# Micro four thirds - does the crop factor apply to MFT lenses as well?

Started 5 months ago | Question thread
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 Re: Let's answer this correctly and simply. In reply to Great Bustard, 5 months ago

Great Bustard wrote: ....

50mm f/2 on 4/3 (mFT) is equivalent to 62.5mm f/2.5 on 1.6x (Canon APS-C), 67mm f/2.7 on 1.5x (DX), and 100mm f/4 on FF, where "equivalent to" means:

• The photos have the same AOV (diagonal angle of view) and aperture (entrance pupil) diameter: 50mm / 2 = 62.5mm / 2.5 = 67mm / 2.7 = 100mm / 4 = 25mm.

• The photos have the same DOF (as well as diffraction softening) when they have same perspective (subject-camera distance), AOV, aperture diameter, and display size.

• The photos have the same motion blur and the same total amount of light falls on the sensor when the aperture diameter and shutter speed are the same (usually attained by upping the ISO as required).

• The photos have the same same noise when the same total amount of light falls on the sensor if the sensors are equally efficient (less noise if the sensor is more efficient, more noise if the sensor is less efficient).

• Other elements of IQ, such as resolution, bokeh, flare resistance, etc., as well as elements of operation, such as AF speed/accuracy, size, weight, etc., are not covered in this use of the term "equivalent".

Hope this clears the whole matter up for you!

Good explanation but it might help to add some examples regarding "upping the ISO", maybe something like

1/200@F2 and ISO 200 with mFT equals 1/200@F4 and ISO 400 with FF, 1/100@F2 and ISO 1600 with mFT equals 1/100@F4 and ISO 3200 with FF, 1/10s@F2 and ISO 6400 with mFT equals 1/10s@F4 and ISO 12800 with FF for equally efficient sensors.

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Edited 5 months ago by acahaya
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