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Old Sep 14, 2008, 10:53 PM   #1
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´╗┐Hello,

I have had my Olympus SP-570 for only two weeks so my experience is limited. Of course, one of my first pictures outdoors was at 20x zoom, and I was disappointed to see that it had some chromatic aberration (red-blue fringing) where there was particularly strong light-dark edge contrast. I experimented by taking a couple dozen pictures to see where in the zoom range noticeable chromatic aberration 'kicked-in'. I could go to about 3/4s of the zoom scale (15X?) before there was any fringing. Oddly, on one of my pictures at full zoom there was none. Looking at this picture closely (magnifying it on the computer) I could see that the picture had very good focus exactly on the area where chromatic aberration was evident in other pictures. Since chromatic aberration in a lens is caused by differential focus of components of light with different wave lengths, I wondered if being a bit out of focus was the culprit in my camera. I subsequently adjusted the camera's automatic focus settings from the default of iESP to SPOT, and yesterday I took more than a dozen pictures at full-zoom of objects having strong light-dark edge contrasts, daring the camera to produce chromatic fringing. NONE was evident, however, ANYWHERE in the pictures. Another characteristic of using 'SPOT' is much shorter automatic focus time.

I am wondering if I found a solution to maximum-zoom chromatic fringing by setting the focus to SPOT, or if I was just lucky in my test pictures. Would you please tell me on this group what your experience is in this regard. I've used SPOT focus for years with my older digital camera so I am quite used to it.

The zoom capability of the SP-570 is awesome and a lot of fun. Sometimes I use a monopod to reduce camera shake, but shaking does not seem to be a huge issue anyway.

Thank you for your interest in this topic.

Cornwaab
Nova Scotia, Canada

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Old Sep 15, 2008, 9:59 AM   #2
PJM
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iESP and SPOT aren't autofocus options--they're metering options.
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Old Sep 15, 2008, 8:24 PM   #3
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Hi PJM,

Thank you for reading my posting. The camera is new to me, so I could have misinterpreted the settings.

However, according to my Olympus SP-570 manual (page 41) and built in camera menus the AF (autofocus) Modes are 'Face Detect', iESP, SPOT, and AREA.

There are three light Metering Modes: ESD, something like 'centre image' (icon) and 'area' (icon).

My non-chromatic abberation pictures were taken with the SPOT autofocus Mode 'on'.

The more I 'play' with this camera the more I like it, and learn about it.

--- Cornwaab

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Old Sep 16, 2008, 10:07 AM   #4
PJM
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I stand corrected. I don't have an SP-570, so my Olympus DSLRs don't have those AF modes.

Interesting that an autofocus mode would affect chromatic aberration, but-hey-if it improves CA go with it.
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Old Sep 17, 2008, 3:21 PM   #5
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Very interesting observation, I think that there is logic in your guess.
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Old Sep 18, 2008, 11:38 AM   #6
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Now that I think about it, this may make sense. Most P&S cameras tend to use maximum or a large aperture in auto modes, so autofocus may be a tad off. Using Spot AF probably yields more accurate focus so CA is more likely to occur in out of focus areas and spot gives a finer focus resulting in less CA.

Following this train of though, we know CA can be reduced by stopping down, so using aperture shooting mode and stopping down a couple of stopsshould accomplish the same correction.
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