Testing the HD Pentax-DA 1.4x Teleconverter with the D FA 150-450mm on Full Frame

Conclusion

On paper, a 150-450mm lens and a 1.4x teleconverter might appear like a match made in heaven. And to some extent, it is.

Vignetting tests show that, sadly, the pair cannot reliably be used in full frame mode, as this yields completely black corners. It is possible to force the camera to shoot in full frame mode and then crop manually. This will deliver a slightly wider frame than letting the camera control the crop mode, in which case it will default to APS-C.

The all-important sharpness test shows excellent results. Using the teleconverter yields images equal to or better than using the lens alone and up-sampling. This means that the teleconverter is able to pull additional detail from the lens (incidentally, it also shows that the 150-450mm can out-resolve the K-1's sensor).

The teleconverter has no negative impact on chromatic aberrations and purple fringing, preserving the lens' superb output. Things are worse for flare and ghosting, where results are perfectly usable but below what we have come to expect from Pentax.

Using the lens and teleconverter is easy. The small size of the teleconverter makes it unobtrusive and handling is comparable to that of the lens alone. Being weather resistant, it matches the camera and lens in this regard. 

The Bottom Line

Using the HD Pentax-DA 1.4x AW AF with the HD D FA 150-450mm yields an impressive effective maximum focal length. Optical performance remains comparable to that of the lens alone. The pair cannot be used in full frame mode but, apart from that, there is nothing to stop users from pairing the two.

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