I've had the Art 30 for about a month now, and since this is a lens that a number of K-01 shooters are interested in, I thought I'd share my opinion. For starters, you really should read the PF in-depth review of the 30 / 1.4 DC HSM “Art”. Sigma 30mm F1.4 DC HSM "Art" - Introduction - Pentax Camera Forums
I'm going to concentrate on using the Art 30 on the K-01 and comparing it to the older Sigma EX 30/1.4, along with some subjective thoughts.
About me
I’m just a hobbyist. I like to explore musty old museums, “collecting” pictures of whatever catches my eye. Musty old museums usually have dim lighting and bans on flashes and tripods, so I've always depended on fast glass and slow breathing. While low-light sensor performance has improved tremendously, it’s still nice to have a bright lens. For me, shallow Depth of Field is a useful technique, but it’s not the primary attraction for an f/1.4 lens.
Musty old museums also tend to be rather quiet, where screw drive lenses echo around the room and draw unwanted attention. Additionally, I enjoy getting away from the viewfinder and shooting with the K-01, but prefer it with smaller lenses. A small-ish fast “standard” lens with HSM focusing was something I was very interested in.
General handling  
The Art 30’s handling on a DSLR is okay. It's a big barrel – like a typical 17-50 zoom, but shorter. Unlike many lenses, the lens barrel does not get thinner at the mount end. This makes it seem even bigger. At 435g, the Art 30 is fairly heavy, but the balance point is right around the lens mount, and it doesn’t feel nose-heavy. Using a two-hand grip, with the left hand cradling the lens, the bulge for the AF/MF switch makes a convenient thumb rest. Fingers are a bit crowded if you have large hands – the right fingers wrapped around the grip and the left fingers around the stubby lens can get in each others’ way. On a longer or thinner lens, there's more room for fingers.
For street shooting, the Art 30 is NOT small or discreet, especially with the hood installed. Fortunately, it is flare-resistant enough that I could leave the hood off, even outdoors on a sunny day. The (relatively) small front element and wide beauty ring also help when shooting without a hood– there's less chance of getting fingerprints on the glass.
(Mostly) for DSLR shooters 
Handling is not a problem on a larger body, but on a small body like a K-x, there's just no place to put your fingers. It depends on how small your hands are.
The AF Issue on DSLRs: I easily reproduced the slow AF / AF fail problem with a K-5II and K-30. The behavior is like the camera can’t find one AF point that it likes more than the others, so it dithers, and sometimes just gives up. The K-3, K-5IIs, K-5II, K-50, and K-30 are known to have problems with the lens. I have read a couple discussion threads about the Art 30 in Nikon or Canon mount that described similar AF problems, which makes me think it’s an optical property of the lens.
The good news is that I was able to avoid the AF problem on the K-5II and K-30 by using center-point Spot AF or Select AF instead of 11-point/5-point Auto-select. Using Spot AF, focusing with the Art 30 was no slower than, say, the DA 35/2.4. I used only manual-focus film bodies for over twenty years, so center-point focusing seems “normal” to me.
Older bodies like the K-r and K-x didn’t seem to have the AF problem (due to larger AF points, maybe?), although their SDM algorithm behaves differently, focusing by tiny steps with a slight tap-tap-tap sound.
(Mostly) for K-01 shooters
Yes, I’m one of those crazy people who uses a K-01 by choice. I prefer smaller lenses on the K-01, and the Art 30 is about as big or heavy as I would want to go. Because the K-01's grip is thinner than a DSLR, fingers on the right and left hand don’t compete as much for the same space, and handling is in some ways better. Overall weight is more than I like for one-handed shooting.
While the K-01 has a nice quiet shutter, because of the way its CDAF works, screw-drive lenses with shrill gear noise can exhibit a distinct “hee-haw” sound as it hunts. Of course, I’ve used MF and focus peaking plenty of times, but sometimes I just don’t want to be bothered. HSM AF on the Art 30 was silent, of course, and it took some getting used to the lack of audible feedback when focusing. This actually got me in trouble once, when I switched lenses to a DA 15 and bumped the AF/MF switch. I had gotten so used to silent focusing (and the lens was close enough to hyperfocal distance) that I didn't notice anything was wrong for several shots. (The pictures were okay, but not great.) There is some vibration and tactile feedback when the lens is turning. I don’t usually use AF Autozoom, but I turned it on until I felt I could trust AF with the lens.
The aperture rattles a bit when the K-01 “squints” in bright light. In sunlight, it gets a workout and often hits the limits of minimum ISO and maximum shutter speed. An ND filter may be in order for outside work. In a museum with white ceilings, white walls, white curtains, white pedestals, and light wood floors, the K-01 + Art 30 was a real chatterbox. At least it didn’t sound like I was hanging drywall with a cordless drill.
The AF issue on the K-01: The K-01 did not have any AF problems with the Art 30, apart from the K-01’s usual CDAF quirks. Focusing was as quick as any lens I own.
Manual focusing was a bit of a mixed bag. While the big aperture and thin DoF work well with focus peaking, the size of the lens and rather stiff focus ring meant I had to use an overhand grip and “ratchet” the ring (grab and turn, grab and turn). Maybe it will loosen up with use.
Depth of Field
Yes, it’s thin. Real thin. Wide open, the DoF is only 6mm at the 30cm Minimum Focus Distance and 6cm at 1 meter. (For the metric-ly challenged, that's about 1/4” at one foot, and two inches at three feet). Stopped down to f/16, it’s about 6cm at MFD and 75cm at 1 meter.
Image quality
Did you read the PF in-depth review, like I asked? :p I agree with everything in the review regarding sharpness, CA, distortion, vignetting, etc. Even wide open, the Art 30 is plenty sharp in the center, and the corners are pretty good once you stop down some. I don’t do large prints, but I like to be able to crop when glass cases or other barriers keep me from getting into the optimal position. The Art 30 gives me lots of usable “fabric”.
 100% Crop (when viewed at 1200x800) 
Pixel-peeping, there is some color fringing when wide open in bright light. In some cases, I’m not sure if it was chromatic aberration or just bokeh blur on the edges of flower petals. Mentioning bokeh, it’s not busy like some bright lenses, and (to my tastes) pleasant even at middle apertures. There is a little barrel distortion, and no one (that I know of) has a lens correction profile yet. I tried the PTLens profile for the older Sigma EX 30, and thought it did an adequate job.
 Corrected with PTLens 
Shooting at f/1.4 can be tricky. Usually with a fast lens, you know you are going to give up some sharpness wide open. With the Art 30, the center sharpness is still there, but DoF is so thin that sharpness can be a moot point if you are close to the subject. Also, if there is bright light or high contrast subjects, there will be CA. It's a balancing act. You can't just crank the lens open and blast away.
f/1.4  f/1.4  f/5.6  f/5.6 -1EV  Random samples
I have LOTS of sample shots in my flickr album. I tried to keep everything simple, even when it wasn’t flattering to the lens or photographer: Av mode, Auto-ISO, multi-segment metering, no exposure compensation (except when I couldn't stand it any more). All shots were handheld. I left everything Straight-out-of-the-Camera, even when it needed some “post”. All images link back to the originals, available full-size on flickr.
I tried to get a mix of subjects (using various museums around Raleigh and Durham, NC) as well as a few series where I stepped through the apertures (which is just as boring as it sounds). Considering I wanted the lens for dim indoors work, my sample pix are kind of bright-sunlight-tulip-heavy, but Duke Gardens were especially pretty this year. Because the K-01’s AF can’t resist flower stems, most of the tulip shots were done with the K-5II.
So, where are the usual review-type pictures of people and cats? Yeah… I’m not good at getting in people’s faces, and I’m sure you can find those elsewhere. 30mm is kind of wide for portraits anyhow. Here’s a stuffed owl and red wolf.
 100% crop (when viewed at 1200x800)  
What about video? I don’t shoot much video, so I really don’t have the knowledge to give an informed opinion.
Comparison to the older Sigma 30/1.4 EX DC HSM lens 
I picked up an EX 30 when B&H closed it out. The older Sigma lens has a strongly curved focal plane, giving it (in)famously soft corners, which can be artistically useful. The Art 30 is a different optical design, with much more usable corners. I think this makes the Art 30 a better general-purpose lens.
The Art 30 is larger in all dimensions and heavier, and while both lenses have 62mm filter rings, the hoods are not interchangeable. Despite the ‘HSM’ in the name, the Pentax-mount EX 30 was screw-drive, rather loud, and the focus ring would twist under your fingers when auto-focusing. While the manual-focus ring on the EX 30 has been criticized as “gritty”, mine was always smooth, if a little plastic-y, and easy to turn with just thumb and forefinger. The ring on my Art 30 is much stiffer.
Art 30  EX 30  Art 30  EX 30 
In my head-to-head comparisons, the Art 30 seemed to expose just a little darker than the EX 30, but colors were very similar. The Art 30’s bokeh seems to have a little more blur for each f/stop. The minimum focus distance on the Art 30 is a little shorter. The EX 30 can give nice stars at f/5.6 or higher; the Art 30 is very flare resistant and doesn’t seem to want to star at all (may need to revisit next Christmas).
Comparison to other APS-C “standard” Field of View lenses 
This was summed up well in the PF review. You should read it!
This may be the LBA talking, but with the possible exception of the FA 35/2 and DA 35/2.4, each of those lenses has a slightly different specialty. No one lens can replace all the others.
If IQ is more important to you than price and/or size, you should look to the FA 31/1.8 Limited or Sigma 35/1.4 Art. If you were wanting the Art 30 to be a 31 Ltd at less than half the price, remember: Realistic expectations are key to being happy in life. It's not gonna happen.
The Sigma Art 35 is close in size and weight (600+ grams) to the Samyang 24/1.4, which I find to be nose heavy on the K-01. Over 500g, a thicker grip and viewfinder are needed to stabilize the camera. Another alternative to the Art 30 is the Sigma 28/1.8, but from what I could find, the Art 30 is smaller, lighter, sharper, and quieter, at about the same price.
If small size is more important than HSM focusing or paper-thin DoF, there’s the FA 35/2, the DA 35/2.4, the DA 35/2.8 Ltd., and in used glass, the FA 28/2.8. This is the direction I would go for outdoors or street shooting, where screw-drive noise doesn't matter as much. The 35 Ltd costs 50% more than the Art 30, and its focusing may not be fast enough for everyone on the K-01.
If you are into manual focus, the Samyang RokinonBowerEtCetera 35/1.4 is a nice chunk of glass, but on a K-01, it’s just too unwieldy. Even on a DSLR, it depends on the body and the shooter. For my hands, it's fine on a K-5, but uncomfortable on a K-30.
In used lenses, depending on how much you are willing to give up (f-stops, auto-aperture, A-contacts, sharpness, sanity), there are thousands of manual-focus 35s, 30s, 29s, and 28s out there. Some of them might be very good, but be warned: this way leads to LBA madness!
Conclusion 
I like the Art 30 a lot. It does everything I hoped it would do. It’s sharp, bright, quiet, and not too large. To be honest, a FA 35/2 with DC focusing would meet 95+% of what I need/want (WR would seal the deal), but the Art 30 is at least 90% - the missing 5%, minus some points for size.
For use as a general-purpose “standard” walk-around lens, it’s a little bulky. The results may be worth it. Even if I don’t shoot it wide open all the time, I like having the option to do so. Because I prefer center-point AF, the slow/no AF problem on a DSLR is a non-issue for me, but it could be a deal breaker for some.
If I was going on a museum crawl and could only take one body and two lenses, it would probably be a K-01, the Art 30, and a 17-50/2.8, or if there was going to be much outdoor shooting, my K-5II, Art 30, and DA 18-135 WR. (In either case, I’d cheat and have my DA 15 Ltd hidden somewhere on my person, but that goes without saying, right?). I’m sure the Art 30 will be a regular in my bag.
See more samples, comparisons, and 100% crops in my flickr album. |
