Use of extension tubes instead of macro lenses

k.udhay

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Hi,

I just got to know that extension tubes serve as a less expensive solution to shoot images of closer detail. But it is also said that macro lenses, though expensive, are much better in image quality. Can you pl. share some images to show what kind of problems we face using extension tubes? Kindly share the reasons as well. Thanks.
 

KenC

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AFAIK, extension tubes do not provide lower IQ than macro lenses, at least not if you use a good lens on the end of the tubes, and I never noticed any difference. The problem with extension tubes, especially in the field, is that you have a narrow focus range and magnification, so every time you want to shoot something more than a little bit closer or further away, you need to change the tubes.
 
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k.udhay

k.udhay

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Thanks KenC. I also read that extension tube reduces amount of light. Is that true? If so, pl explain the reason.
 

Judobreaker

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The IQ thing is because of the magnification.
You're also magnifying the lens errors so using a less well designed lens with tubes gets less IQ than a macro lens.
Macro lenses are designed well because of the magnification. If you'd use a well designed lens with tubes there's no problems though, the tubes have nothing to do with IQ.
 

Gavjenks

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The main issue is that macro lenses are much faster/brighter at the same magnification.

IQ may legitimately be an issue, too. When you just put a tube on, you're expanding the image circle beyond its design parameters. However, many normal lenses are already made near the technical limits they can be (nicer normal lenses), and macro couldn't be made all that much better. So I doubt you lose much IQ if you're using some sort of $800 normal prime lens. You probably will lose IQ though if using a kit lens at 50mm.
 

Buckster

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While you won't get all the benefits of an $800 dedicated 1:1 macro lens with a $200 set of electronic Kenko tubes or a $15 set of non-electronic basic tubes, they are a VERY good value for the money if you want to get into macro and are on a budget. I used them for years with very good results before I finally got a real, dedicated 1:1 macro lens.
 

Gavjenks

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I don't know about macro lenses, but tubes suffer from a fierce lack of DoF.
That's an optical property of magnification / distance.

You will get the same narrowing DOF effect whether you use macro lenses, tubes, bellows, anything to magnify.
 

Nat.

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I've never had the fortune to use a dedicated macro lens. Is it the same reason that decreases the DoF for telephoto lenses?
 

Overread

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Also don't forget that you can't just use smaller and smaller apertures to increase the depth of field. The effect of diffraction will start to take effect around after f8 to f10 (shifts depending on the lens). This means that the overall sharpness decreases, remaining generally usable up to around f13 to f16 or so before sharpness starts to drop off more significantly.

The actual point where the loss of sharpness is too much compared to the gain in depth of field depends on:
a) The lens itself

b) The size of photo that the photographer needs; depending on the output use it will vary; for example online display is very forgiving especially once resized and sharpened properly.

c) The photographers personal standards


Also be aware that most modern macro lenses reduce the effective aperture as they focus closer, so whilst the lens might be listed and might show f2.8 as the maximum aperture, the actual aperture might be closer to f5.6 (this shift remains constant through the aperture range, so the smaller apertures are also affected).
Extension tubes and other methods of focusing closer can also have a similar effect upon the effective aperture.

Nikon cameras do report this effective aperture change on macro lenses; which is why Nikon lenses can't shoot at f2.8 and Canon ones can (remembering of course that the actual aperture in both cases is the same its just a difference in how the camera is reporting the aperture to the user).
 

480sparky

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..........Also be aware that most modern macro lenses reduce the effective aperture as they focus closer, so whilst the lens might be listed and might show f2.8 as the maximum aperture, the actual aperture might be closer to f5.6 (this shift remains constant through the aperture range, so the smaller apertures are also affected).
Extension tubes and other methods of focusing closer can also have a similar effect upon the effective aperture.

Nikon cameras do report this effective aperture change on macro lenses; which is why Nikon lenses can't shoot at f2.8 and Canon ones can (remembering of course that the actual aperture in both cases is the same its just a difference in how the camera is reporting the aperture to the user).

Mine doesn't to that.... focus to minimum and it's still 2.8.
 

Buckster

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When I got my Sigma 180mm f/3.5 EX DG IF HSM APO Macro Lens in 2008, I did extensive testing to figure out where it would give me the very best sharpness and image quality for my macros, regardless of DOF.

That optimum aperture turned out to be f/22 for that particular lens. That's now my go-to aperture to use whenever I'm shooting macros with that lens.
 

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