How many "hot pixels" are ok? (EOS 550D)

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rinon

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Hi all, I hope this is the right place as i'm new here.

Basically, after discovering that my 1-2 year old or so camera seems to have a few hot spots that show up on night photography (I like astronomy) I wondered how many there were and took this with the lens cap on (highlighting all the obvious ones):

http://www.taniquetil.com/IMG_2810.JPG

Some are of course entirely invisible in normal shots, but 3-5 are absolutely visible in dark shots with long exposures.

Is this normal, or should I be thinking of sending it to Canon?

Thanks,

Mike.
 
according to your exif, that was a 30 second exposure at iso 100.

i'd not worry about it. hot pixels are a fact of life with digital. they come and go over time and with temperature.

if they don't notice in normal usage i very much doubt canon would be able to do much about it and if you use adobe lightroom and shoot raw it automatically fixes them anyway.
 
There's a chance that a small utility in the firmware might remap them for you.
Remove the lens and install a body cap. Go to the menu and select "manual sensor clean", wait 30 seconds and then turn off at the power switch.

Repeat the test shot and see what you've got.

Bob
 
Canon Bob said:
There's a chance that a small utility in the firmware might remap them for you.
Remove the lens and install a body cap. Go to the menu and select "manual sensor clean", wait 30 seconds and then turn off at the power switch.

Repeat the test shot and see what you've got.

Bob
Click to expand...
I believe that's an urban myth....
 
Canon Bob said:
There's a chance that a small utility in the firmware might remap them for you.
Remove the lens and install a body cap. Go to the menu and select "manual sensor clean", wait 30 seconds and then turn off at the power switch.

Repeat the test shot and see what you've got.

Bob
Click to expand...

This is what I tried before I did it - no change. I'm sure judging from comment on the youtube vid i've seen it helped some people, but I guess it's just people who misinterpret dust for hot pixels maybe? It didn't help in my case anyway.

Still like you guys say (and thanks very much for the responses!) I guess it;s something that needs to be expected to some degree, and indeed it's entirely un-noticable in normal photography, but for astronomical purposes it certainly is for the more prominent ones. But then I suppose at the end of the day, it can easily be remove as it IS only a half dozen t dozen or so amongst 18 million.

Thanks for putting me a bit more at ease!
 
I get a fair few come and go on my 450D when i do astro stuff or night time long exposures. Taking a dark frame with the lens cap on and subtracting it from the files sorts it fine.
 
rinon said:
..... but I guess it's just people who misinterpret dust for hot pixels maybe?
Click to expand...
You wouldn't find dust using an exposure without light, you'd need to shoot a white target for that.

Bob
 
+1 for using RAW and Lightroom.
Doesn't matter how long the exposure is, Lightroom sorts them out.

I know my 5DII has a few hot pixels because I occasionally catch a glimpse of them in the embedded thumbnail before Lightroom indexes my images and makes it's own preview.
 
Hot pixels become more evident with long exposures as the sensor heats up. It's one reason why long exposure noise reduction is available on many cameras.

Not sure if it's possible on the 550D, but it is possible to map out persistant hot pixels on some cameras. Might be worth seeing if it is available on your camera if it bothers you.
 
Does the on board noise reduction really help? I've been doing a few long exposure without it and I get a good few (12-15) hot/cold pixels aswell as quite abit noise in general? Not sure when I would get out so would be great to know.
 
POAH said:
Nope worked for both my 40D and 5D2 although I had to leave it for more than 30s
Click to expand...
Interesting. I tried it and it didn't work and I've seen a post somewhere (not about to go searching for it on t'internet) where someone claimed a Canon tech said this was untrue.

Will try it next time I find some hot pixels.
 
Pixel mapping is certainly achievable if the code is present. Olympus first put the functionality in their C4040Z back in 2001 and subsequently provided compliant firmware updates for some of their older bodies.
I can''t comfirm or refute the idea that it's a myth on Canon's bodies but there are no shortage of happy people....placebo or otherwise.

Bob
 
arad85 said:
Interesting. I tried it and it didn't work and I've seen a post somewhere (not about to go searching for it on t'internet) where someone claimed a Canon tech said this was untrue.

Will try it next time I find some hot pixels.
Click to expand...

I left my 5d2 for about 2 minutes to get rid of the hot pixels
 
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