Use a digital camera as a lightmeter for a film camera?

Started Nov 21, 2012 | Discussions thread
Jack Hogan Veteran Member • Posts: 6,160
Re: Use a digital camera as a lightmeter for a film camera?

Donald B wrote:

Its always bugged me as my cheap sigma 18 200 is brighter than my more expencive 24 60 2.8 lens ? also a while ago i was shooting with a mate he was using a d300 nikon with a 70 200 2.8 and my tamy 70 300 was brighter through the view finder ? go figure.

Doing some more digging I came across this quote which looks like it should be at the top of the list above:

  1. "F-stops are purely geometrical, the ratio of aperture to focal length, regardless of actual light transmitted. Since all lenses absorb some portion of the light passing through them (particularly zoom lenses containing many elements), f-numbers do not accurately correlate with light transmitted. F-numbers corrected to measure light transmission rather than aperture ratio, called T-stops (for Transmission-stops), are sometimes used instead of f-stops for determining exposure.[6] A real lens set to a particular T-stop will, by definition, transmit the same amount of light as an ideal lens with 100% transmission at the corresponding f-stop."

Of course. All relative formulas in the literature assume a 'thin'lens, which means that ye olde Sunny 16 rule is as accurate as umpiring in the Italian soccer A league

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