Pentax-DA 1.4x AW AF Rear Converter

Image Quality

We illustrate the image quality through a number of sample photos. If you're more to test charts, refer the following pages where we compare three converters and also compare center and corner sharpness.

Overall Image Quality and Bokeh

Shooting parameters of our first image:

• smc Pentax-DA* 60-250mm F4 at 200mm (280mm effective with converter)
• HD Pentax-DA 1.4x Rear Converter
• Pentax K-3
• ISO 100, F8 (effective), 1/180 sec, handheld, Shake Reduction enabled
• JPG from camera, unaltered

Click on image to enlarge

Color rendering and resolution leave nothing to be desired. The DA 1.4x Rear Converter paired with the DA* 60-250mm zoom performs excellently. We also must credit the excellent metering and white balance performance of the Pentax K-3 for the overall quality of this image.

Shooting parameters of our next image:

• smc Pentax-DA* 300mm F4
• HD Pentax-DA 1.4x Rear Converter
• Pentax K-5 IIs
• ISO 200, F8 (effective), 1/125 sec, handheld, Shake Reduction enabled
• JPG from camera, unaltered

Click image to enlarge - Link to original image

We see that the result with the converter is excellent, sharp and contrasty. The bokeh takes a bit of a hit becoming a tad more harsh than we'd like in the far distance, whereas the out-of-focus rendering of the passengers in the near distance (the green car) is pleasant.

Shooting parameters of our next image:

• smc Pentax-DA* 300mm F4
• HD Pentax-DA 1.4x Rear Converter
• Pentax K-5 IIs
• ISO 400, F8 (effective), 1/500 sec, handheld, Shake Reduction enabled
• JPG from camera, unaltered

Click image to enlarge - Link to original image

First we notice how compressed the image looks which, of course, is nothing but a consequence of the magnification of the image, here due to the long focal length (420 mm). To be able to achieving this "telephoto effect" without cropping an image could be a valid reason in its own for acquiring a 1.4x rear converter.

Second we notice the very shallow depth of field. We focused on the edge of the engineer's cab and basically got the engine in focus and not much else. This shallow depth of field is often considered a desirable characteristic.

Back to the evaluation of image quality. We find it excellent in the area which is in focus, and the bokeh is very good. We have no hot spots in this image which could have looked harsh as we saw in image 1 above.

Chromatic Aberration

A rear converter amplifies lens flaws and then adds its own. As the above images show, the HD Pentax-DA 1.4x converter produces excellent results in the area of focus, but what about the out of focus areas? We have already seen some harshness to the bokeh and will take a look at the chromatic aberration often present in out of focus areas.

Shooting parameters of our first image:

• smc Pentax-DA* 300mm F4
• HD Pentax-DA 1.4x Rear Converter
• Pentax K-5 IIs
• ISO 200, F6.7 (effective), 1/500 sec, handheld, Shake Reduction enabled
• JPG from camera, unaltered

The scene:

100% crop:

We see the characteristic purple and green false colors where the subject is out of focus, but it is well controlled and not visible unless one pixel peeps. The DA*300 F4 lens as well as the DA 1.4x Rear Converter controls chromatic aberration well and what little is present can be removed in post-processing if desired.

Comparison With and Without Rear Converter

For this test we shot with and without the rear converter on our DA* 60-250mm zoom. We changed the focal length between the shots so that the magnification was the same with and without the converter - or at least as close as we could make it.

Shooting parameters:

• smc Pentax-DA* 60-250mm F4 at approx. 130mm effective
• Without (left) and with (right) HD Pentax-DA 1.4x Rear Converter
• Pentax K-5IIs
• ISO 200, F8 (effective), 1/180s, camera on tripod
• JPG from camera, unaltered, but cropped ("100% crop")

Links to larger "100% crops" of the images: Without converter, with converter.

The image shot without the rear converter is marginally sharper (resolution, contrast) and has a smoother bokeh (as we also saw earlier). But the difference is truly marginal. We consider this converter to be an outstanding performer.

Conclusion on Image Quality

The HD Pentax-DA 1.4x Rear Converter is an outstanding performer. As any rear converter will do, it does reduce image quality compared to not using a converter, but the loss of image quality with this converter is truly marginal and we can unconditionally recommend it for use in connection with top shelf lenses like the DA* telephoto lenses or telephoto zooms for the added convenience that it delivers in the field.