In this case, however, not more expensive.
Since my travel kit now includes the SMC F 70-210 f4-5.6, rather than the Sigma 70-200 f2.8, I decided on some formal tests to see what I am losing (other than two stops at the long end). The answer was surprising.
Everything shot on a tripod with the *ist D, ISO 200. Imported into Photoshop through Pentax's raw converter. Once in Photoshop the only transformation was Auto Levels.
Firstly, the F 70-210 against itself, 210 mm., f5.6 through 11. To my surprise, f5.6 was sharpest, nudging out f8. F11 looked weakest, although I must say that this was at 1/20 second on the tripod and the day was windy. Anyway, I am now very confident shooting this at 210 mm at f5.6.
Next I tested it against the Sigma. Both at 200 mm. on the tripod. Across the board, the old SMC F has a warmer rendition and better contrast than the Sigma. Now the surprise: At 200 mm. wide open (f5.6), the old Pentax consumer lens was slightly sharper than the Sigma "pro" lens at f5.6. At f8 and 11 the Sigma was sharper, but again the Pentax's rendition was warmer and with better contrast.
Hmmm. Maybe that old SMC F 70-210 will stay in my travel kit after all. Except for the gap between 50 (my FA 50 f1.7) and 70, perhaps I am not so anxious after all to see Pentax bring out a DA 50-200 f4. Maybe I'm also going to reconsider buying any more Sigma lenses.
I don't think that Pentax has subsequently brought out any consumer telezoom that rivals this oldie. What a pity that they didn't just bring out an FA version of it. Of course, what they did do was bring out the power zoom FA 70-200 and the lightweight F/FA 80-200 f4.7-5.6 (which is not bad, but not as good as the old F 70-210). And of course they brought out the 100-300 and 80-320.
How extraordinary that a lens first brought to market in 1987, in Pentax's first generation of autofocus lenses, works so well with my *ist D.
Coming up: Comparison of Sigma's 20 f1.8 to the FA* 24 f2.0 and the DA 16-45 f4.0.
Joe
