Sigma OS question

[Cage]

How do you tell when the OS is active on Sigma lens?

With Tamron the focus point stabilises in the viewfinder but with my new Sigma I can't see any change in the viewfinder, hear any motor noise or any other indication that it is working, or not.

[ameerat42]

When you shake, rattle and roll... - and the image in viewfinder does not.
Kiddingly not, you will see it only sometimes. I used to notice it most when
doing hand-helds of the moon.

What lens, btw? I suspect a 150-600? Make sure the OS button is on the desired OS setting,
either Always On, or shutter depress ON. I have a 50-500 with the 2nd option set.

[arthurking83]

See my reply in your lens thread too(lower half of the reply).

My Tammy 24-70 'appears' to be more stable than what the Sigma OS appears to do.
Same with my Nikon 105VR too .. ie. image 'appears' to be more stable.

IIRC your Tammy was the 70-200/2.8VC ??
If so, the reason I'm using 'appears' in quotation marks, is that it could be the illusion that the Sigma isn't working as well as the Tammy simply because of the focal lengths involved.

Are you assessing the Sigmas OS mainly at 600mm?
If so, then you need to take into account that at 600mm, (3x 200mm focal length), you will always have more magnified movement looking through the lens, than you'll see at 200mm.

The way I'd describe the way my 150-600 locks it's OS is that before OS locks, I get a slightly trembly feeling of the image through the vf, then when OS locks on, I get a very short sideways snap motion and then the image though the vf still moves around but no trembling feeling.
But I'm not steady enough to hold it perfectly still, so I'm always seeing some movement.