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Old Jan 10, 2007, 11:52 AM   #1
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With the camera in normal "horizontal" position, the Olympus C-750 auto-focuses on "vertical" "lines" or edges in the focusing area. It can not auto focus on subjects with only horizontal lines. Other cameras focus by maximizing image contrast.

What auto-focus method is used by the Panasonic FZ30?

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Old Jan 10, 2007, 12:23 PM   #2
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Contrast detection versus dSLR using phase detection--

http://en.wikipedia.org/wiki/Autofocus

For FZ-xx, see Bryan's page at:

http://www.ishots.net/fz1-2faq/focusing/index.htm






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Old Jan 10, 2007, 1:27 PM   #3
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Thanks for your prompt and authentic reponse and links to some useful references of your own and to others. The FZ30 seems to be inconsistent in focusing on occasion. Focusing with Spot Focus on a fixed subject that fills the focus area seems to respond differently when the shutter is repeatedly half-depressed to focus. I have wondered at the specific detection algorithm used by Panasonic.
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Old Jan 17, 2007, 11:50 AM   #4
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Telecorder --
Thanks for confirming that most prosumer digicams use some variety of image contrast auto focus.

My question was about what specific contrast method is used by Panasonic. There are many possibilities. The operational definition of "Contrast" depends on the focussing algorithm used.

Cameras that sense contrast by detecting vertically-oriented pictorial features (edges) scan the pixel raster row-by-row (i.e., "horizontally). Contrast is measured as brightness differences between adjacent pixel pairs accumulated over the focus area. As restricted by processing speed, several alternatives are possible. The raster could be scanned vertically by column, diagonally on adjacent rows, or by a combination of these. It could detect immediately as the scan is performed or by following analysis of the full scanned array, etc.

Olympus apparently uses the horizontal contrast method, as specifically implied in their user manual. I questioned what algorithm Panasonic uses. The manual offers no clue. Focussing alternately on targets with lines horizontal and then with the lines vertical should offer an empirical answer, shouldn't it?
Thanks for your response.
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Old Jan 17, 2007, 11:54 AM   #5
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Can't really comment or help with the specifics you're looking for. I would point out that Pany suggests rotating the camera 90-degrees if one is having problems getting AF lock so it may be an issue of contrast on vertical contrasts within the metered AF area(s)...
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