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Pentax 100mm f/2.8 WR
© KenRockwell.com. All rights reserved.

Intro   Specs   Performance   Recommendations

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Pentax 100mm f/2.8 D FA WR

SMC Pentax 100mm f/2.8 D FA WR (35mm and APC-S coverage, 49mm filters, 11.865 oz./336.3g, 1:1 macro, 1'/0.3m close focus, about $550). enlarge. I got mine at B&H; I'd also get it at Adorama or at Amazon.

This ad-free website's biggest source of support is when you use those or any of these links to approved sources when you get anything, regardless of the country in which you live. Pentax does not seal its boxes, so never buy at retail or any other source not on my personally approved list since you'll have no way of knowing if you're missing accessories, getting a defective, dropped, damaged, returned, store demo or used lens. My approved sources ship from remote automated warehouses where no salespeople or lookie-loos can ever get their greasy fingers on your new lens before you do. Buy only from the approved sources I use myself for the best prices, service, return policies and selection. Thanks for helping me help you! Ken.


July 2015   Pentax reviews   all reviews

How to Shoot Macro

Best Macro Lenses


Introduction       top

Intro   Specs   Performance   Recommendations

Adorama pays top dollar for your used gear.

B&H Photo - Video - Pro Audio

This SMC Pentax 100mm f/2.8 D FA WR is the world's smallest and lightest 100mm macro lens, and it also has superb optics as we expect in any 100mm macro lens.

It makes a great general-purpose telephoto and can focus close enough to fill the frame with something smaller than a postage stamp.

You may grab the ring at any time for instant manual-focus override. Pentax calls this "Quick Shift."


Formats & Compatibility

This 100/2.8 D FA WR lens is optimized for full-frame, and of course works great on all Pentax digital SLRs.

It mounts, meters, manually focuses and shoots on Pentax's classic 35mm cameras, but since it has no aperture ring, it always meters and shoots at f/22 on my K1000. Viewing and focussing is wide open, but you have to imagine that it's always set to f/22.


Specifications        top

Intro   Specs   Performance   Recommendations



Pentax calls this the SMC PENTAX 100mm f/2.8 D FA WR.

SMC means Super Multi Coating; all Pentax lenses have been SMC since the 1970s.

D means it works on Pentax digital cameras.

FA means it covers full frame.

WR means weather resistant.


Optics       top

9 elements in 8 groups.

The rear groups are fixed, while the front section extends to focus more closely.

Multicoated, branded as both "Super Multi Coating" (SMC).


Diaphragm       top

Pentax 100mm f/2.8 D FA WR

Pentax EF 100mm f/2.8 D FA WR at f/22.

8 rounded blades.

Stops down to f/32.

There is no mechanical or electronic meter compensation as focussed more closely; the effective aperture becomes much smaller as focussed more closely.


Focal Length        top


On Pentax digital cameras it will see angles-of-view similar to what a 150mm lens would see on a 35mm camera.


Angle of View

16º diagonal on Pentax digital.

24.5º diagonal full-frame.


Close Focus       top

1 foot (0.3m) from the image plane.


Maximum Reproduction Ratio        top

1:1 (1.0x) at close-focus distance.


Hard Infinity Focus Stop?        top


You have to let the AF system focus for you at infinity.


Focus Scale       top



Depth-of-Field Scale       top



Infra-Red Focus Index       top



Filter Thread       top




Hood       top

Pentax 100mm f/2.8 D FA WR

Pentax 100mm f/2.8 D FA WR with hood at 1:1.

The plastic bayonet hood is included.

The lens extends at 1:1, so that the hood doesn't do much. This is good, because otherwise the hood would block the light on your subject.


Caps       top

Pentax 100mm f/2.8 D FA WR

Pentax 100mm f/2.8 D FA WR with caps and reversed hood.

Nice 49mm front cap.

Cheap push-on rear cap, not the usual Pentax bayonet rear cap.


Case      top

Pentax S80-120 case

S80-120 case, Pentax 100mm f/2.8 D FA WR.

The case is a padded nylon pouch, which is perfect for throwing in a backpack, trunk or glovebox.


Size       top

Pentax specifies 2.5" (63.5mm) diameter by 3.2" (81.3mm) long.


Weight       top

11.865 oz. (336.3 g) actual measured weight.

Pentax specifies 12 oz. (340 g).


Included       top



Plastic hood.




Pentax Model Number       top



Price, USA        top

2015 July: $550.

Pentax 100mm f/2.8 D FA WR

Box, Pentax 100mm f/2.8 D FA WR.


Performance         top

Intro   Specs   Performance   Recommendations

Overall    Autofocus    Bokeh   Breathing

Distortion   Ergonomics   Falloff   Filters

Lateral Color Fringes   Macro   Mechanics

Sharpness      Spherochromatism


Overall     performance      top

Pentax 100mm f/2.8 D FA WR

SMC Pentax 100mm f/2.8 D FA WR. enlarge.

The Pentax 100mm f/2.8 D FA WR is sharp, small, inexpensive, handles very well and is reasonably well made.


Autofocus     performance      top

Autofocus is via 1980s technology: a motor in the body connected via a screw coupling.


AF Speed

AF is pretty fast as mechanically-autofocussed 100mm lenses go. It may be noisier than Canon and Nikon's electronic-autofocussing lenses, but at least it's about as fast.


Auto/Manual Switching

Just grab the ring at any time the camera isn't trying to autofocus.

The ring turns during autofocus; keep your fingers away until it stops.


Manual Focus

Manual focus is easy; just turn the ring.


Bokeh     performance      top

Bokeh, the quality of out-of-focus areas as opposed to the degree of defocus, is good and neutral.

Pentax 100mm f/2.8 D FA WR Bokeh

Pentax 100/2.8 D FA WR shot on Pentax K3 II at f/2.8. Camera-original © JPG file.


Focus Breathing     performance      top

Focus breathing (the image changing size as focused) is mostly of interest to cinematographers who don't want the image changing size ("breathing") as the lens is focused among different subjects.

The image from the Pentax 100mm f/2.8 D FA WR gets larger as focused more closely.


Distortion     performance      top

The Pentax 100mm f/2.8 D FA WR has no visible or measurable distortion, even uncorrected.

This is superb, and as we expect for a macro lens.

on digital
100' (30m)
30' (10m)
10' (3m)
3' (1m)

© 2015 KenRockwell.com. All rights reserved.


Ergonomics     performance      top

Pentax 100mm f/2.8 D FA WR

Pentax EF 100mm f/2.8 D FA WR at 1:1.

This little lens handles great, except for the focus ring turning by itself during autofocus. As soon as autofocus stops, you can grab the ring for instant manual focus.

There's no outside mounting index dot; you have to squint and look for the red dot hidden on the mount. It's obvious here in this close-up and well-lit studio shot, but usually invisible in the field.



Falloff     performance      top

There's no visible falloff, even at f/2.8, on APS-C digital. This is excellent.


Filters, Use with     performance      top

The plastic 49mm filter threads are big enough that quite a few stacked filters won't cause any vignetting on full-frame or digital.

There is no need for expensive "thin" filters.


Lateral Color Fringes     performance      top

There are no visible lateral color fringes at 24MP, but there is some minor purple fringing visible on Pentax K3 II.

This is excellent performance, as expected for a macro lens.

It does have spherochromatism, which is a different aberration.


Macro     performance      top

It gets to life-size at the sensor.

Since an APS-C sensor is 16 x 24mm, your close-ups can fill the screen with something as small as 16 x 24mm or 0.6 x 0.9:"

Pentax 100mm f/2.8 D FA WR Macro performance

Rolex Submariner at close-focus distance shot on Pentax K3 II at f/22.

Of course it's super-sharp. Sharpness in macro shots depends much more on your technique than the lens.


Mechanics     performance      top

Pentax 100mm f/2.8 D FA WR

Pentax EF 100mm f/2.8 D FA WR. bigger.

The Pentax 100mm f/2.8 IS is reasonably well made with metal on the outside with engraved markings, and a plastic front barrel and filter thread.


Filter Threads



Front barrel



Hood mount




Engraved into the focus ring.


Focus Ring

Anodized aluminum.


Focus Scale

Engraved into anodized aluminum.






I see what looks like mostly metal.


Moisture seal at mount







Mostly engraved and filled with paint.


Serial Number

Engraved into focus ring and filled with white paint.


Date Code

None found.


Noises When Shaken

Mild clunking.


Made in



Sharpness     performance      top

Image sharpness depends more on you than your lens, and lens sharpness doesn't mean much to good photographers. It's the least skilled hobbyists who waste the most time blaming fuzzy pictures on their lenses, while real shooters know that few photos ever use all the sharpness of which their lenses are capable due to subject motion and the fact that real subjects are rarely perfectly flat.

The Pentax 100 D FA WR is super-sharp at every aperture, as most macro lenses have been for many decades.

It's sharp way past the corners on digital because this is a full-frame lens.

Of course all lenses get much softer at f/22 and f/32 due to diffraction, and usually f/22 to f/32 is where we shoot them for serious macro shots of 3D objects just to get any depth-of-field! That's why for real macro shots, lens quality doesn't matter much.


Spherochromatism     performance      top

Spherochromatism, misnamed "color bokeh" by laymen, is when out-of-focus highlights take on color fringes at full aperture.

Spherochromatism is a completely different aberration from lateral color fringes.

I see moderate spherochromatism; background highlights will have slight green fringes and foreground highlights will have magenta fringes. If anything it helps bokeh for outdoor portraits, but you will see it if you're shooting at larger apertures.


Recommendations         top

Intro   Specs   Performance   Recommendations

This is a great little lens for any Pentax. It's small, sharp, fast, light and tough.

It offers essentially perfect optical performance and is the world's smallest and lightest 100mm macro lens.

If you find my work here helpful, my biggest source of support for this free website is if you get yours at B&H, at Adorama or at Amazon. When you use those or any of these links to approved sources when you get anything, regardless of the country in which you live, it helps me keep adding to this free website — but I receive nothing for these efforts if you take the chance of buying elsewhere. Unlike a bottle of milk or a CD, DVD or Blu-Ray disc, Pentax doesn't seal its boxes so you have no idea if you're actually getting a used product if you risk buying at retail. Never buy at retail.


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Mr. & Mrs. Ken Rockwell, Ryan and Katie.


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06 July 2015