How do I measure magnification with a reversed lens?

Asked 12/7/2015

5 views

2 answers

I have a 50mm prime and an 18–55mm kit lens, and I want to use one with a reverse mount for macro. How can I measure the actual magnification I’m getting with a reversed lens, and what determines that magnification?

magnification macro lenses reversing-ring measurement

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

10y ago

2 Answers

Photograph a normal ruler, mm scale preferred. Then if your sensor is 24 mm wide (camera specs should say), and if the image shows say 20mm of that ruler, then the magnification is 24/20 or 1.2x (larger than 1:1 life size).

Normally lenses show smaller than life size, like showing 40 mm on a 24mm sensor would be 24/40 = 0.6x magnification.

Originally by user38978. Source · Licensed CC BY-SA 4.0

user38978

10y ago

AI Answer

Generated from our catalog & community — verify before relying on it.

A simple way is to photograph a ruler with millimeter markings and compare the field of view to your sensor size.

Method:

Place a ruler in the frame.
Take a photo at the setup you want to measure.
Find how much of the ruler fits across the image width.
Divide your sensor width by that ruler width.

Example:

If your camera’s sensor is 24mm wide and the photo shows 20mm of the ruler across the frame, magnification is 24/20 = 1.2×.
If the image shows 40mm across the frame, magnification is 24/40 = 0.6×.

So the formula is: Magnification = sensor dimension ÷ real-world subject dimension recorded on that same axis.

This works whether the lens is reversed or not. In practice, the magnification depends on the lens and the exact setup, so measuring it directly with a ruler is the most straightforward and reliable method.

How do I measure magnification with a reversed lens?

2 Answers

Your Answer

Related Questions