How to determine if there is dust on ccd

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Hi All,

I've been to take some photos with my Nikon D70 camera and I used maximum
resolution. When I had a look at the photos in actual pixels view, I noticed
I had around 20 places where the image was showing dark areas. I presumed
they might come from the lens or filter. I am curious however what is the
best system to check if there is dust on ccd? I tried an experiment today, I
took a photo of a blank piece of paper and the image doesn't show any spots.
I want to know if I need to focus the image on the paper (I think that if
there is dust on CCD, it should appear as a focused spot on the photo
despite of an out of focus photo).

Any advice appreciated. I don't intend to clean myself the sensor, in case
there is dust on it, I just want to know what is the situation.

Regards,
Nicolae
 
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Nicolae Fieraru <nospam@please.com> wrote:

> I am curious however what is the best system to check if there is dust on
> ccd? I tried an experiment today, I took a photo of a blank piece of paper
> and the image doesn't show any spots. I want to know if I need to focus
> the image on the paper (I think that if there is dust on CCD, it should
> appear as a focused spot on the photo despite of an out of focus photo).

That's right, focus shouldn't matter. Indeed, since you want to be able to
tell the difference between the dust spots and actual spots on whatever it
is you're photographing, being out of focus should help matters.

But, when you do the dust-test shot, it is important to stop down to the
minimum aperture. Large apertures will hide the dust. So if you saw the
spots in an outdoor picture shot at, say, f/11, and then did your test
shot in the house wide open, you've hidden the dust.

Find a blank white wall that is relatively evenly lit. Shoot a picture
of it at minimum aperture; assuming it's lit by a table lamp, the exposure
will be very long, several seconds. During the exposure, move the camera
around so that any detail in the wall will be completely blurred out of
existence. Now look for spots.

--
Jeremy | jeremy@exit109.com
 
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Thanks Jeremy, I've done the test and unfortunately now they show up as in
my photos.... So it wasn't on the lens...
I just locked up the lens and has a visual inspection, the CCD looks perfect
to me, can't see any speck of dust on it, therefore I think this is a job
for a repair shop... It is extremely easy to make it worse and too hard to
make it better :)


Regards,
Nicolae
 

Stacey

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Nicolae Fieraru wrote:

> Thanks Jeremy, I've done the test and unfortunately now they show up as in
> my photos.... So it wasn't on the lens...
> I just locked up the lens and has a visual inspection, the CCD looks
> perfect to me, can't see any speck of dust on it, therefore I think this
> is a job
> for a repair shop...

If you EVER change the lens, you'll just be right back where you are now.
You need to learn how to clean it yourself or it's going to spend a lot of
time in the repair shop..

--

Stacey
 

Paul

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Stacey wrote:

> Nicolae Fieraru wrote:
>
>
>>Thanks Jeremy, I've done the test and unfortunately now they show up as in
>>my photos.... So it wasn't on the lens...
>>I just locked up the lens and has a visual inspection, the CCD looks
>>perfect to me, can't see any speck of dust on it, therefore I think this
>>is a job
>>for a repair shop...
>
>
> If you EVER change the lens, you'll just be right back where you are now.
> You need to learn how to clean it yourself or it's going to spend a lot of
> time in the repair shop..


Give a shot at just blowing it off. Then try a 'sensor' brush, if the
dust has been on too long & got glued on with moisture & such, you need
the volitile solvents and wiping method. It's not too bad though really.
Theoretically frequest brush treatment could be adequate.
 

steve

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On Sun, 24 Apr 2005 23:07:05 -0700, paul <paul@not.net> wrote:

>Stacey wrote:
>
>> Nicolae Fieraru wrote:
>>
>>
>>>Thanks Jeremy, I've done the test and unfortunately now they show up as in
>>>my photos.... So it wasn't on the lens...
>>>I just locked up the lens and has a visual inspection, the CCD looks
>>>perfect to me, can't see any speck of dust on it, therefore I think this
>>>is a job
>>>for a repair shop...
>>
>>
>> If you EVER change the lens, you'll just be right back where you are now.
>> You need to learn how to clean it yourself or it's going to spend a lot of
>> time in the repair shop..
>
>
>Give a shot at just blowing it off. Then try a 'sensor' brush, if the
>dust has been on too long & got glued on with moisture & such, you need
>the volitile solvents and wiping method. It's not too bad though really.
>Theoretically frequest brush treatment could be adequate.


I have tried something called DSLRClean which are dry stcks you can
obtain from:

www.intemos.com

I was scared of touching the sensor at first but I have managed, with
some perseverence, to totally clean the sensor on my D70 with these.

Anyway - do as you will but learning to clean the sensor yourself is
really the only way unless you leave the same lens on all the time.
The DSLRClean sticks are relatively cheap.
 
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In message <426c6299@duster.adelaide.on.net>,
"Nicolae Fieraru" <nospam@please.com> wrote:

>(I think that if
>there is dust on CCD, it should appear as a focused spot on the photo
>despite of an out of focus photo).

The sharpness of the dust is related to f-stop. It doesn't matter if
the subject is in focus or not, other than the fact that it is harder to
see if the subject in that area is detailed and sharply focused.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
 
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