Equivalent focal length for MFT lenses

Started Apr 12, 2013 | Discussions thread
Detail Man
Detail Man Forum Pro • Posts: 16,782
Re: Equivalent focal length for MFT lenses

draleks wrote:

There is a lot of talk about comparing lenses for MFT with APS or full format lenses. So I want to check if the following comparison is correct. If I have an MFT 300 mm f/6.7 lens, and a full format 600mm f/6.7 lens that is of a worse manufacturing quality and just happens to be twice as soft as the MFT lens.

You've scaled the Focal Length by the ratio of the Crop Factors (for FOV), but haven't scaled the F-Number by the ratio of the Crop Factors (for DOF). "Twice as soft" is a vague phrase. The spatial frequency response of subject-matter across the image-frame is different than Depth of Field.

Then, on equal ISO values, those two lenses will be an exact match. Right?

Shutter Speed is what you want equal. Exposure/Total Light are not functions of ISO Sensitivity.

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