Macro questions - DPChallenge Forums

Canon EF-S 17-85mm f/4-5.6 IS USM

05/18/2005 12:42:48 AM · #1

I've tried using my sigma 70-200mm lens with a 50mm reversed in front of it. When I look through the viewfinder of the camera, the subject covered the entire frame, but the pictures only had a circle in the center of the frame. The subject only covers the circle. Am I doing this wrong?

Do extension tubes do this too? Does anyone own the Sigma 70-200mm and use extension tubes with it?

Do teleconvers enable a lens to have a higher magnification?

Message edited by author 2005-05-18 00:43:49.

Zed Pobre

Canon EOS-20D

05/18/2005 01:02:21 AM · #2

Are you shooting at your widest possible aperture?

Sony 24-70mm F4 Vario-Tessar T* FE OSS

05/18/2005 01:22:36 AM · #3

No. I'm shooting at around f/16. Does aperture affect the coverage of the lenses system over a sensor?

Bear_Music

Samsung Galaxy S24 Ultra

05/18/2005 02:16:58 AM · #4

Originally posted by autobahn123:

No. I'm shooting at around f/16. Does aperture affect the coverage of the lenses system over a sensor?

It sure as hell does when you are stacking 2 lenses back-to-back. The viewfinder view is wide open, but the image is shot stopped down. Use your depth-of-field preview to see what's really gonna happen...

Robt.

Sony 24-70mm F4 Vario-Tessar T* FE OSS

05/19/2005 12:08:44 AM · #5

Thanks guys.

But will this also happen with an extension tube and a telefoto lens?

Bear_Music

Samsung Galaxy S24 Ultra

05/19/2005 01:51:46 AM · #6

Originally posted by autobahn123:

Thanks guys.

But will this also happen with an extension tube and a telefoto lens?

No. The optics of a tele-extender are designed with this application in mind. And it does not even have the potential to happen if you are using macro extension tubes, which have no glass in them at all. The problem is the reversed 50mm lens is an entire optical system in itself, and it has a completely different synergy with the optics of the lens mounted on the camera depending on the relative apertures the two lenses are set at.

Robt.