C750 white dots

Fantomas · Jul 26, 2003

John Hilmer said:
Consider that this thread is posted by Pieter so that he can
discover if he has a problem that would warrant returning a camera
because he thinks that it may be faulty.

He isn't sure if this is the truth or not.

He asks for help in determining if it is faulty.

You insert your comments that serve your interests,

my interests?
ok, thats enough, I don't answer inflammatory messages, sorry

John Hilmer said:
and these may
confuse Pieter because he isn't aware of all that you are doing, in
many threads, to learn what you want to understand.

This could cause Pieter some confusion.

It may be a difficulty with the languages or tenses, but it seems
to me that it is a matter of respect.

If someone asks a question, I think that the thread that they
started should work towards answering that question, and those with
other issues should post a thread and ask their question.

Again, I'm not the forum police, I'm just voicing an opinion to try
to help everyone here.

If you don't understand this post, I'm not sure that I can help
further.
--
John,

'Superstition and peer pressure direct human activity in the
absence of knowledge.' Issac Azimov.

Adrian Tung · Jul 26, 2003

Pieter03 said:
Yes indeed,
the more experiments I do, the more I think it's noise.
I did a shot of 16 seconds and got the most beautiful collection of
stars you can imagine. (also very colourful)
In other cases it turned out with less then 10 very soft points.
(dark grey, no white)

But it did make a difference after pixel mapping. I'll try to make
the same kind of portrets tomorrow - just to compare the "before
and after pixel mapping" in normal situations.
I guess the lens cap test was a rather stupid idea...

If somebody can give more advise on how I really can figur out
whether my camera has too many dead pixels, that would be very
welcome. But I don't want to rush to my dealer without a good
reason.

thank you all

Pieter

I think the difference between dead pixels and hot pixels is consistency. If you have dead pixels, the dots will always be at the same spot but with hot pixels, they'll only be in the same spot if you immediately take a second shot. Further more hot pixels should only appear on exposures of 1 second or longer (at least that's the case with my 750).

So IMHO you can still use the lens cap method, but use shutter priority (or manual) and take shorter exposures (e.g. 1/30 sec). This way you can eliminate more hot pixels and track down the issue better.

Another thing you can try is not to just judge with a black background (i.e. lens cap), but try other colours such as white, red, green and blue. Try to avoid 1 second or slower exposures to avoid hot pixels, this should help you decide better whether it is a camera issue or not.

Hope that helps....

--

atwl
http://www.imageevent.com/atwl77

OlyC750UZ, TC17, WC07, Suntax9000M

Henry Falkner · Jul 27, 2003

Pieter03 said:
wgeebee said:

Pieter03 wrote:
Did you run the Pixel Mapping yet? It should be done on a new
camera, and the book says about every year thereafter.

gb

Click to expand...

Yes, I did... now
and did straight away the same test with the lens protector
result: only about 15 "stars", and quite softly
(before I had hundreds!)
Still, shouldn't it turn out completly black?

thank you for your advice

I did the pixel mapping when I got the camera. When I did a shot with the lens cover on, I noted that the exposure was 4 seconds. I got a few pixels that were not black, but would expect those due to the long exposure time.

On the boy's face I did not see white dots, due to viewing the picture at 640x480, a considerable reduction in resolution.

However, I have noted that the sharpening on both my C-40ZOOM and the C-750UZ is excessive at setting 0. I see edge effects. Excessive sharpening also brings up noise. On the C-750 I set the sharpening at -3. I note that the sharpening employed in the Camedia software does not create edge effects on a picture of a disembarking Boeing 747 plane.

Pieter03 said:
The manual should point more on the need of pixel mapping before
first use.

It should. The complaint has been expressed about previous models of the series. Which is one of the reasons why I waited for the C-750. Another reason was, I need that hot shoe for the external flash.

Henry

--
H. Falkner

Corne26033 · Jul 27, 2003

Pretty sure it's noise too, and not a faulty camera. I've got a feeling it's related to use of the flash. Or do you see it in non-flash shots too? Anyway, I haven't seen this before. Might be worth mailing the little boy picture to tech-support along with an explanation of the problem. Maybe they can tell you why this happens. There's a link to mail them on the Oly Europe website http://cf.olympus-europa.com/consumer/digimg/service/hotline.cfm
Oh and tell them to post their reply here too, we're curious haha

Pieter03 wrote:
!

Pieter03 · Jul 28, 2003

Vera said:
Vera said:

This is noise or just the perspiration and glow of the little lad. I ran median filter at 2 then faded it. I did this really quickly. i use ps 7. if it was my photo after running the median filter I would have used the history brush to bring back the eyes etc as the median filter tends to blur just a little.

Click to expand...

large file

--
Vera

thanks for your advice, Vera

the hair is very black and very reflecting
the picture was taken closely with flash

I think I'll lower the build in sharpening of teh C-750

Pieter03 · Jul 28, 2003

Henry Falkner said:
However, I have noted that the sharpening on both my C-40ZOOM and
the C-750UZ is excessive at setting 0. I see edge effects.
Excessive sharpening also brings up noise. On the C-750 I set the
sharpening at -3. I note that the sharpening employed in the
Camedia software does not create edge effects on a picture of a
disembarking Boeing 747 plane.

I've written in some reviews about the excessive sharpening of the C-750.

The problems the camera had with the black but very reflective cousins' hair were augmented with the build in sharpening.

Pieter03 · Jul 28, 2003

Vera said:
If however its noise just run a noise> median filter at the lowest
number and it should clear it up.

noise median radius 1 does not clean it up, radius 2 does but a lot of detail is lost this way

Vera said:
By the way the little boy has the most magic eyes.

it's a little girl, she's my cousin, magic? yes!

Pieter03 · Jul 28, 2003

Adrian Tung said:
So IMHO you can still use the lens cap method, but use shutter
priority (or manual) and take shorter exposures (e.g. 1/30 sec).
This way you can eliminate more hot pixels and track down the issue
better.

I did some short exposer tests: 1/30 and less.
result: black all over

thanks

Pieter03 · Jul 28, 2003

Fantomas said:
http://www.imaging-resource.com/PRODS/C750/FULLRES/C75LL107MNR.HTM

as you can see, in a 16-second shot, it is normal to have many hot
pixels.

yes, that's exactly what I got with the lense cap tests
with shorter exposure there was no problem anymore

Fantomas said:
But the photo of your son, is just 1/125 seconds, and I think the
hot pixels shouldn't show up.

Also, hot pixels are colourful, and the ones in your son's shot are
white, and don't appear in the background.

I really don't know what they are.

The picture was taken closely with flash.

Could it be possible that the camera has a difficult job in taking a correct picture of my cousin just because she has a dark skin and very black and reflective hair? I don't have this problem with my own children (who are white). The contrast of the warm an dark coloured skin with the reflection of the flash in the droplets of moisture and the hair is just over the edge. And the excessive sharpening of the C-750 makes it even worse.

Fantomas · Jul 28, 2003

Pieter03 said:
The picture was taken closely with flash.
Could it be possible that the camera has a difficult job in taking
a correct picture of my cousin just because she has a dark skin and
very black and reflective hair? I don't have this problem with my
own children (who are white). The contrast of the warm an dark
coloured skin with the reflection of the flash in the droplets of
moisture and the hair is just over the edge. And the excessive
sharpening of the C-750 makes it even worse.

oh, it was your cousin, sorry.
well, I don't see any moisture droplets in the skin... there were any droplets?

I have also seen some hot pixels at Adrian Tung's gallery:
http://imageevent.com/atwl77/c750test

get the photo number 10. This photo is at ISO400, shutter speed 1/10.
You see colorful pixels.

Get photo number 22, and you will see some more hot pixels, but they are visible only in dark areas.
So it seems your cousin's dark skin is prone to show up these pixels.

But I still wonder why they appear at such short exposures.

Fantomas · Jul 28, 2003

Pieter03 said:
Pieter03 said:

So IMHO you can still use the lens cap method, but use shutter
priority (or manual) and take shorter exposures (e.g. 1/30 sec).
This way you can eliminate more hot pixels and track down the issue
better.

Click to expand...

I did some short exposer tests: 1/30 and less.
result: black all over

then it is not hot pixels.

what about dust in the CCD? that would explain why they don't appear with the cap on.

check if they appear always in the same place.

Pieter03 said:
thanks

Adrian Tung · Jul 29, 2003

Fantomas said:
then it is not hot pixels.
what about dust in the CCD? that would explain why they don't
appear with the cap on.

check if they appear always in the same place.

I've had dust on the CCD of my 740 before I got my 750. It certainly isn't the case here; the dust would look like a large, soft darkened spot. Anyway, to test for dust just take a shot of a pure white surface at 1 second or more.

I used to have pics of my 740's dust-on-CCD but I took them out of ImageEvent already.

--

atwl
http://www.imageevent.com/atwl77

OlyC750UZ, TC17, WC07, Suntax9000M

Fantomas · Jul 29, 2003

well, it is clear that they are not hot pixels:
-they don't appear in a dark shot of the same exposure time
-hot pixels are colorful, not white

so maybe are dead pixels, but dead pixels would also appear in a dark shot (cap on), isn't it?

Adrian Tung said:
Fantomas said:

then it is not hot pixels.
what about dust in the CCD? that would explain why they don't
appear with the cap on.

check if they appear always in the same place.

Click to expand...

I've had dust on the CCD of my 740 before I got my 750. It
certainly isn't the case here; the dust would look like a large,
soft darkened spot. Anyway, to test for dust just take a shot of a
pure white surface at 1 second or more.

I used to have pics of my 740's dust-on-CCD but I took them out of
ImageEvent already.

--
atwl
http://www.imageevent.com/atwl77

OlyC750UZ, TC17, WC07, Suntax9000M

Pieter03 · Jul 29, 2003

Adrian Tung said:
I've had dust on the CCD of my 740 before I got my 750. It
certainly isn't the case here; the dust would look like a large,
soft darkened spot. Anyway, to test for dust just take a shot of a
pure white surface at 1 second or more.

thanks for the reassurance

Seems there's nothing wrong with my camera. I did a kind of test you describe before and it turned out okay.

Can I summarize it this way?:

With a digital camera you have to know very well what you're doing, even more than with an analogue. Since I'm new with DC, I pushed some things over the edge, without being aware of it, resulting in... noise.

Pieter03 · Jul 29, 2003

Fantomas said:
well, it is clear that they are not hot pixels:
-they don't appear in a dark shot of the same exposure time
-hot pixels are colorful, not white

reflexions of the flash, augmented by the build in sharpening?...

sonyv12002 · Jul 29, 2003

Pieter03 said:
Pieter03 said:

I've had dust on the CCD of my 740 before I got my 750. It
certainly isn't the case here; the dust would look like a large,
soft darkened spot. Anyway, to test for dust just take a shot of a
pure white surface at 1 second or more.

Click to expand...

thanks for the reassurance

Seems there's nothing wrong with my camera. I did a kind of test
you describe before and it turned out okay.

Can I summarize it this way?:
With a digital camera you have to know very well what you're doing,
even more than with an analogue. Since I'm new with DC, I pushed
some things over the edge, without being aware of it, resulting
in... noise.

somynex · Jul 29, 2003

i remembered this excellent post and have finally found it. do take the time to read =) according to the article, they are stuck pixels. pixel mapping will probably get rid of them, but imho i wouldn't accept so many in a new camera. anyway hope this helps =)

http://forums.dpreview.com/forums/read.asp?forum=1008&message=5513746

Somy

Pieter03 said:
I'm new to this forum although I follow the posts for some months
now. And it's been of great value for me. Since two weeks I own the
C750. I've taken nice pictures so far but there's one problem that
keeps my attention:
Often I have white dots, like kind of fault pixels.

Is this normal? Is there a problem with the CCD? Should I lower the
sharpening maybe?

Maybe it makes no sense but I did the following test: I took a
picture whit the lens protector on. The result turned out black
(hehe) but with a lot of white dots again, some strong ones and
other softer, exactly like a nice sky of stars. What's wrong?

Possibly this all make no sense but when I look at portrets of my
brothers children, the white dots in their faces are very annoying.

Thank you for helping a newbe!

Fantomas · Jul 29, 2003

Pieter03 said:
Fantomas said:

well, it is clear that they are not hot pixels:
-they don't appear in a dark shot of the same exposure time
-hot pixels are colorful, not white

Click to expand...

reflexions of the flash, augmented by the build in sharpening?...

no, I don't think the sharpening can have such an impact. Just my oppinion.

Fantomas · Jul 29, 2003

tiny dust that shines like crystals in certain conditions
and they look like white pixels.

That is why they don't show up in a dark shot.

I like this theory.

sonyv12002 said:
Pieter03 said:

sonyv12002 said:

I've had dust on the CCD of my 740 before I got my 750. It
certainly isn't the case here; the dust would look like a large,
soft darkened spot. Anyway, to test for dust just take a shot of a
pure white surface at 1 second or more.

Click to expand...

thanks for the reassurance

Seems there's nothing wrong with my camera. I did a kind of test
you describe before and it turned out okay.

Can I summarize it this way?:
With a digital camera you have to know very well what you're doing,
even more than with an analogue. Since I'm new with DC, I pushed
some things over the edge, without being aware of it, resulting
in... noise.

Click to expand...

C750 white dots

Leading Member

Senior Member

Forum Pro

Senior Member

Member

Member

Member

Member

Member

Leading Member

Leading Member

Senior Member

Leading Member

Member

Member

Member

Senior Member

Leading Member

Leading Member

Keyboard shortcuts