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03-06-2009, 05:52 PM   #1
Junior Member

Join Date: Jan 2009
Location: SE Connecticut
Posts: 38
Focus Issues

Camera is *ist DS, purchased new (dealer demo) a month ago, and sent back for service today.
Been using the camera for macro, specifically digitizing old 35mm slides. Setup includes a 105mm Takumar lens, a bellows, a short extension tube (so the bellows clears the flash snoot), and a light box for the slide (strobe & opal glass). Distance from camera to slide is adjusted and fixed to give desired magnification. Focus is accomplished by moving the bellows and lens.
Anyway, focus using viewfinder (diopter adjusted) with lens at f2.8. Stop down to F5.6 or so and expose (Vivitar 283 with 10K resistor). Initial results not really sharp. Added a dial indicator to track lens position, and started bracketing the viewfinder zero position. Found sharpest images with the lens .080" closer to the camera than the 'best' viewfinder position. Tested repeatability of viewfinder 'best' focus - +/- .010" on lens position. Repeated sharpest image test 3 times - consistent at about -.080". Hmmm... What about autofocus??
Mounted the kit lens, set to Av f5.6, and mounted on a tripod about 6 ft from the garage wall. Zoom at 55mm. Taped a resolution chart to the garage, used AF, and made exposure #1. Shifted to MF and moved the lens about 1/8" towards infinity and made exposure #2. Refocused in AF, shifted to MF, moved the lens 1/8" away from infinity and made exposure #3. Results? Exposure #2 is way out. Exposure #3 is far superior to exposure #1.
Conclusion? Camera is FUBAR. If lens mount to view screen is 46mm, then the distance to the CCD is 47mm+. Don't know how the AF works, so can't really comment on what's out of whack there.
Moral? Check your camera. Don't assume that since it's new out of the box, things are in A1 shape. Comments by thread reply or to:


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af, camera, dslr, exposure, focus, garage, infinity, lens, mf, photography, position, viewfinder
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