Would a screw in 2x converter double the minimum focusing distance?

What you bought is called a close-up lens or perhaps a supplemental lens. The close-up lens is a cousin of the lenses used in reading eyeglasses. When you mount such a lens, it changes the minimum distance, camera-to-subject. Now many will tell you that that’s not the way to go because they degrade the quality of the resulting image. I tell you that in most cases they work just fine, you will hardly notice any hindering.

Photo-grade close-up lenses are constructed using two lenses mounted together. This tried and true method mitigates an aberration called chromatic. Chromatic aberration shows itself as a rainbow fringe around the edges of objects in your image. The power of a close-up is labeled as +1 or +2 or +3 etc. Sometimes they are called 2X or 3X or 4X etc.

The value as labeled uses a language common to an optician. A +1 has a focal length of 1000mm. When mounted on your camera, and your camera is focused on infinity ∞, objects 1000mm from the front of your camera will come to focus (about 1 yard). Mount a +2 and now you start at 500mm = 20 inches. Mount a +3 and you start at 333mm = 13 inches. Mount a +4 = 250mm = 10 inches. Mount a +5 = 200mm = inches. Mount a +6 = 166mm = 6 ½ inches.

Because camera close-up lenses are simply refined reading glass lenses, you can go to the drugstore and at the reading glass display, hand-hold any of the spectacles before your camera lens. What you see is what you would get, as to magnification. Remember, photo grade lenses are what you want. In a pinch, I have used store bought lenses from the drugstore, and this worked out OK.

I just tested some cheap 2x and 0.5x converters that screw onto the filter threads of other lenses. I don't know if these results apply to all such attachments.

• The 2x converter increased MFD, but not by double.

• The 0.5x converter decreased MFD, but not by half.

Notably, subject magnification is greatest with the 0.5x converter because of the shorter MFD. Image quality is also very poor, which is typical of such cheap attachments.

Depending on your camera system and needs, you can consider some other options with better image quality:

• Using a longer lens, with or without macro.

• Adapting vintage lenses, with or without macro. Macro photography often requires using manual focus. Cheaper than an AF lens.

• Using extension tubes with pass-through electronics. May retain AF, depending on the particular lens.

• Using bellows or focusing helicoids – most likely paired with a manual focus lens. Depending on your camera system, some helicoids allow lenses to be used normally, allowing focus from a few inches to infinity.