PanoTools:
Re: FOV value in exif accuracy
Erik Krause 2005-Jun-16 22:14:40
On 16 Jun 2005 at 19:17, alexandre jenny wrote:
> Just some wonder today about some measurement with a zoom lens.
> When moving slowly the zoom on the lens and shooting, it appears than even
> when some zoom has occured, the value in exif hasn't changed.
>
> Some measurement for a Sigma 28-300 mm :
> Exif values can only be 28, 34, 40, 46, 55, 65, 75 ... I cannot get any
> value between these.
>
> Does anyone heard of that before ?
I knew it from unscrewing some Sigma and Canon EF lenses. Focal
length is encoded electrically using 4 stripes of contacts that are
interrupted in some binary order. Hence there are only 16 possible
steps.
Before there was digital photography it wasn't necessary to be more
exact since the main purpose of the focal length encoding was to
adjust the zoom reflektor of a flash.
The good news is that in lenses with lower zoom factor there are 4
stripes, too. Hence the accuracy should be significantly higher in a
12-24mm zoom.
best regards
--
Erik Krause
Ressources, not only for panorama creation:
http://www.erik-krause.de/
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