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05-02-2017, 06:13 AM   #1
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Teleconverter vs. Macro Rings

Is the only difference that teleconverters generally have glass?

Or do macro rings not have the same effect for long distance focusing?

05-02-2017, 06:36 AM - 4 Likes   #2
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Not sure what you mean by "macro rings" but there are 4 main categories of accessories for macro:

1) Teleconvertors (tube with glass mounted between camera and lens):
* multiplies magnification by a specific ratio;
* doesn't affect lens-to-subject distances;
* significantly reduces light levels

2) Extension Tubes (tube with no glass mounted between camera and lens):
* adds to magnification by an amount related to focal length;
* significantly reduces lens-to-subject distances;
* somewhat reduces light levels (becomes significant with long stacks);
* (Note: bellows are like variable extension tubes)

3) Close-up Lenses (ring with glass screwed to the front of the lens):
* adds to magnification by an amount related to focal length;
* reduces lens-to-subject distances;
* doesn't affect light levels

4) Reversal Rings (ring with no glass that lets you flip the lens and mount it)
* magnification depends on the lens (tends to be high);
* has very low lens-to-subject distances;
* tends to reduce light levels (but it's complicated);
* (may require extension tubes to get focus)
05-02-2017, 06:38 AM   #3
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I meant extension tubes.
05-02-2017, 06:47 AM - 1 Like   #4
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QuoteOriginally posted by timw4mail Quote
I meant extension tubes.
Photoptimist's summary tells you most of what you need to know at the high level.

All I'd add (and I think this may have been partly what you were asking) is that a tele-converter still allows focusing out to infinity, whereas extension tubes reduce both the minimum and maximum focus distance - hence, they're only for close-focus work.

05-02-2017, 06:59 AM   #5
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Essentially, extension tubes and reversal rings change the focal length, and allow you to focus more closely, but teleconvertors and close-up lenses optically bring the subject closer?
05-02-2017, 07:03 AM - 2 Likes   #6
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QuoteOriginally posted by timw4mail Quote
Essentially, extension tubes and reversal rings change the focal length, and allow you to focus more closely, but teleconvertors and close-up lenses optically bring the subject closer?
I'd make a distinction between teleconverters and macro teleconverters, the second kind also sporting an helicoid, thus working like a teleconverter cum variable extension tube.

Fully in, you still get infinity focus.
Fully out, you get max magnification and no infinity focus.

You have to understand that with most old lenses (50mm normal lenses anyway), the whole lens moves when focusing: it's just all the elements moving away and towards the sensor/film, not changing the relation between one and another.
Thus, there's no difference between focusing with the focus ring, adding a tube between lens and camera, freelensing away from the mount, turning the helicoid on a teleconverter (supposing you've removed its glass, as some do) etc.
05-02-2017, 10:54 AM - 2 Likes   #7
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QuoteOriginally posted by timw4mail Quote
Essentially, extension tubes and reversal rings change the focal length, and allow you to focus more closely, but teleconvertors and close-up lenses optically bring the subject closer?
Hmmm... it's a bit messier than that. All of the techniques change the "focal length" depending on how you define it.

A teleconvertor actually directly changes the focal length: a 50 mm lens with a 2X teleconvertor becomes a 100 mm lens. The composite lens has the same infinity-to-minimum focus distance range as the old 50 mm lens but the image is magnified 2X by the "reach" created by the teleconvertor.

Close-up lenses also change the focal length, slightly reducing it. The combination of the positive diopter glass in the close-up lens and the main lens forms a composite lens that has a shorter focal length than the original lens. But the combination also shifts the center of the lens further from the film or sensor so that even at the infinity setting of the original lens, the composite is more closely focused. A +1 diopter closeup lens focuses at 1 meter if the lens is set to infinity, a +2 at 1/2 meter, a +4 at 1/4 meters, etc.

Extension tubes also change the focal length somewhat. A 50 mm lens with 50 mm of extension (tubes plus the lens' helicoid length) will have the narrowness of field of view of a 100 mm lens.

Reversal rings are strange beasts if used with complex SLR lenses. With a very simple lens with only a few small elements, the forward and reversed focal lengths are the same. But reversing a retrofocus wide angle lens or a zoom might result is a longer or shorter focal length than the original lens.


Regarding "focusing more closely": extension tubes, close-up lenses, and reversal rings all involve moving the lens closer to the subject (reducing the minimum focus distance that's printed on the lens). It's only teleconvertors that let you keep your distance while magnifying the subject.

05-02-2017, 11:44 PM   #8
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Can't recall where I came across this (haven't tested it myself) but someone has noted that a prime reversed on a lens tends to give better IQ than the same prime reversed on extension tubes. Thomas Shahan has used primes reversed on teleconverters or for some of his work.
05-03-2017, 12:01 AM   #9
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QuoteOriginally posted by Thagomizer Quote
Can't recall where I came across this (haven't tested it myself) but someone has noted that a prime reversed on a lens tends to give better IQ than the same prime reversed on extension tubes. Thomas Shahan has used primes reversed on teleconverters or for some of his work.
I'd say that this way at least you'll get some SMC surfaces the correct way round... reversing a lens nullifies the advantage of our lenses having some of the best coatings in the whole industry.
05-03-2017, 04:00 AM - 4 Likes   #10
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I am surprised no one has got all the explanations right, to this point

Let's begin with a couple of simple explanations,

From the nodal point of the lens, magnification is the ratio of image distance to subject distance, and magnification equals 1:1 when the image distance and subject distance are equal, and also equal 2x the focal length of the lens.

Focal length is defined as the distance from a lens to the focusing plane with an infinitely far subject .

Given these 2 points, neither reversing rings or extension tubes alter the focal length of the lens. They simply permit you to increase the distance from the lens to the focusing plane, in order to permit the lens to focus closer to the subject, thereby increasing magnification.

Extension tubes usually allow for coupling of aperture linkages, and depending on design, for Pentax cameras may also allow for transfer of lens data for flash exposure and focus information. This is important if you want to use flash, and / or change aperture of the lens. To achieve 1:1 reproduction you need to add an extension tube equal to the lens focal length

Reversing rings are a simple mechanical mount to out the lens backwards on the camera. You may have no aperture control, and focusing might only be possible by physically moving the camera, useable magnification depends on the lens focal length, with shorter lenses offering very high magnification because they are mounted in reverse, usually at distances well in excess of their focal length.

Close up lenses, shorten your focal length, causing the lens to lose its ability to focus at infinity, but allowing reduced focusing ranges, and higher magnification. Also by reducing the lens focal length, but not changing the diameter of the lens opening, the resulting combined lens is faster, allowing for brighter view finder images.

Teleconverters, are focal length multipliers, you get more magnification by doubling focal length, but they otherwise do not change the lens's close focus ability.

It should be noted that all Adaptors, except for close up lenses result in image darkening as magnification increases, as noted above close up lenses offer brighter images due to increasing the ratio of diameter to focal length
05-03-2017, 07:44 PM - 1 Like   #11
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Goudge makes a good point overall regarding nodal point and other variables, but the last point regarding the "advantage" of close up lenses offering brighter images is pretty much like saying the light from a nearby atomic bomb detonation is brighter than anything you've seen previously - or quite obviously ever again. The compromises of sticking a simple magnifying glass in front of a good lens are much greater than the other compromises related to adapting a non-macro lens.

Every lens design responds differently, based on issues related to diaphragm placement, nodal point, other overall optical design considerations, and coatings. For some lenses, reversing is a good option, but not often. Use of a quality TC is often a good compromise, especially for standard lenses in the 50 to 85mm range. Possibly the best overall "compromise" is the extending TC, such as the Vivitar 2x macro. I have the better green numerical version (confusingly designated P/K-A R-P/K but does not have the Ricoh pin problem): optically very good as a continuously variable extender - and not bad as a TC. Short of going for a dedicated macro lens, it probably qualifies as the most versatile and simple solution to yield good results.
05-04-2017, 12:44 AM   #12
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QuoteOriginally posted by ScooterMaxi Jim Quote
Possibly the best overall "compromise" is the extending TC, such as the Vivitar 2x macro. I have the better green numerical version (confusingly designated P/K-A R-P/K but does not have the Ricoh pin problem): optically very good as a continuously variable extender - and not bad as a TC. Short of going for a dedicated macro lens, it probably qualifies as the most versatile and simple solution to yield good results.
I can vouch for that, not only because it's my main macro solution, but because I've done some tests and I can say that with a 7 elements TC like mine (a Kenko 2X), a good 50 at its sweetspot (f/5.6, goes to 11.2 with the multiplier) like the M 50/1.7 is definitely better than an upscaled image from the same lens at f/11.

On another test, the M 100/2.8 at f/5.6 with the multiplier came out to be better than the M 200/4 at f/11 and better than an upscaled image of the 100/2.8 at f/11.

So I'd say that teleconverters, even 2X ones which are often regarded as rubbish, don't necessarily deserve the bad rap they usually get. It's just that one has to know what to do and set the lenses you use with them at or near their "sweet spot".
05-04-2017, 03:39 AM   #13
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QuoteOriginally posted by ScooterMaxi Jim Quote
Goudge makes a good point overall regarding nodal point and other variables, but the last point regarding the "advantage" of close up lenses offering brighter images is pretty much like saying the light from a nearby atomic bomb detonation is brighter than anything you've seen previously - or quite obviously ever again. The compromises of sticking a simple magnifying glass in front of a good lens are much greater than the other compromises related to adapting a non-macro lens.
.
Note, I am not promoting one version over another, and all of the devices mentioned are in the majority of cases devices applied to non macro lenses, but for most people starting out, a set of close up lenses is usually the first thing they try, and a bright viewfinder is a big advantage. But it is not everything, I agree.

I highlighted this point because it is the one distinguishing factor of a close up lens compared to all other methods.

---------- Post added 05-04-2017 at 06:48 AM ----------

QuoteOriginally posted by ScooterMaxi Jim Quote
Every lens design responds differently, based on issues related to diaphragm placement, nodal point, other overall optical design considerations, and coatings. For some lenses, reversing is a good option, but not often. Use of a quality TC is often a good compromise, especially for standard lenses in the 50 to 85mm range. Possibly the best overall "compromise" is the extending TC, such as the Vivitar 2x macro. I have the better green numerical version (confusingly designated P/K-A R-P/K but does not have the Ricoh pin problem): optically very good as a continuously variable extender - and not bad as a TC. Short of going for a dedicated macro lens, it probably qualifies as the most versatile and simple solution to yield good results.
The vivitar macro TC is a good option for what it does, but these are getting somewhat rare and are not always cheap. I have one and like the versatility of the focusing helix, but note my initial intent was not to recommend any one solution but to explain the technical differences, which no one had gotten right to this point in the thread.

I have tried virtually every macro form available, including an enlarger lens mounted on a bellows, extension tubes used with and without focusing helix, macro lenses, (50, 90, and 100mm) close up lenses, and even an oddball sigma 135 mm close focus lens with 2 focusing rings, one on the whole group, and one just to move the front element for close focus.

Each has uses, and drawbacks, and if you play on the used market, macro lenses are plentiful in manual focus, but depending on what you are actually doing, a close up lens is smaller lighter and pretty good for casual use, or if you want capability just in case.
05-04-2017, 04:54 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
to explain the technical differences, which no one had gotten right to this point in the thread.
Since you are still stressing this point, would you mind telling me where did I make factual errors in my explanation?
I'm curious and always eager to learn.
05-05-2017, 07:06 AM   #15
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QuoteOriginally posted by LensBeginner Quote
Since you are still stressing this point, would you mind telling me where did I make factual errors in my explanation?
I'm curious and always eager to learn.
it was more in the comparison of the 4 options, not single comments
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