new Metabones adapter gives nex crop factor higher-quality full frame look.

blue_skies wrote:

You are over thinking this. Adding another lens element, in the adapter, changes the focal length of the lens.

Aperture is merely defined as lens focal length/lens diameter. So by reducing the lens focal length, you also reduce the aperture, making the lens faster.

A tele converter does the opposite, making the lens slower.

Problem with converters has always been IQ, or lack thereof. Because the lens is added between the exit of the lens and the sensor, it can cause all sorts of side effects.

But I applaud Metabones, the thought of taking a FF lens and compressing it into a DX lens is a clever one.

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Cheers,
Henry