# What is mFT FoV?

Started Jan 27, 2013 | Questions thread
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 Re: String theory In reply to Guy Parsons, Jan 27, 2013

Guy Parsons wrote:

gollywop wrote: Gee, Guy, you surprise me. This comment misses the point in just about every conceivable way.

My excuse that it was way too early here and the brain hadn't got out of bed yet.

I can relate to that.

Anyway the piece of string argument still applies to FoV arguments, it's as wide as you like corrected or not depending on lens and where you stand.

Indeed, but I want to measure from where I ﻿am﻿ standing, not where I could be. You see, that's what zooms bring to the party.

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?

FoV is always deemed to be the diagonal of the frame and we have to assume refers to the FoV of the in-camera corrected frame, which you see in live view. Again I assume that would be the diagonal at 4:3 ratio to get the best number for marketing reasons.

But here's where the string reappears, there is so much slop in quoting focal lengths on lenses and variations due to aspect ratio choices that it really only a matter for arguing about and not there to be considered for any practical reason in the real world when we take photographs.

As I said, the view gets bigger anyway when you use a RAW converter that does the corrections but also allows the edge pixels to be included.

Problem there is that, if there is substantial rectilinear correction required, the converters producing the "bigger" images are producing distorted images. In the example I gave above to Anders, that distortion is obvious in the PN rendering, particularly to one who knows what the scene looks like. The telephone pole, for example, in the PN image looks fairly straight and nearly vertical. It is, in fact, quite curved and out of plumb, just as depicted in the ACR conversion.  The brick walk simply doesn't "sit" like that.

Often the elbow just chopped off in a jpeg can sneak back into a RAW full frame extraction. So the FoV result can vary quite a bit for the one lens and may or may not actually be truly a 12mm lens due to the way the focal length can vary with initial design (is it really 12mm or 11.8mm or 12.2mm?) and with internal focus lenses as they focus closer.

I stand by my string argument.

I stand where I'm standing, and that's where I want my angle of view.

take care,

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gollywop

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