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Galah
02-18-2009, 05:09 PM
This may already have been discussed, if so, I beg everyone's indulgence.

I wonder if someone could, please, compare the advantages and disadvantages of extension rings vs teleconverters with regard to close focusing?

For example, if using a 50mm or 24mm lens and wishing to engage in close focus photography (say, up to around 1:1), is there any advantage in using, say, a 25mm extension ring over a 2x teleconverter? Ditto regarding a 50mm Macro lens?

What are their respective advantages/disadvantages?:confused:

Fred Aspen
02-18-2009, 05:15 PM
I think you want a comparison between extension tubes and close up lenses.

Do an APUG search on extension tubes and you will be reading for an hour or so.

-Fred

David A. Goldfarb
02-18-2009, 05:16 PM
A true macro lens (and not a lens that is merely close focusing) is optimized for high magnification.

An extension tube adds nothing to the optical path, so it's usually a better option than a teleconverter or a close-up lens that screws to the front of the lens like a filter. If you're new to macro photography, get an extension tube, because you can always use it, even if you get a dedicated macro lens later or find another solution.

A teleconverter usually isn't the best solution for macro photography optically, but it will give you more working distance, if you need it for placement of lighting.

MattKing
02-18-2009, 06:36 PM
There is a neat Vivitar tele-convertor that has a very flexible close focus capability. Essentially, the Vivitar unit is an adjustable extension tube, with glass, and as such is really handy.

Matt

Christopher Walrath
02-18-2009, 10:05 PM
The two affect the viewing area in the eyepiece, however, in different ways.

Extension tubes magnify the subject area but knock the DOF down to darn near nothing. Great for macro isolation.

Teleconverters magnify the subject by doubling focal length. DOF is reduced in regards to increased focal length. However you may experience poorer image quality and a slight light fall off.

As to which might be suggested would completely depend upon what you wish to do.

Q.G.
02-19-2009, 11:14 AM
DOF is affected by magnification and f-stop. So no real difference between tubes and extender there.

Listen to David:
Teleconverters add a mostly not very well corrected assembly of optics to a (hopefully) well corrected lens.
Extension tubes allow the lens to show what it is made of.
I'd chose extension tubes any time.

Christopher Walrath
02-19-2009, 12:10 PM
I second QG

AgX
02-19-2009, 02:16 PM
Teleconverters will narrow the angle of view, thus making exposure more susceptible to camera shake (tilt).

Extention rings will even broaden the angle of view a little bit.

Sirius Glass
02-19-2009, 03:32 PM
Teleconverters will narrow the angle of view, thus making exposure more susceptible to camera shake (tilt).

Extention rings will even broaden the angle of view a little bit.

Finally someone clearly spelled it out. There are two different products with two different goals.

Steve

Galah
02-19-2009, 04:51 PM
OK, I have read your responses (thanks :)) ) and I also have done some homework reading and the message I get is that:

You lose some light with both.

Both give a "magnified" image, though there may be some image degradation with a teleconverter -depending on its quality.

Extension tubes result in a reduction of "working distance", whereas a teleconverter retains the lens' original "working distance". (This could be good with live subjects and from the point of perspective and lighting.)

Is there anything else?

With regard to the "light loss": is this "automatically" compensated for by TTL metering for both tube and converter?

Q.G.
02-19-2009, 04:59 PM
With regard to the "light loss": is this "automatically" compensated for by TTL metering for both tube and converter?
Yes.

Galah
02-19-2009, 05:16 PM
Thanks for the quick response, OG.:)

I have heard that some photographers use a mixture of both tubes and teleconverter in the one exposure.

Has anyone here done that, and do they have any comments as to the advantages/disadvantages of such a technique?

Q.G.
02-19-2009, 06:01 PM
I have a comment: it's a bad technique that cannot be discouraged enough.

What it does is either enlarge the faults the lens itself may show more when used at close range, and add the poor correction or the extender.
Or enlarge the poor correction of the extender and what that thing makes of the perhaps somewhat lesser performance of the lens that's on it.

In short: having the extra glass somewhere between subject and film is still not a good idea.

Bosaiya
02-25-2009, 09:30 AM
Any reason you can't use bellows? That would be the best bet.

Galah
02-25-2009, 05:28 PM
OK, I have read your responses (thanks :)) ) and I Is there anything else?


Actually, yes, there is: with extension tubes you lose "infinity focusing", with teleconverter you don't.

Bosaiya, at this stage, I'm only interested in "close focus", as opposed to actual "Macro", so bellows would be overkill for me at this stage.

It would seem that some practitioners are not overly fussy about their choice of equipment (close focus lenses, tubes or tele-extenders) and some mix them and match them at will. See the attached link (once open, make sure to go on to "part three":

http://www.shutterfreaks.com/Tips/tomhicksmacros.html

Q.G.
02-26-2009, 12:08 PM
Actually, yes, there is: with extension tubes you lose "infinity focusing", with teleconverter you don't.
When your goal is to get close, infinity is the least of your worries. ;)

Galah
02-26-2009, 04:45 PM
When your goal is to get close, infinity is the least of your worries. ;)

Yes, if that's your only purpose. But, imagine strolling about a botanic garden or park: now you're photographing a flower close up, next you see your partner looking over the parapet of a romantic bridge. It could be helpful if you didn't immediately have to remove your extension tubes or change lenses.:)

glbeas
02-26-2009, 05:06 PM
Thanks for the quick response, OG.:)

I have heard that some photographers use a mixture of both tubes and teleconverter in the one exposure.

Has anyone here done that, and do they have any comments as to the advantages/disadvantages of such a technique?

I've done that when I had a Minolta set. I found I got the best magnification when I put the extender between the lens and the telextender, got about a .8 inch field of view. Stopped down with a flash for illumination got some pretty sharp images.

Galah
02-26-2009, 05:20 PM
Thanks, Gary.

2F/2F
02-26-2009, 05:22 PM
They are two different birds built to acheive two different aims.

A teleconverter magnifies the image, but actually reduces close focusing ability. They are used to decrease the angle of view; usually of a lens that is already at least a medium-long lens. They are not made for close-up photography. They contain optics. Infinity focus is maintained.

Extension tubes increase close focusing ability at the expense of far focusing ability. They do not contain any optics. They are made for close-up photography. They simply move the glass farther from the film so you can focus on closer objects. Infinity focus is not maintained.

A bellows unit is the same basic idea as an extension tube, but lets you vary the length of the extension as needed. It is more versatile, but also less portable, of course.

Diopers are accessory lenses that are mounted in filter rings. They screw into your filter threads and increase the close focusing ability. Though these are the worst option for optical quality, there are good ones out there that give fine results, and they can certainly give "special" effects if that is what you want!

TCs, extension tubes, and bellows units all cut light by making it travel farther from the glass to the film. A 2x TC doubles FL, but the physical aperture of the lens remains the same, therefore you only transmit 1/4 as much light at a given f stop (or 1/2 as much with a 1.4x TC). I have only screwed around with diopters; never taken a pic with them, so I am not sure if they cut light to a notable degree or not, but I don't think that they do.