Is added adapter similar to extension tube?

Started 3 months ago | Questions thread
Lightshow
Lightshow Veteran Member • Posts: 7,474
Re: Is added adapter similar to extension tube?

In summation, an adapter is a device designed to place the adapted lens at its designed/engineered distance from the sensor/focal plane (ie. infinity focus at the infinity position of the focus ring) also known as flange back distance and back focus among other things, they are basically the same thing but they reference different things of the lens (the mount and the optical centre of the lens). An adapter is just a glorified shim.

So, if the adapter places the lens too close to the sensor, the lenses focus range is shifted away from the camera, out past infinity which decreases focus range because anything past infinity by definition is impossible and will be out of focus.

On the flip side, placing the lens too far from the sensor will end up with the lenses focus range being shifted closer to the camera, and like with an extension tube, it includes the loss of infinity focus.

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