lens speed

Discussion in 'Mirrorless Digital Cameras' started by g_lindzey, Jan 26, 2017.

  1. I have always tended to buy the fastest lenses I could (given avaiabiity and affordability) for a given focal length and camera. This was partially based on the ease of focusing a 35mm SLR film camera with a fast lens over a slow lens.
    I am currently thinking of moving to a mirrorless system camera (specifically the fuji x-t2) and I started wondering if the electronic viewfinder was brighter with faster lenses or if the electronics compensated for slower lenses so that the image remained the same brightness. Does anyone know if there is a difference in brightness in the evf for different speed lenses?
    thanks
     
  2. Come to think of it, I never noticed any difference between F1.4, 1.8, 2.8 and even higher. If I judge it by Large Format, and ground glass has to be taken into account, anything lower (numbers) than F8 is fine, tho F12 would be somewhat problematic.
    Les
     
  3. This would depend on two modes. 1. In screen mode, Preview EXP./WB IN MANUAL MODE EXP/WB PREVIEW EXP.WB: ON OR OFF. Set to on.
    2. Also on the shutter speed dial if in manual mode, I like too go to X on the dial, then use the front command dial in 3rd stops, you can visualize the screen darkening or lightening in this mode, therefore: If for a test sake you set a shutter speed with a f4 lens open at f4, then replaced that lens with a 1.2 lens open to f1.2, keeping the same shutter speed, you would indeed see a brighter screen because of the faster lens variant.
     
  4. On my Sony A7, finder brightness can be kept pretty much constant regardless of aperture set, which matters to me as I use manual lenses. If finder brightness is your only concern, you can probably manage well with relatively slow lenses.
     
  5. Sony A7 cameras have an option to display live effects, which include exposure settings, compensation and various pictorial attributes. When this option is off, the display is relatively constant, regardless of the lens and shutter settings, and scene brightness. In extremely low light, the sample interval of the viewfinder is lengthened. causing a jerky display. This occurs at levels to dim to see the controls of the camera with your eye, like back stage in a darkened theater.
    I prefer the latter mode for focusing and composition, but have a button programmed to display the effect of lens settings.
     
  6. Thanks for all of the responses.
     
  7. Even with SLR optical finders, there was very little
    point in going above f/2 as far as viewfinder
    brightness went.

    The optics of SLR (and DSLR) finders is such that
    any aperture above f/1.8 gets effectively cut off
    and you can detect no difference in brightness or
    depth-of-field by eye. Nor for that matter with an eyepiece photometer.

    OTOH, a mirrorless EVF will show the true depth-of-field as captured by its sensor. Although the gain of the EVF is usually automatically adjusted to give a constant brightness - except in manual exposure mode where, usually, the EVF reflects the end result of the image as it will be captured.
     

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