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Pentax HD PENTAX DA AF 1.4X AW Rear Converter Review

Pentax HD PENTAX DA AF 1.4X AW Rear Converter Review - Gary Wolstenholme reviews the Pentax HD PENTAX DA AF 1.4X AW Rear Converter for Pentax Digital SLRs.

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Category : Convertors and Other Adaptors
Product : Pentax HD PENTAX DA AF 1.4X AW rear converter
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Handling and Features

HD PENTAX DA AF 1.4X AW rear converter
This 1.4x tele-converter fits between a lens and your Pentax camera, increasing the focal length of the lens by 40% and reducing the maximum aperture by one stop. This particular converter sports Pentax's HD lens coatings and is designed to be water and dust resistant, when used with a Pentax lens offering the same levels of sealing. In this review, we'll take a look at how it performs when used with a Pentax 50-135mm f/2.8 lens.

HD PENTAX-DA AF 1.4X AW Rear Converter Handling and Features

Pentax 14x Rear Converter (3)

Weighing only 126 grams, this 1.4x converter is an ideal way of adding extra focal length, without adding much extra weight to carry around. The Build quality of the converter is very good, with tough plastics and metal used in combination for much of the converter's construction.

There are few controls on the converter, with only a release latch for locking the converter to the camera sticking out of the side. A red rubber gasket on the rear of the converter provides a seal against the camera body to help prevent the ingress of dust and moisture. The seal on a water resistant Pentax lens then presses against the flat front of the converter.

The full complement of electronic contacts to support even Pentax's old Power Zoom lenses are supplied, and even the mechanical focus screw is carried through the converter. The lens diaphragm is operated by a lever inside the converter. The converter is easy to fit, and the close focusing distance of the mounted lens remains unaffected, allowing more of the frame to be filled with less of your subject.

When used with the 50-135mm f/2.8 lens, focus speeds seem largely unaffected in good light conditions. As light levels drop, the converter can cause the lens to focus more slowly, or even hunt a little for lock, but only when conditions are pretty murky.

Pentax 14x Rear Converter (1)

HD PENTAX-DA AF 1.4X AW Rear Converter Performance

To test the converter, we checked the sharpness with the 50-135mm lens at either end of the zoom range. Overall, sharpness is reduced compared to using the lens on its own.

As you might expect, there is a slight reduction in the sharpness delivered by the 50-135mm lens, when the 1.4x converter is attached, especially at maximum aperture. Even so, the lens and converter combination is still capable of delivering outstanding sharpness levels when stopped down to f/5.6 and beyond.

MTF@50mm (without converter)

How to read our charts

The blue column represents readings from the centre of the picture frame at the various apertures and the green is from the edges. Averaging them out gives the red weighted column.

The scale on the left side is an indication of actual image resolution. The taller the column, the better the lens performance. Simple.

For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Levels of chromatic aberrations are increased to levels that may be noticeable along high contrast edges. At both ends of the zoom range, fringing exceed one pixel width at maximum aperture, towards the edges of the frame.

CA@50mm (without converter)

How to read our charts

Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.

Apochromatic lenses have special lens elements (aspheric, extra-low dispersion etc) to minimize the problem, hence they usually cost more.

For this review, the lens was tested on a Pentax K-5 IIs using Imatest.

Falloff of illumination towards the corners of the frame is vastly reduced with the converter in place, to the point where illumination is visually uniform across the frame. Without the converter, the corners of the frame are 0.8 stops darker than the image centre at 50mm and at 135mm the corners are 1.2 stops darker.

Distortion is also reduced, with only 0.32% barrel distortion at the wide end of the zoom and 0.8% pincushion distortion present at the telephoto end. Without the converter, Imatest detected 0.7% barrel distortion at 50mm, which is replaced by 1.68% pincushion distortion at 135mm.

With the converter in place, contrast is pretty much the same as without, even when shooting into the light at maximum aperture.

Pentax HD PENTAX DA AF 1.4X AW rear converter Sample Photos

Value For Money

Being priced at around £380, this converter offers a cost-effective way of gaining extra telephoto reach with existing lenses.

Although this may seem like excellent value, compared to forking out for a longer telephoto lens, Kenko produce a Teleplus 1.4x converter, which costs only £109. Although this converter will offer the same gain in telephoto reach, it doesn't offer any protection against dust, or the elements.


  The Pentax-DA AF 1.4X AW Rear Converter is lightweight, compact, weather sealed, and does not compromise on image quality.

HD PENTAX-DA AF 1.4X AW Rear Converter Verdict

In the past, tele-converters gained a reputation for poor image quality, forcing too many compromises from your existing lenses. Pentax has proved with this converter that you need not compromise on image quality with a tele-converter, nor on weather sealing, or handling. This converter will be well worthy of consideration by those who already own compatible lenses.


HD PENTAX-DA AF 1.4X AW Rear Converter Pros

Only a very small reduction in sharpness with converter
Excellent build quality
Reduced falloff and distortion with converter
Weather sealed

HD PENTAX-DA AF 1.4X AW Rear Converter Cons

CA levels are raised by the converter
Less expensive alternatives are available


Pentax HD PENTAX DA AF 1.4X AW rear converter Specifications

Effective Magnification1.4x
Box Contents
Box ContentsNo Data
WeightNo Data
WidthNo Data

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21 Jun 2014 11:04AM
Looks like a great bit of kit. How about a review of the Kenko Teleplus so we can compare?
19 Feb 2015 2:39PM
Hi Gary

New to Pentax.

I have been told that the kenko 1.4 converter does not allow all functions on the camera ie auto focus.

Is this why one costs three times as much

cheers derek
16 Apr 2015 3:15PM
First of all; great and nice review !

Second; you wrote there are "Less expensive alternatives are available" ?
Can you please suggest which one ?

Many thanks in advance !
17 Apr 2015 12:33PM
Recently lashed out for this. Well worth the money and it's now going for less than 300.
I've used it a bit with my Tamron 90mm macro and I can now get frame filling butterflies without having to get too close.

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