Live View Grid on Canon

[tesfoto]

I own both the Canon 1DsMKIII and 5DMKII and wondering about the gridlines on live view.

The 5DII grid lines go exactly down the middle, while on the 1Ds this is not the case.

Does anyone know if it is possible to have gridlines down the middle with a 1Ds (Firmware update? etc), I know the new 1DMKIV have this feature?

Thanks.

TES