I dont mean when for example 35mm on a crop sensor “equals” a 50mm on a full frame camera. My question is a bit weird, here we go.

So i have a 18-55mm lens (on a crop camera) and people say that 50-55mm is the focal length of the human eye. Here, my experiment comes into the play:

My camera has a 1.5x crop factor so 35mm looks like 50 mm on a full frame because of narrower field of view right? So when people say field of view of a 50mm on a full frame is the same as your eye, my first thought is 50mm on a full frame = 35mm on my camera. Then what i do is i take my camera put it on 35mm and then look at the vizor. What i expect is no zoom at all but the objects look smaller in the vizor (so fov is higher). When i put my camera at 55mm, the objects size match up with exactly what i see. But from what i learned 35mms should be like a 50mm on a full frame therefore it should match my eye.

So here comes my question:

Are the numbers of focal lengths on my lens already multiplier by 1.5x ? So do i have to subdivide the numbers to get the full frame equivalent ?

Sorry for spelling mistakes.

  • Primary_Mycologist95@alien.top
    BEnglish
    1·
    1 year ago

    Focal length is focal length. It is a property of the lens, not the camera.

    A lens focuses light at a certain point (the film/sensor plane of the camera). It projects this light as a circle (the image circle).

    Most cameras have sensors that are rectangular. To maximise your imaging you need a sensor that is smaller than this image circle. Imagine for 35mm/full frame format, a rectangle that has its points close to or on the line of the circle. Now draw a smaller rectangle inside your larger rectangle. This is the relationship between larger and smaller sensors, and why it is referred to as crop-factor - you are literally cropping the image supplied by the lens by using a smaller sensor. The physical properties of the lens remains the same (aperture, focal length etc) regardless of sensor used.

    Where people get hung up is equivalency. If you want to use a lens on a smaller format to mimic the appearance of an image taken with a larger format, then you have to do the math for focal length and depth of field.