aperture and shutter speed for canon film Rebel series cameras

Discussion in 'Modern Film Cameras' started by alan_rockwood, Jan 29, 2011.

  1. In doing some experimentation with aperture settings and shutter speeds, it looks to me like there are some gaps in the possible settings. In particular, the settings shown in the viewfinder seems to mostly go by 1/3 stop increments. However, in some cases the numbers are closer to 1/2 stop increments, and in some cases there are "missing" increments. Does anyone know what settings are allowed in canon Rebel 2000, and/or Ti, and/or T2 cameras?
    I once saw a comment somewhere that the camera uses 1/6 stop increments internally, but the viewfinder results are as described above, and also some film testing experiments I have done are consistent with the "missing increments" hypothesis.
     
  2. Download the manual. Many of the fancier models had what would now be called parameter settings that let you choose the increments in bracketing, for example, as well as other variables. A manual for a specific model should tell you about how the stop-increments work, etc.
     
  3. My earlier 500N (I believe this was the Rebel G over there) only had 1/2 stop increments for shutter speeds and apertures. There were no custom settings to allow 1/3 stops, as is the case now for most modern cameras. I don't think the difference between 1/2 and 1/3 stop, which is 1/6 stop if my math is right, is even visible on most films.
     
  4. I have a Rebel T2 and both my own experience (when using Tv priority), as well as the user manual, confirm the shutter speed increments are in 1/2 stops. None of the Custom Function settings change that, which is OK by me; I find 1/2-stop increments adequate for any negative film I have ever shot over the decades.
     
  5. It is confusing to me because while in the Rebel there seems to be one increment between each standard f-stop (e.g. one between f/1.4 and f/2), the values displayed in the finder for these increments are often closer to third stop values (e.g. f/1.8) than half stop values (e.g. f/1.7). Therefore, I have been, and to some degree remain, confused.
    This all came up when I was doing some film testing. I won't go into the details, but I noticed apparent anomalies, both in the the settings for aperture and and shutter speed displayed in the finder, and some hard to understand bumps in the curves relating density and exposure.
     
  6. I'm a little confused here with the terminology, are we talking about settings you can set, or settings the camera can set? My understanding was that both speeds and apertures, to the extent they are set automatically in most any modern camera and a lot of pre-modern ones, are essentially stepless. In older cameras they might be truly stepless with the use of analog circuits, but in cameras with microprocessors they would increment in 1/6 or 1/8 of stop or even finer, which is as good as stepless for most purposes. The value shown in the display would just be an approximation. Certainly many cameras are promoted this way. I'd be surprised and a little disappointed if this is not how it works.
     
  7. he values displayed in the finder for these increments are often closer to third stop values (e.g. f/1.8) than half stop values (e.g. f/1.7).​
    It's because no EOS lens has a maximum f/1.7 aperture.
     

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