tele converter/extension tube

[jbevans]

This is probably apparent to everyone but me but since I have been reading about macro I see some that use extension tubes to obtain greater magnification and some that use a tele converter. Maybe someone could help me understand the different effects and when to use one or the other. Thanks.
John

[swampler]

A teleconverter is used to make your lens longer, i.e. a 2x TC would make your 200mm lens become a 400mm lens, for shooting distant subjects.

Extension tubes are used for macros and are used up close to make high magnification of the subject.

[jbevans]

This is true but I was speaking of using a teleconverter to inable your 200mm lens to be a 400mm lens and focus close.

[swampler]

A teleconverter doesn't affect your minimum focus distance, so you would want an extension tube for closer focusing.

[LordV]

Both can give greater magnification and as commented above a TC preserves working distance but at the expense of some IQ loss. Ext tubes just allow you to focus closer and have a negligible affect on IQ.

TCs work the same with just about any lens, Ext tubes give greater magnification effect with lenses 100mm or less whilst add-on doptres give greater magnification effect with lenses longer than 100mm.
Having said that I quite often use ext tubes on a 200mm prime to get closer for butterfly or dragonfly shots.
Brian v.

[Gautam]

I assume you are thinking about using them with a macro lens. A TC will increase the maximum magnification by the TC factor (x1.4 or x2) without reducing the focusing distance. That is advantageous with skittish subjects, such as insects or when you cannot approach the subject for any other reason. However, you are adding extra glass, so some degree of deterioration of image quality can be expected. In practice this is often negligible if you use a good quality TC.

With ET you are increasing the magnification by being able to get closer to the subject. It is suitable for the subjects which are unlikely to move away. No extra glass is added, so there is no deterioration of IQ. Some purists will object to that last sentence for various optical reasons but again in practice these effects are negligible. One additional problem with ET is that often your focusing distance is so small that illuminating the subject can be tricky. How much magnification you would get by adding ET(s) can be derived from the formula

m' = extension/Focal Length, m" = the inherent maximum magnification of the lens
the total magnification (m) is m' + m"

FL in this case is the actual focal length and not the nominal FL. Macro lenses get the FL reduced as they approach the minimum focusing distance. Thus a 100mm macro lens actually becomes ~70mm at 1:1 magnification. This also happens with normal lenses but the effect is much smaller and can be ignored.

HTH

gautam

[moxi1]

Hi jbevans,

I have got both, but by adding all this gear to your lens you get an awful top-heavy rig, even a heavy duty tripod has problems to hold it steady, as it does have some movement in itself.
I have to add that this magnifies up to 4x life-size and that is very big and the depth of field is almost non-existant.

If you don't want to do a lot of macro shots, buy a tele-extender that might be more versatile for other photography.

I don't know your budget - a very good tele extender can cost almost as much as a Sigma or Tamron macro lens.

Extension rings are much cheaper but limited in use.

Cheers Moxi1