Pentax-D FA 100mm F2.8 Macro WR

Construction and Handling

Welcome to the guided tour of the D FA 100mm macro WR! On this tour we will look at the lens from every angle, up close, so you can know beforehand what to expect if you decide to add this lens to your bag. If you prefer to preserve some of the mystery, skip to the next section!

Front Element

The front element is a large piece of glass by all accounts, but a smaller one than what could be expected for such a focal length and aperture. It is free of any markings and lettering, leaving all the room for the glass.

The lens takes 49mm filters, like many other Pentax lenses (including all the Limited primes). This is a welcome change from previous versions of this lens from the film era, which used the more expensive 58mm. The front element is covered with the SP (Super Protect) coating, which in our experience does an excellent job to protect the glass and repel grease and other contaminants. The cap is the regular Pentax pinch type.

The front element is significantly recessed inside the lens tube, by almost 2 cm.

Lens body and External Focus

The lens body is all metal, with a smooth, minimalist, almost retro style. The inner barrel extends by a fair amount when focusing at close distances, which is common for macro lenses. The thick focus ring (2 cm) rotates when focusing. The focus throw is very long, at 270°. A significant part of this, around 200°, is devoted to the macro range (with magnification greater than 1:3). This allows very fine tuning of the focus point. The pivotal point is for a focus distance of about 50cm. Smaller magnifications, up to infinity, take up the remaining 70°.

The focus ring's operation is silky smooth and extremely well damped. It compares favorably with purely manual lenses (like the K and M lines) and trumps most of the current AF lenses. It is also better than what was found on the FA 50mm and FA 100mm macro, both of which needed focus clamps to obtain a smooth movement. The ring comes to hard stops at both ends. It has no focus limiter, which can be annoying in some situations, especially when doing macro work with AF. Quick-shift can be used as a viable, if imperfect solution by letting you manually focus the lens from one extreme to the other while retaining AF capabilities.

The name of the lens is engraved on a plate near the base.

A ring near the front element also bears the name of the lens, along with the filter thread size and the serial number.

The lens shaft shows two ribbed rings. The first, near the base, helps to mount the lens on a camera. The second is the focus ring. Similar to Limited lenses (and old M models), a cutout from the body shows a distance scale as well as enlargement values. The lettering is engraved and painted white, with a blue touch for values in feet. The main body displays depth of field ranges for two apertures. These markings are mostly cosmetic, however.

Surprisingly absent is the green ring that is present on every DA lens (HD coatings did not yet exist in 2009). The only touches of color are the blue "WR" letters on the plate and near the front element. This design approach has not been repeated so far with any other Pentax lens, although the lettering type is akin to the one used on HD Limited lenses and the texture of the ribs resembles what is found on many recent WR lenses (see the comparison with other lenses, below). The general look is reminiscent of K, M and A lenses.

The sides are devoid of any markings. The back of the lens shows the CE certification and country of assembly at the bottom, but nothing else.

The design is extremely elegant, even more so in person than in pictures. It's made at least as well as any DA Limited.

Aperture

The lens offers no aperture ring, which might disappoint users of older film cameras, bellows or macro tubes. The lens features 8 blades, rounded to deliver a more pleasing bokeh.

Lens Mount and Weather Sealing

The lens mount is all metal and shows the red o-ring which attaches to a WR body to prevent water ingress.

The lens is screw-drive, and lacks the contacts for silent SDM or DC autofocus.

The following image illustrates the seals that Pentax included in the lens to ensure protection against the elements.

Lens Hood

The lens is provided with a cylindrical lens hood which, at 6 cm in length, covers most of the lens' length when reversed (up to the first ridge, starting from the bottom). In a rare omission for Pentax, the hood does not offer the removable window to allow easy access to polarizers. This is in part because the hood attaches to the outer barrel and does not move with the inner barrel when the latter extends. This means that the hood serves little purpose when shooting macro images at close distances. The hood is textured, on the inside, to minimize reflections.

Because of its size and positioning, we feel that the hood is the weakest element of this lens' design. Luckily, some savvy Pentax users have discovered that, with an APS-C sensor, the cumbersome hood can be replaced with a more compact solution.

By using a step-down ring from 49mm to 28mm, it is possible to block stray light just as well, essentially creating a compact hood which maintains its usefulness even when the inner barrel is extended. Coupled with the recessed front element, it ensures performances similar to the dedicated hood, while creating no vignetting.

A simple 28mm snap-on cap completes the setup and makes it permanent. When retracted, the barrel is not much thicker with the step ring than without it. It has the added advantage of further protecting the front element and almost looks as if it's part of the lens itself.

This solution, similar to the hoods of lenses such as the DA 21mm Limited and DA 40 mm Limited, will not be applicable if the lens is used with a full frame camera. 

Attached to Pentax Cameras

The images below show how the lens looks when mounted on a K-3 and K-50.

Comparison with Other Lenses

Here is the 100mm macro WR compared to the DA 18-55mm WR and DA 18-135mm WR, with and without hoods.

Verdict

There is very little to complain about regarding the D FA 100mm macro WR. It is a beautifully crafted lens, and many people feel that it deserves the "Limited" tag. The care taken for its design and assembly is obvious and welcome. The sleek finish of the barrel is very resistant to scratches. We appreciate the minimalist aesthetics, textured focus ring and engraved focus distance scale. It is reminiscent of the best lenses of the manual era.

Pentax decided to remove the focus limiter and clamp found on earlier models. This is possibly due to weather resistance requirements, but more likely to preserve the looks and keep the cost down. Quick-shift works well to replace the limiter, in most (but not all) cases. The clamp is not needed, thanks to the fantastic feel of the focus ring.

The one thing we dislike is the hood, which is large and cumbersome. When reversed, it covers most of the lens and hinders its manipulation. For this reason, when using an APS-C camera, the simple and inexpensive solution of using a step-down ring is probably the best workaround.