3:2 and 4:3 equivalent how?

Great Bustard wrote:

First of all, the most efficient aspect ratio for a sensor inscribed in the image circle (as opposed to circumscribed about the image circle) is the aspect ratio that is closest to the aspect ratio of the final photo. For example, a 1:1 sensor is the most efficient for 1:1 photos, a 4:3 sensor is the most efficient for 4:3 photos, a 3:2 sensor is the most efficient for 3:2 photos, and a 16:9 sensor is the most effieient for 16:9 photos.

That said, let's consider a 16 MP 4:3 sensor. A 1:1 sensor with the same diagonal would have 16.7 MP (4% more), a 3:2 sensor with the same diagonal would have 15.4 MP (4% less), and a 16:9 sensor with the same diagonal would have 14.2 MP (11% less) -- in other words, not that much different at all.

On the other hand, cropping one aspect ratio to another can result in a substantial loss in pixels:

• 1:1 <--> 4:3 results in a 25% loss of pixels.
• 1:1 <--> 3:2 results in a 33% loss of pixels.
• 1:1 <--> 16:9 results in a 44% loss of pixels.

• 4:3 <--> 3:2 results in an 11% loss of pixels.
• 4:3 <--> 16:9 results in an 25% loss of pixels.

• 3:2 <--> 16:9 results in an 16% loss of pixels.

Anyway, which aspect ratio gives you the best "bang for the buck" depends entirely on which aspect ratio you are displaying your photos at.