martinairyyz
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Joined: Fri Nov 28, 2003 6:42 am

Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 9:56 am

Hello,

I recently purchased an Olymupus C-720uz and when I do night shots, and long exposures (1/6 to 8") red,blue, and green dots appear all over.

How can I fix this?

Thanks so much!
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xenon
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 10:06 am

Martin,

Maybe you should post some examples, so the pros can
evaluate this problem.

Regards,

Daniel
AirTeamImages -ATI-
 
Guest

RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 10:09 am

Hey,
Have you tried taking your long exposures with a tripod? The red, blue, green dots might simply be the fact that you have moved your camera. If you have used a tripod then it might actually be a problem with the camera.

Like Daniel said easiest way is to post an example...

Cheers,
Tim
 
martinairyyz
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 10:42 am

Hey Tim,

I have tried (although my tripod is plastic crap, it holds fairly still)

Here is an example:
(notice how the picture is VERY slightly blurred but the dots arent :-o)

http://www.geocities.com/mvtpuff/pp1.html

Martin
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 10:53 am

Martin,
I've never come accross that problem. I'm sure some other people will be able to give you an answer, probably down to either your memory card or your CCD (Image Sensor). I'm sure someone like CKW will be able to nail down your problem.

Cheers,
Tim
 
TWAMD-80
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:05 am

Hi! I had the Olympus C-740 and I tried a few shots at the night sky and I got some dots, however it wasn't to the extent as yours. I would get some small light-rust color dots, but I think those were normal and related to the Image sensor.

TW
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martinairyyz
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:07 am

Yes.... those wouldn't be too much of a problem. Too bad you can't shoot B&W directly. If you could I think it would solev your problem... Can you though? I don't think so....  Sad
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:13 am

You try shooting in RAW? Not that it might make a difference but still worth a try.

In all honestly, I'd be awfully upset to get those dots on my photos and I'd try to exchange my camera against another model.

Just my 0.02 cents,
Tim
 
xenon
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:31 am

Hi,

Can't it be that the exposure speed was to long?

Daniel
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martinairyyz
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:36 am

Can't it be that the exposure speed was to long?

No.. look at these 2 photos, with the same camera:


View Large View Medium
Click here for bigger photo!

Photo © Antoine Ossadzow



View Large View Medium
Click here for bigger photo!

Photo © Antoine Ossadzow



Martin
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yegpix
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 2:26 pm

Martin, unfortunately your camera does not have any form of noise reduction built in so not alot can be done about the noise I see in these pics. This is the same type of noise I saw in my old C700UZ. The C730, 740, 750UZ have automatic noise reduction built in which would kill the noise. Sorry to bring on the bad news.
 
JeffM
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 3:51 pm

"You try shooting in RAW? Not that it might make a difference but still worth a try.

Maybe you missed the part where he mentioned he used an Olympus C-720?

I took some long exposures at night with my old C-700 and never got that amount of noise. They almost look like 'stuck' pixels.. I suppose you could try using something like Fred's High ISO noise removal actions.
 
redfox
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 5:15 pm

Agreed with JeffM

The dots do appear to be dead pixels. To confirm this take several shots of the same scene using a tripod but vary the exposure time. If the 'dots' are brighter when the exposure is longer then its definitely dead pixels. Do not worry about it as every CCD will have an amount of dead pixels that are 'stuck' on or off.

Try using the clone stamp tool in photoshop to remove them.

Stephen
 
707CMF
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 8:34 pm

Martin, thanks for the plug  Big thumbs up

Those shots were taken with a C700, not a C720, but it ois fairly similar.

One advice I give is to keep the ISO as low as possible, high ISO = lot of grain.

Also, you still need to have a certain ammount of light. Plus not enough light = difficulty to focus, and might cause those dots.

As for dead pixels, I don't think it is the case. There are always a few dead pixels (I have 4 or 5 on my C700), but it is not "all over"

Cheers,

Antoine
 
Staffan
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 9:58 pm

I think you can take a second exposure with the lens cap on. Then you subtract the second exposure from the first one (since all the hot pixels are the same in both shots). I've heard that astronomy photographers shooting digital does it that way. Do a search on it...

Staffan
 
martinairyyz
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:33 pm

Dead Pixels? So many?!??! Sheesh! I bought this camera 3 days ago and it still has a 90-day OLYMPUS warrenty. Should I get it exchanged? Will echanging for a newer model be a posibility?

Cheers!
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707CMF
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RE: Help Please With Long Exposures On Digital Camera!

Sat Jan 17, 2004 11:48 pm

Er, maybe you could post here an exemple of the pictures you are reffering to.

As said above, I am fairly sure it is not a dead pixel problem.

707
 
martinairyyz
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RE: Help Please With Long Exposures On Digital Camera!

Sun Jan 18, 2004 12:28 am

I did post a link above but here is a pic:



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Granite
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RE: Help Please With Long Exposures On Digital Camera!

Sun Jan 18, 2004 1:02 am

Hi all

Could be 'Hot Pixels'

There is some software on the Net that can erase most of them. Tyr typing in 'Hot Pixels' and see what you can come up with.

Cheers

Gary Watt

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