With macro the DOF can be very small. The goal would be to get the
whole bug in sharp focus rather than just his eyes. Frank's
description of the fence going from near to far is a good way to
visulaize it, but the problem is even more common with macro.
Many of the bellows macro lenses have short focal lengths (Zuiko 20mm
& 38mm). Stopping down the aperture very much causes diffraction
problems. Although the Zuiko 135/4.5 can be stopped down to f45,
diffraction probably limits the picture quality at f16 and beyond.
For either tilt or shift you need a larger than normal image circle. I
haven't seen a good macro lens with the necessary image circle.
-jeff
On 2/16/07, Frank Wijsmuller <Frank@xxxxxxxxxxxxxx> wrote:
>
> One of the reasons is the possibility of increased DOF by tilting camera and
> lens relative to each other:
>
> http://en.wikipedia.org/wiki/Scheimpflug_principle
>
> In short Scheimpflug says that if the lines through object, lens and film
> (sensor ;-) plane intersect at one point, the object will be in focus (hope
> my English is correct here)
>
> In a C*n*n brochure they always illustrated this by a fence which appeared
> completely sharp, but was not parallel with the film plane.
>
> A bigger image circle might come in handy for the shift, maybe for the tilt
> too.
>
> Frank.
>
>
> 2007/2/16, Scott Peden <scotpeden@xxxxxxxxxx>:
> >
> >
> > Sorry for the dumb question, but what is the purpose of a shift bellows? I
> > think I have read all the links and all I got out of this was that it was
> > hard to find a lens or attach your camera.
> >
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