It seems like a shame that Pentax's 55mm fast prime does not have full-frame coverage, but given that there is currently no full-frame Pentax body (other than older film cameras) this may not be such an important gripe. In isolation this would be a good lens once it has been stopped-down slightly, but amid a field of fast primes its slight weaknesses limit its overall score.
Sample images


Score
Score in detail
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Design 100
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Image Quality 90
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Performance 85
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Value 90
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Features 90