rabbitmountain Offline Upload & Sell: Off
|
After reading discussion in another topic, I did the following write up about how motion blur can be reduced by cleverly adding weight.
We're talking about camera shake induced motion blur. The driving force is the "shaking" of the camera by the hands of the photographer. As long as the photographer were to only move the camera up, down or sideways, there would be a minimal amount of blur. However, we photographers tend to rotate what's in our hands, without being aware of it. Small amounts, but still it's rotating all the time. Just put on a long lens, switch off any IS and look through the viewfinder. Your image will be dancing up and down, left and right.
Rotation - multiplied by the distance - gives us the motion blur. Because long lenses reach much farther, rotation blur will increase linearly by focal length. Anything that could help us reduce the rotation will reduce the rotation blur. When you add weight, like a battery grip, you add weight. Yes. But added weight by itself will not reduce any rotation. The keyword is Rotation inertia. Inertia is what counters movement. This is why cord dancers hold a bar in their hands. Rotating a wide bar is quite hard. The objective is to place as much weight as possible towards the ends.
Back to cameras. Attaching a battery grip adds weight off centre. This is especially effective with short and light lenses with a long FL. If we attach a 70-200/2.8 and zoom to 135mm, our rotation inertia (officially called "moment of inertia" - if my english is correct) is much larger because the lens is longer so we have more weight off-centre. Adding a battery grip will add more percentage to the stability of the camera + 135L than to the 70-200/2.8. For small kit lenses like a light and cheap 70-300, adding a grip is most effective.
Additionally, when adding a battery grip, the photographer has a more "fixed" grip than without. The more rigid the connection between arm and camera (i.e. the hand holding the camera), the more the rotation inertia of the combo will grow, because now also the arm of the photographer becomes part of the inertia. Lots of extra off-center weight.
As an experiment, one could attach a monopod to a camera, turn off IS, lower shutter speed and shoot away. The result will be that the monopod adds inertia in the up-down rotation of the lens and the tilt left/right rotation, but not the left-right rotation. Most of the blur will be stripes left-right. If you should fix a stick to the monopod pointing horizontally (perpendicular to the monopod in any direction) you just built your own home made Image Stabilizer. This is exactly the principle I applied while traveling, attaching my walking sticks to my camera.
So even if you don't intend to walk around with walking sticks on your camera, adding a grip and gripping it firmly (but not shaky) will maximize the stabilizing effect.
And always insert two batteries, even if you don't need them for power!
Ralph
Edited on Jan 02, 2017 at 04:39 PM · View previous versions
|