[The Photo-Vet]

What is the problem with it being on the conservative side?

Exactly...better having the flash a tiny bit wider than the actual focal length on the lens thus avoiding vignetting... Metz probably has it set up that way anyhow...

[Prudhoe]

I just bought the Metz 50af-1 and after reading the posts here that said the display was out of tack with either the lens focal length or the flash focal length I decided to try it out with my F 35-80 and FA 28 - 105 lenses. The flash had previously been used with an A 50 1.7.
With the 35-80 fitted to camera and half press shutter release the set focal length (35) was multiplied by 1.5 and the Metz set its zoom to 50mm causing the zoom to move from its previous position.. Each adjustment of lens was followed by an automatic adjustment of the flash zoom up to 70mm on lens corresponding to 105mm on flash, i.e. the camera relays the effective focal length to the flashgun. This was repeated with the same results using the 28-105.
Setting S Zoom to the ON position the Metz puts its zoom in exactly the same physical position as it did before but the display shows the same focal length setting as the lens. So it works as it says it does.