Hot & Dead pixels

> My EOS 20D with DeadPixeltest shows these results at 30" without lens and
> cap on:
>
> 100 ISO 7 HOT
> 400 ISO 30 HOT
> 800 ISO 67 HOT
>
> should I be worried?
>
> regards.

Seems like a high number to me, but I would ramp down the exposure so
you know at what point they actually appear, and then consider how
often you would be using that shutter speed.

I don't *believe* that these things generally get worse over time.
 >> Stay informed about: Hot & Dead pixels 

"Maggie" <levami_laNO**SPA**M@hotmail.com> wrote in message
news:459c2dc3$0$4250$4fafbaef@reader1.news.tin.it...
> dear all,
> I have got a question on hot and dead pixels.
> What I understood was that both are defective pixels: one always coloured,
> one always black.
> If the hot is a defective pixel I think it is defective at any exposure
> condition so I should find it everytime in the same position and in every
> frame I take. Correct? Why most take more pictures with different exposure
> conditions to individuate them?
>
> Regarding the software to see them, is DeadPixeltest affidable?
> Is there any other software?
>
> Thank you very much!
>
> Mag
>
Close.

A hot pixel shows in longer exposures and is typically not visible in normal
shooting (daylight)
A stuck (dead) pixel can be on or off or, perhaps somewhere in between. It
is not responsive under any condition.

Hot pixels are common but may be hidden by the camera noise reduction or hot
pixel removal algorithm. Stuck pixels are rare. I've not seen one in any
camera I have or had.

John
 >> Stay informed about: Hot & Dead pixels 

"BD" <robert.drea DeleteThis @gmail.com> ha scritto nel messaggio
news:1167867638.877863.116760@42g2000cwt.googlegroups.com...
> To spot the dead pixels, I would take a piece of posterboard, hang it
> on a wall (or focus the camera on some other uniformly colored surface,
> and take pictures at a variety of shutter speeds. No flash.
>
> To spot the hot pixels, I would take a series of images with the lens
> cap on, and the shutter speed starting at maybe a second, and working
> up to 30 seconds.
>
> My Canon Rebel does have a couple of hot pixels, but they only show up
> after about 20 seconds.
>

My EOS 20D with DeadPixeltest shows these results at 30" without lens and
cap on:

100 ISO 7 HOT
400 ISO 30 HOT
800 ISO 67 HOT

should I be worried?

regards.
 >> Stay informed about: Hot & Dead pixels 

"BD" <robert.drea RemoveThis @gmail.com> wrote in message
news:1167871624.828389.100990@v33g2000cwv.googlegroups.com...
>
>> My EOS 20D with DeadPixeltest shows these results at 30" without lens and
>> cap on:
>>
>> 100 ISO 7 HOT
>> 400 ISO 30 HOT
>> 800 ISO 67 HOT
>>
>> should I be worried?
>>
>> regards.
>
> Seems like a high number to me, but I would ramp down the exposure so
> you know at what point they actually appear, and then consider how
> often you would be using that shutter speed.
>
> I don't *believe* that these things generally get worse over time.
>
I would inspect the image visually. How many of these hot pixels can be
easily picked out?

Hot pixels can appear at a later time. I test my cameras for hot/stuck
pixels right after purchase. I retain the test images and have noted new hot
pixels showing in later images.
-S
 >> Stay informed about: Hot & Dead pixels 

Maggie wrote:
> dear all,
> I have got a question on hot and dead pixels.
> What I understood was that both are defective pixels: one always coloured,
> one always black.
> If the hot is a defective pixel I think it is defective at any exposure
> condition so I should find it everytime in the same position and in every
> frame I take. Correct? Why most take more pictures with different exposure
> conditions to individuate them?
>
> Regarding the software to see them, is DeadPixeltest affidable?
> Is there any other software?
>

Very affordable: DeadPixelTest is a free download.

Phil
 >> Stay informed about: Hot & Dead pixels 

Maggie wrote:
> "BD" <robert.drea RemoveThis @gmail.com> ha scritto nel messaggio
> news:1167867638.877863.116760@42g2000cwt.googlegroups.com...
>> To spot the dead pixels, I would take a piece of posterboard, hang it
>> on a wall (or focus the camera on some other uniformly colored surface,
>> and take pictures at a variety of shutter speeds. No flash.
>>
>> To spot the hot pixels, I would take a series of images with the lens
>> cap on, and the shutter speed starting at maybe a second, and working
>> up to 30 seconds.
>>
>> My Canon Rebel does have a couple of hot pixels, but they only show up
>> after about 20 seconds.
>>
>
> My EOS 20D with DeadPixeltest shows these results at 30" without lens and
> cap on:
>
> 100 ISO 7 HOT
> 400 ISO 30 HOT
> 800 ISO 67 HOT
>

No. Pretty typical.

But you should be testing at a range of exposure
times: 1/100, 1/10, 1, 2, 5, 10, 15 and 30 sec for
example.

The ones you care most about, the true hot pixels,
will show up at even fast shutter speeds. The
ones at 30 sec may just be noise.

Phil
 >> Stay informed about: Hot & Dead pixels 

BD wrote:
>> My EOS 20D with DeadPixeltest shows these results at 30" without lens and
>> cap on:
>>
>> 100 ISO 7 HOT
>> 400 ISO 30 HOT
>> 800 ISO 67 HOT
>>
>> should I be worried?
>>
>> regards.
>
> Seems like a high number to me, but I would ramp down the exposure so
> you know at what point they actually appear, and then consider how
> often you would be using that shutter speed.
>
> I don't *believe* that these things generally get worse over time.
>

Actually, they do .. in the short term .. as the
camera heats up.

At 30 sec, these are not bad results. At 10 sec
they would be.

Phil
 >> Stay informed about: Hot & Dead pixels 

> No. Pretty typical.
>
> But you should be testing at a range of exposure times: 1/100, 1/10, 1, 2,
> 5, 10, 15 and 30 sec for example.
>
> The ones you care most about, the true hot pixels, will show up at even
> fast shutter speeds. The ones at 30 sec may just be noise.
>
> Phil

I have done again the test, with these results:

SPEED ISO HOT

1/30" 100 0
4" 100 1
15" 100 6
30" 100 8
1/30" 400 0
4" 400 2
15" 400 31
1/30" 800 0
1" 800 1
3,2" 800 7
4" 800 10
15" 800 51



What do you think?

Thank you!!

M
 >> Stay informed about: Hot & Dead pixels 

Maggie wrote:
>> No. Pretty typical.
>>
>> But you should be testing at a range of exposure times: 1/100, 1/10, 1, 2,
>> 5, 10, 15 and 30 sec for example.
>>
>> The ones you care most about, the true hot pixels, will show up at even
>> fast shutter speeds. The ones at 30 sec may just be noise.
>>
>> Phil
>
> I have done again the test, with these results:
>
> SPEED ISO HOT
>
> 1/30" 100 0
> 4" 100 1
> 15" 100 6
> 30" 100 8
> 1/30" 400 0
> 4" 400 2
> 15" 400 31
> 1/30" 800 0
> 1" 800 1
> 3,2" 800 7
> 4" 800 10
> 15" 800 51
>
>
>
> What do you think?
>

I find that acceptable. Key is zero at 1/30 sec
... if there was a true hot pixel, you would see it
even at 1/200 sec and above (been there, done that).

The ones at 4 sec, 15 sec and 30 sec are noise ..
and you will see more of those at higher ISO
levels (which is why higher ISO means larger files).

Your ISO 100 results tell me you have a very good
camera.

Phil
 >> Stay informed about: Hot & Dead pixels 

"Phil Wheeler" <wt6uh-ng7.RemoveThis@yahoo.com> ha scritto nel messaggio
news:45a04961$0$5199$4c368faf@roadrunner.com...
> Maggie wrote:
>
> Your ISO 100 results tell me you have a very good camera.
>
> Phil

Thank you Phil!
These words are encouraging for a newbie!
 >> Stay informed about: Hot & Dead pixels 

And lo, Maggie <levami_laNO**SPA**M@hotmail.com> emerged from the ether
and spake thus:
>
>> No. Pretty typical.
>>
>> But you should be testing at a range of exposure times: 1/100, 1/10, 1, 2,
>> 5, 10, 15 and 30 sec for example.
>>
>> The ones you care most about, the true hot pixels, will show up at even
>> fast shutter speeds. The ones at 30 sec may just be noise.
>>
>> Phil
>
> I have done again the test, with these results:
>
> SPEED ISO HOT
>
> 1/30" 100 0
> 4" 100 1
> 15" 100 6
> 30" 100 8
> 1/30" 400 0
> 4" 400 2
> 15" 400 31
> 1/30" 800 0
> 1" 800 1
> 3,2" 800 7
> 4" 800 10
> 15" 800 51
>
>
>
> What do you think?
>
> Thank you!!
>
> M

Can I just butt in for a moment and announce how much I hate those
"hot" pixels in long exposures? I know they're unavoidable, but I
still hate them!

--
Aaron
http://www.fisheyegallery.com
http://www.singleservingphoto.com
 >> Stay informed about: Hot & Dead pixels