Macro Tube Experiments
Why Macro Tubes?
Fuji don’t have a 1x macro lens yet, they have the 60 f2.4 0.5x but that’s too close to the 56, not very fast and not enough magnification for me to justify another lens. 2016 should bring the 120mm 1:1 macro so for now I have to wait, or play with macro tubes. Macro tubes are tubes that sit between a camera lens and body. They have no optical elements, but reduce the minimum subject distance by moving the lens further from the sensor. This also limits the focal range.
Limited working distance
Before ordering the extension tube I was aware that using a tube would limit the focal range of the lens, what I wasn’t expecting was quite how limited that range would be. I expected for example that I’d be able to focus anywhere from minimum subject distance to 1m for example but not to infinity. However what I discovered is that with the 16mm tube, there is only one working distance that will be in focus, and that working distance is <10cm. Changing the manual focus on the prime lenses I tried (23, 27, 56) seemed to have little effect on the focus distance and merely changed the focal length (!). When I experimented with the 50-140, I found that the zoom became the focus, this gave a wider range of working distances than the primes.
The 10-24 was unusable because the subject distance is so low that it introduces weird distortion.
The 10-24 lens exhibited massive edge distortion when focused very close. I’m not sure if this is a defect of my copy or a result of focussing closer than the lens was designed for.
Limited Depth of Field (DoF)
DoF reduces with subject distance and was often limitingly small when using the macro tubes. This means that a small aperture will be required, which requires more light. This is also problematic as the lens is blocking out quite a lot of light when it’s <10cm away from the subject. Now I see why 1:1 macro lenses have longer focal lengths, and why macro ring lights exist.
A few more examples
What I really want is a great picture of my son’s eyes. However a small aperture will still give a miniscule DoF, so really a tripod is needed for getting the focus spot on. This also means a long exposure can be used to compensate for the small aperture. However tripod and long exposure are not ideal for taking pics of an active baby! I also don’t want to blind him too much with flash… so may have to keep waiting for the 120, but will also keep experimenting 🙂