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Help Please With Long Exposures On Digital Camera!  
User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Posted (10 years 8 months 1 week 4 days 19 hours ago) and read 4629 times:

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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18 replies: All unread, jump to last
 
User currently offlineXenon From Belgium, joined Aug 2001, 494 posts, RR: 12
Reply 1, posted (10 years 8 months 1 week 4 days 19 hours ago) and read 4595 times:

Martin,

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

Regards,

Daniel



AirTeamImages -ATI-
User currently offlineBoieng747-400 From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 8 months 1 week 4 days 19 hours ago) and read 4584 times:

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


User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Reply 3, posted (10 years 8 months 1 week 4 days 18 hours ago) and read 4586 times:

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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User currently offlineBoieng747-400 From , joined Dec 1969, posts, RR:
Reply 4, posted (10 years 8 months 1 week 4 days 18 hours ago) and read 4568 times:

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


User currently offlineTWAMD-80 From United States of America, joined Oct 2001, 1006 posts, RR: 4
Reply 5, posted (10 years 8 months 1 week 4 days 18 hours ago) and read 4561 times:

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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User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Reply 6, posted (10 years 8 months 1 week 4 days 18 hours ago) and read 4571 times:

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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User currently offlineBoieng747-400 From , joined Dec 1969, posts, RR:
Reply 7, posted (10 years 8 months 1 week 4 days 18 hours ago) and read 4558 times:

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


User currently offlineXenon From Belgium, joined Aug 2001, 494 posts, RR: 12
Reply 8, posted (10 years 8 months 1 week 4 days 17 hours ago) and read 4559 times:

Hi,

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

Daniel



AirTeamImages -ATI-
User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Reply 9, posted (10 years 8 months 1 week 4 days 17 hours ago) and read 4559 times:

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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User currently offlineYEGPIX From Canada, joined Mar 2002, 159 posts, RR: 2
Reply 10, posted (10 years 8 months 1 week 4 days 14 hours ago) and read 4533 times:

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.

User currently offlineJeffM From United States of America, joined May 2005, 3266 posts, RR: 51
Reply 11, posted (10 years 8 months 1 week 4 days 13 hours ago) and read 4523 times:

"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.


User currently offlineRedfox From United Kingdom, joined Sep 2003, 172 posts, RR: 1
Reply 12, posted (10 years 8 months 1 week 4 days 12 hours ago) and read 4506 times:

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


User currently offline707cmf From France, joined Mar 2002, 4885 posts, RR: 29
Reply 13, posted (10 years 8 months 1 week 4 days 8 hours ago) and read 4477 times:

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


User currently offlineStaffan From , joined Dec 1969, posts, RR:
Reply 14, posted (10 years 8 months 1 week 4 days 7 hours ago) and read 4461 times:

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


User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Reply 15, posted (10 years 8 months 1 week 4 days 5 hours ago) and read 4439 times:

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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User currently offline707cmf From France, joined Mar 2002, 4885 posts, RR: 29
Reply 16, posted (10 years 8 months 1 week 4 days 5 hours ago) and read 4434 times:

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


User currently offlineMartinairYYZ From Canada, joined Nov 2003, 1209 posts, RR: 7
Reply 17, posted (10 years 8 months 1 week 4 days 4 hours ago) and read 4427 times:

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






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User currently offlineGranite From UK - Scotland, joined May 1999, 5568 posts, RR: 63
Reply 18, posted (10 years 8 months 1 week 4 days 4 hours ago) and read 4418 times:
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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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