Archived posting to the Leica Users Group, 2003/01/14
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At 4:21 PM +0100 1/14/03, animal wrote:
> > Whoa Totally twisted! It looks like a great deal of unnecessary fun.
>> All you have to do is focus normally and then slide the camera sideways
>> to the composition you are after*. Some lenses have a curved field and
>> then just rotating the camera is the best way. No fuss, no muss and no
>> stress marks.
>>
>Does a curved field mean that it is circular i.e that no matter at what
>angle, the subject would remain in focus?
>simon jessurun
Not likely, but in rare circumstances, yes.
Field curvature can take different shapes and degrees, and besides
varying by lens also varies by focussed distance (and focal length,
in zooms). Most fast lenses display fairly significant field
curvature at closer distances, so trying to apply the complex
trigonometric calculations based on a lens having a perfectly flat
field like Martin Tai does is largely pointless. In 35mm generally
only macro lenses have as one of their design goals a flat field, and
even there it is not perfect.
The good thing about field curvature in relation to this discussion
is that the imaged field is usually concave as seen from the camera.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
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