Extension Tubes for Macro Photography

I’ve found that I don’t do much macro photography, so I no longer own a dedicated macro lens, however once in a while, I do want to get closer to a small subject than my regular lenses will allow. My solution is to use extension tubes, a much less expensive / lighter weight option to have in the camera bag compared to owning / carrying a macro lens. Extension tubes fit between your lens and camera body, and thus extend the lens away from the body, allowing for closer focusing than the same lens normally would on its own. Extension tubes do not contain any optics, so unlike teleconverters, they do not change your focal length nor cause image quality loss in quite the same way that a teleconverter might. While the tubes themselves do not block any light, just the act of moving the lens away from the camera causes a dimming of the image since you can imagine the same amount of light getting spread out over a larger area. If you are using a DSLR, you will see a dimmer than normal viewfinder image when using extension tubes but with mirrorless cameras, you generally won’t notice at all. Note that I wrote about extension tubes back when we first got the Fujifilm ones into stock. Here is a link to our old blog (opens in a new window), so you can see what they look like with some examples of how the tubes can affect the closest focus of a lens:

http://beauphoto.blogspot.com/2014/12/arrived-fujifilm-extension-tubes.html

You might want to experiment with one of your lenses off the camera in a darker environment. Point the lens at a light source, like a small flashlight, and project the light’s image onto a white card. As you get closer to the bulb with the lens, you’ll need to move the card  further away from the back of the lens to make the projected image sharp. As you get further away with the white card, you can imagine the projected light is spread over a larger and larger area. You should be able to see the projected image on the card getting dimmer when you are closer to the light with the lens, and thus farther from the back of the lens with the white card in order to focus the light.

All the photos in this post were taken in the desert plant section of the UBC Botanical Gardens. Click on any of the below images to see a larger version (opens in a new window), however note that while I used one or more extension tubes on every image here, I do not exactly recall for every shot exactly which tubes were used. Note that all the photos were handheld too and almost always, I shot multiple frames, since even the slightest bit of back and forth movement between focusing and shooting can bring the plane of focus away from where I wanted it…

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/8 at 1/900

Extension tubes are generally named based on the millimetres of extension they provide. On my Fujifilm system, the two available ones are an 11mm and a 16mm tube, and they are designated MC-EX11 and MX-EX16 respectively and sell for $129.95 each. We do keep them in stock here at Beau Photo, as well as the extension tubes for the GFX system in 18mm and 45mm sizes. The tubes can be used singly or stacked together. One very important thing to note is that any given extension tube will have a completely different effect when used on different lenses, or on different focal lengths on a zoom lens. For example, put an 11mm tube on a telephoto lens, and the improvement in close focus will be minimal. Put that same 11mm tube on an wide-engle lens, and you might not be able to focus until your subject is practically touching the front element! In fact, with really short focal length lenses, if you use too much extension you’ll never be able get your subject sharp since the effective point of focus might actually be behind your front element!

Billy Luong from Fujifilm Canada was kind enough to provide some updated extension tube technical sheets, one for the X-System and one for the GFX, which show all of their lenses (including announced but not yet shipping ones) and how extension tubes affect their closest focus and magnification ratios. Note that the charts do not show any info for using both tubes stacked, even though it is very possible to do so with many lenses. Links will open a PDF in a new window…

X System Lens + Extension Tube Chart

GFX System Lens + Extension Tube Chart

As an example, if you look at the behaviour of the upcoming XF 16-80mm f/4 zoom, shown on the first X System chart, it provides a clue on how tubes can vary wildly in their effect based on focal length. Before I delve into that, let me explain the  “Max Magnification” column. When the number in that column is 1.00, that means the image is reproduced “life-size” on the camera’s sensor. So, the image of a one cm wide flower projected on the sensor will be one cm wide on the sensor as well. A number of 0.5 means half life-size, so the image of that one cm flower will only be 5mm wide on the sensor. Most dedicated macro lenses will max out at either half life size, like the Fujinon XF 60mm f/2.4 Macro, or at full life-size like the Fujinon XF 80mm f/2.8R OIS WR Macro. With both tubes added to the XF 60mm, I believe one can get very close to a 1.0 full life-size magnification. Those two Fujinon macro lenses can also be used for regular photography since they focus to infinity, but there are some very specialized lenses from other manufacturers, such as the Canon MP-E 65mm f/2.8 1-5x Macro which will not focus to infinity at all and is totally dedicated to macro work, but that lens can achieve a whopping 5x magnification ratio without adding any extension tubes. The MP-E 65mm is basically designed with a big helicoid extension tube built right in.

The yellow flower in the shot below was very small, maybe only 4 or 5mm across, and I did use both tubes on my 50mm for that photo…

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + 11mm & 16mm tubes, ISO 400, f/8 at 1/750

Looking at that 16-80mm lens then, at the 16mm wide end, it only achieves a magnification of 0.06x of life-size, however with the smaller 11mm tube, the magnification leaps up to 0.74x, albeit at a working distance of only 0.3mm! So to be sharp, your subject will essentially need to be touching the front element! That could be interesting if you are trying to photograph a small bug crawling on the front element (I’ll have to try that!), but rather useless for anything else. The column for the 16mm tubes is grayed out since the point of focus would be inside the lens with anything more than 11mm of extension.

However, now look at the behaviour at the 80mm end. Maximum magnification is 0.25 (1/4 life-size) which is quite decent for a zoom but when you add the 11mm tube, you get 0.41x life-size at a useful working distance of 9.4cm. With the 16mm tube, you get nearly half life-size at a still manageable distance of 6.9 cm from the front element.

One thing that can throw people off the first time they try extension tubes, is getting the subject in focus at all. This is because adding a tube to a lens will severely restrict the useable range of focus. Here is a hypothetical example when using an extension tube with a lens that focuses from infinity down to 25cm. With the lens focused to infinity, the subject might actually be sharp at 12 cm when using the tube, and at the lens’ closest focus distance, it might be sharp at 9cm. So, instead of having a range from infinity down to 25cm for the lens by itself  with no tube, the range in this example would be 12cm down to 9cm with a tube. Again, theses are purely hypothetical numbers in this example, just to make a point. Therefore when using an extension tube, if you are a little too close or a little to far from the subject, you’ll never be able to manually focus, nor will the camera’s AF ever be able find focus – it will just hunt. My technique is to manually rack the lens’ focus to about midway between infinity and closest focus, then look through the viewfinder and start approaching my subject, getting closer and closer until suddenly it comes into focus. Then I know I have a little bit of framing leeway, I’ll move back and forth, then activate the AF on the camera for it to fine tune. If I am too far away for my ideal framing, I’ll switch to a longer tube, or stack both tubes, and if I am too close, I’ll use less extension.

If you think about the very limited range of focus you get with any given size tube, it becomes apparent why it is actually very useful to have more than one tube on hand. This is presumably why many third party extension tube sets, like those from Kenko, come with a total of three tubes, which can be used singly or in any combination. Note that the more extension you use, the narrower the effective range of focus of your lens becomes too.

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + 11mm & 16mm tubes, ISO 400, f/8 at 1/1250

Finally, note that even though there are no optics in extension tubes, and you might think that image quality won’t be negatively affected, some lenses do behave better than others when extended. The more extension you use, the larger you are magnifying the projected image circle on the sensor, and the more loss of a lens’ ultimate resolution you will get. For an extremely sharp lens, like the XF 50mm f/2 that I used for these shots, the quality loss is relatively minimal even with two extension tubes, but for a lens that is not all that sharp to begin with, adding a lot of extension could yield mushy results. Also not that most dedicated macro lenses have a flat plane of focus, whereas many others have some curvature, which often doesn’t matter much at normally focusing distances. However as you add extension and thus magnification, and as your depth of field also then becomes narrower, this curvature can start to effect image quality… at least that’s my theory and what seems to happen. I’ll admit that, strictly speaking, I am not entirely sure if that explains why some lenses with too much extension start looking rather bad at an image’s periphery or if there is some other effect at play? The best thing to do, if you extension tubes, is just to experiment with your lenses and see which one works the best for close “tubed” macro work…

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/8 at 1/500

Lastly, note that the closer you focus, the narrower your depth of field becomes at any given aperture. Even f/11 will often only give you a mere sliver of depth of field (DOF). Shooting macros can be a challenge since you are often fighting for DOF, but stopping a lens down too far to try and increase DOF can compromise sharpness at the plane of focus due to diffraction. For the Fujifilm system, optimal sharpness is reached at roughly f/8 and stopping down too much further will actually yield a slightly softer image at the plane of focus, although more of the image will seem sharp. Personally, I usually try to shoot in such a way that my plane of focus intersects several items of interest in the shot, to make it look like more of the shot is in focus, and will often keep my aperture at f/8 or less to ensure that what is in focus is really sharp.

So, hopefully you found this brief tutorial helpful. Feel free to contact me if you have any questions. For now, here are a few more shots to look at…

 

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/10 at 1/680

 

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/8 at 1/480

 

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/10 at 1/640

 

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + extension tube(s), ISO 400, f/8 at 1/500

 

Fujifilm X-Pro2 with Fujinon XF 50mm f/2R WR + 11mm & 16mm tubes, ISO 400, f/8 at 1/500

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