I received my cheap macro extension tube yesterday from China. For US$ 7.85 I didn't expect much to tell you the truth. I did some tests in the evening and thought I had to share the experience with you.
Keep in mind though that extension tubes work best with lenses of short to medium focal lengths and they are less effective with telephoto lenses.
The main advantage of extension tubes is that you can use them with any of your lenses. If you buy more than one, you can join two extension tubes together to give you even more magnification. The impact though is on light coming in and hitting the sensor.
First, the one I bought is a manual extension tube and not the electronic one (Canon cost around US$ 160) therefore you have to focus manually. The thing is, focus is done through approaching and retrieving the camera to and away from the subject. I learn't this the hard way.
Second, the biggest drawback of these manual extension tubes is aperture. If your lens don’t have manual aperture rings (i.e. the aperture setting is controlled by the camera) then the aperture will remain locked wide open at '00'. You cannot change it. After doing some research on YouTube, it turned out to be there is a workaround for Canons and not for Nikons:
- Select a short to medium focal length lens. I selected my prime fixed 50mm lens that I adore.
- Set the aperture to let's say f/8 for a better depth of field across the photo.
- Hold down both the DOF button and the lens eject button and remove the lens. The lens is now set at f/8 instead of being wide open. What we did is telling the lens to stay at f/8.
- Put the extension tube on the body and then the lens on the extension tube.
- Put the lens on manual focus and remember, the closer you can focus, the more magnification you get.
- Use a tripod
- Use off-camera flash
- Try different objects.
Depth of field is very narrow when you shoot close-ups. Thank God you can raise your ISO in to get a small enough aperture to for a bigger depth of field.
If you are hand-holding the camera, you need to use a faster shutter speed and a flash. The magnification also magnifies camera shake, so with the flash use a shutter speed of 1/100 or higher.