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I have a Nikon D90 and until recently it has been working just perfectly. While viewing a set of photos I had taken I'm starting to find these little nasty dead pixels:
alt text http://img225.imageshack.us/img225/7391/d90noise.png
They only show up when zoomed in - however now that I know they are there I can pick them out of just about any photo I shoot. What are some techniques to go about removing these?
Adobe Lightroom (I know, broken record) has a tool to spot clean. Once you define the area, you can apply it to all photos in a collection.
As Mister Shaw has commented on, some camera's have dust delete capabilities, which may work.
Also, have you considered (out-of) warranty repair on your body?
Many raw converters have tools to map your hot pixels and then automatically remove them, but I don't know details. E.g., Pixie for Bibble. I'm sure there's equivalents for other software too.
Adobe Camera Raw removes them from raw files automatically. I would assume Lightroom does also as it's basically the same thing. I do not know if this works on jpegs.
Its pretty easy in Photoshop, all you need to do is use the retouch or clone tool.
You could even do this with the free paint.net
Just select the clone stamp tool, hit the right ctrl key to select an adjacent region you want to clone on to the area, and then clone away.
Some cameras have a menu option for pixel mapping, which runs an internal check for stuck-on pixels and maps them out (even from RAW files). This is the best and most convenient way to avoid this problem, since you basically don't ever have to worry about it again.
Unfortunately, it appears that neither Nikon nor Canon make this feature user-accessible. Both of them, however, will provide the service for you if you send the camera in under warranty. (Or, I'm sure, for a charge out of warranty.) Several years ago, my Pentax K100D had half a dozen hot pixels, and I was very glad that I sent it in. (Having 6 pixels out of 6 million missing from the equation has no effect, but having 6 making bright red and blue dots was annoying.)
Currently, I believe Olympus includes this on all of their cameras, even their cheapest point & shoot models. And Pentax now includes it on all of their dSLRs. Sony has a pixel mapping feature, but it's only for the back LCD screen, not for the sensor — although rumor is that the camera automatically runs a sensor hot-pixel mapping monthly. (If I were a Sony user, I'd contact tech support and see if I could get a confirmation of that in writing.)
Having the in-camera mapping is so convenient that it's on the "plusses" list for any camera I'd buy in the future. But since you can also send in the camera for it to be done for free (well, for the cost of shipping), I wouldn't rate it a deal-breaker. (The same goes for the ability to fine-tune auto-focus.)
Taken from this answer to my question about purple spots, if you're working with RAW files, Pixel Fixer can purportedly fix them up.
the first time I noticed hot pixels in my camera (an old Olympus 3000Z) was in a night sky shot. I never tested for the presence of dead pixels, but I assume it also has some too. dead and hot pixels are present in all pictures my camera takes, and now that I know where they are, they are the first thing I see in some of my pictures.
I think that, in writing a tool that corrects then, one must use this knowlegde: location and intensity of dead and hot pixels in a set of pictures. if I had to choose a tool, I would axpect it to let/require me (to) provide this information.
the main problem I see in correcting non raw pictures is that jpeg compression induces compression artifacts around the defective pixels.
IMO the compressing software in the camera is the best place where one has the chance to reduce the impact of defective pixels. once the data has been compressed, the task is a lot more complex.
still IMO, the second best place for dead and hot pixels correction is in the software you use to collect pictures from the camera on your computer. this software "knows" the camera and "knows" that the pictures have exactly those defective pixels and are still unhandled.
so, if you don't want to correct defective pixels by editing each of your pictures by hand, file a feature request for the software you use to gather pictures from your camera.
if you're using the GIMP, check for example this hot dot fix script.
If you happen to be using iPhoto, you can use the "Retouch" tool (with a small circle). Just click over the dead pixel and it should be nicely removed.
Most, if not all, processing softwares allow to correct this small details. In Photoshop you can apply the spot heal tool, or the clone tool in the Gimp, and so on, depending on what you use.
