Aperture range changes

edited February 2016 Posted in » Canon T5i / 700D Forum
I am shooting with a 18-55 stm in M mode with AF on. I notice that the my aperture settings will sometimes allow me to go as big as, 3.5 but not always. A lot of the time it only allows me to go to 4 or 4.5. I am a newbie in the world of photography so forgive me if there is an easy, obvious explanation to this. Thanks!


  • edited February 2016
    Unless you have a zoom lens with a constant aperture such as f/2.8 or f/4 throughout the zoom range, your problem will always occur with zoom lenses.
    f/3.5 is only possible with the lens fully open at 18mm. It will start to close the moment you move the zoom ring until it reaches the telephoto end where it will be f/5.6.
    Some lenses are more tolerant than others ie. they will allow some movement before the F stop starts to change. Other lenses can be very tight and just moving from 18mm - 18.5mm is enough to change the F stop.
    So, if you want f/3.5, then make sure the lens is fully at 18mm.
    Hope this answers your question.
  • edited February 2016
    Ah ha! That helps, thanks for the response!
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