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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12789
Loc: Cumberland, R I , USA42N71.4W
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Re: Vixen Foresta 7x50 porro
05/20/08 06:23 AM
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Checked field sharpness. Aprox measures - 60 arcsec seen out to 75% of field, about 120 arcsec total aberration at 100%. About equal with the Oberwerk Mariner. Better than all the other 7x50s except for the Prostar (which is on the order of 4x-5x better).
At 70% out about half to 2/3rds of aberration is curvature. At 100% about half to 40% is curvature. At edge seems like mostly astigmatism, but compared to all others is well controlled. Overall, I'd say field sharpness rates very well.
Checked resolution. Normal resolution = 11.5 arcseconds line pairs. that's 80 arcseconds apparent res. Excellent, equal with the few better results obtained, puts it into the top ten. Equalled the Prostar. the WO7x50 exceeded that resolution. Boosted 6x resolution also very good, 4.8 arcsec, in the top 12 best.
Rechecked light beam transfer. Very well balanced, no tilt. However, shows the least area of 100% full beam of all 7x50s tested. Out of 15 different 8x40/42s and 7x50s, 10 show a wider area of the objective lens that projects a full 100% beam into the exit pupil. The Fujinon BFL 8x42 shows a full 100% of a 5° beam transfered into the exit pupil from every position anywhere with the center 50% diameter of the objective lens. The Prostar shows the full beam from the center 30% of diameter. The average of all binoculars is 20%. Half of all the roofs show 0% to 10%. The Foresta shows only 5%.
Almost fast focus from 30m to 100m, with 75° of focus dial turn. Very slow focus from 30m to 4m, almost 1 complete dial turn.
edz
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