What is mFT FoV?

Started Jan 27, 2013 | Questions thread
Detail Man
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Re: What is mFT FoV ?
In reply to gollywop, Jan 27, 2013

gollywop wrote:

If one has, say, a 12mm lens on an mFT camera, it presumably implies some FoV. However, these days a large number of mFT lenses do software correction for lens distortions, and the image as rendered in, say, ACR is significantly different from the uncorrected version of the same image.

My question: is the 12mm FoV relevant to the FoV of the original image or the FoV of the corrected image, which is, typically, significantly smaller than that of the original?

I agree that the diagonal FOV (thus the 35mm equivalent focal length when the crop factor is considered) of the default (rectilinear distortion corrrected) 4608x3456 pixel size is designed to be relatively close to the intended specification.

There do exist additional photo-sites on M43 image-sensors. They are in the horizontal sections. Some of those photo-sites are unusable - because they are masked-off, and used in order to report black-level offset information only. There are only a few extra photo-sites in the vertical dimension (but they are apparently set aside for use in implementing rectilinear distortion corrections).

The image-file meta-data for your E-M5 (4:3 AR) only reports "Image Dimensions" the calculated diagonal FOV of which is only very marginally different from the default value of 4608x3456. Those pixel-dimensions (for the 3.73 Micron pixel-pitch of the E-M5's image-sensor) calculate out to be only very marginally "longer" (in 35mm equivalent focal length), meaning "narrower" (in FOV) than the specification value.

See: http://forums.dpreview.com/forums/post/50738679

However, it is clear (from your posted example as well as another poster's example) that the E-M5 image-sensor does have some extra (horizontal) photo-sites that are not reported in the E-M5's image-file meta-data.

GH2 RW2 (4:3 AR) image-file meta-data reports "Sensor Dimensions" of 4760x3472.

See: http://forums.dpreview.com/forums/post/50738731

DxO Optics Pro 7.23 (only when automatic distortion corrections are enabled, and "Keep Aspect Ratio" is unchecked) widens the horizontal field (only), and produces output images that are 4668x3457 (as compared to it's default output image pixel-size of 4609x3457). The wider horizontal pixel-dimension yields a diagonal dimension that is 0.821% larger than default diagonal pixel-dimension.

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