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Thread: Extension tubes

  1. #1

    Extension tubes

    Hi!
    I was wondering, how much extension should I use to gain a magnification boost of 1:1 on an APS-C camera.
    I mean if a have (for example) a 50mm lens should I use 50 or 80mm of extension to gain a magnification boost of 1:1. I already learned, that I should use 50mm of extension to get this boost on a FullFrame camera but is it the same on a cropped body?

    Anyway I would like to ask you that the extension tubes or close up lenses are better if i'm ONLY care about the image quality (and money to some degree of course).

    Thank you very much for your answer.

    PS.: This is my first post on CIC, so i hope that post is correct.

  2. #2
    Shadowman's Avatar
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    Re: Extension tubes

    Extension tubes use a ring, lens stacking and lens reversing add mm in the form of focal length.

    http://www.earthboundlight.com/photo...s-bellows.html

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    Re: Extension tubes

    You probably do not need 50mm extension with a 50mm lens because the lens itself has the ability to focus some of the way.
    Double extension or 1:1 is that and depends of the lens not the 'crop factor' which just gives you a smaller subject area.
    I think the expression 'double extension' dates from when cameras had bellows and the lens was moved out on a rack and one achieved 1:1 when the lens was racked out to twice what was needed to focus at infinity.
    My 'jack-hammer' photo illustrates what you can do with a longer lens which can help with lighting and other reasons by keeping you away from the subject. Here using a 135mm lens.
    Extension tubes

    EDIT A note of caution ... I assume you have a 'modern' 50mm lens which doesn't have an aperture ring and very likely if you buy the 'cheap' extension tube set it will have no connection to the cameras and defaults to wide open ... good for focusing but undesirable for the actual photo.
    I only have plain 'cheap' tubes so work with my legacy lenses for this stuff. Without aperture control you will need the more [very?] expensive tubes with electric coupling to enable the camera to close the aperture .... because of the lens itself being able to focus it is likely that the shorter 'auto-tubes' would do the job for you but I have no experience of them.
    I got a spam message from Amazon today which listed a Kenko set for a Nikon at US$198 but shorter and cheaper ones are around

    Second edit ... the gear in my photo hasn't been used for real in ages becuase I have a long zoom and most of what I want to shoot can be done with a 2 or 4 dioptre close-up lens just using the narrow angle of view of the long zoom to achieve tight framing. Here a shot with my 430mm lens of my bridge camera with a pair of 2 dioptre CU lenses stacked.
    Extension tubes
    Note this is not double extension or 1:1 but just tight framing which is the end result one is after
    Last edited by jcuknz; 20th June 2013 at 11:49 PM.

  4. #4
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    Re: Extension tubes

    I found this tutorial to be useful in using my extension tubes. Cambridge in Colour Tutorial. It has a calculator where you can enter the native magnification of your 50mm lens (found in your specs) and it will give you the magnification and focusing distance.

    I like my extension tubes way better than the cheap closeup lenses that I had. Of course this is in part because I bought the Kenko extension tubes that provide auto focus capability and full capability using AV. I tried some cheap tubes that did not have the electronics and they were way too much trouble to use.

  5. #5
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    Re: Extension tubes

    I was wondering, how much extension should I use to gain a magnification boost of 1:1 on an APS-C camera.
    Just to clarify: "1:1" does not refer to a boost in magnification. The ratio refers to the amount of magnification, either native (before adding tubes) or final. 1:1 means that the image size on the sensor (any sensor, crop or FF) is life size. At 1:1, a 1 cm object casts a 1cm image on the sensor (regardless of sensor size).

    Terri's answer is the right one: you can't determine the final magnification unless you know the native magnification of the lens. Look that up for your lens, and then use the calculator that Terri suggests.

    Another option is to buy a set, like the Kenko set, which gives you three tubes of different lengths, which can be stacked. This gives you a range of 12mm to 68mm of extension. You can then just add or take away tubes to get the amount of magnification you want.
    Last edited by DanK; 21st June 2013 at 03:51 PM.

  6. #6

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    Re: Extension tubes

    The function of the extension tube is to move the lens further from the focal plane, ie the sensor. The lens moves away from the sensor as you focus closer, hence why some lenses extend out as you focus. All the extension ring does is add to that extension. So "in theory" a 50mm extension on a 50mm lens will give you 1: 1 magnification and the ability to focus. However on a crop sensor it makes no difference to the ability to focus, but of course the magnification is greater because of the crop sensor.

    As mentioned above the lens retains some focus ability, and so with tube fitted there is a range over which it may focus.

    And the Kenko sets have a lot of users, no glass so no worry about inferior optics, and a set is a lot cheaper than a single OEM tube, and much more flexible as you can stack them.

  7. #7

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    Re: Extension tubes

    What are your subjects and what is the current minimum focusing distance of your lens?

    Extension tubes will allow you to move closer to the subject; hence a larger image. But they aren't any good if you are physically prevented from moving closer.

    In that case, a lens converter (ie 1.4x) might be the way to go; providing it is suitable for your lens.

  8. #8
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    Re: Extension tubes

    [QUOTE=SolidMetal;319733]

    Anyway I would like to ask you that the extension tubes or close up lenses are better if I ONLY care about the image quality (and money to some degree of course).
    [/QUOTE

    1) Extension tubes only have air in them.

    2) Extenders have optics (lenses).

    3) Extension tubes will not degrade the image quality, but an extender will.

    4) An extender is much more expensive that extension tubes - by about a factor of 10.

    5) The best buy would be a set of three Kenko tubes - I use mine extensively.

    Glenn

  9. #9

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    Re: Extension tubes

    I don't know whether any clarification of the real issues with extension tubes or closeup attachment lenses would ease or aggravate the confusion.

    As has been mentioned before here, tubes have only air in them, and with the notion that they would thus not degrade image quality, optical performance.

    WRONG! They will, much in a similar fashion as front attachments, change the properties of the optics and throw the optical system into a state in which it was not conceived to work when it was calculated and engineered.

    A lens is always a compromise design, and all lenses do their best at the distances that they are made for. In modern cameras, some error properties are supposed to be corrected by software, but basically, all lenses work best at the distances for which they were calculated. When you extend a modern lens from the sensor plane, you do indeed introduce refraction errors that they are not corrected for, regardless of the fact that you are only entering more air into the path of the rays behind it. What happens in front of it is that you make its angle more narrow and the light path through the lens goes through different parts of its elements, using only central parts of the front components. In fact, it becomes a totally different optical system, performing differently.

    That is the reason why at very short distances we prefer to turn the lens end for end, making the optical path through it closer to what it was designed for.

    So extension tubes indeed change the properties of the lens and may degrade image quality just as much as a front attachment lens could.

    Then we may have a look at the closeup lenses, which indeed have some very desirable properties.

    When you put a lens in front of your glass, you only introduce those errors inherent in that lens. I.e. if your attached lens has chromatic aberration, it will be present in the light path of the system, and other errors as curvature of field and coma are also introduced to a degree determined by the magnitude of those errors in the attached lens.

    Most simple closeup lenses are just a simple meniscus lens, that introduces all of those errors to a degree determined by their refractive power. Hence a high diopter value would introduce more of all errors than a low diopter value. A one diopter lens will hardly introduce any noticeable error at all, and if you have a telezoom lens that won't focus closer than about a metre, a one diopter lens is a very good way to cover the distances from a metre down to a half metre. There will be no noticeable image degradation, and you can use the lens closer than without it with about linearly double size of objects photographed.

    Higher diopter values introduce more of the errors, and the most noticeable one is chromatic aberration, causing loss of sharpness as well as colour fringing. This can be partially cured with software in pp, but a better option is to use an achromatic lens, which will only introduce coma and curvature of field, but not chromatic aberration, so it will render the images crisper, with better sharpness. For most of our subjects in nature, curvature of field is not an issue, it only is important when we wish to reproduce linear things as postage stamps and the like. In fact, a telezoom lens with an achromatic closeup lens may render closeups of insects and flowers just as sharp as a macro lens would, provided the lens itself is of good quality. However, even a prime lens with the closeup attachment would not reproduce a postage stamp well, due to curvature of field and distortion, issues that are unnoticed in nature shots.

    When it comes to focusing with "phase detection" AF systems, the attached lens will make no difference for the focusing system, so it will work as designed, although the distances are shorter. Also image stabilisation will work when a closeup lens is mounted. There will be no difference in functions. On the other hand, an extension tube will throw off both AF and stabilisation. None of those will work as designed in a camera with "phase detection" AF system when an extension tube is mounted between lens and body.

    The range within which focusing will work is determined by the attachment diopter strength and the original close distance of the lens, which corresponds to a diopter value. A telephoto zoom that focuses to 1,1 m has a dioptric power of +1 at that distance (Nikkor 55-200) and will add between 0 and +1 diopters to the diopters of the attached lens by focusing. A superzoom lens that focuses to 45 cm (Nikkor 18-105) will have a dioptric power of +3 at that distance, hence it can add up to +3 diopters to the attachment that is put in front. This also tells us that it is meaningless to use a power of less than +3 on that particular lens, and with that refractive power an achromatic lens is required to render a sharp image.

    To calculate the refractive power of the close distance of your lens, divide one metre by the distance between the front of the lens at close distance setting when it is in focus, i.e. when the subject is its close distance away from the sensor plane. Hence the close distance that is relevant is the one from the front of the lens and the close distance for the lens is calculated to be from the sensor plane. For the kit zoom that focuses to about 30 cm, about 10 cm should be subtracted from those 30 to get the dioptric power of focusing, hence it is more than +4 and more akin to +5 diopters. For the 18-55 kit lens it does not really make sense to use a closeup lens, but if you want one, the one that will get you closer is +5 diopters, and it must be achromatic, otherwise it cannot render any sharp image at all.

    And if you want really small objects large on your sensor, that same kit lens can serve you well with only one simple accessory, a reversal ring. You mount the lens reversed, end for end, with its front toward the camera, with the reversal ring screwed into the filter thread. You find focus about five centimetres (2") from the lens, and you can adjust focus distance and magnification with the zoom ring. Stopping down the lens in reverse position is a special raindance, but it can be done.

    (In the text, I have used "phase detection" with citation marks, to indicate the most common AF method in DSLR cameras, often denoted "PDAF". The citation marks are there because the system has nothing whatsoever to do with phase detection, phase of optical waves is something completely different from what this focusing system is designed to work upon. The "PDAF" system is a contrast detecting system that uses double images, in a similar fashion as an optical see-through distance meter. Iterating contrast detection systems are not thrown off by altering the distance between camera body and lens.)
    Last edited by Inkanyezi; 22nd June 2013 at 08:57 AM.

  10. #10

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    Re: Extension tubes

    Thankyou Urban for that and the person who gave up CU lens for tubes I wonder at what strength they were and how they were made. Also what focal length lens was used. It is pretty pointless using the CU lens on a short lens but when you combine the narrow angle of view of the longer lens and use the CU lens to overcome the inability of the camera lens to focus close you start to cook with gas . The camera in my photo could only focus to 2m at full x12 zoom or 430mm. Neither can the later model which I now have.

    The CU lens is a boon to the bridge camera user and because of the cost less viable for the DSLR user with large diameter lens. ie a 77mm mount lens is about $145 whereas a 55mm mount only $26 Both B+H from B&H.

    I repeat the final; sentance of my earlier post [ in a different way] Most people believe they need to get close, to get magnification by being close, as indeed I used to think, but the bridge camera taught me that there is another way and although one is using a long lens there is no difference in depth of field and several advantages of being back off the subject. These days many SLR owners have longer lens when in my SLR days all I had was a 50mm so picked up tubes when they were cheap at sales .... on one occasion I had one set on the 50mm and the other on the camera and used a plastic drainpipe to hold them more or less in line. The subject was part of a 16mm movie frame which featured my son and HM the Queen*. So it is worthwhile considering a good quality moderate lens. With a 430mm AoV lens I find the 2 dioptre good but since getting MFT all I have is 280mm so have a B+H 4 dioptre on its way to me. I have played with more powerful CU lens but the results were drack Except for a 7 dioptre lens made for a Polaroid 5x4 copy camera set-up presumably designed for flat to flat use.

    This is the link to auto extension tubes on Amazon
    http://www.amazon.com/s/ref=nb_sb_no...xtension+tubes
    and this is a search for CU lens at B&H
    http://www.bhphotovideo.com/c/search...=&usedSearch=1
    Sorry that is used department new is this
    http://www.bhphotovideo.com/c/search...o%3C%2FSPAN%3E

    Enjoy

    *I was in the cellar with the film backlit in a projector gate I had and cellar lights turned off.
    Last edited by jcuknz; 22nd June 2013 at 10:23 AM.

  11. #11

    Re: Extension tubes

    Thank you for the answers! I think I got the answer, and gain even more information about the topic.

    And yes, i meant 1,0X boost of magnification, not 1:1.

    About diopters: Does it degrade the corner shapness significantly?

  12. #12

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    Re: Extension tubes

    Quote Originally Posted by SolidMetal View Post
    About diopters: Does it degrade the corner shapness significantly?
    There isn't a simple answer, unless you are reproducing flat objects at right angle. In that case, there is no corner sharpness with a closeup lens attached, and the reason is that its field of sharpness is not flat.

    Real world images is another thing. At close distances, depth of field is often negligible, and curvature of field can sometimes make corners sharper than they would be with a perfect lens or a macro lens. The macro lens is for flat field reproduction and will reproduce postage stamps and similar objects very well. When you shoot insects or flowers, you wouldn't be very interested in sharpness in the corners of the image, as your main subject mostly covers only part of the image, and the depth of field never will cover the entire scene.

    So using closeup lenses is not a significant tradeoff for photographing nature objects as flowers, insects or small animals. If you use an achromatic lens, sharpness may be similar to a macro lens. The curvature of field may work for you or against you, depending on subject. There is sharpness in the corners, but probably not at the same distance as in the centre.

  13. #13
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    Re: Extension tubes

    I sometimes use a Raynox DCR-250 - a 3-element close-up lens. A good feature is it's universal mount (52-67mm).

    It is 8-diopter and there is also a 4.8-diopter version DCR-150.

    For more info: http://raynox.co.jp/english/digital/egdigital.html

    Very good quality images, BTW.

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    Re: Extension tubes

    I once briefly saw a Raynox DCR250 and am left with a nagging feeling that it only works properly with lenses of a relatively small diameter ... on bigger lenses there would be a mis-match resulting in light loss.

    BTW not mentioned I think so far is the light loss factor when using extension tubes, similar to when using tele-converters, which is negligable when using a CU lens. With a good match between camera and tele-adaptor as with my FZ50 and Raynox 2020 or TCON x1.7 there is about a third of a stop loss but with a mis-match such as my TCON x1.7 on my Lumix 14-140 I loose about 1.6 stops of light. With TTL AE the loss is not a serious factor except that with a slow lens the resultant loss of light may affect or stop PDAF workings .... thankyou Urban for that abreviation

  15. #15
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    Re: Extension tubes

    Quote Originally Posted by jcuknz View Post
    I once briefly saw a Raynox DCR250 and am left with a nagging feeling that it only works properly with lenses of a relatively small diameter ... on bigger lenses there would be a mis-match resulting in light loss.
    Interesting thought. Depends what is meant by "works properly" but I tested it just now on a Sigma 70mm EX DG (full frame) f/2.8 macro lens attached to a Sigma SD9 DSLR (crop factor 1.7). At both f/8 and f/16 there was approx 1/2 stop light loss when the DCR-250 was put on the lens.

    This is the lens and camera on which I use the DCR-250 to get extreme close-ups of watch parts.

  16. #16

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    Re: Extension tubes

    The PDAF sensors are a bit strange, but you might understand them easier if you have ever worked with old SLR cameras with their split image and microprism spots. PDAF reception of the image in fact works exactly as the split prism in the centre of many focusing screens. One half of that split prism is pointed at one side of the lens, the other half is pointed at the other side of the lens. To work properly, the lens must have a sufficiently large exit pupil.

    The image that is received by one half thus is taken from the right side, and the other half looks at the left side. Effectively, the PDAF sensor is squint and cannot see the centre of the lens, but half of it sees one side, and half of it the other. The resulting images will coincide when in focus but they will be shifted when out of focus. As anyone technically minded might understand, the PDAF system has nothing whatsoever to do with phase detection. They just took the name because it is good sales blurb. Sounds better than "squint image autofocus" - SIAF.

    It is not light loss that causes this system to stop working, but it is its squint. When the lens is stopped down, the diaphragm shrinks its exit pupil, so that the squint AF sensor will not see light, but only the backside of the diaphragm blades. Similarly, when using extensions to put the lens further away, the exit pupil will be too far away from the squint sensor, which will again only see the sides of the lens, not the light that enters. A similar thing happens when using a tele extender, the exit pupil moves away and becomes smaller, so the PDAF will not have images to work upon. The loss of AF images first affects those that are away from the centre of the image, as those will lose one of the images, but not the other, at an earlier stage. The centre one might still work when the other sensors cannot.

    "Light loss" with extension tubes hence is due to the simple optical law; when extending to twice the focal length with an extension tube the same length as the focal length, two stops are lost. For the light meter, this is not a problem, as it works just as before, only with less light and provides longer times, due to the smaller relative aperture.

    A closeup lens is a different thing altogether. Effectively, it decreases the focal length of the system, without changing its exit pupil. When you put a +1 diopter closeup lens on a 50 mm prime lens, you change its diopter value from +20 ti +21, in fact effectively increasing its relative aperture somewhat. But as it is still the same distance from the sensor, it is not focused at infinity, but at a closer distance, so effectively, there is no change in the amount of light that enters it. There is no "light loss" other than the diminutive loss of transmission through the glass.

    The Raynox attachments are a bit different, and they can throw off meter readings, but they cause no light loss.

    When the Raynox is put on a wide angle lens its entrance pupil will be far behind the attachment, and the Raynox then causes vignetting. The light meter is affected when measuring integrated, as the outer parts of the image are cut off and there is only a circular image in the centre. With an integrated reading, this will cause over-exposure of the image.

    When the Raynox is put on a large entrance pupil lens, it will cut off the peripheral rays, effectively making the aperture smaller. If the focal length is sufficiently long, it will not cause vignetting, but it will shring the entrance pupil, and accordingly also the exit pupil. PDAF will not work if the resulting exit pupil aperture is too small. The light meter will also be thrown off totally, as it will have a smaller aperture than the one that it is programmed for when it measures wide open. Stopped down metering will work with those cameras that can measure stopped down.

    But the Raynox does not cause light loss. Only when it cuts off the entrance pupil of the prime lens will it cut off light from the outer part of the lens, which affects the light meter, so that it will assume that for example f/2.8 is the measured aperture, while in fact it might be f/8. The effective aperture is the one you see from front as the new entrance pupil with the lens attached, and the exit pupil will become smaller accordingly.

    PDAF focusing systems mostly make no double-check that focus is achieved, but they generally analyse the two images of the PDAF sensor and rack the lens to the calculated position according to the firmware algorithm. There's many a slip twixt the cup and the lip, and PDAF systems often fail. Roger Cicala has described some of the issues on his blog at LensRentals: http://www.lensrentals.com/blog/2012...-canon-cameras

    So for closeup systems, PDAF is out, but iterating contrast detecting systems might work. Mostly though, we focus by moving the whole camera system, or the subject itself.

  17. #17

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    Re: Extension tubes

    Urban ..So for closeup systems, PDAF is out, but iterating contrast detecting systems might work. Mostly though, we focus by moving the whole camera system, or the subject itself.

    I can assure you that 'CDAF' systems work fine with CU lenses. I do it all the time
    Though how satisfactory it is depends on the size of what I call the 'target area' .... some cameras such as the Panasonic G3 have the ability to use a very small TA which helps in getting the focus one wants. Others are pretty large and hopeless and pre-setting focus and moving camera or subject is needed as you suggest. What we need is an AF system with a connection to the human brain But the G3 is the best I have encountered to date.

    I think in much of what you are writing that we are looking into the same tunnel but from different ends and reaching different conclusions.
    Last edited by jcuknz; 23rd June 2013 at 09:24 PM.

  18. #18

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    Re: Extension tubes

    I think i made it rather clear, that a closeup lens in front of your lens will not change its behavior substantially, but only affect the region within which sharpness is achieved. With a closeup lens mounted, both PDAF and contrast detecting systems work as designed, so there is no problem with any of them to fine tune focusing as long as you are within the possible span of distances that your attached closeup lens will allow. This is the main reason why I regard closeup lenses as more easily managed than a macro lens, even though the macro will include many more possible distances, as its range goes all the way from infinity to very close.

    When instead using a closeup lens, the range of focusing remains the same for the lens where you attach it, so it does not have the large span where to hunt for focus. It will hunt and fail, if you are outside the boundaries set by the system, but when you are within the possible range, it will work fast and reliably. A telezoom with a closeup lens and a piece of string with knots for the far and close distance is a good tool for the flower and bug photographer. In most circumstances, you'll find focus quicker and more reliably for close objects than with a macro lens.

  19. #19

    Re: Extension tubes

    Best of the macro shooting and save your the money. High quality and magnification more than real macro lens. Please click to: http://www.MacroExtensionTube.com/ for products detail and view the macro gallery.
    Attached Images Attached Images

  20. #20

    Re: Extension tubes

    Good to have found this thread I managed to buy a Sigma 105mm f/2.8 rather cheap off my brothers friend, whilst I love this lens one to two things confuse me.

    I've been told 1:1 is true macro but when I use this I don't always seem to be able to fit all the subject in the frame, do I need to use a different setting than 1:1 or would I fare better with some extension tubes, also if I use say 1:2 is this still classed as a macro photo . I tend to use it mostly for flower pictures and seed heads etc.

    New to photography so everything is a challenge at the moment and sorry in advance for stupid questions.

    KarenO.

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