K20D Help

I'm curious as to what you would have done if you never had the pixel mapping function.

Nothing, you would only see a faulty pixel at 100% zoom so no real need to go over your photos searching for a spot.

I'm talking about the warranty issue. I have to agree with Unlockers
comment on this. Does it mean then that because a camera has a function to put right a defect it's ok, surely all parts are guaranteed for the fixed term.

Ah okay Richard.
I'm not sure but I believe you have the same warranty as with TFT screens so 3 out of a 1000 or something like that are allowed to be faulty. If they would be below that value and can do a dark frame then you they must replace the sensor.

With 14.6 million photosites I would guess that the potential is there for the odd one to misfire once in a while.

I suppose the question is whether or not it is currently possible to make a totally fault free sensor with the technology we have. I don't know the answer to that, but I suspect there may already be compensating electronics in the sensor of every digital camera.

The same is true of a memory card, which has error correcting mechanisms built in.

I think that if sensor and screen manufacturers were obliged to replace every unit that had one bad pixel, the cost would rise considerably. So it's in the interests of all to have a little give and take.

G

I agree with George I think there has to be a balance made between absolute perfection and cost.

Don't do this unless you are prepared to be disappointed but I have found the best way to check for hot pixels is to turn off slow speed shutter noise reduction (custom 17 on the K20D or 18 on the K-7), set a low fixed ISO, say 100, (to avoid high ISO noise reduction), set the camera to manual focus and take a couple of shots with the lens cap fitted on the lens. Inspect the result at 100% magnification or better. If you find anything then check if it is in both shots and then also check the same point on a recent normal shot.

But please don't blame me if you don't like what you find

Glyn

Edit - Just realised that you can't turn off slow shutter noise reduction on a K20D, only set it to auto or on, so this test only works best on a K-7 although I can see at least one hot pixel on my K20D doing this test with slow shutter noise reduction set to auto - Apologies, Glyn

Thinking about it slow shutter noise reduction probably makes no difference to this test. SSNR is looking for low level noise differences between the actual shot and a shutter closed shot. A hot pixel, having such a large change in brightness, probably will not be classed as noise and not be removed.

So the test becomes: Set a low fixed ISO, say 100, (to avoid high ISO noise reduction), set the camera to manual focus and take a couple of shots with the lens cap fitted on the lens. Inspect the result at 100% magnification or better. If you find anything then check if it is in both shots and then also check the same point on a recent normal shot.


Glyn

Edit - removed comment about non-white hot pixels as results of testing not consistent.

If you have paid approx £600 plus for your camera do you want to be more concerned as to how to stop hot pixels or to take quality photo's from a quality camera. Nobody wants to mess around with ISO or Noise reduction settings to fix a problem. I know that everyone has there own views. So as the saying says lets all agree to disagree.

sorry if this is a bit abrupt but i have just come home and logged on and read the following post's after a couple of double gin & tonics....Hic

What exactly is the issue? If pixel-mapping, done once, fixes the problem, what are you concerned about?

G

I'm not concerned whether pixel mapping fixes the problem or not its a good idea, my argument is that surely it'a an warranty issue if you have a hot pixels problem when the camera is under warranty.

We all like to think of things we buy as being perfect but life is not like that, whether or not it is a warranty matter would depend on if the item is suitable for the use for which it is purchased and that depends on the owner. Does the dead pixel (correctable) render the item useless or faulty to the point when it can not be used as intended? Personally I would say it does not but if you feel it does fight your case.

Richard, I doubt that any of our D-SLRS are hot pixel-less (is that a word :blush we are talking about much much smaller geometries than LCD displays together with the thermal challenges of a camera sensor so the incidence of rogue pixels will be higher. This is exactly why camera manufacturers employ pixel mapping. It is a means to a wholly satisfactory end, otherwise your camera would have cost a great deal more than it did.
The real issue for me would be if pixel mapping did not effectively mask the problem of defective photosites.

It's another variant on the old 80:20 rule. It'll cost 80% more to effect a 20% improvement.

Or, in reality, perhaps a 25% higher price for a pixel-perfect sensor.

I know which I'm in favour of.

G

I can't believe that all this has come from my original question.
But thats life.