dead pixel in K-7

Szalik · Dec 21, 2009

Could You tell me if this is normal.

I've did long exposure shot with my K-7 and I have already saw 10 dead pixels 2 are big red ones the others are white. I didnt do the pixel maping yet.

I have a camera only 5 days and already something like this happens.
I thought that in this class of equipment you dont have such a problems.

and another question, could it because I did 2 shoots almost directly to the bright sun without using UV filter ?

ehhh :/

Zebooka · Dec 21, 2009

1) Use noise reduction for long exposures (see user functions)
2) Use in-camera pixel mapping function.

PS: If you don't know - most of such large sensors have defect pixels. But they are remapped.

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Szalik · Dec 21, 2009

thx for reply, but if I use mapping should they all be gone ? if not send back camera or just leave it the way it is , this is my first DSLR, thats why I am asking, not everything is obvious for me

awaldram · Dec 21, 2009

Szalik said:
Could You tell me if this is normal.

I've did long exposure shot with my K-7 and I have already saw 10 dead pixels 2 are big red ones the others are white. I didnt do the pixel maping yet.

All sensors have pixel failure during long exposures, Its nothing to worry about unless it happens at normal exposure durations.

Re-mapping wont help as unless they appear during a normal exposure there not really dead pixels but hot spots during the long exposure.

Switch on dark frame subtraction and forget it
http://en.wikipedia.org/wiki/Dark_frame_subtraction

Szalik said:
I have a camera only 5 days and already something like this happens.

As it will for any digital camera durin long exposures

Szalik said:
I thought that in this class of equipment you dont have such a problems.

Its a fact of life you cant buy your way out of the problem.

Szalik said:
and another question, could it because I did 2 shoots almost directly to the bright sun without using UV filter ?

Nope it couldn't

Szalik said:
ehhh :/

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viking79 · Dec 21, 2009

Just to add, many RAW developing tools will automatically remove dead pixels. An example is Lightroom or ACR.

As someone else said, try running the pixel mapping feature, and also use the dark frame noise reduction (it will increase exposure duration by roughly the length of time of the original exposure or a little less).

Eric
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Pete Dee · Dec 21, 2009

Szalik said:
thx for reply, but if I use mapping should they all be gone ? if not send back camera or just leave it the way it is , this is my first DSLR, thats why I am asking, not everything is obvious for me

Just map them and be happy that the K-7 does it in camera and that you don't have to send it back for service.

Pete

cr0100 · Dec 21, 2009

it's worth mentioning that what you are describing is "hot" pixels. A dead pixel is when it always shows up black. Hot pixels are common in long exposures and there really isn't much you can do about it.

If you're going to be doing a lot of long-exposure shooting, I'd recommend using RAW. Many RAW converters (Adobe Camera Raw, for one) will remove hot pixels automatically - saving you a ton of time trying to edit out those little blobs in Photoshop...

-Charles

Akar · Dec 21, 2009

Exactly. The dead pixels and hot pixels (probabely in your case) are different things. Just switch the long exposure noise reduction "on" and it should help. If you have bad (dead) pixels in short exposures, just remap them using a custom function. It is a big advantage of the K7 (K20D too) over the older cameras.
Andrzej
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Szalik · Dec 21, 2009

thx for You reply.

I have checked and in short exposure modes I seem to have no hot pixels.

You say that the hot pixels during long exposure modes cant be erased ?

Becasue I hace Pixel Mapping
and Sensor cleaning option

use one of these? or It wont help for the long exposure and what is the difference between theese two ?

And Is it good to have dust removal set on every start-up action ? And do I have to put the camera on white object so the camera could remeber the image and remove the dust on every start-up , is this how it works ?

thx for any help.

And Could someone give me simple anwser to all these questions, I would be gratefull

This is new for me thx again for any help

awaldram · Dec 21, 2009

Szalik said:
thx for You reply.

I have checked and in short exposure modes I seem to have no hot pixels.

Good your camera is fine

Szalik said:
You say that the hot pixels during long exposure modes cant be erased ?

Hot pixels during long exposure is normal, Dark frame subtraction will remove them this is the same as long exposure noise reduction enable it in the menu.

As has been stated some raw converter will remove the hot pixels for you as well.

Szalik said:
Because I have Pixel Mapping

This will only remap failing pixels , you don't have any.

Szalik said:
and Sensor cleaning option

This is to remove dust so is of no use here.

Szalik said:
use one of these? or It wont help for the long exposure and what is the difference between theese two ?

See abovr

Szalik said:
And Is it good to have dust removal set on every start-up action ?

Well I do.

Szalik said:
And do I have to put the camera on white object so the camera could remeber the image and remove the dust on every start-up , is this how it works ?

No the white image dust show function is so you can see where the dust is to manually remove it (not something you want to be doing yet)

Szalik said:
thx for any help.

And Could someone give me simple anwser to all these questions, I would be gratefull

This is new for me thx again for any help

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Szalik · Dec 22, 2009

awaldram said:
awaldram said:

I have checked and in short exposure modes I seem to have no hot pixels.

Click to expand...

Good your camera is fine

awaldram said:

You say that the hot pixels during long exposure modes cant be erased ?

Click to expand...

Hot pixels during long exposure is normal, Dark frame subtraction will remove them this is the same as long exposure noise reduction enable it in the menu.

Thank You for You reply, that would be everything I want to know

One thing that only worries me is that the pictures were taken with medium noise reduction and eaven though I had hot pixels. But it was JPG maybe RAW wont show anything, I didnt hae the chance to chceck because I am working 13 hoursa day.

I will try it again and tell you my results.

And another question

Is it possible eaven during long exposures not to have any hot pixels ?

steelski · Dec 22, 2009

Szalik said:
Szalik said:

Szalik said:

I have checked and in short exposure modes I seem to have no hot pixels.

Click to expand...

Good your camera is fine

Szalik said:

You say that the hot pixels during long exposure modes cant be erased ?

Click to expand...

Hot pixels during long exposure is normal, Dark frame subtraction will remove them this is the same as long exposure noise reduction enable it in the menu.

Click to expand...

Thank You for You reply, that would be everything I want to know

One thing that only worries me is that the pictures were taken with medium noise reduction and eaven though I had hot pixels. But it was JPG maybe RAW wont show anything, I didnt hae the chance to chceck because I am working 13 hoursa day.

I will try it again and tell you my results.

And another question

Is it possible eaven during long exposures not to have any hot pixels ?

Possibly,

Its called Slow shutter speed NR (noise reduction) its custom function 18 according to DPreview
http://www.dpreview.com/reviews/pentaxk7/page12.asp

try it with auto and standard.

What the camera will do is take a picture, then take the picture again without actually producing an image. and subtract any hot pixels from the two pixels.

But what others have not said really is that this is normal for any other DSLR. Even the very highest end will have hot pixels. And they all deal with it in the same way. through slow shutter NR/ dark frame subtractions.
Do not worry about it. Always shoot RAW for very long exposures.

Matthew Miller · Dec 22, 2009

Szalik said:
One thing that only worries me is that the pictures were taken with medium noise reduction and eaven though I had hot pixels.

Noise reduction doesn't really address this issue.

Szalik said:
But it was JPG maybe RAW wont show anything, I didnt hae the chance to chceck because I am working 13 hoursa day.

This isn't inherently a RAW-vs-JPEG thing. It's just that some converter software has a feature to automatically map out pixels which seem wrong.

Szalik said:
Is it possible eaven during long exposures not to have any hot pixels ?

Yes, but unlikely.

Remember, there's fifteen million pixels.

--
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Szalik · Dec 22, 2009

Thx ...

Oh , now never mind the pixels, I was looking at my photos and noticed a spot, like something dirty on my images , in the same place.

First it was sharp and looked like a piece of dust somewhere , now it is blurry and wider, just like dirty spot. I can see it without any zooming on short exposure(normal) photos .

And I tried pixel maping and dust removal, but nothing.

Then I brouth the mirror up but didnt saw nothing.

Blow air on the sensor to clean this ?

ehh new camera..... always something

Matthew Miller · Dec 23, 2009

Szalik said:
Oh , now never mind the pixels, I was looking at my photos and noticed a spot, like something dirty on my images , in the same place.

First it was sharp and looked like a piece of dust somewhere , now it is blurry and wider, just like dirty spot. I can see it without any zooming on short exposure(normal) photos .

Yep, that's dust. The appearance will vary with aperture -- it'll be most clear with small apertures (high numbers, like f/22), and blurrier wide open. I have no idea why this is, since the dust is of course on "this side" of the aperture anyway. If anyone can explain this, I'll be grateful.

Szalik said:
Blow air on the sensor to clean this ?

Yeah, that's the first step. Make sure to use a proper blower so you're not just putting more dust in. (And don't use canned air -- you don't want to risk getting spots of propellant in the camera. And it's too much force anyway.)

--
Matthew Miller « http://mattdm.org/ »

Szalik · Dec 24, 2009

But the strange thing is when I do the dust alert I cant see any dust, not eaven a spot, and before when I did It I have noticed few objects but it was propably because i didnt pointed the camera on my wall right, it was to dark. And even though it wasnt near that spot I am seeing now on all my images, strange.

I noticed few spots of dost on the mirror, or could it be on the other side of the lens ?

If I am gonna blow the air inside is there no risk I am gonna put then more on the sensor , or then just do it again but on the sensor ?

Thx for help.

Now I cant do that because I am on a vessel and have no proper and clean equipment to do that :/

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dead pixel in K-7

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