shutter speeds and apertures on EOS rebel 2000, Ti, and T2 cameras.

Discussion in 'Modern Film Cameras' started by alan_rockwood, Sep 19, 2011.

  1. I wonder if someone can enlighten me on what shutter speeds and f-stops are available on EOS rebel 2000, T2, and Ti.
    During the course of some film testing I shot a blank wall and changed the iso setting by 1/3 stop increments to vary the exposure. The viewfinder showed shutter speeds and f-stops. Mostly they changed by 1/3 stop increments, but in a few cases there were "holes" in the increments. That started me wondering what shutter speeds and f-stops these cameras are capable of, and whether they have all the slots covered or if there are "holes" in the shutter speed and/or f-stop scale.
    Real information would be appreciated, but of course speculation is also welcome.
  2. No holes, you are experiencing rounding "error". The camera will use the closest aperture/f-stop, but if it is near the boundary, it is hard to know which one it will pick. I am certain if you vary the light in a more continuous manner (instead of varying the ISO), you would hit all the increments. Inside, try a lamp dimmer, or outside slowly move your camera view from a dark to light area.
  3. I checked the manual settings on my T2 with an F/1.4 lens. Here are the results.
    Shutter speeds: 4000, 3000, 2000, 1500, 1000, 750, 500, 350, 250, 180, 125, 90, 60, 45, 30, 20, 15, 10, 8, 6, 4, 3, 2, etc.
    Aperture: 22, 19, 16, 13, 11, 9.5, 8, 6.7, 5.6, 4.5, 4, 2.5, 2, 1.8, 1.4
    Considering just the apertures, of the "tweener" settings (19, 13, 9.5, 6.7, 4.5, 2.5, 1.8), there is only one tweener setting between each major setting. Five of the tweener match pretty closely to 1/3 stop settings and three of them match pretty closely to 1/2 stop settings.
    It's all rather confusing, but if I had to guess I would say that the numbers are somewhat fictitious, especially the ones that match up with 1/3 stop settings. Most likely they are really 1/2 stop increments, incorrectly labeled in five cases with 1/3 stop numbers.
  4. Continuing, if we assume the f-stops are really 1/2 stop increments, even though a few are labeled with 1/3 stop numbers, the maximum error from the mislabeling is 1/6 stop, which isn't much.
  5. Can anyone else shed some light on this topic?
  6. Not Canon-specific, but it's likely that if you're using autoexposure (Av, P, Tv modes) the exposure is actually correct but the display numbers are being rounded to the nearest 1/2 or 1/3 step depending on the camera & configuration. The in-camera computer calculates to a much finer precision and the shutter and aperture are essentially stepless unless you specifically fix one of the variables (Av / Tv). So probably no 'holes', at least when using autoexposure.
    For manual mode, you'll be limited to 1/2EV increments -- you can bias the meter in 1/3EV steps but the actual film sensitivity is fixed and shutter and aperture can only be adjusted in 1/2 EV steps on this camera.

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