I am a Pentax K20D owner, and now I'd like to buy my first macro lens.

Candidates I consider are:

50 mm lenses I considered initially:

My questions are/were:

  1. (not important now, as I decided to go for 100 mm) How does Sigma 50 mm compare against Pentax 50 mm?
  2. (answered) What's the difference between 100 mm and 100 mm WR (beyond weather-resistant sealing)? (UPDATE: I also found a comparison)
  3. (answered) Which other lenses should I consider? (UPDATE: thanks for pointing me to other Sigmas and a Tamron)
  4. Is there anything I should be aware of with Tamron 90 mm?

I am going to use it as a secondary lens during my outdoor activities (mountaineering, backpacking), either as complementary to the kit lens or to the midrange fix (I am about to buy the new 35 mm f/2.4 too). So, the weight and durability matter. WR is a big plus for me. But I am not sure about the focal length. On one hand, it is very likely I'll shoot without a tripod sometimes, so a shorter f might be more convenient. On the other hand I lack moderate telephoto (I own an old FF 135 mm manual lens, but as a beginner photographer, I don't have anything in between the kit and that lens yet). Being able to use the same lens as macro and telephoto is an attractive option.

Please share your suggestions.

UPDATE: I decided to get a focal length around ≈ 100 mm, and finally chose Tamron 90 mm F2.8, it is told to be even sharper than Pentax 100 mm WR, is not much heavier, and much cheaper. And after few months of use I am very happy with its ergonimics, build and image quality. It also makes a nice portrait lens for outdoors. It doesn't have a QuickShift focus system, so I have to be careful to always switch the camera in MF mode before rotating the focus ring, and without WR I have to pay more attention under the rain (I just put an umbrella above it, and after the session I let the accidental water drops dry up by leaving the lens in extended state); but 200€ of price difference outweight these inconveniences for me.


3 Answers 3


You should decide on a focal length first. The big difference is the working distance you will get. There are pro's and con's to each.

For small subjects, a small working distance means you can be right up to the subject, making lighting much more difficult. Bugs, for one, are sensitive to sunlight changes (i.e. shadows) and carbon dioxide.

On the other hand, with short working distances, you get to use the left-hand brace technique. This is very useful for composition. You also get to use slower shutter speeds, and if you are using a flash in one hand, you can adjust the lighting more.

The Pentax 50mm is supposed to be one, if not the sharpest of their lenses. However, pretty much all of these macros are ridiculously sharp.

Other options:

  • Sigma 105mm
  • Tamron 90mm
  • Sigma 70mm
  • Sigma 50mm

Some lenses actually adjust their focal length to get 1:1 at close focus, which means you don't get as much working distance as other lenses.

Some say Pentax lenses have better coatings for better color and flare protection. WR is great for outdoors, and only one lens has it. I recommend against the 50mm since there are other great 50's (1.4, 1.2, helios, etc.), and you can use the longer ones for more than just macro.

  • \$\begingroup\$ Thank you very much. I decided to get longer 90 mm or 100 mm. Actually, after reading about Tamron 90 mm now, I think it's my favourite. It is told to be as sharp or even better than Pentax WR, and it is light. I don't think I am paying 200€ more for a 60 g advantage and WR. Also thank you for pointing to left-hand brace technique. I didn't know about it. \$\endgroup\$
    – sastanin
    Commented Oct 26, 2010 at 8:38

Not having used any of these lenses, I can't offer much. I did read up on the two 100mm lenses, though. Outside of the weather sealing on the WR version, the non-WR version has one thing REALLY going for it: the size of the focus ring. Prime lenses don't have any zoom, and the only thing you really do with them is focus. Particularly for macro photography, where getting focus within millimeters (or quite possibly less, if you use extension tubes) is critical, having a nice, wide, rubbery focus ring that is easy to find and grip is a huge bonus.

From what I could tell, the non-WR 100mm macro has a beautiful, big focus ring with a rubbery grip. The newer WR version, while sporting a more durable metal body and metal focus ring, has about 1/3rd of the area dedicated to the focus ring. It may be a personal taste thing, but metal focus rings always feel a bit rough to me, and the smoother metal surface sometimes makes it difficult to get a light grip for fine-tuning your focus. Personal taste aside, the considerably smaller focus ring on the WR version is not really the most ideal feature for a macro lens.

  • \$\begingroup\$ Thank you. This is an important detail. I'll try to evaluate both if they are available at the local shop. \$\endgroup\$
    – sastanin
    Commented Oct 22, 2010 at 12:52

Of the four, I would pick the Pentax-D FA 100 mm F2.8 Macro WR. There are a couple of reasons for this:

  1. 100mm gives you more working distance for macro work and that can be important, especially when dealing with insects. However, it's also useful when doing things like water drop shots, etc.

  2. It's weather sealed. You have a weather sealed body and, with a weather sealed lens, you gain a lot of freedom outdoors that you would necessarily get with any of the other options.

I wouldn't be too worried about being able to shoot the 100mm handheld. Part of it is simply practice, but the 100mm isn't that long a focal length and you're often going to be shooting above the 1/100s or faster shutter speed, so coupled with the shake reduction system, you'll be fine. That's been my experience with the K20 and, as a smoker, I don't have the steadiest hands going! :)

In regards to the other options... Sigma can be a hit or miss choice for lenses, but I think they've gotten much better in recent years and reviews are starting to show that. I have two of their lenses in the K mount, both telephoto (70-300mm macro and 120-400mm) and I've been happy with them. The remaining two are Pentax lenses, both good. One could argue that having the classic 50mm focal length in your arsenal is a good thing, but f/2.8 is slow for a 50mm, so I think you'd be better off with a non-macro with a wider aperture if that was the case.

  • \$\begingroup\$ Thank you, John. Your reasons sound very convincing in favour of 100 mm WR. \$\endgroup\$
    – sastanin
    Commented Oct 22, 2010 at 12:57

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