Control of Focus range during autofocus - Script Writing - CHDK Forum

Control of Focus range during autofocus

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Control of Focus range during autofocus
« on: 25 / December / 2012, 07:27:29 »
I have tried the manual focus in SX130IS but it is difficult to set it correctly outdoors.

I want to control the Auto-focus range while clicking.
Situation is "I know that I am at about 2m from my subject." (Since subject is small autofocus focuses on the background)

So while doing autofocus the script should search for focus only between minimum to 2m. Is This Possible?


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Hyperfocal Distance
« Reply #1 on: 26 / December / 2012, 00:43:42 »
CHDK has a a Depth Of Field (DOF) display you can activate from the CHDK option in the main <alt> menu. Of particular interest is the "Hyperfocal Distance", which is the nearest you can focus while keeping infinity in focus. With my camera zoomed out, it's about 1 meter. See if you can activate the DOF display and try the following:

You may need to put your camera in manual focus mode for this to work.  Then press the <alt> button to go into <alt> mode. Now press <down>. The camera should focus at the hyperfocal distance. If your subject is further away than this distance, then both your subject and the background will be in focus.

The concept of hyperfocal distance is very interesting. For example when you get a pair of glasses, they always set them to focus at infinity. If you want to see closer, the lens of the eye has to be able to change shape enough to focus closer. But the lens hardens with age and can't change shape. The solution is bi-focals or "progressive" lenses which focus closer as you look down.

But you can also set the focus of your glasses a little closer than infinity. I found that setting them at 1/4 diopter closer allowed me to see the dashboard clearly while driving, and still see the road(infinity) quite well. I wonder why optometrists haven't discovered this.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b

Re: Control of Focus range during autofocus
« Reply #2 on: 26 / December / 2012, 11:55:36 »
Thanks for your reply. It's good understanding about the hyperfocal distance.

I think you have provided trick  to  get  the focus from
2m to infinity while I need it to be
0.5m to 2m

check these pics one taken on auto focus mode auto.jpg
and second tried to bring the flower at 2m in focus using manual focus. manual.jpg

I need to see the foreground flower in manual.jpg to be in focus

(I think that changing the aperture will be useful but I need to do some experiment this weekend)

« Last Edit: 27 / December / 2012, 10:51:28 by yndesai »


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