Hot & Dead Pixels - Many Threads - Could DPR or photo engineer clarify & explain?

Started Feb 5, 2010 | Discussions thread
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lightxray New Member • Posts: 7
Hot & Dead Pixels - Many Threads - Could DPR or photo engineer clarify & explain?

Firstly a big thanks to DPR for a great site - I'm learning a lot from it. I'd love to see more lens reviews as it seems in the digital era lenses become even more important and that they are the real long term partners compared with bodies.

Also forgive this rather long posting but it is how I find it best to explain what I mean. Also I mistakenly posted on the canon Talk forum thinking that was a general forum for Canon. But this issue I am sure runs wider than one marque so am posting it here.

I have just picked up on the idea that there could be hot/dead pixels on most sensors (even on Nikons!). This is an old and oft frequented subject which makes one question why so? I confess I don't understand yet the difference between the meaning of "Hot" & "Dead" pixels as I write this - perhaps someone can clarify that point.

Through this site I have skimmed over a lot of posts that date back over several years with great regularity on the subject so it clearly is a problem even in new models in 2009.

Anyway to my point - I have discovered hot or dead pixel(s) on my new 500D. emoticon - sad

But ...perhaps all DSLR's display this? I need to know whether I need to change the camera. I would love this to be cleared up so I can get beyond technical pixel peeping to the real heart of our hobby - making pictures. emoticon - smile

In the last 24 hours I have been checking mine (shooting full RAW, lens cap on shooting for 1, 10 & 20 secs over the whole ISO range). Lo and behold I have at least one at lower ISO's on the 20 second exposure. On shorter exposures it doesn't show so in every day use I guess it may not be a problem.

High ISO's of 1600 - 32000 clearly show the whole field gets fairly hot with several hundreds or if not thousands showing up - just like looking at the stars at 20 secs! On shorter exposure times that effect gradually reduces. So I am also guessing that there is a gradual shift to hot pixels of various colours as ISO and exposure times go up. IS THAT NORMAL??

NB Canon's DPP software needs to be used in the RAW editor mode to see this properly as there is some correction functioning after a few seconds in the normal Edit view.

There seems to be a fix using the manual cleaning function described by other threads here. In the manual it only implies that it's just a facility for physical cleaning. (Perhaps Canon politically do not want to admit any fault here with sensors so keep quiet!?) The Recent threads here on DPR however explain and 'believe' it also does Pixel Mapping which seems to work for some and not others. ( I will try it and see what happens).

Of course there is also software on the market which does that ( and PS cloning etc).

My MAIN POINT is could a photo engineer or DPR folk, with good access to engineers in the industry, really clarify the technical facts for us ordinary users? Perhaps DPR could even write a short article or white paper on the issue. In this way what is maybe a hidden designed function in Canons (even all DSLRs?) could be clarified and so help us distinguish fact from assumption.

My Photo Background:

I recently purchased the 500D and am pleased with it after upgrading from a 1000D I had for about 9 months. The last 9 months or so have been my first decent experience with digital after using low end compacts for snaps etc for some years during the period I had very demanding work. I left behind film in the 90's because of work pressure (I still have my OM Kit with two bodies and several lenses - a sweet light weight system). I have more time now as I approach retirement so am getting back into photography.

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