Question About Sigma 50-500mm

[wchowdhury]

One of the lenses on my wish list is the SIGMA APO 50-500mm F4-6.3 EX HSM.

Can anyone explain the difference between the RF & DG version.
From what I could find on the net the DG seems to be the newer version (with a new coating on the lens) & is slighty cheaper.

Sigma4less is the only place where I found both lenses listed:
Sigma Zoom Normal-Telephoto 50-500mm f/4-6.3 EX APO RF HSM Autofocus Lens for Nikon AF-D (735306) -
Sigma Zoom Normal-Telephoto 50-500mm f/4-6.3 EX APO DG HSM Autofocus Lens for Nikon AF-D (736306) -

Would appriciate any light that can be shed on this. Thanks in advance.

Wasim.

[notsotechie]

Well I googled and found this on the sigms website Not sure if this helps

RF (Rear Focus)
This lens is equipped with a system that moves the rear lens group for highspeed , silent focusing

DG (DG Lens)
These are large-aperture lenses with wide angles and short minimum focusing distances. With an abundance of peripheral illumination, they are ideal lenses for Digital SLR Cameras whilst retaining suitability for traditional 35mm SLRs.

[wchowdhury]

Thanks notsotechie.

I came accross the following review by Andrzej Wrotniak.
The Old Bigma and the New Bigma:
wrotniak.net: Sigma 50-500 mm F/4-6.3 DG Lens for the Four Thirds System

I am wondering if anyone here has used both versions. If so is there any real difference. The one review I found (on Sigma DG Vs non DG Tele Converters) says there really isn't much difference.
DG vs non-DG TCs Photo Gallery by Miljenko Devcic at pbase.com

Thanks.

Wasim.