I’m a little concerned about the focus performance of my Pentax K10D DSLR. Before I get too far into it, let me  establish a little background first…

Two years ago I was looking for an upgrade to my then 2 year old Canon Digital Rebel XT (350D). I really didn’t have much more than the kit lens and a cheap-o EF 50mm f/1.8 II, so I didn’t feel too married to Canon. I did my research and decided the then new Pentax K10D represented a better value for the $1,800 I had to spend than the more expensive Canon 30D. So, I gave my Rebel to my sister-in-law and ordered up a K10D body, Sigma 18-50mm f/2.8 EX and Sigma 10-20mm EX from B&H Photo.

The ergonomics, features, IQ, and interface were all so much better than my old Rebel that there wasn’t much time for  retrospection. I embraced my new rig and started shooting like mad. Six months and 20K snaps later I had added the excellent DA* 50-135mm f/2.8 to my kit. To my surprise, Santa (in the form of my mom and step dad) gave me a $1,000 Wolf Camera gift certificate for Christmas 2007. Suddenly I found myself in a quandary.

You see, I had become somewhat smitten by the full frame Canon 5D we had at the office for the Marketing team I managed. It had always seemed so out of reach to me and now suddenly it was all-too-close. After a few days of agonizing over what to do, I ended up selling off my K10D kit to a co-worker friend and added the proceeds to my gift certificate. 2008 began with a brand new Canon 5D body (the $3,000 body was all I could afford). Fortunately, my old 50 1.8 was collecting dust in the bottom of a drawer so I was able to actually use the 5D while I saved up for some better glass.

It was hard to draw many comparisons between the 5D and K10D. They really are quite different cameras- with the 5D being much more like a 35mm film camera than a high-tech digital. Plus, the clunky old 50mm prime I started out with on the 5D really wasn’t anything like the Sigma EX zoom lenses I had had on my K10D. What I didn’t know was that I would decide to leave my six figure job in April to return to school and finish my undergraduate degree. This move required scaling back across the board and my beloved 5D (and all the L glass I hoped to own) suddenly seemed like an excessive luxury. I decided to sell it, my EF 50 f/1.8 II, and the EF 28 f/2.8 and EF 85 1.8 USM I had acquired on Craigslist and invest the proceeds into my college fund. For the first time in 7 years I was without a DSLR.

In September of last year my former co-worker felt pity for my situation and gave me back my old K10D with the kit lens off his new K20D! Since then I have been shooting like mad with the kit lens and a 20-year-old SMC-A 50mm f/1.7 manual focus lens I picked up off of eBay. In the past couple of months that former co-worker of mine has also shared his DA* 16-50 f/2.8 and DA 35mm f/2.8 Macro Limited lenses with me to test on my blog. I wasn’t too impressed by the 16-50 (see review) and my experience thus far with the 35mm macro has been mixed (review here).

While I was at PMA a few weeks ago I played around a bit with all the various cameras on display. Both Pentax and Canon had similar demo set-ups for their top-of-the-range telephoto lenses. While using the DA* 300mm f/4 in the bright tradeshow lighting I tried focusing on a subject standing a few meters away and the SDM motor woooshed close then dunk, da-dunk, “beep-beeped” into focus lock. I then swung the lens up and selected a far away subject- woooosh, dunk, dunk, da-dunk, “beep-beep”. Selecting a subject a few feet away from the second the DA* 300 went dunk, dunk, da-dunk, “beep-beep”. This all seemed quite normal to me. From my experience shooting both the DA* 50-135 f/2.8 and DA* 16-50 f/2.8 SDM equipped lenses.

Then, I moseyed over to the Canon booth where they had a very similar display set up with a 1D Mark III and EF 400mm f/2.8 L IS USM lens. Repeating the short-to-long focus test (this time with a much heavier f/2.8 lens) the Canon went woosh, “beep-beep” to the close subject then woosh, “beep-beep” to the far subject. Selecting a nearby subject to the far one I got bump, “beep-beep”. Surprised I tried several more times, panning the camera around and selecting subjects that were just out of focus. Each time I simply got bump, “beep-beep” as the subject popped into near instant focus. At the time I merely chalked this up to the near 10X cost difference between the two set-ups and continued on my way.

Fast forward a few weeks to yesterday and my niece’s 3rd birthday party. I found myself two-fisting my K10D with 35mm f/2.8 Macro Limited and my sister-in-law’s Canon Rebel XT with kit lens (my old camera) while capturing both indoor and outdoor birthday party action. I was immediately aware at how much faster the 4 year old Rebel was locking focus than my K10D was. It was almost exactly like the performance difference I had experienced at PMA.

While the kids were busy taking turns in the kayak (and out of decent photo range for any of my lenses) I took a moment to do a little non-scientific focus testing. I manually set both cameras to infinity focus, selected the center focus point, 35mm focal length (on the Canon) and (in bright sunlight) focused on my hand at around 18″ away, then on the far side of the lake (infinity), then back to a post about 6′ away with the 35mm Macro on the K10D and the 18-55mm kit lens on the Rebel XT. In all cases the Canon nailed the focus point with zero hunting… zip, “beep-beep”, ziiip, “beep-beep”, ziip, “beep-beep”. The Pentax however, struggled a bit. The focus test went weeeee, tick, tick, tick-tick, “beep-beep” for the close subject, then weeeeee, tick, tick-tick, “beep-beep” for the far subject. Then, the camera completely missed the post 6′ away and went weeeeeeeeeeee all the way to it’s closest focus distance than weeeeeeeee, tick, tick, tick-tick, “beep-beep” on the post. (To be fair, this is a macro lens).

Thinking that the Pentax 35mm Macro might have been to blame (which it was), I pulled out my Pentax 18-55 Mark I kit lens and repeated this test again. The results were nearly identical with the exception that the Pentax kit lens did not overshoot the post and merely ticked around a couple of times before locking focus. Also, the lighter less damped focus action on the kit lens did make it seem a tad snappier when focusing between the close subject and the far subject. Incidentally, this time to reach the correct focus distance was basically identical for both the Pentax and the Canon kit lenses. The exception being all the tick, tick, ticking the Pentax lenses did before locking focus. (In case you were wondering I also repeated a similar test inside under poorer lighting with the two kit lenses and got nearly identical results as outside).

Discussing this with my co-worker friend, he relayed the results of a similar test he decided to try with his K20D as follows:

I just did back to back comparisons of the K20d + FA 50/1.4 and my Rebel + EFII 50/1.8. In indirect sunlight, using the center focus point I swapped focus between the front hedge at about 10M away and my left hand outstretched.
The Canon will ziiiiip, stop, confirmation beep.
The Pentax ziiiiips from 10M to my hand quickly just like the Canon but then it quickly zips one (or two!) more times before focus confirmation… Almost like it has momentum from the first movement.
I’ve been fully aware of this (and failure to focus–maddening) but had assumed that after twenty years of screw-driven, TTL autofocus technology this was the best the world could do. Seems it’s the best Pentax can do.
IMHO this is the worst aspect of my K20d.

Keep in mind that his test was done with a state-of-the-art $1,000 K20D + FA 50mm f/1.4 vs a $300 6 year old Canon 300D + 50mm f/1.8 II eBay find.

In hindsight I realize now how many shots I have missed over the years with my Pentax due to its slow autofocus performance. The most frustrating part is that the vast majority of shots I’m missing are while the camera is tick, tick, ticking its way towards focus lock, not because it has mis-focused. Once it gets there it is generally just as accurate as any other camera I have used. I hope Pentax is listening and improves the performance of their next generation of DSLRs. In my opinion, this is much more important than live view, more megapixels, movie recording, higher frame rates, and/or higher ISO performance. Pentax’s DSLRs are some of the best values on the market. Bring the AF speed up to par with the competition would end a lot of arguments in Pentax’s favor.

What do you think?

PS- I excluded Nikon from this comparison because I have very limited experience with their modern DSLRs. However, I did borrow a friend’s D300 + 50mm f/1.8 to take some studio shots of my K10D for my DA* 16-50 f/2.8 review. The camera was set up to use all 50-something focus points in AI mode. Being unfamiliar with Nikon’s focus confirmation implementation I didn’t realize until after I was done shooting that when all those grey boxes popped up in the viewfinder that the camera had locked focus. In hindsight I now realize that it was happening so fast that I was unaware that the camera was focusing. To get my shots BTW, I ended up switching over to manual focus ;-)

UPDATE: First of all I want to make it clear that I am not suggesting that Pentax’s autofocus system is any less accurate than anyone else’s. It is clearly quite effective. Also, I fully understand that Pentax has to pick and choose where they spend their limited development funds and I am happy they put it where they have (weather sealing, in-body shake reduction, user oriented controls, etc). In fact, that is why I chose Pentax over the others in the first place. My main reason for publishing this article was to attempt to draw the same comparisons so many Pentax users have over the past few years in a more objective manner so that those who haven’t experienced the differences themselves could be more fully informed. Too many consumers buy products today based on too narrow a point of view and then blame the product when it doesn’t meet their expectations.

My friend Stephen loaned me his Pentax SMCP-DA* 16-50mm f/2.8 ED AL (IF) SDM lens so I could put it through its paces and compare it to my kit lens (SMCP-DA 18-55mm f/3.5-5.6 AL). If you don’t know already, Pentax’s DA* (”D-A-star”) line of lenses are their highest quality zooms. They feature very high quality construction, weather sealing, silent ultrasonic focus motors (SDM), and Pentax’s best SMC coatings (SP) to date. Retailing at close to $700 this lens seems like it should be a huge step up from the $99 kit lens.

This isn’t a technical review. If you want MTF and distortion charts go here. Instead, I’m just going to cover my observations during real world everyday use. Keep in mind that I do have a unique perspective here so take my opinions with an appropriate grain of salt. Here are my overall findings. Feel free to read on for a more in-depth look at how I formulated my opinions.

PROS:

• Excellent build quality
• Useful zoom range
• Silent SDM focus motor
• Weather seals
• 9 bladed aperture

CONS:

• Very soft around the edges wide open
• Distracting CAs below f/4
• Big and heavy
• Very long for a 50mm lens
• Pronounced barrel distortion at 16mm
• Expensive

CONCLUSION:

While I would normally suggest upgrading the standard kit lenses from Canikon, Pentax has done an excellent job with their SMCP-DA 18-55mm f/3.5-5.6 AL and this gussied up DA* lens only helps to prove that point. Had I bought this lens myself I would have sent it back after the first day and put my money to better use. This is a big, heavy and expensive lens that does not prove a significant upgrade to the kit lens in everyday use. Get and/or keep the kit lens and put your money towards a dedicated ultra-wide angle lens and/or some fast primes to compliment the kit lens (some suggestions can be found at the end of this article).

REVIEW:

Purchasing a lens for me encompasses four primary areas of concern: image quality, build quality, handling, and value. There is no standard order of importance here as all of these issues carry different weight depending on the intended application of the lens in question. In this case, the 16-50 seems ideally positioned as an upgrade to the standard kit lens. This makes it an all purpose lens that should perform equally well in all four areas while handily outperforming the kit lens (which is why I am comparing the two here).

Image Quality

I think the crop above says it all. Shoot this lens at 16mm with anything less than f/4 and the color fringing (chromatic aberrations or “CAs”) and edge softness are quite disappointing. F/8 is required to eliminate the problem altogether from wide shots. The fringing persists all the way up to 50mm but is generally less of a problem at the longer focal lengths due to the shorter depth of field at f/2.8 (CAs get lost in the bokeh). Center sharpness is pretty good wide open (f/2.8) at all focal lengths and becomes tack sharp at f/4 and above. Overall color and contrast are very good (as it is with all Pentax lenses).

My biggest issue here is that the three main advantages this lens should have over the kit lens are sharpness, speed and the wider field of view (FoV). I found myself stopping down to at least f/4 for most of my shots with this lens, only using f/2.8 in extremely low light hand-held situations and when controlling the depth of field (DoF) was critical. The extra 2mm on the wide end (16mm vs. 18mm in the kit lens) are noticeable due to the greater FoV but more notably for the exaggerated barrel distortion. This isn’t a deal breaker for me but is disappointing at this price point.

On the other hand, stopped all the way down to f/22 and opened up wide to 16mm, this lens produces some very nice results for landscape photography. Its nine bladed aperture creates awesome 18 pointed starbursts with very little flare. This is one of the areas where the higher build quality of the DA* really shines (pun intended).

That 9 bladed aperture also produces very nice bokeh even when stopped down. The image above was taken at 16mm and f/8 and exhibits very smooth blurring of the background with mostly circular out of focus highlights. This shot also illustrates the 16-50’s macro performance. It’s 0.3m (11.8″) minimum focus distance makes it pretty useful for getting in tight even if the 50mm maximum focal length doesn’t provide a tremendous amount of magnification. Keep in mind that the minimum focus distance of a lens is measured from the sensor (ie: film) plane in the camera body and not from the front of the lens. This means that at 50mm you can get up to about 3-4″ away from the subject with the front glass. This may be useful sometimes and a problem at others. Personally, I like shots like this where you get in close with the wide angle to exaggerate scale and perspective. Meanwhile, the kit lens can focus down to 0.25M (9.8″)…

Build Quality

Not much to say here. This lens is built as well or better than the best lenses from any mainstream manufacturer. One heft and you will not question its price tag. Typical to the DA* line, the 16-50 features gasketed seals to prevent dust and moisture penetration, including a seal at the lens mount to seal it to the camera body. Combined with Pentax’s weather sealing on the K10/20D bodies this makes for a very practical all-weather combination. I’m sure this is a useful upgrade but I have shot in some pretty nasty conditions with my kit lens and have not had any problems with moisture penetration. (I have to wonder if most non-professional photographers would put their cameras through the kind of abuse this level of construction suggets is possible). The zoom and focus rings are well damped and buttery smooth with nicely ribbed rubber rings. There is no slop or wiggle between the various moving parts anywhere throughout the zoom range.

Handling

For me this is one of the most conflicting areas for this lens. On one hand Pentax has included some very nice design features that make this lens a worthy step up from the kit lens. On the other hand, the sheer bulk of this lens really gets in the way. Here are a couple of the nicer design features:

The access port on the lens hood is a nice touch common to all Pentax lenses. It allows access to the control ring on rotating filters without removing the lens hood (like polarized, graduated and special effects filters). This is a very user-friendly feature that all lens makers should adopt. After all, you usually find yourself needing to use these types of filters and the lens hood at the same time anyway, right?

Another nice feature of this lens is the SDM ultrasonic focus system. This lens focuses absolutely silently. This can be a bit strange at first considering how loud the screw drive focus system is with standard lenses. It’s not noticeably faster or more accurate than the screw drive system (still hunts too much IMO) but its silent operation draws less attention to the fact that you are taking pictures (if only the extra-loud shutter wouldn’t betray us so). The focus ring can be used anytime to fine tune the focus. However, it is not directly coupled to the focus mechanism so it does not stop turning when you reach the either end of the focus range. Pentax has included an AF/MF selector switch on the lens for those times when you want full time manual control. This is a lot easier to use than the switch on the camera body and is a nice touch.

Why does Pentax make me spend $700 to get a decent center pinch lens cap?

Now for the bad news. This lens is a brick. On my kitchen scale the 16-50 weighs 20oz while the 18-55 kit lens weighs in at 8oz and my old 50mm f/1.7 is only 5 3/4oz. (BTW, the K10D body w/ battery weighs 28oz). I realize that there is a weight penalty to step up to f/2.8 in a zoom but, considering this lens’ lackluster performance at f/2.8, I really have to question the benefit here. I mean, why carry around all this glass if you’re going to be shooting at f/4 anyway?

Mounting this lens to the front of my K10D felt very awkward. The grip on the K10D is a bit shallow and hanging all that weight off the front of the camera made it very difficult to hold securely with one hand. I found myself carrying the camera by the lens and having to use two hands for most of my shots. (Adding a battery grip would help balance the camera and provide better leverage with the heel of your right hand). Don’t get me wrong. I don’t mind a heavy and expensive lens if the performance and application justifies it. (Canon’s EF 70-200mm f/2.8L IS USM is one of my all time favorites). Overall this did not prove to be a very good walking around combination. I find this interesting since this sort of everyday use seems to be the main focus of lenses in this zoom range.

Another negative aspect the comparison photo in the section above illustrates is how long this lens is. The 16-50 is at its longest (5 3/8″ to the mount) at 50mm and its shortest (4″) at 16mm (as shown directly above with lens hood). The kit lens is only 3 1/8″ at its longest which is at 55mm and 18mm. As you zoom from 18mm to 55mm the kit lens starts off long then retracts to its shortest length of 2 3/4″ at 35mm then back out to 3 1/8″ at 55mm. This double action means it only has to extend half as much (percentage wise) as the 16-50 does throughout its zoom range. I point this out mainly because 50mm on a 1.5X APS-C sensor is the equivalent of 75mm on a full frame sensor and 35mm film. This puts it right in the sweet spot for close portrait photography. However, when you point this thing at people they tend to back away as if you’ve just aimed a bazooka at them. I imagine it would be fine in studio situations but for candids and street photography the kit lens (or better yet, a 50mm prime) is clearly the better choice.

Not to belabor the point too much here, but another aspect that should be considered with respect to lens size is how much space it takes up in your bag. Here you can see the 16-50 f/2.8 DA* and kit lens both suited up for travel with hoods and caps. As you can see, the 16-50 will require a pretty massive hole in your bag (4 1/8″ X 4 7/8″). If you are anything like me you have to consider very carefully what goes in your camera bag. Which brings me to my conclusion…

The advertised advantages of this lens are its wide FoV (16mm), speed (f/2.8), SDM focus motor, build quality, 9 bladed aperture, weather sealing, and sharpness. However, in actual use I don’t find any of these things in combination to be a significant enough improvement over than the kit lens as to justify the price and bulk of the 16-50 f/2.8 DA*. In fact, if this were the kit lens I would be looking to upgrade. If you have $700 burning a hole in your pocket there are a number of better choices out there.

I suggest you look at the Pentax SMCP-DA 12-24mm f/4 ED AL (IF) ($670). It is a re-badge of the stellar Tokina 12-24mm f/4 AT-X 124AF Pro DX ($490) and makes a much more useful ultra-wide angle addition to the kit lens. (It is a bit frustrating that we Pentax users have to pay an extra $200 for the same lens the Canikon folks can get directly from Tokina). It is still pretty heavy (15oz) and will take up just as much room in your bag as the 16-50, but the ultra-wide angle shots you’ll get with this lens will absolutely blow you away. If speed and sharpness are what you are looking for pick up a fast prime or two like the Pentax SMCP-FA 50mm f/1.4 ($200) and/or the Pentax SMCP-DA 35mm f/2.8 Macro Limited ($480). If you really feel a burning need to try out a DA* lens, check out the new Pentax SMCP-DA* 200mm f/2.8 ED (IF) SDM ($890). Its bulk is easily justified by its extra reach and speed (just beware of some nasty purple fringing in high contrast scenes).

Finally, if you are buying a new Pentax body and are looking for an upgraded alternative to the kit lens, don’t. The kit lens is one of the best values available for these cameras. If you are determined, take a look at Sigma’s 18-50mm f/2.8 EX DC Macro ($420). This was the lens I originally bought with my first K10D back in ‘07. It is not nearly as big and heavy as the Pentax 16-50 f/2.8, has almost identical image quality, and adds a very useful macro focus capability across the entire zoom range. I shot several thousand shots with it in 2007 in several parts of the world and can attest to its quality. That being said, I now know that the Pentax 18-55mm kit lens makes better pictures ;-)

Some sample photos taken with this lens during testing.

UPDATE:

A number of readers have suggested that Pentax’s $380 SMCP-DA 16-45mm f/4.0 ED AL might be a better upgrade choice over the 16-50mm f/2.8 DA*. I have no experience with this lens so I did not mention it as an alternative. Reading over the photozone.de test report I can see that at only 12.9oz it is considerably lighter than the 16-50 DA*. Size wise it is slightly smaller than the 16-50 DA* with the added benefit of being at its shortest at 45mm (opposite of the 16-50). Also, it features an 8 bladed diaphragm which should result in decent bokeh and nice starbursts when stopped down. Resolution seems to be very good with distortion and vignetting similar to the 16-50 DA*. The only real noteworthy negative mentioned is heavy CAs at the edges of wide angle shots. If I can get my hands on one of these I will definitely post a similar review and find out if this lens is worthy of consideration.

After writing this review it was brought to my attention that the 16-50mm f/2.8 DA* has suffered from some quality control issues. It is entirely possible that this example is flawed. However, in researching this a bit more I still find a number of reviews pointing to similar image quality problems on lenses that are supposedly in proper working order. Potential QC problems aside, my opinion remains unchanged about this lens.

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