[X-posted as a review here: ] Pentax Forum - Camera & Photography Community - PentaxForums.com
There is an ongoing discussion about the pedigrees of the Pentax FA 28-105/4-5.6 IF and the Tamron AF 28-105/4-5.6 IF (179D). I finally had the opportunity to compare the two side-by-side.
Short story: exact same optics and body design with differences in zoom grip pattern, style of lettering and, apparently, some difference in coatings. Subjective results are nearly identical. -- well within my tolerance for lens-to-lens variation.
Focusing: This Tamron had a very slight tendency to front focus in all situations compared to the Pentax. Range and feel of the focusing mechanism and AF speed are identical.
Rendering: The Pentax seemed to consistently expose about a 1/3 stop lighter with slightly more saturated colors with EXIF data recording identical numbers. The Tamron was slightly cooler. The Tamron was prone to slight purple fringing but not as prominent as the typical 70-300 zoom lens. Any differences were easily reconciled in PP.
IMO, any differences in the rendering of the two lenses may very well be attributed to the presumed use of SMC or BBAR coating. Surface reflections off the objective lenses do have different characteristics. The histograms may also reflect the coating differences. I could observe no difference in flare sensitivity but the light available wasn't conducive to flare.
Cosmetics: The Pentax looks somewhat more refined and its lettering is easier to read. It can also be found in the silver finish if desired and looks equally attractive on the black bodies. Build quality is essentially identical and common to the better poly-carbonate materials of the era.
Category: In terms of general satisfaction, both lenses fall between the DA 18-55's and the DA 16-45. Used with the same care as the kit lenses, they produce similar quality images. Paired as the long-normal choice of FL with the DA 16-45, either lens would produce comparable results for light-weight, outdoor trail use. They work acceptably well with the Tamron Pz-AF 1.4X TC for occasional shots into the 150mm range but the DA 50-200 or one of the economy 70-300 zooms would better serve the long shots with similar IQ.
I'd value either lens at about the same used price as the DA 18-55 AL ll. Perhaps a bit more for the silver FA.
H2
On K200 & K100 bodies with DA 18-55
-
Tamron on the left