Review: Pentax 28-105mm f3.5-5.6 ED DC WR (Pentax K Mount)

If you were to choose one walkabout zoom lens for the Pentax K-1, it would most likely need to be the Pentax 28-105mm f3.5-5.6 ED DC WR. This lens has a very versatile zoom range and despite its variable aperture, is still highly capable of doing quite a bit for any photographer who holds it in their hands. Designed as a general use lens for many photographers, this lens can prove great in the hands of portrait photographers, landscape photographers, and so many more that choose to buy into Pentax’s full frame camera system. Then combine the fact that you’ve got weather sealing designed into the lens, plus the great sensor at the heart of the Pentax K-1, and this lens could be the only single zoom lens you’ll need if you’re the type to stick to all prime lenses.

Pros and Cons

Pros

  • Weather sealing
  • Smallish size
  • Really good image quality for what’s essentially a glorified kit lens in many aspects
  • Pentax’s rubber grips around the lenses are spectacular.
  • Incredibly affordable!

Cons

  • For some photographers, a variable aperture may not be so appealing.

Gear Used

We tested the Pentax 28-105mm f3.5-5.6 lens with the Pentax K-1 DSLR.

Tech Specs

Specs taken from the Pentax press release page

Focal Length 28-105mm
Equivalent to 43-161mm in 35mm format
(when attached to PENTAX APS-C size DSLR cameras)
Maximum Aperture F3.5-5.6
Minimum Aperture F22-38
Lens Construction 15 elements in 11 groups
Angle of View (Diagonal) 75-23.5°(when attached to PENTAX 35mm full-frame SLR cameras)
53-15.5°(when attached to PENTAX APS-C size DSLR cameras)
Mount KAF3
Minimum Focusing Distance 0.5m (1.64 ft.)
Maximum Magnification 0.22x
Filter Diameter 62mm
Diaphragm Control Fully automatic
Number of Diaphragm Blades 9
Rounded diaphragm (28mm: F3.5-6.3 105mm: F5.6-10)
Lens Hood PH-RBC62 (included)
Lens Cap O-LC62 (included)
Lens Case S80-120 (optional)
Maximum Diameter x Length approx. 73.0mm x 86.5mm (approx. 2.9in. x 3.4in.)
Weight approx. 440g / with hood approx. 463g
(approx. 15.5oz./ with hood approx. 16.3oz.)

Ergonomics

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-4-of-9iso-4001-125-sec-at-f-2-0

When you look at a lens like the Pentax 28-105mm f3.5-5.6, you see something that inherently seems like it was designed to be a kit lens. But when you look at it closer and think about it in terms of its ergonomics, it’s not the typical kit lens.

To start, it’s weather sealed–then consider the fact that most of the body is dominated by that big giant zoom ring. Like some of Pentax’s other lenses, this rubber ring is textured and grippy. It’s awesome and feels wonderful in the hands.

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-5-of-9iso-4001-125-sec-at-f-2-0

When zoomed all the way in, it almost doubles in size. But for the most part, the lens is still very compact overall. In fact, it feels like it was designed for a smaller camera.

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-3-of-9iso-4001-125-sec-at-f-2-0

The front of the lens is pretty straightforward. You’ve got the filter ring, and no markings at all. Why? I’m not sure honestly. It’s just how they designed the lens.

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-7-of-9iso-4001-125-sec-at-f-2-0

Turn to the side of the lens and you’ll see that there are no controls on it. Why? Part of this has to do with the fact that the Pentax lenses are controlled partially by the body. Want to switch from autofocus to manual? Use the switch on the camera body!

Build Quality

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-6-of-9iso-4001-125-sec-at-f-2-0

During our test period, we took the lens and the Pentax K-1 out into the rain. Obviously, it’s weather sealed and it stood up to the elements with no issues. See that red ring towards the back of the lens? That’s a rubber ring designed to sit flush against the camera and keep dust and moisture out.

This means that most photographers using the lens shouldn’t have an issue taking it out into the elements.

Ease of Use

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-8-of-9iso-4001-125-sec-at-f-2-0

Because of the variable aperture, most people using this lens may opt for auto ISO settings. Otherwise, you can also just stop down to f5.6 and keep the entire focal length range at f5.6 throughout the zooming. The lens is mostly defined by that giant rubber, textured zoom ring. For that reason, you’ll enjoy even just gripping onto the lens because of how good it feels in the hand.

Otherwise, it’s just like any autofocus lens out there: slap it onto a camera, point, shoot, and have fun!

Autofocus

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-9-of-9iso-4001-80-sec-at-f-2-0

In our tests, we found the 28-105mm f3.5-5.6 to never really slow down when it came to autofocus performance. When attached to the K-1, it isn’t as speedy as the company’s 15-30mm f2.8 lens, but is also isn’t a slouch per se. On the wider end, it’s obviously faster to focus due to the laws of physics. In lower light situations, just be sure to place the focusing point on the camera over a contrasty area to get the most of what this lens is capable of doing.

Image Quality

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-1-of-26iso-1001-80-sec-at-f-5-6

This is a variable aperture general zoom lens for a full frame camera. Of course, you have to expect it to have some flaws, right? In all honestly, it’s really not too shabby when it comes to the image quality. Can it replace the beautiful sharpness and bokeh of some prime lenses? Oh heck no! What about the constant zoom lenses? Nope, not even close. But this lens is meant to be a jack of all trades–in many ways though, it surely is a master of none.

Bokeh

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-17-of-26iso-1001-80-sec-at-f-5-6

From the wider end, you shouldn’t really expect to see any bokeh. But as you go to the longer end of this zoom lens, you’ll surely spot it! It’s overall pretty nice, and the general user I’m sure will be pleased.

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-20-of-26iso-2001-80-sec-at-f-4-5

For fairly right portraits, it’s also pretty nice. But again, there are better options out there. Using an 85mm f1.8 lens or something equivalent can obviously do a better job if you’re looking mostly at using prime lenses.

Color Rendition

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-22-of-26iso-2001-30-sec-at-f-3-5

Perhaps the strongest point of this lens is the color rendition. Overall, it’s pretty decent. But again, there are better options out there. I’ve used some beautiful Pentax primes in the past that I’ve enjoyed much more for their color.

Chromatic Aberration

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-10-of-26iso-1001-160-sec-at-f-5-0

For the most part, this lens doesn’t have a lot of noticeable chromatic aberration when you look at the whole image–which is what most folks will look at. You’ll see it in the corners, but even so it still isn’t image breaking at all.

Sharpness

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-26-of-26iso-2001-60-sec-at-f-5-6

The lens exhibits a nice sharpness overall. In the hands of a skilled studio photographer and when used with the Pentax K-1, this lens can create images that absolutely sing with beautiful sharpness.

Extra Image Samples

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-25-of-26iso-2001-200-sec-at-f-5-6

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-24-of-26iso-2001-200-sec-at-f-11

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-23-of-26iso-2001-100-sec-at-f-4-5

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-21-of-26iso-2001-250-sec-at-f-7-1

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-19-of-26iso-2001-60-sec-at-f-3-5

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-18-of-26iso-2001-100-sec-at-f-5-6

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-16-of-26iso-1001-250-sec-at-f-7-1

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-15-of-26iso-1001-200-sec-at-f-6-3

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-14-of-26iso-1001-200-sec-at-f-3-5

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-13-of-26iso-1001-200-sec-at-f-8-0

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-12-of-26iso-1001-200-sec-at-f-8-0

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-11-of-26iso-1001-40-sec-at-f-5-6

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-9-of-26iso-1001-160-sec-at-f-5-0

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-8-of-26iso-1001-100-sec-at-f-5-0

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-7-of-26iso-1001-100-sec-at-f-5-0

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-6-of-26iso-1001-50-sec-at-f-6-3

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-5-of-26iso-1001-50-sec-at-f-4-5

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-3-of-26iso-1001-400-sec-at-f-5-6

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-2-of-26iso-1001-100-sec-at-f-5-6

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-sample-images-4-of-26iso-1001-50-sec-at-f-3-5

Conclusions

Likes

  • Weather sealing
  • Pretty good image quality
  • Compact size
  • Rubber ring
  • Affordable

Dislikes

  • Jack of all trades, but master of none

Do I like the Pentax 28-105mm f3.5-5.6? Yes. It’s a pretty great lens. But I absolutely must say that a lot of what this lens can do can be replaced by a few good prime lenses. I’m biased towards prime lenses, as are most of the Phoblographer’s readers. But this one isn’t too bad overall.

four-star-Phoblographer-Star-rating

The Pentax 28-105mm f3.5-5.6 ED DC WR lens receives four out of five stars. Want one? They’re pretty affordable on Amazon.

Recommended Cameras

chris-gampat-the-phoblographer-pentax-28-105mm-f3-5-5-6-review-product-images-1-of-9iso-4001-30-sec-at-f-2-0

Let’s be honest here: the Pentax K-1 is the only camera you’ll want to use this with.