Experimenting with 25mm Extension Tube On Canon EF 500mm f4 L IS

I was at Stodmarsh NNR very little going on so I decided to use the time and see just what effect putting a 25mm extension tube had on my 500.
I used a Kingfisher perch as the target I focused on a little red bug right at the tip of the perch, here is shot 1 this is my 500 + a 25mm Extension Tube

Canon5dmk4 500mm 1\332 f9 iso800

So the first thing you notice when using an extension tube is you can no longer focus to infinity, you do gain the ability to focus a bit closer than the Minimum Focal Distance (MFD) of your lens, I would estimate that instead of the MFD of 14.6ft with the tube it was more like 10ft so quite a difference and no real loss of quality either, on the downside the focal range is severely curtailed, I would guess that the maximum I could focus out too was around 13m.

Ok next up is no extension tube but adding a 1.4 x extender instead.

Canon5dmk4 700mm 1\512 f9 iso800

Again focusing on the little red bug, notice the magnification which is far superior to using the 25mm ext tube, if anything I would say that the quality of this shot is better than with the ext tube, we also have the ability to focus to infinity restored, our MFD is back to 14.6ft, quality is in my opinion better then the extension tube image plus magnification is better too.

So for my final attempt I use both the 1.4x and the 25mm extension tube !

 

Canon 5dmk4 700mm 1\332 f9 iso800

Ok with this configuration we do get a better magnification but the image is a lot softer, I also noticed that I could focus out to maybe 20m.

Summing up my quick test for me the obvious choice is always going to be the 1.4x extender, quality of shot, ability to focus to infinity wins hands down.

That said 25mm extension tube works wonders on my 70-200mm for a bit of close up work.