Sensor dust? - DPChallenge Forums

Canon EF 28-135mm f/3.5-5.6 IS USM

08/10/2006 02:51:39 AM · #1

This is a section from a full sized photo I just took of my cat. What's with all the colored spots? Is that sensor dust? I did have a UV filter on which I'm reading more and more that I shouldn't, but we won't go there. I noticed a blue spot a few weeks ago when I was shooting without the UV also. I figured it was a star that just caught light funny.

Sensor Dust?

mist

Canon EOS-60D

08/10/2006 02:54:08 AM · #2

Try taking a picture of a piece of white card, if you still see dots in the same place, it could be sensor dust.

Edit - just noticed you don't have an SLR, so it's unlikely.

Message edited by author 2006-08-10 02:54:42.

Canon EF 24-105mm f/4.0L IS

08/10/2006 02:58:07 AM · #3

Originally posted by mist:

Try taking a picture of a piece of white card, if you still see dots in the same place, it could be sensor dust.

Edit - just noticed you don't have an SLR, so it's unlikely.

Yea, I'm not sure what else to call it. I've cleaned all my outside glass, and it's still there. There is one piece of noticable dust inside the actual camera that I can see, but all those spots are just too much.

lyta

Canon EOS-40D

08/10/2006 03:16:22 AM · #4

Hot pixels maybe?

Azrifel

Fujifilm X100VI

08/10/2006 03:30:10 AM · #5

Yeah, those are hot / stuck pixels. Either because of a long exposure time / high iso, perhaps even high temperature or because some of the photodiodes are starting to fail.
This has nothing to do with dust or the lens. Purely related to the photodiodes of the sensor.

Message edited by author 2006-08-10 03:30:56.

08/10/2006 03:39:31 AM · #6

Originally posted by Azrifel:

Exposer time was 2sec. The ISO was 100. And it's not hot. Which leaves these failing photodiodes..

So what can I do? I'm trying to google it right now and I'm not getting much of a result.

Message edited by author 2006-08-10 03:41:15.

Azrifel

Fujifilm X100VI

08/10/2006 05:28:25 AM · #7

Hmm, your camera is quite an old design / has an old design sensor in it. In those days (I sound like an old man, but the tech is progressing so rapidly) it was quite common for a ccd to show hot pixels on exposures from 1s and up, even at the lowest iso setting. Only when a pixel is bright in all your exposures (even the ones in daylight) you have a failing photodiode (a stuck pixel). I've seen those on brand new camera's in the past, but from 2005 onwards hot pixels and stuck pixels are well handeled by the processing software in the cameras so that you don't see them no more.

This is a page from 2003, not written by a manufacturer but the info is ok.
//webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html

I think not much can be done about it and it is something that most cameras of this age will have.

Nikon AF Nikkor 50mm f/1.8D

08/10/2006 05:46:45 AM · #8

Originally posted by Azrifel:

Thanks so much. I've learned a lot. I can't wait to retire my antique.

deapee

Kodak V803

08/10/2006 09:08:00 AM · #9

It's not just a camera age thing. Every camera that every person on this site has will have dead pixels. Mapping out the dead pixels is part of the manufacturing process. Through software, they take the pixels that are dead and replace those dead pixels with pixels from a close surrounding area. No one will ever notice the couple of pixels getting swapped around.

You could try and call Sony and ask them if they can still remap your sensor. I know it's possible with all nikon dslrs and canon dslrs.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

08/10/2006 09:55:53 AM · #10

Having those hot pixels mapped out is one possibility; of course there's the cost of having it done and the inconvenience of being without the camera. It doesn't look like the 707 has long-exposure noise reduction, but you could do it manually. Google "dark frame subtraction" and read up on the technique. It could help you correct most if not all of the visible hot pixels, with a little effort.

quiet_observation

Canon EOS-7D

Canon EF 70-200mm f/2.8L IS USM

08/10/2006 10:13:46 AM · #11

This is an article about dark frame substraction using Adobe Photoshop. Is this technique legal under the basic or advanced challenge editing rules?

Canon RF 24-70mm f/2.8 L IS

08/10/2006 03:43:51 PM · #12

Ooo.. this is pretty cool. I feel so smart now.

kirbic

Canon EOS R5

08/10/2006 04:23:10 PM · #13

Originally posted by maryba:

This is an article about dark frame substraction using Adobe Photoshop. Is this technique legal under the basic or advanced challenge editing rules?

The bugger is, it's legal in both Basic and Advanced *only* if done in-camera :-P
It's not legal in either Basic *or* Advanced if done in post, since it requires combining two exposures :-(
This is one of the stranger conundrums of the rules.