Full frame lens aperture vs. MFT Lens aperture?

Hi, I was looking at full frame lenses with an aperture of around f/1.8. I know roughly what this aperture looks like when taking pictures, but how does this compare to a Micro Four Thirds lens with an aperture of f/1.7? Apparently, MFT f/1.8 is equivalent to a full frame f/3.6.

does this mean that a full frame lens with aperture f/1.8 will have a shallower depth of field than a MFT lens with aperture f/1.8?

please help me understand this, thanks! 


quick note, i’m looking at buying a mft prime lens with a huge aperture, that’s why i’m wanting to understand this.

3 Answers

  • qrk
    Lv 7
    2 months ago
    Favorite Answer

    The aperture, when described with the f-number, has the same light gathering capabilities across all sensor sizes.

    With an aperture of f/1.7, the depth of field on a 4/3 sensor will be equivalent to the crop factor times the aperture when compared to a full-frame sensor. Thus, you are almost right, it will be equivalent to a f/3.4 on a full-frame sensor (m4/3 has a crop factor of 2).

    The smaller sensor will have a harder time with selective focus. This is an advantage when you want a wide depth of field.

    Visit http://www.dofmaster.com/ for more information.

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  • Anonymous
    1 month ago

    Generally, the smaller format will have greater depth of field for any given lens aperture. That is because the smaller format uses shorter focal lengths as normal lenses.  50mm lens will be an equivalent of a 75mm lens on an APS-C camera and it will be the equivalent of a 100mm lens on a 4/3 camera. Therefore you will need a 25mm lens to give it as wide an angle of view for a 4/3 camera as you would get from a 50mm lens on a FF. To give you the same shallow depth of field of a 50mm f/1.8 lens for FF, you need a 25mm f/1.8 lens for the MFT format. The f number is a ratio that is calculated by dividing the diameter of the front lens element by the focal length of the lens. That means a 50mm f/2 lens has a front lens element diameter of 25mm.

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  • Sumi
    Lv 7
    2 months ago

    Because MFT cameras use a sensor that is 1/2 the size of a full-frame camera, they all have a crop factor of 2x.  This not only means that a 50mm f/1.7 lens will have the equivalent angle of view as a 100mm on a FF camera, but it also means that at f/1.7 on the MFT camera, it'll produce a depth of field equivalent to using a 100mm lens at f/3.4 on a FF camera.  You have to multiply the focal length and the aperture by two in order to get the equivalent focal length and depth of field in FF format.

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