OM extension tubes

[SalveSlog]

I want extension tube(s) for my Olympus OM1. The "auto" ones are rather expensive, while non-"auto" is more affordable. Can someone help me understand in detail the consequence of the tubes being non-"auto"?

 

[MattKing]

The "auto" tubes permit open aperture metering. That means your viewing and composing and metering is done with the aperture wide open, and therefore maximum visibility. The aperture will then stop down to whatever you set automatically, at the moment of exposure.
The non-auto tubes require that you use stop down metering. Most likely you will find yourself frequently adjusting the aperture - open up to view, compose and focus, then stop down to select depth of field and meter.
AFAIK, the actual Olympus OM tubes are all auto tubes. They are well made and beautifully finished. That is part of the reason that they are more expensive then third party tubes.

 

[chriscrawfordphoto]

There are non-auto Olympus extension tubes; I have a set of them. They were, I think, the early version of the tubes; later ones were auto.

 

[AgX]

The auto-feature typically will benefit fast photography. With a complicated studio-like set-up, the stop-down metering and lack of auto-diaphragm etc. will have have lesser impact.

Unless you use lenses designed for that resulting scale, extension tubes will bring your lenses into a range for what they were not designed concerning image quality.

 

[SalveSlog]

Maybe I uderstand now.. the following question will show:
If the light is right for it and I want to take a picture with the lens wide open anyway, there will be no difference between using the auto or non-auto tube?

AgX,
I will be using the standard 1:1.8 50mm lens. That one is OK, nicht wahr?

 

[AgX]

No. Standard lenses are designed for small image scales. That the extension with most of these ends at 0.5m is not only due to the otherwise complicated stacked helical barrel, but also for the decreasing image quality with larger extensions.

That one nonetheless can do so shows the fact that each and every SLR manufacturer had extension tubes or even bellows on offer, some of them not even offering a macro lens..

 

[SalveSlog]

I'm not interested in true macro (1/1) but down to maybe 15mm distance from the lens. The 50mm macro lens would still give a better result than tube(s), anyway?

 

[MattKing]

I'm not interested in true macro (1/1) but down to maybe 15mm distance from the lens. The 50mm macro lens would still give a better result than tube(s), anyway?

When you are discussing close focus work, and the qualities of different approaches to the problems, it can be helpful to speak in terms of magnification, rather than focusing distance, because that permits more meaningful comparisons between lenses and accessories.
The 50mm (and other) macro lenses are certainly more versatile than extension tubes, because you can use them for distance work as well. With extension tubes mounted, you are restricted to close work.
One of the most important design criteria for macro lenses is that they provide flat field performance - if you focus on a flat surface that is parallel with the film, the corners are in the same focus as the centre. For a lot of people, their close focus work doesn't demand that - think of flowers or insects.
A basic 50mm f/1.8 standard lens used with an extension tube won't usually offer great flat field performance, but you may be content with the centre sharpness, and that may (or may not) meet your needs.
Extension tubes are relatively light and small - certainly lighter and smaller than an extra lens. They do reduce light intensity at the film plane though (as does a macro lens focused close).
Even lighter and smaller are so called close-up filters (actually diopters). They involve a resolution loss, but they also have benefits - light and small, no loss of light and more convenient working distances.
And by the way, when you are working close, the depth of field is tiny. You will almost always want to use smaller apertures.

 

[Digger Odell]

Olympus made auto and manual, as described above. Get the Vivtar auto tubes. I have both, and the made in Japan Vivitar tubes are NICER than the oly ones. I got a whole set of 3 for about 12 bucks at KEH. If you can't see the words "auto" on the tube in the pictures on eBay, don't assume it is auto. (I got burned on this)


Also, the 50mm macro lens, natively only goes to 1/2 macro. to get to 1/1 you still need an extension tube.

For 12 bucks, get the tubes and play around with them on your current lenses, I have gotten some very nice results with them.


Best regards.

 

[AgX]

A basic 50mm f/1.8 standard lens used with an extension tube won't usually offer great flat field performance, but you may be content with the centre sharpness, and that may (or may not) meet your needs.

Yes, someone taking a photograph of a stamp or coin full frame has different expectations of lens performance than someone photographing a blossom in center of the frame, with objects staggered in depth, thus only partially in focus anyway, and all objects in center.

 

[PaulQ]

There's a set of auto aico tubes on eBay UK for £17 at the moment. I made one extension tube by removing the optics from a cheap teleconvertor.

 

[AgX]

There even was a series of 2x teleconverters, that by design could be converted simply into an auto extension ring by just taking out the lens assembly, that sits in its own bayonet mount.

 

[dynachrome]

I agree that the Vivitar auto tubes are a good place to start. I must have several sets. If you are shooting flat subjects then reversing the 50/1.8 lens will give much better results. You lose auto diaphragm operation this way. The Panagor Auto Macro Converter is sometimes found at reasonable prices and can give decent results with the 50/1.8. Good results can also be had with lenses in the 85-135 range with extension tubes.

 

[AgX]

I agree that the Vivitar auto tubes are a good place to start. I must have several sets. If you are shooting flat subjects then reversing the 50/1.8 lens will give much better results.

With lenses designed for small scales reversing makes sense above scale of 1/1.