Hi, Some Nikon and Canon lenses have a feature that help them reduce vibration or increase stabilization while shooting with low light. These lenses are either VR or IS, depending on the brand name, Nikon or Canon. Anyways, suppose you are using an older camera model with max. ISO of 1600. Your minimum aperture value for the lens you are using is f/3.5 This is NOT a VR or IS lens and is getting dark. With 1/8th of a second and holding your breath, your picture turns out ok but perhaps a bit blurry. Now, suppose the same situation as before at right the exact time, but now with a VR or IS lens. What happens if your lens can not be opened any wider than f/3.5 ?? These companies say that there is a compensation of up to some three stops with the VR or IS. So the compensation is in speed, right? I could theoretically under this situation with the VR or IS now shoot with 1/60th of a second, or if it gets darker, I could still shoot at 1/8th. A situation that without the VR or IS would be perhaps impossible. Thank you very much in advance, kind regards, igmolinav : ) !!! P.S. This is a quote from the lens I have interest in: The innovative VR or IS system allows handheld telephoto zoom shooting even in poorly lit conditions. It minimizes image blur caused by camera shake, and offers the equivalent of shooting at a shutter speed 3 stops (8 times) faster. P.S. Does it also mean that ider focal lenghts like 18 mm. in DX format it does not work ??