Sony pancake 16-50mm vignettes at 16mm.

Started Dec 17, 2012 | Discussions thread
viking79 Forum Pro • Posts: 14,148
Re: Rectilinear correction and diagonal FOV

Erik Magnuson wrote:

viking79 wrote:

I think it uses data/coefficients embedded in the RAW file that Lightroom knows how to interpret

So then is the issue that the data is not embedded or that Lightroom doesn't know how to interpret it?

I think Sony does things differently.  They require a separate lens profile that you have to apply manually.  Samsung and Olympus are applied automatically with no option not to apply them.

(remember, focal length is an intrinsic property of the lens, it relates to the field of view, but how much you crop the lens changes your you field of view).

Then you remember wrong - the focal length/FOV relationship only applies to lenses that have the same amount of rectilinear correction. A 15mm fisheye has a 180 deg diagonal FOV (on a FF camera). A 15mm rectilinear lens has only ~110 deg.

What I was meaning is focal length is intrinsic to the lens (it is a physical property of the lens, the field of view is dependent on a variety of factors including crop and focal length), a 15mm fisheye has properties that make it 15mm regardless of what size the sensor or image circle is.  Meaning, if you put a smaller sensor under it you would get a tighter field of view than 180 degrees.

The point you bring up is the Sony is likely 16mm focal length, but but the fisheye like distortion gives it a wider field of view than a rectilinear 16mm.

The Sony 16-50mm lens is undercorrected and so has a larger diagonal FOV at 16mm than a perfectly corrected lens. Once corrected to rectilinear projection via software, it's essentially the same FOV as an optically corrected lens.

That is fine, and that makes sense why it would be the same field of view after correction.  I will have to look into what an effective/calculated focal length really means (based off magnification). I think it is valid when comparing fields of view, but it definitely isn't measuring the true focal length of the lens.


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