 Jose Gil |
Variable Aperture on Zoom Lens? My 35-140 zoom lens has the lowest/largest aperture at 3.8-5.3 depending on my zoom level. 1) Does ONLY the lowest setting change as I zoom? Or does the aperture f/8 (for example) also change as I zoom in? 2) Is there a way to reliably estimate what the variable aperture is at different points between 35 and 140?
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John A. Lind |
Joey, Only a handful of variable aperture zoom lenses are "constant" aperture when stopped down from wide open. Nearly all of them vary similarly at all f-stop settings. The f-stop markings on them are typically for shortest focal length, although the manual (usually more like a data sheet) for the lens should clarify this. The variable range you gave, f/3.8~5.3 is an entire f-stop. If it's set at f/8 for 35mm focal length, it would be f/11 at 140mm focal length. You have a 4X zoom (35 X 4 = 140). To approximate the effect, you can divide this into thirds and think of it as narrowing the aperture in 1/3-stop increments with where the focal length being used falls withing three ranges: 35-70mm, 70-105mm and 105-140mm. With nearly all films, if you're within 1/3-stop on the exposure, you're OK.
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Jose Gil |
Thanks for the info
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