[dave9t5]

[quote name='Klaus' timestamp='1312662890' post='10437']

Well, the focal length is the focal length is the focal length. This is a physical spec. I agree that this is meaningless from a user perspective though.

I still keep on wondering why they did it. Olympus manufactured some of the finest lenses around in the FT scope and now they are free floating some abberations which they should be able to master based on their design capabilities. We are not talking about a budget lens here.

[/quote]



The physical spec of this lens must be wider than 12mm. Ergo, the focal length (12mm) is not the focal length (<<12mm).

[Brightcolours]

[quote name='dave9t5' timestamp='1312736815' post='10456']

The physical spec of this lens must be wider than 12mm. Ergo, the focal length (12mm) is not the focal length (<<12mm).

[/quote]

No, it does not have to be SHORTER than 12mm.

It is not much corrected, and as is well known, uncorrected lenses are "wider" than corrected lenses.



Example.



Canon EF 15mm f2.8 fisheye (uncorrected lens). Angle of view (horizontal): 141°54'.

Canon EF 14mm f2.8 L USM (corrected lens). Angle of view (horizontal): 104°.





Ergo, of course it is wider when not corrected. Just the rules of the optical game. 12mm is 12mm, but field of view depends on level of correction.

[Tiz]

@Brightcolours



Please have a look at the following image (same RAW; version 2 was developed with LR lens profile enabled). It seems to me that the distortion/vignetting of the SX220 is so strong that you have to cut away a certain amount of the image (in addition to stretching the edges) and also correct the center. But this may be different with respect to mFT lenses.



Version 1: http://www.abload.de/img/cmp_crw_0126wkd6.jpg



Version 2: http://www.abload.de/img/cmp_crw_0126-2wjcm.jpg

[Rainer]

[quote name='dave9t5' timestamp='1312736815' post='10456']

The physical spec of this lens must be wider than 12mm. Ergo, the focal length (12mm) is not the focal length (<<12mm).

[/quote]



A strictly rectilinear corrected lens would have to be a bit wider than 12mm to

fulfill the observed behaviour (angle of view in the corrected image matches 12mm exactly).



But imagine, this lens is not a strictly corrected rectilinear lens ... this way, it can as well

have a focal length of 12mm and be a bit wider than a rectilinear 12mm lens is.



Like the Samyang 8mm (stereografic fisheye) has the same field of view than a 10mm

(equisolid) fisheye (both on crop-1.5/1.6).



Just a thought ... Rainer