Specifically, it compensates for pan and tilt (angular movement, equivalent to yaw and pitch) of a camera or other imaging device. It is used in image-stabilized binoculars, still and video cameras, and astronomical telescopes.
With still cameras, camera shake is particularly problematic at slow shutter speeds or with long focal length (telephoto) lenses.
With video cameras, camera shake causes visible frame-to-frame jitter in the recorded video. In astronomy, the problem of lens-shake is added to by variations in the atmosphere over time, which cause the apparent positions of objects to change. - Wikipedia
There are two way stabilization can be incorporated into still cameras, the mechanism can be built into the lens or in the camera body.
As early as 1995 Canon and Nikon has brought out lenses with IS for their film cameras, there was no other way; can you imagine trying to MOVE your film left, right; up and down to counter camera shake?
That was the historical reason why Canon and Nikon based their image stabilization around the lens and have continued to do so even when DSLRs have grown in popularity.
There are two school of thoughts when it came to which method of IS is better.
The "in-lens" fan boys reckoned since each stabilization hardware is dedicated to a single lens, the performance parameters can be tuned to that particular lens and thus optimising the effect.
The "in-body" fan boys point out the primary advantage of body based stabilization is that it's effective with every lens mounted on the camera. It doesn't matter if it's the latest autofocus super-duper zoom, ultra-wide or a 40 year old manual focus prime lens!
I tend to lean towards the "in-body" group, think about it; with IBIS (in body image stabilization) you only PAY ONCE for the mechanism when you buy the camera body!
The stabilized lens is also more bulky and heavier than one without the IS.
However, when using long lens; especially manual focus primes, the IBIS often failed to provide stabilization effectively. This is because the IS cannot shift enough to counteract the movement of a really narrow field of view of really long optics. More importantly, do the world first 5 axis IBIS in the OM-D E-M5 work for my prime Nikon telephotos?
I decided to do a simple test.
Nikkor 300/4.5 IF-ED and Nikkor 1.4X extender, this combo effectively became 420 mm and since the lens is use on a M4/3 format; it give a field of view of 840 mm super tele!
So logically, the typical rule of thumb for hand holdable shutter speed, which is 1/(35mm equivalent focal length); I would need at least 1/1,000 second to get a sharp image!
We will see!
I thought it will be nice if I can do the test at Mt Vic, I gave up that idea with outside temperature dropping to 2C and the lens felt like a cold steel in my palm! I decided to shoot from the deck of our house ;)
What about by adding the 1.4x extender to the 300mm? Will the IS still work? Take a look below.
After shooting dozens of shots with this combo, I find the minimum shutter speed to tame the shake in this whopping 840mm (equiv) is 1/640 sec!
A nagging question... is the E-M5 IBIS that much better and more advance than the older version?
Luckily I still got my 3 year old E-P2 and this is what I find...
I did not bother to test the older camera with the 1.4x extender combo ;)
Famous Last Word...
In conclusion, the E-M5′s In body IS system is still effective even with very long legacy lenses. To retain more keeper images I would try to use 1/500 and above whenever possible. The HLD-6 grip is a must have when using a really long lens!