Primes vs. Zooms---Stop loss??

Discussion in 'Lens Lust' started by ERAUGrad04, Sep 16, 2008.

  1. ERAUGrad04

    ERAUGrad04

    271
    Jan 15, 2008
    IL
    I was shooting this past weekend with my portable studio and shot about 75 shots with my 50mm 1.4 AF-D lens. The camera was is Manual Mode and set to 1/200 sec, f/4 and the commander was set to fire CH-A at 1/8 power(SB-800) and CH-B at 1/16 power(SB-600). The exposure was perfect with the 50mm 1.4 lens. I changed lenses to my 17-55 2.8 lens and retained all original settings. The images with the 17-55 were at least 2/3's of a stop underexposed. After bumping up the strobes to 1/4 & 1/8 respectivly, the exposure was back on track.

    Is this common with primes and zooms? I have heard that with less elements in prime lenses, they are actually faster at the same aperture of a similar zoom. True of false?

    Thanks for the input!
    Morgan
     
  2. Nikkor AIS

    Nikkor AIS

    Jun 5, 2008
    Alberta
    There is a term called T-stop which is the actual light transmition to the film/sensor. I dont think F/stops are always right on the money where as T-stops are..Iv wondered about if all F 2.8s are really 2.8 my self with my classic Nikkor 80-200 ED AIS having a 86 mm front filter:eek:, and the AF versions only having a 82mm. The other thing I noticed is that at minimum focus ranges(non IF) and using tubes you lose light.

    Gregory