Yesterday I bought a Nikon 1.7x TC for my 300f4 lens. This is for my current D7000 body which I will upgrade soon.

I tried it in the shade outside the store and the AF seemed to work ok. So far its working great and the IQ is better than expected.

My question is that the EXIF data is showing 500mm as opposed to the 510mm it should

Is this because the converter is not quite 1.7x, because the camera rounds the numbers or is there another reason.

It's a non issue for me as it works great but just curious as to the reason

Thanks