convenient.

[RonHendriks1966]

That is a crappy focal length to look for a lens. When I look at tests for that Sigma then it isn't very good wide open, wich is the only advantage for the lens being faster then DA 21mm/f3.2 Ltd. I think that you'd still be better off with the Pentax lens and buy by end off the year the successor off the K-r to go with that.

[Pentaxor]

If you went with the flash solution you might get away with keeping your kit lens and Sigma 18-50. But if you decided you wanted better sharpness and contrast (at least better than the kit lens - I haven't used the Sigma) along with the flash, then there are a number of lenses available to you because they don't have to be ultra fast. Two Pentax lenses I can recommend are the DA 21mm f/3.2 Limited prime and the DA 12-24 f/4 zoom. If the 12-24 is too expensive, then you can go with Sigma's 10-20 zoom for less money as has already been suggested (although distortion is a bit higher than with the Pentax 12-24). That DA 21 is awfully light, small and convenient.

the OP needs something that he could use for poor/low light.