Extension Tubes

[Alex1994]

Are they are a credible alternative to expensive macro lenses? Any compromise on image quality, sharpness, aperture etc? I'm thinking of getting some for my OM SLR system.

All help much appreciated

Alex

[miketoll]

The more extension you use the more light you lose, I think that with a 50mm lens and 50mm tube which would give 1:1 you will lose a couple of stops. Obviously you lose some quality in that the, say, 50mm lens is not designed to work primarily that way but the quality is still excellent and no worry. Light is the main thing but no problem with static subjects and a tripod, as a cheap alternative to a pucker macro lens it is excellent and I would go for it. Indeed even if you got a proper macro lens one day they can be used with that too to give even closer focussing. I bought the Kenko automatic tubes to work with my Canon lenses but I know nothing of the availability of the old Olympus mount.

[Alex1994]

Olympus did a variety of extension tubes for the OM system and there are also third-party ones. I'm currently looking at a 25mm tube for use with the 50mm f1.4 lens. Since this is a very fast lens I'm thinking that even if I lose 2 stops I still have f2.8. The 50mm has a min focussing distance of 0.45 metres, if I add a 25mm extension tube what min focussing distance will I get?

[miketoll]

Not sure of distance but my understanding is that a 25mm tube on a 50mm lens will give you half life size. Aperture is fine especially as in macro one is usually stopping down for increased DOF which is minimal in close up work.

[yelvertoft]

I wouldn't say you lose quality with extension tubes, there is no glass in them, they do not actually change the image.

[miketoll]

What I meant Duncan is that a normal 50mm lens is not optically designed to work at it's best at macro distances so you will not get the flat field a true macro lens will give and no doubt there are other optical corrections missing at these distances but I agree for normal use like close up of flowers and what have you there is no discernible difference. Convenience and versatility are the main differences, as you say there is no new glass in the optical train. Are the tubes you are looking at auto tubes Alex? Much easier to use if they are.

[andy153]

Also Alex have you considered a reversing ring? I remember years ago when I first tried Macro - I got a reversing ring for my 50 mm standard lens on my Nikkormat FTN - can't remember details very well, but I remember the results were great - again - no extra glass to interfere, I seem to remember the focus distance was very short.

[miketoll]

I briefly used a reversing ring back in the days when I had a Praktica Super TL. Certainly gave excellent results but was slow and awkward to use as all connections between lens and camera body were lost necessitating using stop down mode using my finger to push in the aperture lever. I think you could get another ring with a connection to a remote control to do that but I never did as I preferred the close up filters as being easier to operate while still giving very good results if stopped down to f8 or so. The subject to lens distance was very small with the reversing ring and gave 1:1 magnification which was fixed, focussing was by moving the camera backwards and forwards.

[Alex1994]

Had a look into reversing rings as well - thanks for the tip. I don't think I want to do extreme close-up work, since my compact canon digicam has a great macro mode. I think I'll be getting an extension tube just for reducing minimum focus distance - helps when I photograph cats close up.

[miketoll]

If you just want to reduce the minimum focussing distance then an extension tube is the way to go.