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08-02-2010, 01:48 AM   #1
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[langtitle=it]Optio W90 purple stripes in movie clips[/langtitle]

Hi all!

I'm using a W90 with a certain degree of satisfaction of canyoning shots and movies. The only defect i notice is that most of the time with movie clips, when some high light spot is visible on the frame (sun reflects over water for example) a vertical purple stripe on the pixel column relative to the spot is visible. Something like an "out of level signal".

I noticed that this issue is present even when framing a photo shot, but it disappears on the final shot. Noticed this issue also on many other compact cameras and it's not a really issue for me, if this would not appear even on movie clips.

Does someone know how to avoid this artefact? Is there some setting i can use to lower that effect?

I didn't notice that issue on other compact cameras while taking movie clips... It looks strange that only Pentax does...

Thanks! Umberto

08-02-2010, 02:50 AM   #2
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Sounds like lens flare to me, TBH. I don't think you can avoid that effect unless you shield the lens using your hand.

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08-02-2010, 05:40 AM   #3
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I don't think it may be considered lens flare...

Please have a look at the attached screenshot. Do you notice the three vertical purple lines? They follow high lights (some high lights appear to be a bit out of the frame, but they are).

Maybe is this due to front glass diffractions? Looks strange to me. Usually this issues appear only on framing phase, not on recording phase. But, maybe, this cam doesn't filter the input during clip recording hence the issue...


Any hint?

Attached Images
08-02-2010, 05:45 AM - 1 Like   #4
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This happens because of the data transfer whhen the camera reads out the CCD, when a light source saturates the CCD. It happens during Live Preview because of the speed of the readout. It does not happen with your pictures because at that time the readout is not done at the same speed, in the same way. Not all pixels are used to make the video preview, either.

It will happen during films because then, the readout is more similar to the one used to make the preview.

Why it does not always happen with other cameras is because your w90 has a much wider angle of view than most lenses, but at the same time the lens design (folded optics, no recess in any kind of lens barrel) doesn't particularly protect the lens from this effect.

The solutions are to avoid filming with a bright light source in your frame, or to zoom in a bit. This should help.

08-02-2010, 05:58 AM   #5
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I agree with the idea of lens flare. I have the same matter with my P80.
This is most noticeable (for me) when you take the movie with one (or several) light souces facing the camera.

The image below is from one video during a live performance, with the purple stripes clearly visible.
Name:  lensflare.jpg
Views: 1062
Size:  106.3 KB
... and I have to add it's perfectly normal, as stated at some point of the user's manual (at the beginning I think, but I'm sure I've read it)
08-02-2010, 01:31 PM   #6
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Well, i had a look at the manual, but didn't really full examined in each paragraph. I missed that notice, sure

Next time i'll go out for movie clips i'll try a bit of zoom to see if it helps in reducing purple lines. Too bad because i really loved the 28mm equivalent lens. Sigh

Thank you guys... Umberto
08-02-2010, 01:49 PM   #7
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From the Optio 80 user's manual, french version, page 1 :
"Si vous dirigez l’appareil photo vers un objet lumineux, une bande lumineuse
est susceptible d’apparaître sur l’écran. Ce phénomène est connu sous le nom
de « smear » et est parfaitement normal."
... and as I'm too lazy to dl the english version, here's my translation :
"If you bear the camera in the direction of a lighting object, a lighted stripe is prone to appear on the screen. This phenomenon is known as "smear" and is perfectly normal".

08-03-2010, 12:37 AM   #8
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Hello G.T.

Found it on the manual, thank you

Well, given that in some occasions is really difficult to avoid this smearing, is there a known way to fix them at least in post-production? Any kind of "unsmear filter" in some video processing tool?

Thanks! Umberto

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