Think its the same lens...just not all the letters after its name![]()
They only do one 150-500mm which is hsm and os( Correct me if I am wrong)
Sigma said:HSM - This lens incorporates HSM (Hyper Sonic Motor), which ensures a quiet and high-speed AF as well as full-time manual focusing capability.
APO (APO Lens) - In order to attain the highest quality images, the APO lens has been made using special low-dispersion (SLD) glass and is designed to minimize color aberration.
RF (Rear Focus) - This lens is equipped with a system that moves the rear lens group for highspeed , silent focusing.
OS (Optical Stabilizer) Function - This function utilizes a built-in mechanism that compensates for camera shake. It dramatically expands photographic possibilities by alleviating camera movement when shooting by hand held camera.
Conv (APO Teleconverter EX) - This lens can be used with the APO Teleconverter EX. It can increase the focal length and will interface with the camera's AE (automatic exposure) function.
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.
i have a Nikon d3100 and i like to treat my self but bit confused
whats the difference
1 Sigma EX 150-500mm 5-6.3 APO HSM other sites
2 Sigma 150-500mm f5-6.3 RF DG OS
3 Sigma 150-500mm f5-6.3 APO DG OS HSM amazon

Nick
If your going to be working at 500mm do consider getting a decent tripod to go with it if you don't have one. I used to have the 170-500mm Sigma version and it takes some holding to keep it still. The OS version will still take some effort the hold after a time.
Realspeed
I used my 150-500mm oon the D3 yesterday handheld - just about to import to lightroom![]()
Mine is the HSM OS version too
your right and wrong in pentax and sony mount the 150-500mm did not have os but it does now.You're right - the first and only Sigma 150-500mm was introduced in 2008 when the 170-500mm and the 50-500 did not come with OS (though the 50-500mm does now) and the launch was conspicuous partly due to that.
your right and wrong in pentax and sony mount the 150-500mm did not have os but it does now.