Re: [OM] IMG: More Insects, New Approach

[Chris Trask]

>
> I have a set of 3 Pentax M42 tubes, which match this lens.  Might give it
a
> try with the shortest one.
>

    You probably already know this, but in case you don't the magnification
will be roughly:

    MAG = (FL + EXT)/FL

where FL is the focal length of the lens and EXT is the length of the
extension tube.  The drawback to using extesion tubes is that the amount of
light falling on the film/sensor is the square of the reciprocal of MAG.
This becomes a bit of a problem in low-light situations such as a flower in
dense shade, especially if you need the short DOF advantage of a large
aperture to defocus background clutter.

Chris

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