In article <328A44D2.120646AF@cs.rice.edu>, wiensk@cs.rice.edu says...

>If I get it right I have 3 options to go [for close-ups]:
>
>1 - A macro lens, 1:1 magnification
>2 - Close-up lens attachments
>3 - Tube extensions.
>
>Assume I want to photograph an object with size 0.5 x 0.5 x 3 inches
>that is a miniature of a railroad car. I want it to look like
>the viewer is seeing the real thing, i.e., I want to picture
>the miniature in perspective.
>
>I had some experience with a homemade pinhole device (aluminium foil
>with a 0.2mm hole on center, covering a 50mm lens). Had to use
>long expositions, etc... but it worked.
>
>I want to improve my results, but I am concerned with the depth of
>field. Which of the above will give me better DOF?

They should all be the same at the same magnification and effective
aperture. The only way (without tilting the plane of focus) to get
the effect of greater DOF is by using smaller apertures (or less magnification). Diffraction reduces sharpness as the aperture is
reduced in size beyond about f8 (which is why the pinhole photos
are not very sharp). You may want to try a Canon 90mm Tilt-Shift
lens (or maybe the 45mm version), or the Nikon PB-4 Tilt-Shift
bellows with a 100mm enlarging lens on it - being able to tip the
plane of focus to more nearly parallel the railroad car may help.

>I know that the close-up lens and tube ext. decrease DOF.
>Question is: Do the DOF decrease in the same proportion as
>magnification increases ?
>Other question: Will a $600 macro lens 1:1 give me more DOF
>than a normal 100mm 1:5 lens with enough close-ups and tub-extension
>to achieve the same 1:1 magnification ?
>(Of course sharpness, color distorsions and other things will be
>better in a macro lens. But regards the DOF only, will the macro
>be better ?)

No.

>Finaly, one last question:
>Last night, while browsing the Kodak web page, I read that
>a 2x teleconverter, not only doubles the focal lengh,
>but also keeps the original minimal focus distance of
>the lens.
>That means: It will double the magnification of any lens!!
>Is that true ?

Uh-huh! The best use for short-lens 2X converters may be for
increasing magnification in macro work, since the small apertures
required for good performance are also desireable for increasing
DOF. F11-16 marked apertures with the 2X (f22-32) can provide good
results.
Hope This Helps