As we do a lot of small item photography at PhotoArk, a macro lens is a fundamental requirement for our business. Not that we do not have one already - two exist in our collection; an Olympus Digital Zuiko 50mm f2 and the Olympus Zuiko 80mm f4. Given that Ethan now uses a K-5 it made sense to get a dedicated macro lens for the Pentax system.
We have a preference for long macro lenses as they allow good working distances and double up as very useful short telephoto’s – ideal for portraiture. It did not take long to nominate the 100mm f2.8 over others in Pentax’s line-up as this fitted the bill perfectly.
This lens is very well made and most of the external finish is metal which, in comparison to most of today’s polycarbonate and rubber offerings, is a breath of fresh air. It gives it a little bit more weight which makes it feel substantial without being cumbersome. Externally, a distance scale is present which is actually part of a rotating focus ring. Care is needed as to where fingers are placed when the lens is focussing as it is easy to put them on this, preventing or slowing the focus mechanism – not good for the longevity of the internal motor. Switching to manual focus gets around the problem, and something we prefer to do when fine focussing. Letter and numerical values are engraved into the barrel, not printed.
This is not an optic that uses ultrasonic motors and as such, therefore is quite noisy when gaining focus. However, it is not as noisy as the Digital Zuiko 50mm f2 macro lens. Nor does it cycle through the entire focus range as often when the subject is missed (like the Zuiko does). Focussing is fast and very accurate both at close distances and infinity. Also similar to the Zuiko (and other macro lenses of this nature) the barrel racks out a long way when focussing closely.
The front element is deeply recessed – deep enough to act as a moderate hood in most cases, although a separate one is included in the box. Pentax seem to have made a real effort keeping the dimensions to a minimum (something we like) and this is borne out by the small 49mm filter size. The rear of the lens exhibits a striking red environmental seal located around the outer edge of the lens mount (not visible when mounted on the camera) which prevents dust and moisture getting onto the rear element and camera internals.
Image Quality is excellent throughout the range and it really shines when used as intended – for macro shots. Tiny details are resolved beautifully with a three dimensional quality , wonderful colour palette and smooth bokeh, the latter probably influenced by its 8 bladed circular diaphragm. It can be used confidently at f2.8 although a small amount of chromatic aberration is present in high contrast areas at this aperture. This is gone when stopped down to f5.6 and is the setting where the lens turns in its best performance (along with f8). Designed to perform at its best when focussing closely, other aberrations such as pincushion distortion are non-existent. The exception to this is diffraction, which affects many lenses when closed down toward their tiniest aperture, in the case of this 100mm optic, f32.
As intimated earlier, this 100mm makes an excellent 153mm telephoto lens when mounted on an APS-C type body such as the K-5. This results in a superb portrait lens, particularly head and shoulder style shots, although it may be considered a little too long by some users for this purpose. As I am a great fan of the 135mm focal length, it ticks the right box for me. Other subjects such as candid and tight landscape subjects also fall easily into the lenses remit. And this is what I like about telephoto macros – their versatility to perform well in many aspects of photography makes them a real winner.
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