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05-26-2010, 10:25 PM   #16
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thank you all for the inputs! i am NOT condident on myself... so i decide to use warranty to send it back to pentax, hope they can fix the problem. i may send them together a group of "spot" photoes

05-26-2010, 11:14 PM   #17
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You sent your camera back to Pentax because of sensor dust?
05-27-2010, 10:22 AM   #18
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Too late now if you've already sent it off, but I agree with the above - sending a camera off for repair because there's a dust spot is like sending your sofa back to the manufacturer because you got dirt under the cushions. Every once in a while, you need to clean the thing, and that's just something you need to know how to do yourself. It takes minutes (as opposed to weeks sending to Pentax), and it's not going to be under warranty forever...
05-27-2010, 09:00 PM   #19
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ok...thank you , i will do it myself. i am just not that confident at these things.

another question,


is this dark strip also caused by sensor noise?

05-27-2010, 09:32 PM   #20
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Actually, that looks like dust as well.
05-28-2010, 12:25 AM   #21
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QuoteOriginally posted by shang Quote
ok...thank you , i will do it myself. i am just not that confident at these things.
Its not that difficult - and with the correct tools its fine. The rocket blower is a dSLR photographers best friend IMHO.

QuoteOriginally posted by shang Quote

is this dark strip also caused by sensor noise?
QuoteOriginally posted by Wheatfield Quote
Actually, that looks like dust as well.
From the size and shape, its fluff - but its so lightweight it comes off easily.

BTW - point the camera down when you use a blower - gravity is a wonderful thing.

Cheers
05-28-2010, 02:04 AM   #22
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I have a dark spot problem on my K7
The spot appears almost dead center of the image and around f16 is a tiny almost circular black spot but becomes less defined and fuzzy at larger aperatures
Dust alert shows a completely clean screen so this points towards a failed pixel.
If this was the case then surely a dead pixel would be visible on the white dust alert screen?
Running pixel mapping has absolutely no effect the spot is still there.
Am I right in thinking that pixel mapping should correct a dead pixel as well as correcting hot pixels.
Although dust alert shows a clean sensor I have gone through a wet clean routine as a precaution and this has had no effect and the spot still remains.
I take it that pixel mapping is completely automatic and requires no additional input from me?
I read somewhere that someone had a similar problem but this disappeared after a firmware update.
But I have done this and am currently running Ver 3.
Is it possible for a dead pixel to become active again or is this unlikely.

Any help would be very much appreciated .
dino1
05-28-2010, 04:24 AM   #23
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QuoteOriginally posted by dino1 Quote
I have a dark spot problem on my K7
The spot appears almost dead center of the image and around f16 is a tiny almost circular black spot but becomes less defined and fuzzy at larger aperatures
Then it is not a dead pixel, it's dust. A dead pixel would be the same on all of your photos, regardless of the aperture you used. Dust alert is not perfect, sometimes it also shows me no dust while on my macro shots (f16-f22) it's clearly visible.

05-28-2010, 12:42 PM   #24
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thank you, MoiVous!

another question is, what is the mirror used for? I found there is some dust on the mirror, does that have any impact on the images? if so, and there is dust on the back of the mirror.... then what should i do? thank you again!
05-28-2010, 12:45 PM   #25
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QuoteOriginally posted by shang Quote
ok...thank you , i will do it myself. i am just not that confident at these things.

another question,

is this dark strip also caused by sensor noise?
Looks like dust to me. Try taking a close-up shot of something at F22. All your dust will become crystal clear and very easy to spot

Adam
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05-28-2010, 12:46 PM   #26
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QuoteOriginally posted by shang Quote
thank you, MoiVous!

another question is, what is the mirror used for? I found there is some dust on the mirror, does that have any impact on the images? if so, and there is dust on the back of the mirror.... then what should i do? thank you again!

The mirror is what gets the image from the lens up into the viewfinder. It has no effect on image quality, since when you take a photo, the mirror goes up, and the shutter opens behind it.

From Wikipedia:

Cross-section view of SLR system:
1 - Front-mount lens (4-element Tessar design)
2 - Reflex mirror at 45-degree angle
3 - Focal plane shutter
4 - Film or sensor
5 - Focusing screen
6 - Condenser lens
7 - Optical glass pentaprism (or pentamirror)
8 - Eyepiece (can have diopter correction ability)

Adam
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05-28-2010, 01:31 PM   #27
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thanks a lot, Adam! that's so helpful!
06-05-2010, 01:44 AM   #28
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Thanks for your reply simico . Apologies for the delay in acknowledging this.
In view of your opinion that my problem is due to dust I have made 2 more attempts at removal using a wet cleaning process both proved unsuccessful.
I have since found that by going into Live View and accessing maximum enlargement the offending spot is resolved as a perfectly square black dot which leads me return to thinking that the problem is a dead pixel.
Your thoughts on this would be appreciated.
dino1
06-05-2010, 09:15 AM   #29
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Hard to say without seeing the image. Posting an unresized crop would help. But since you say it's dependent on aperture, I say there's an almost zero chance it's anything but dust.

Last edited by Marc Sabatella; 06-05-2010 at 12:45 PM.
06-05-2010, 09:54 AM   #30
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Don't fear the sensor!

I too was once terrified of getting dust on the sensor, but then I found Just Ltd - Cleaning Products for Cameras and all Optical Equipment (no personal or commercial connection whatsoever). It was here I learned that it is very difficult to damage the actual sensor as it is protected by an anti-alias screen and that cleaning the sensor is much less difficult than most camera manufacturers/shops would have you belive. The site is a mine of useful information and sells cleaning products at prices that are good value, at least in the U.K. The proprietors, in my experience, are helpful and friendly and will not try to sell you kit you don't need. If you send them a jpeg of the dust on the sensor they will even advise you as to whether it is really is worth cleaning at this stage.

I was lucky in that there premises (home, actually) is only 15 minutes drive from where I live, so I was able to have a free (cost of consumables only) tutorial and a mug of tea!

Remember, the only way to have a perfectly clean sensor is to leave your camera at home, unused in a dust-free environment. Personally, I'd rather take photographs and clean when absolutely necessary.

Incidentally, unless used with great care, and a little luck, a blower is more likely to simply redistribute dust than remove it.
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