*istD dead pixels?


Link Posted 21/08/2004 - 12:22
Does anyone know what the pentax photo browser software does when it converts RAW to TIFF?
I shoot in RAW, and have noticed what appears to be a dead pixel in the middle of the sensor. (very bright blue speck) Consistent across many shots.
I think this means that I need to get the body replaced (only 3 weeks old) but when I did a conversion to 8 bit TIFF, all the dead pixels went away...

Problems very apparent in browser software and on camera LCD display when magnified, completely OK on TIFF output

Has anyone else seen this?
Should I get my body replaced?

Thanks in advance


Link Posted 31/08/2004 - 19:55
found the same problem, had the first camera replaced, same problem again! there is a dead pixel
I will get a refund and buy something else.



Link Posted 01/09/2004 - 09:28
Dead pixels are a fact of life with CCDs. Incidentally, the CCD in the *ist-D (where the dead pixels occur) is made by Sony, the same CCD as in the Nikon D100

Some of the issue is down to dead pixel management. RAW is as it says - you get what the CCD saw. Most cameras (and the *ist-D included, I believe) have some form of dead pixel management that hides the duds for regular JPG shooting. The free convertor dcRAW includes the ability to create a dead pixel history so the convertor can map them out of the RAW file on convert.

(Of course the other thing is dust that produces grey blobs on the image.)

Maybe Pentax can improve their dead pixel management in a firmware upgrade...

(For gallery, tips and links)


Link Posted 01/09/2004 - 22:30
Curiouser and curiouser.

Thanks for the info on the sensor.

The problem seems to have "gone away" - I had some images with a consistent bright blue pixel in a particular place which I could get back to by viewing an image, magnifying to x6, and moving right 8 times.
After finding it and contacting the place I bought it, I took it out and about anyway, and then even RAW images don't exhibit the problem any more. (It was never a problem with JPEG, which corroborates your technical explanation)

So I'm leaving it for the time being.



Link Posted 14/09/2004 - 13:57
I have been having the same problem, but only in long-exposure shots. I only shoot in jpg, but figured out that if I shoot in "Noise Reduction On", the problem goes away (the camera edits the spots out). Because it only effects a few pixels oin a photo it's easy to edit them out in PS if needed, because waiting for Noise Reduction to do its job after a 15 minute exposure is a right pain!
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