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I am adding Kenko tubes to my Nikon 50mm 1.8 D lens. I need some advice. This is my first time using extension tubes. I can't focus. I'm just getting a blurred image. Any advice would be welcome.

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    \$\begingroup\$ Thank you everybody for your wonderful advice regarding the kenko extension tubes with my 50mm. I took all the advice, took just the 13mm extension tube first to practise with and was really happy with my first attempts. If it wasn't for all the good advice I would most likely have sent them back. Thinking I didn't have the know how to use them effectively. I didn't take a tripod but took my first shots handheld with fast shutter speed and high iso. Will continue now practising all elements everyone has contributed. Thank you very much \$\endgroup\$
    – Laura
    Jun 14, 2023 at 16:45
  • \$\begingroup\$ Noting everybody else's answers, but you might also find a set of supplementary macro lenses to be useful: many autofocus cameras don't notice them. \$\endgroup\$ Jun 15, 2023 at 16:15
  • \$\begingroup\$ Thank you, Mark \$\endgroup\$
    – Laura
    Jun 15, 2023 at 17:16
  • \$\begingroup\$ Definitely Mark, I agree. I'm looking into a Nikon macro 105mm . \$\endgroup\$
    – Laura
    Jun 15, 2023 at 17:21
  • \$\begingroup\$ I think Mark meant lenses that screw onto the front of your existing camera lens like a filter does. This is an example. \$\endgroup\$
    – BobT
    Jun 15, 2023 at 19:16

4 Answers 4

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Extension tubes do two things you may not yet have noticed.

  1. They reduce the amount of light reaching the sensor*.
    This is often enough to prevent autofocus from working at all. It's usual to abandon autofocus altogether for extreme macro & do everything manually.
    *This is because you have a much smaller area to capture light from, not because the tubes physically restrict light in any way.

  2. They bring the farthest focus point much closer. This depends on how much extension you have & how long your lens is initially. Longer lenses don't suffer as much as normal to short lenses for this, but infinity is lost with any extension.
    With a standard set of extension tubes, 12mm, 20mm, 36mm, then on a 50mm lens, if you put all 68mm of tubes on - your farthest focus is actually so close it's inside the lens!

To get used to how this all works, start with one of the shorter tubes. This won't give you as much magnification, but as you gradually step up the tube section lengths, you will start to get a feel for your maximum focus length.
You'll also start to notice that the focus ring itself doesn't really seem to do much any more.

With 36mm of tube on a 50mm lens, your focus will be at about 2½", 60mm. Your minimum to maximum focus distance using the ring is probably less than 3mm. You've reached the point where it's almost become pointless. As you breathe things will go in & out of focus.

This is where macro starts to become as much art as science. You either practise at framing rapidly if your subjects are likely to get spooked & fly away, or you do still life and buy a tripod ;)
If you're trying to capture insects that will fly away, you would actually fare better with a longer lens, as you don't need to get so close.

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  • \$\begingroup\$ Than you very much for your generous guidance. I shall practise with the shorter tube first. \$\endgroup\$
    – Laura
    Jun 14, 2023 at 8:46
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When you add extension tubes, your camera become myopic, it will no longer focus to infinity (the ring shifts the focus range towards you). The thicker the ring or the shorter the lens, the more pronounced the effect. With the same 21mm ring on my 17-70 lens, at 70mm infinity focus is brought to 15cm while at 17mm it must be somewhere inside the lens.

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  • \$\begingroup\$ Thank you very much for this explanation. I now understand why my camera lens is behaving as you described. \$\endgroup\$
    – Laura
    Jun 14, 2023 at 8:48
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What everyone else said... Try looking at something relatively close (flowers on a table, etc.) and focus by moving closer or further away. You'll find that the focusing ring may have little effect, especially with longer extensions. Another odd effect is that when used with a zoom lens the zoom will change focus as well.

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    \$\begingroup\$ I use extension tubes on zoom lenses and find the zoom is a great way to focus. Very roughly speaking, the distance from the lens to the object sets the magnification and the zoom focuses it. If you don't choose the right distance you can't focus at all. \$\endgroup\$ Jun 13, 2023 at 21:04
  • \$\begingroup\$ Thank you for this tip. I also have two zoom lens and will try the tubes on them to see the effect. \$\endgroup\$
    – Laura
    Jun 14, 2023 at 8:49
  • \$\begingroup\$ Thank you, Bob T. I did as you suggested and moved in and out with the camera body for focusing. Good advice. \$\endgroup\$
    – Laura
    Jun 15, 2023 at 17:19
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Best to place the camera with tubes mounted super close to the subject and then slowly move the camera, further and further away from the subject. In other words, achieve sharp focus by camera movement. Best it camera is on a tripod. Once focus is achieved you can touch up with the camera' focusing knob.

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  • \$\begingroup\$ Thank you, Alan. I followed your advice and achieved focus by moving in and out from the subject. Previously, I've only used zoom lens. The 50mm was my first prime lens. And the extension tubes another first fir me. Loving the learning curve and images I'm capturing of flowers. \$\endgroup\$
    – Laura
    Jun 15, 2023 at 8:31

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