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General photography questions and answers: Discuss Hot Pixels...I noticed the other night what I believe are a couple of hot (red) pixels on a couple of shots ...
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Old 28-08-2007, 07:33   #1 (permalink)
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Hot Pixels

I noticed the other night what I believe are a couple of hot (red) pixels on a couple of shots @ iso 800 & above........not long exposures just high ISO.

Now I tried the lens cap test.....ISO 1600 5 sec & 30 sec exposures but nothing really showed up other than noise

The other thing is if I open the image up in Capture One I can see the hot pixel but if I load the same RAW image with ACR it shows for a second or two while RAW settings load but then disappears ........this then can be loaded in to CS and the pixel is gone

Any thoughts anyone?

EDIT: I've just read that ACR automatically removes hot pixels.

Last edited by P-E; 28-08-2007 at 07:49.
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Old 28-08-2007, 07:53   #2 (permalink)
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Re: Hot Pixels

This is a strange one as they are not showing in all software packages

If it is definitely hot pixels it should show up on all shots, at all settings, in all formats (jpg/raw) and in all software packages (with the exception of software designed to remove them automatically).

I think it is time for some serious testing to check it out properly.
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Old 28-08-2007, 07:57   #3 (permalink)
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Re: Hot Pixels

Sorry Steve I just edited my post above as you were posting

It appears that ACR automatically removes hot pixels.....only read this on the net so but it does appear that ACR is removing them.

Funny I'm not seeing them with the lens cap test though
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Old 28-08-2007, 08:09   #4 (permalink)
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Re: Hot Pixels

Does Lightroom do the same?

Yeah there is still something amiss there if the hot pixels are not showing on the lens cap test. I am just guessing here but it maybe worth trying a few shots of plain coloured backgrounds and check to see if the stuck pixel only appears under certain circumstances?
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Old 28-08-2007, 08:18   #5 (permalink)
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Re: Hot Pixels

Just tried LR and the pixel still shows........only ACR auto takes them out to my knowledge.

I will try as you suggest Steve
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Old 28-08-2007, 08:22   #6 (permalink)
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Re: Hot Pixels

I think the latest Canon software does as well...but I don't know if that is backwardly compatible with your camera.

I wondered about LR because with it also being made by Adobe there may have been a chance of it doing so as well. Thanks for checking
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Old 28-08-2007, 08:30   #7 (permalink)
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Re: Hot Pixels

Aha the lens cap test does show them I must have been viewing them with ACR last night

Right lens cap test;

ISO 100 @ 5sec: No hot pixels showing.

ISO 1600 @ 5sec: 2 hot pixels showing.

ISO 1600 @ 1/4 sec: 5 hot pixels showing (funny I thought the 5 sec exposure would show more )

This hot pixel thingy appears to effect most digital cameras so not too worried.

Just couldn't get me head around why it was not showing up in ACR.........I will put it down to user error or an early senior moment
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Old 28-08-2007, 09:19   #8 (permalink)
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Re: Hot Pixels

You could always have the sensor re-mapped if they begin to bother you.

Somehow I think you are more likely to change your camera before that occurs though
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Old 28-08-2007, 09:30   #9 (permalink)
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Re: Hot Pixels

LOL I won't be changing my camera body for a long time......I've just purchased a Canon 300mm IS 2.8L lens

I can live with five hot ones I think......be interested to hear how many people have hot pixels but please don't do the test if you are easily upset

Update to which RAW/Editing programme auto corrects hot pixels.....I read that Raw Shooter does as does Bibble but I can't personally confirm this.

EDIT: If someone does bother to do the test and reports no hot pixels please don't post your result

Last edited by P-E; 28-08-2007 at 09:35.
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Old 28-08-2007, 09:37   #10 (permalink)
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Re: Hot Pixels

For the less technically minded bods on the Forum, would one of you like to explain hot pixels please!?
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Old 28-08-2007, 09:40   #11 (permalink)
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Re: Hot Pixels

I've got to go to work so I will let Steve explain
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Old 28-08-2007, 09:41   #12 (permalink)
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Re: Hot Pixels

Quote:
Originally Posted by P-E View Post
LOL I won't be changing my camera body for a long time......I've just purchased a Canon 300mm IS 2.8L lens
Ohh thats nice...I look after that for you if you ever get tired of it

Quote:
Originally Posted by P-E View Post
I can live with five hot ones I think......be interested to hear how many people have hot pixels but please don't do the test if you are easily upset
I was just about to say that I know that there is one on my 10D and none on my 20D until I saw the bit below...

Quote:
Originally Posted by P-E View Post
Update to which RAW/Editing programme auto corrects hot pixels.....I read that Raw Shooter does as does Bibble but I can't personally confirm this.
I have been using RawShooter Premium pretty much exclusively for all my post processing but I recently changed to Lightroom. I have never noticed any stuck pixels with RS but since you are saying it corrects stuck pixels too I am unlikely to. Having said that I have not noticed any on the (few) shots I have processed in LR.

To be certain I will have to do some testing
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Old 28-08-2007, 09:51   #13 (permalink)
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Re: Hot Pixels

Hot or 'stuck' pixels are individual pixels (or 'photosites') on the sensor which are always stuck on - or at least which stick under certain combinations of exposure time and ISO setting. They appear as bright dots which may be any colour depending on which photosites are faulty.

Turning up the ISO increases the gain or amplification - like increasing the volume on an audio amp - and is more likely to show hot pixels. Similarly a long exposure increases the load on the sensor and can cause hot pixels to appear.

P-E - Your camera doesn't seem to have a problem at normal exposures so I wouldn't worry about it. The number of hot pixels can vary according to temperature, phases of the moon etc , so you may see more on one occasion than on another.

I'm not aware of any automatic hot pixel correction in either Rawshooter or Bibble. It is in the newer versions of ACR. Not sure about Canon DPP - there is a dust elimination feature for the 400D, but I didn't know that this also dealt with hot pixels.

Personally I'd rather deal with it manually in case the software mistakes stars or distant lights for hot pixels, but if it seems to work OK that's fine.
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Old 28-08-2007, 18:35   #14 (permalink)
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Re: Hot Pixels

Quote:
Originally Posted by Steve View Post
Ohh thats nice...I look after that for you if you ever get tired of it
I bet you would

Quote:
Originally Posted by Steve View Post
I was just about to say that I know that there is one on my 10D and none on my 20D until I saw the bit below...
Impressive if you have non on your 20D

Cheers for your input Silkstone
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Old 29-08-2007, 03:22   #15 (permalink)
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Re: Hot Pixels

I'm curious now---what is the lens cap test? I did have two hot pixels on my Rebel XTI for a few shots. Then they just went away--I was happy to see that happen.
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Old 29-08-2007, 07:31   #16 (permalink)
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Re: Hot Pixels

Re lens cap test;

What I did was;

(1) Leave lens cap on.
(2) Set lens to manual focus.
(3) Set camera to manual.
(4) ISO 1600.
(5) 5 sec exposure.
(6) Take a shot.

Above is basically what I did plus I tried differing ISO settings from 100 to 1600......I also set camera to AV mode which gave me approx 30 sec exposures.

I tried ISO 100 @ 1/4 sec which showed 1 hot pixel but I don't think using 1/4 was the correct way of testing
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