Introduction: Macro Tube With F-number Control
This will be a quick explanation of what I did to have control over the focal ratio (f-number) while using a macro tube. My camera is a Nikon D3100, but since all Nikon DSLR cameras use the same type of lens, I think it will serve any Nikon DSLR with F mount. I know for a fact that this won’t work with a Canon EF lens. Any other maker you will have to investigate.
I made a simple macro tube with a body cover, a piece of hot water PVC tube, and a piece of plastic. It is very straight forward and there are a lot of DIYs for making macro tubes, so I won’t explain it over here.
The first time I used my tube, I noticed that when I tooked off the lens from the camera body, the diaphragm (aperture or pupil) of the lens closed to its minimum, what means that it had a bigger f-number. I start thinking how I could extend the connections of the lens, without damaging it, when I notice that in the back of the lens there is a lever that controls the aperture (red mark 1° photo). So I decided that I wanted to move this lever manually. I give it some thought and I realize that the easier way to do this was with a screw that can push the lever, and that’s what I did. Measuring the exact place where the hole should go wasn’t easy but with a lot of patience you can make it.
And it works great, not only I can open the diaphragm but I can control how much it opens.
I hope you found this useful. And I appreciate any remark you have.
P.D. All thought using a macro tube is pretty safe, if you don’t want to put at risk your lens, you shouldn’t make this.