General focusing questions

mujirushi
Posted 23/04/2011 - 22:36 Link
Having to play with my DA 16-45 and DA 55-300 lately... there are some questions which arise on the focusing in general:

1. The distance scale printed on the lens body itself, do they represent the distance bewteen the focus point and the sensor?

2. If I am trying to focus an object that is beyond maximum value on the distance indicator (IE: the lens says the object is at infinity):
- Do I expect the object would still be in focus, or
- Would that simple say "This is the best I can do to focus your target"

Let's put it into perspective:
DA 55-300, trying to focus a deer in a deer park 25 meters away. The lens itself is 1.4m 15m Inifinity printed on it.
Still learning!

Zooms: DA12-24 | DA16-45 | DA*50-135 | DA55-300
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rparmar
Posted 23/04/2011 - 22:53 Link
1. Yes

2. I don't understand you. It may be that some objects near infinity turn out to focus at infinity. Not sure if that addresses any part of what you are asking.

Please note that the range of what will register as "in focus" to the camera is actually wider than what you might actually see as in focus.
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Dangermouse
Posted 23/04/2011 - 23:13 Link
In general, infinity is supposed to cover everything from a couple of miles to the moon (depending on the lens - some wide angles reach the infinity mark much closer to the camera than a telephoto zoom, for example).

In the case of my SMC K 28/3.5, if I set it to infinity a car will be in focus when I'm standing far enough back to get all of it in the frame (about 4-5m is usually far enough), and so will the mountain 5Km away.
Matt

Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
pentaxian450
Posted 23/04/2011 - 23:42 Link
Beyond a certain distance, the circle of confusions become too small to make a difference. When you reach that point, your lens is set at infinity. If you pass that point with your lens, you'll actually have a decrease in sharpness.
Yves (another one of those crazy Canucks)

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