Best walkaround zoom for Pentax K100D

November 22, 2007 7:04 PM

I bought the Pentax K100D dSLR, partly on recommendations from here, and I love it. I have the 18-55 kit lens and the 50-200 zoom lens, which I mostly use. Now I would like to buy a faster in-between zoom, somewhere from 24-28 at the low end to 75-135 at the high end. I am trying to figure out whether to buy a Pentax, Tamron, or Sigma lens and am getting confused with all the contradictory reviews. The Tamron 24-135 is praised to the skies by some and trashed by others. I am leaning towards the Tamron 28-75 but would like something closer to 100 mm. Any advice?
posted by blue shadows to media & arts (7 comments total)

A 75mm lens on the K100 will act like a 100mm lens on a standard 35mm SLR. The CCD isn't exactly 35mm size, which is why all the new Pentax-branded lenses come in weird lengths.
posted by backseatpilot at 7:13 PM on November 22, 2007

Pentax has a crop factor of 1.5--so multiply the focal length by that to get an understanding of what you'll actually get out of the lens you buy. (I also have a K100D and love it shamelessly.)

Ultimately, you can't depend completely on reviews--people have all kinds of strange biases about one brand over another. Pentax glass is almost universally outstanding, but I have a Sigma lens (20mm, f1.8) which kicks serious ass. But you want to pick the lens that will work for your photography goals.

Check out pixel-peeper.com for comparison of lenses based on actual photographs taken with 'em!
posted by gsh at 7:26 PM on November 22, 2007

If you're on the fence between those two Tamrons, given the two lenses you're starting with I'd absolutely recommend 28-75mm f/2.8. A constant f/2.8 lens will give you a noticeable advantage shooting action / available light and will give you a really fun shallow depth of field. Especially at the longer end -- 75mm f/2.8 is a huge difference from the other Tamron's 75mm at f/5ish. I traded in a Nikon 28-200mm f/3.5-5.6 for an 80-200mm f/2.8 and the loss of the wide end was totally worth the lovely aperture!

Mmmmmm, aperture.
posted by mindsound at 8:33 PM on November 22, 2007

Oh, and fwiw, Flickr seems to have more interesting love for the 28-75mm than the 24-135mm.
posted by mindsound at 8:35 PM on November 22, 2007

One thing that you'll find is that lens quality can be variable. That's why reviews vary. Some QC by some manufacturers is better than others. Off brands may be worse.

But some big time lenses like the canon 24-70 2.8, which is a serious pro lens, has famously variable build quality. So if you buy one of these lenses and it doesn't seem up to snuff, return it and get another copy.
posted by sully75 at 8:02 AM on November 23, 2007

I use the Tamron 28-75mm f/2.8 on a K100D and K10D. It's an exceptionally good lens for the price, in my opinion. Autofocus works well with the Pentax system and it's as sharp as anything similar made by anyone.

As you say, lots of reviews out there... [1, 2, 3, 4... among many]. None of them bad, although reviews always have to be taken with a pinch of your preferred condiment and interpreted in the light of your own style and use, of course.

The Tamron is only slightly wider than 'normal' at the short (28mm) end. Not as wide as your 18-55mm. You might find this unsatisfying if you like to take lots of wide-angle pictures. If the idea of a faster, wider lens appeals to you (once you discover faster lenses you never go back), the Sigma 18-50mm f/2.8 is generally also well thought of.

If you want something fast just for wider pictures, I can also highly recommend the Tamron 17-35mm f/2.8.

As an aside, all of these lenses so far mentioned have full 35mm frame coverage. That makes them a little bigger and heavier than similar designs made only for the Pentax (and many other DSLRs) APS-C-sized sensors. The advantage is that if Pentax ever makes a DSLR with a bigger sensor (unlikely in the near-term), these lenses will still work fine with such a (hypothetical) camera.

If you're flush with cash, there's Pentax's own 16-50mm f/2.8 that has 'weather sealing' and supports the newer SDM focus motors, if you ever plan on upgrading to a K10D. It's probably a very nice lens in lots of ways, but whether it's nearly $1K nice is a matter of some debate among the Pentax nerds.

QC seems to be a problem with all lenses these days, if internet discussion forums are our evidence. My suspicion is that it's a bit over-stated, based upon the dissatisfied being the most likely to shout loudest and factoring in a touch of the inexperienced not understanding what they're seeing. Never had a problem with any brand myself, and I own more lenses than can sensibly be justified. Just buy from a reputable source and you should be covered. Tamron offer a 2-year warranty (I think) in the US, and from what I've heard they honor it.
posted by normy at 12:04 PM on November 23, 2007

i recently bought the 28-200 zoom from tamron. its small and lightweight and awesome. works great for band photography since i can switch from wide to zoom without changing lenses.
posted by kneelconqueso at 9:03 PM on November 25, 2007