Sigma 50-150 is TIGHT

A couple of weeks ago, I got a Sigma 50-150 2.8.  Here's a review from a family photography perspective, and some quick demos to show the usefulness of a telephoto lens.
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RATIONALE:
I like the Tamron 17-50 VC but it's not long enough for telephoto shots, even with a camera with a 1.5x crop factor.  Long lenses are useful not just for photos of distant subjects.  In terms of composition, long lenses can have shallower depth of field.  (After all this time, I'm still a sucker for shallow DOF.)

Just as important for me, a telephoto lens captures a much smaller field of view.  It's great to include the background where you're someplace nice like a fancy vacation resort.  But for other occasions when the background isn't perfect (which is like 99% of the time), having a small field of view makes it easier to get a simple and clean background.  In terms of lighting, a small field of view also allows the light source to be positioned more closely to the subject without showing up in the photo (suddenly even the small Lumiquest SBIII looks useful!).

Interestingly enough, just as I got the Sigma 50-150, I saw these related blog posts from Neil van Niekerk and David Ziser regarding using a long lens to get tight composition:

• Neil van Niekerk's Tangents: http://neilvn.com/tangents/2010/09/19/wedding-portraits-simplifying-composition/?utm_source=rss&utm_medium=rss&utm_campaign=wedding-portraits-simplifying-composition
• David Ziser's DigitalProTalk: http://digitalprotalk.blogspot.com/2010/09/technique-tuesday-big-light-and-long.html

In addition to the smaller field of view, long lenses have different perspective.  Please check out this related post on why zooming with your feet is not a substitute for having different focal lengths (and cropping works for perspective and field of view, but not necessarily for depth of field): http://betterfamilyphotos.blogspot.com/2010/09/whats-point-of-having-different-lenses.html

ALTERNATIVES CONSIDERED:

When I decided that a long lens would be useful for me, I considered several alternatives to complement the Tamron 17-50 VC (these are Nikon-centric alternatives but other brands have similar choices):

• Nikon 55-200 VR: very inexpensive for a tele zoom yet has good image quality. Unbeatable value.
• Nikon 70-300 VR: long reach, with great image quality.  Not cheap but affordable.
• Nikon 55-300 VR: a newly-released lens, it seems to combine the best of the 55-200 and the 70-300, even having VR II.  Best of all, it's priced very reasonably - and less than the 70-300 VR. Nice!  No reviews yet...
• Nikon 18-200 VR: very versatile, with many happy owners.  For a consumer lens, though, I think it's quite expensive.
• Tamron 18-270 VC: exceptional range and a better price than the Nikon 18-200.  I've owned a Tamron 18-250 though and found that it was too slow to focus (with a Pentax K100D) when I needed it most.  I would probably get a 55-200 VR or 55-300 VR before getting this lens.
• Nikon 24-120 f/4 VR (while Canon has the 24-105 f/4L IS): a new Nikon lens - not as slow as variable aperture tele zooms, and can cover wider focal lengths. On a DX body, it may be long enough.  But this semi-pro lens is expensive for me.
• Nikon 70-200 2.8 VR: the gold standard for tele zooms (for Nikon).  Waaaay too expensive for me.  For that price, I can get an Olymus 4/3 DSLR and pair it with the reasonably fast Olympus 50-200 f/2.8-3.5 (equivalent to 100-400mm).  Also too bulky to be practical.
• Nikon 80-200 2.8 or Tamron 70-200 2.8 or Sigma 70-200 2.8: more affordable alternatives to the Nikon 70-200 VR but still too bulky, and they lack image stabilization, which is a must for a lens this heavy and a focal length that long (unless you want to use a monopod or tripod).
• Tokina 50-135 2.8 or Sigma 50-150 2.8: fast, constant aperture tele zooms with good image quality (based on photozone.de reviews) that aren't too big. See here for a size comparison vs. 70-200.  Not cheap but are decent values (how can anyone expect a fast, constant zoom tele lens with good image quality to be cheap anyway?).  Note: the Tokina 50-135 has been discontinued but can still be spotted for sale once in a while.
• Canon users may also want to consider the 70-200 f/4L, while Pentax users have the Pentax 50-135 2.8.

I thought, if money were not a significant issue, I would buy the Sigma 50-150.  So that's what I wanted for a while but was put off by the price.  Then I saw a used one at B&H Photo, in good condition, at more than 20% off the price of a new one.  It made me think seriously about getting one but a couple of weeks later it was gone.  I felt pangs of regret.  I later saw one on ebay (the HSM II version), priced similarly as the one I saw from B&H.  The pictures provided by the seller seemed to show it was in very good condition.  I sheepishly asked my wife for consent to get the lens, and when she said ok, BAM I bought the lens.

A few days later, I got the lens.  It was in as good condition as I had hoped.  It was missing the original lens cap and lens hood, but otherwise was ok.

BUILD QUALITY:
My first impression of build quality was positive.  It does have a metal mount and seems to be reasonably well-built.  It also came with its own padded bag.  Nice.  I wouldn't worry about the build quality on this lens unless you like your lenses to be heavy, all metal, and expensive-looking.

I was surprised by the quietness of this lens (note: this is the second version of this lens, with HSM).  I've owned a few lenses (Pentax 50 1.4, Tamron 18-250, Tamron 28-75, Tamron 17-50 VC) and I've never noticed the sound of my lenses (except perhaps for the Tamron 17-50 VC's audible image stabilization).  This one though was so quiet it caused me to notice.  The focus motor itself has no sound - I can only hear the lens itself as the lens moves back and forth.  I've never owned a Nikon lens (yet) but I would say it's as quiet as the Nikon SWM lenses I've tried in stores.

FORM FACTOR:

size compared with the Tamron 17-50 VC

The key selling point of this lens compared to a 70-200 (from Sigma or any other maker) is the size.  It's much smaller and lighter than a 70-200, and won't look like a medieval weapon. That  said, it's still quite long (compared to consumer zooms) and barely fits with my camera in my smallish camera bag.  When mounted on my D300 without battery grip, my setup becomes a bit front-heavy, though still possible to handhold with one hand (I would be much more comfortable shooting with two hands though).

The front element doesn't rotate when focusing, and I found it interesting that the length of the lens doesn't change when you zoom it.

Other notes: It doesn't have an aperture ring, but does have a distance scale.  There are also labels for common focal lengths.  It doesn't have a tripod/monopod collar (whereas the Tokina 50-135 does).

PERFORMANCE:
With any third-party lens, the issue that worries me most is the number of complaints about focus.  I think some of those complaints are due to user error but it is still a significant concern for me.  So much so that I got the D300 primarily for the AF fine tuning.  Having AF fine tuning, I have since become more confident in getting third-party lenses -- even used third party lenses (oh, the horror!).

This lens is no exception to my research on third party lenses.  If you look around, there are complaints about front- and back-focusing, even both front and back focusing on the same lens. (Is such a thing possible?)  I think many of the perceived focus issues are attributable to user error, but for your comfort, I would suggest buying someplace with a good return policy (or buy it with a credit card that offers a free warranty on purchases).  Also, I would suggest spending a little time with it before concluding that it is front- or back-focusing.

Anyway, I tested the focus by focusing on a TV remote control's buttons.  Looked accurate enough to me that I didn't feel the need to use any AF fine tuning.  Focusing speed was not instantaneous but it still focused pretty quickly (quicker than I expected).  Quick enough that my D300 was able to keep a friend's toddler in focus while running toward at me.  A nice feature of the lens is the ability to tweak the focus manually while in autofocus mode (similar to the A/M mode of some Nikon lenses).

I found the image quality to be reasonably good.  (Note: I'm basing my opinion mostly with my experience with the Tamron 28-75 and Tamron 17-50 VC, which are both well-regarded lenses.) The distortion and vignetting are pretty tame.  Vignetting is supposed to be significant at f/2.8 and 150mm, but in real world shots it has not bothered me.  No complaints about color and contrast.  The sharpness is about as good as I expected from photozone.de 's extensive testing: see here (i.e., quite good).  At 150mm, the image looks noticeably soft/fuzzy, almost as if it's slightly out of focus (compared to shots at other focal lengths).  I was aware of this softness from the photozone.de review though, and I figure it's better than not having that extra reach.  As for bokeh, I'm not a bokeh connoisseur but I think the bokeh looks reasonably smooth (with no outlining).

Straight-out-of-camera JPEG (sharpness):

100% crop of shot above:

 (Note the skin pores.)

Straight-out-of-camera JPEG (bokeh):

CLEANING UP:
As previously mentioned, I wanted to get this lens to simplify composition. A long lens with a wide aperture helps do this by having a smaller field of view and a shallower depth of field. Here are some demo shots to illustrate this point.

Here's the setup shot: I placed junk in front of and behind the subject to see how much of the junk would be visible.

If we use an 18-55 kit lens, the shot we'll get will look kind of like this (using the widest f/5.6 aperture at 50mm):

If we upgraded from that and got a fast 2.8 zoom with a similar range such as 17-55 (or similar lens), then our shot may look like this (f/2.8, 50mm):

The wide aperture made the junk a bit less noticeable because of the shallow depth of field.

If you have a 55-200 telephoto kit lens and you take a shot at 150mm, at its widest aperture f/5.6, it may look like this:

 Although the aperture is not wide, the junk is less noticeable because of the smaller field of view, and the shallower depth of field at longer focal lengths.

Finally, if we have a fast long lens like the Sigma, at f/2.8 and 150mm, we get this:

 Due to the even shallower depth of field, the junk is even less noticeable.

CAVEATS FOR THIS LENS:

A) Minimum focusing distance:
The minimum focusing distance on this is kinda long (slightly more than 3 feet -- 39.4 inches to be exact).  No macro capabilities on this one!  While taking a photo of our kid over a small dining table, I had to crane my head backward to be able to get him in focus.

B) Reach:
A reach of 150mm (225mm equivalent, assuming 1.5x crop) seems long but it's actually not THAT long.  If you're shooting sports from the stands, this will get you closer but *not* very close to the action.  For events though, it's ample, and for portraits, it's great.

C) Image stabilization (or lack thereof):
This is the part where Sony and Pentax shooters get payback.  One issue with this lens is the lack of image stabilization. I think image stabilization would indeed be useful at the longer focal lengths of this lens.  Is it technically feasible?  I think it is.  The filter size of this lens is 67mm, so I'm guessing that image stabilization is not impossible (probably would increase the size to 72mm or 77mm).  In fact, Sigma has a stabilized 17-50 2.8, and just announced a stabilized 120-300 2.8 zoom, so it seems that it should be possible to add stabilization to this one as well.

Having said that, adding stabilization may not be feasible from a business perspective.  It would make this lens even more expensive (perhaps similar to the price of a Sigma 70-200 OS), further shrinking the already small market for non-pros willing to pay this much for a lens.  I mean the Tokina 50-135 2.8 was discontinued, right?  It leads me to think there's not much demand (yet) for a 1.5x-crop format equivalent to a 70-200 at the current price.  Overheard at Sigma headquarters: "The consumers want a fast, constant 2.8 telephoto zoom that's compact, for a budget of how much??? AND they want image stabilization???"  Speculation: I think the apparent lack of demand is partly because this lens costs about the same as a Sigma 70-200 2.8 (which can be used on either a crop or full frame camera).  For me, though, I prefer this lens because of the practical size, and more useful range of coverage (on a 1.5x crop camera).

Back to the topic: so, how's this lens without image stabilization?  It's challenging but usable.  In daytime, I shoot very carefully (bracing myself, etc. when possible), or I use continuous shooting.  In dim conditions, I try using flash to freeze the subject (and camera movement).  Therefore it is possible to get sharp shots with this lens even without image stabilization, though it's not easy at the long end.  (If image stabilization is an absolute must, FYI Sigma has announced a stabilized 150 2.8 macro lens: http://www.sigmaphoto.com/shop/150mm-f28-ex-apo-dg-hsm-macro-sigma with MSRP of $940 - vs. $1150 MSRP of this lens, so the street price will likely be less than that of this lens.)

For Sony and Pentax shooters of course, the absence of image stabilization presents no problems whatsoever because of the built-in stabilization in their cameras.  In fact, the absence of stabilization is great -- it saves on lens cost and size!  For Sony and Pentax, I think this lens is awesome (Pentax also has their own 50-135 2.8 which is similar to Tokina's).

A couple more sample shots:

CONCLUSION:
A long lens is useful for certain types of composition and can be used to select a cleaner, simpler background.  Does it have to be fast as well?  For composition purposes, not really.  Even at f/5.6, the depth of field is narrow enough and the field of view is small enough (especially with a 1.5x crop factor) that you can get a clean background readily. 

However, if you often shoot in low light conditions, a fast 2.8 zoom will give you 2 stops more light than a variable zoom that gives you f/5.6 at longer focal lengths.  Two stops may not seem that much, but when you're demanding a lot of light from a small hotshoe flash by bouncing, feathering, or using a black foamie thing, then the 2 stops may be a determining factor for your shot.

If you love portraits, and want the shallowest DOF with reasonably good bokeh, this lens would be a good choice.  Due to the compact size, location portraits would be convenient.  (If you want clients to be impressed with the size of your lens, then attach the lens hood so it looks longer :D )  I think other good yet affordable choices for portraits would be the Nikon 85 1.8 and the Tamron 28-75.

If your little one is in sports, a wide aperture would also be very useful for freezing action.  In this regard, note that image stabilization offered in other lenses is a useful feature but it's not a substitute for a wide aperture like the one of this lens.  Stabilization may make your camera shake unnoticeable, but it will do nothing to let you use a higher shutter speed to freeze your subject.  Note: the reach on this one is not super long for sports but it's ok.

If you've determined that you need a fast zoom, and you have an APS-C sensor (1.5x crop or 1.6x crop) camera, the Sigma 50-150 is a practical and more affordable alternative to a 70-200 lens.  (Another possible alternative may be to use a slower zoom at a high ISO then use noise reduction software.)

OTHER RESOURCES:

• Photozone review (Nikon version) http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/322-sigma-af-50-150mm-f28-ex-hsm-dc-nikon-mount-review--test-report
• By a portrait photographer (nice sample shots): http://www.ephoto-photo-school.com/sigma-50-150.html
• By Mark Gibson, a photographer who really knows how to use this lens: http://www.flickr.com/search/?s=int&w=21524785%40N00&q=50-150&m=text

Got this lens? Pls. show off your photos in the comments!  And Sigma, if you're listening, perhaps you can make a 50-150 f/2.8-4 OS that won't break the bank. :)