Extension rings vs teleconverter?

Discussion in 'Macro Photography' started by Galah, Feb 18, 2009.

  1. Galah

    Galah Member

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    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:
     
  2. Fred Aspen

    Fred Aspen Member

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    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
     
  3. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    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.
     
  4. MattKing

    MattKing Subscriber

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    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
     
  5. Christopher Walrath

    Christopher Walrath Member

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    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.
     
  6. Q.G.

    Q.G. Inactive

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    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.
     
  7. Christopher Walrath

    Christopher Walrath Member

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    I second QG
     
  8. AgX

    AgX Member

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    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.
     
  9. Sirius Glass

    Sirius Glass Subscriber

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

    Steve
     
  10. Galah

    Galah Member

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    OK, I have read your responses (thanks :smile:) ) 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?
     
  11. Q.G.

    Q.G. Inactive

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    Yes.
     
  12. Galah

    Galah Member

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    Thanks for the quick response, OG.:smile:

    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?
     
  13. Q.G.

    Q.G. Inactive

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    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.
     
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  15. Bosaiya

    Bosaiya Member

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    Any reason you can't use bellows? That would be the best bet.
     
  16. Galah

    Galah Member

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    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
     
    Last edited by a moderator: Feb 25, 2009
  17. Q.G.

    Q.G. Inactive

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    When your goal is to get close, infinity is the least of your worries. :wink:
     
  18. Galah

    Galah Member

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    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.:smile:
     
  19. glbeas

    glbeas Member

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    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.
     
  20. Galah

    Galah Member

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    Thanks, Gary.
     
  21. 2F/2F

    2F/2F Member

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    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.
     
    Last edited by a moderator: Feb 26, 2009
  22. Galah

    Galah Member

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    Dear 2F/2F,

    Thanks for contributing.

    As I understand it, the teleconverter retains the original minimum focus distance of the lens to which it is attached and magnifies the image: the net effect is an enlargement similar to that obtained by an extension tube of the same length as the teleconverter, but without loss of working distance. Whether the image quality is the same for both appears to be a moot point. Both result in light loss.

    As far as I know, a diopter lens has the advantage of no light loss.
     
  23. wayne naughton

    wayne naughton Member

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    extension tubes on a close focusing mid tele is perfect for me.....plenty of space between lens and subject, cheap and portable closeup kit, great for flowers and larger insects.cheap and midrange teleconverters are a waste of money IMO.
     
  24. AgX

    AgX Member

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    The lenght of the extension ring (or bellows) forms an additional extension of the lens.

    The lenght of a tele-converter is of no interest. What is of interest is its magnification factor. This depends on the optics of a tele-conveter, not of its length.
    (Today typical factors are 1,4 and 2)
     
  25. Michel Hardy-Vallée

    Michel Hardy-Vallée Membership Council Council

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    Yes and no: your 50mm lens with a 2x teleconverter will have the angle of view of a 100mm lens. Its close focus and infinity focus distances remain the same.

    Tubes or bellows increase the minimum focus distance, so you can get closer to your subject than you could with the lens alone. But the angle of view of your 50mm on extensions remains the same, AFAIK.

    The difference between the two, in the range of situation where they can give you the same magnification, is thus one of perspective. So yes, the results are "similar" in terms of magnification, but no, they are "different" in terms of perspective (cf. a portrait shot with a 24mm v. one shot with an 85mm).

    With the teleconverter, you could fill up the picture frame with the flower, from a distance of, say, 2m. With the tubes, you could fill up the picture frame with the flower, from a distance of, say, 0,5m.

    I suppose that the people those who use both TC and extensions together do so because their subject require to keep a certain working distance, and they do not have the money to buy the more expensive, longer-focal macro lenses (Nikon, for e.g., has a 50mm, a 105mm, and a 200mm).

    At least that's how I understand it.
     
  26. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Another issue with a teleconverter is transmissive light loss. A good 2x converter usually has seven elements, and a cheap one has four elements. A seven element converter will often have a half stop light loss in addition to the two stop loss due to doubling the focal length while maintaining the same physical aperture diameter, and if you use non-TTL auto flash or a handheld meter, you need to account for it. TTL metering will take of it.

    One situation where people might combine an extension tube and a teleconverter is bird photography, because you are often photographing small subjects with a really long lens that isn't long enough, and if you're lucky, you can be closer than the near focusing distance of the lens, so if you've got a 600mm lens and want to photograph something the size of a sparrow, you'll need a teleconverter, and if you can get within 12 feet, you'll probably need an extension tube.