The DA is F4, I've since tried this same thing with the Tamron 28-75/2.8 and the Tamron SP 90/2.8 Macro. The 90 gave 100% predictable results, the 28-75 was about 80%. The 50s are what baffle me, I use manual focus lenses on the D all the time. Of course I miss every so often but I've found the Ds viewfinder far better than many manual focus bodies. I went out today and got a couple of 4ft "yardsticks", I'll try again tomorrow and see if I can find a pattern of any sort. The light we had today was such that I could easily see the DOF of the grass in the viewfinder, the results didn't match what I saw at all with the 50s. Focus was always way 'behind' what I thought it would be. Even on a tripod, with VERY careful focusing, the image was a surprise. And yet at a distance of 3ft or so all the lenses gave exactly the result I saw thru the viefinder when I did the ruler shots. In another test I shot a tape measure focusing on 7in with the 50/1.4. I repeated this several times. Here is the result:
http://www.donsauction.com/pdml/7inches.jpg Perfect every time. Yet at 20-30 feet or so the results vary widely. I'm still baffled. Don > -----Original Message----- > From: Mark Cassino [mailto:[EMAIL PROTECTED] > Sent: Saturday, April 16, 2005 8:35 PM > To: [email protected] > Subject: Re: ist-D Focus Woes, More Info. > > > Hi Don - > > I just tried out my FA50 f1.7 and *ist-D, and they worked fine > together - I > ran a series of shots up along a 1 hour lab envelope (a nice > hi-res target > with the grid for reprints on it) and the lens/camera snapped into focus > each shot, differentiating a matter of inches each time. They all looked > sharp in the finder - but that finder is pretty small. > > If the camera focuses correctly with some lenses and not others, > I'd suspect > a problem with the lens. In my experience, the *ist-D autofocus with slow > lenses (like f5.6) is not so good, but it is very good with > faster lenses. > Your experience seems to be different - though, what is the > aperture of the > DA 16-45? Maybe you are just seeing the results of more DOF than > you get at > f 1.7 and f 4 with the FA 1.7 ??? > > - MCC > > > - - - - - - - - - - - - - - - - - - - - > Mark Cassino Photography > Kalamazoo, MI > www.markcassino.com > - - - - - - - - - - - - - - - - - - - - > ----- Original Message ----- > From: "Don Sanderson" <[EMAIL PROTECTED]> > To: "PDML" <[email protected]> > Sent: Saturday, April 16, 2005 4:16 PM > Subject: ist-D Focus Woes, More Info. > > > > I'm not sure if I need a camera repairman or a psychologist > > but here goes. > > I tried A50/1.4, the FA50/1.7 and the DA 16-45 on a > > yardstick from about 3 feet away. > > Manual or autofocus were all spot on in 24 shots. > > > > > > I took the 2 AF lenses outside and took shots of the > > flowers, weeds, leaves etc. I found in the grass. > > The reason I chose these is that the grass shows clearly > > whether focus was right on, long, or short. > > It's a bright but overcast day so light is very even, > > speeds were between 1/125th and 1/500th. > > Shots at maximum aperture, AND the FA50/1.7 at 4.0. > > I kept the intended subject centered in the viewfinder > > to make it obvious what I was aiming at. > > > > Here's the score: > > FA50/1.7 at 1.7, 20 misses out of 24, almost all were > > focused long. (Past the intended point) > > > > FA50/1.7 at 4.0, 14 misses out of 24, again almost all > > were long. > > > > DA16-45/4.0 at 45/4.0, *2* misses out of 24, one was > > long, one was short. > > > > Again, all looked sharp in the viewfinder, if it was an > > obvious 'miss' I let the lens re-focus. > > OK, so the DA is my hero. ;-/ > > Any theories as to the extreme inconsistency in the > > FA50 (And A50) ??????? > > > > And the main question:......................... > > HOW can a viewfinder lie, but only SOMETIMES?? > > > > Don (The Thoroughly Frustrated) > > > > PS: I have straight from the camera samples to prove > > I'm not just on "Happy Weed". ;-) > > > > >
