The DOF remains the same.
----------
>Firstly, I know that a 1.4x TC will effectively reduce the light falling on
>the film by 1 stop ( and a 2x TC by 2 stops). Many people say "it reduces
>the aperture" but is this technically correct? Does it increase your depth
>of field to that which would be obtained at the smaller aperture?
>
>ie a 250 F2 used at F4 has y amount of depth of field when focussed at say
>40 feet
>
>If I add a 2x TC to get effectively a 500F4, and leave it set at F4 on the
>lens, do I still get y depth of field? Or do I get the depth of field as if
>I am using the lens set at F8?
You get the same DOF, but your subject is doubled.
>
>Or is the depth of field at (effectively) F8 on a 500mm lens the same as
>dof at F4 on a 250mm.
Yes, that is why it is the same.
>
>I'm sure those of you with more knowledge of optics etc might be able to
>enlighten us as to how this all works.
>
The TC *enlarges* your image. That is all. The dof cannot vary. If you had a
48x72 film size you could get the same image you can get on the "leica size"
film without TC. This enlarging of the image has a cost in terms of light,
as the same light must be spread onto a larger area.
You should be aware the Olympus 1,4 TC has a protruding element that might
be not compatible with every lens. I think a common 1,4 TC of any brand can
do no real harm.
Marco
Marco
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