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 Hot Pixels 
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Joined: Sat Aug 13, 2011 9:13 am
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Post Hot Pixels
I've got a couple of hot pixels on my sensor and they show up in my night sky time lapses. Is there an easy way to eliminate those either in camera or in post? I shoot with a Canon 550D (T2i).


Tue Sep 20, 2011 1:20 pm
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Post Re: Hot Pixels
http://lmgtfy.com/?q=hot+pixels+night+sky+time+lapse :lol:

http://timelapseblog.com/2010/03/22/dar ... btraction/


Wed Sep 21, 2011 1:36 pm
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Post Re: Hot Pixels
mr. ichybob wrote:
http://lmgtfy.com/?q=hot+pixels+night+sky+time+lapse :lol:

http://timelapseblog.com/2010/03/22/dar ... btraction/


Yeah, thanks but I know how to subtract a dark frame. I just don't want to do it hundreds of times manually. Is there a way to easily automate the process or do I need to write macro or script to do it?


Wed Sep 21, 2011 8:40 pm
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Post Re: Hot Pixels
It can be done in-camera by enabling long exposure noise reduction, but that effectively doubles your exposure time which you probably don't want. Instead you can shoot one dark frame (all the same camera settings) at the beginning or end of your shot and subtract that from all your images in post. That process can certainly be automated, but I have not gone this route myself and can't give you specific advice on how to do that.

Another option is to use a clone stamp tool, copying adjacent pixels over the hot ones. This can also be automated, e.g. batch processing in Photoshop. The software you use for compiling your videos may even have a clone stamp tool that will do the job. I've done it in After Effects.

Finally, Adobe Camera Raw can automatically remove hot pixels if you shoot RAW.

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Wed Sep 21, 2011 9:02 pm
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Post Re: Hot Pixels
I'd thought of those ideas. Certainly you could do either and automate the process with a script of some sort. I was hoping there was some obvious tool that I had yet to find that automated the process. I do shot RAW.


Fri Sep 23, 2011 10:56 am
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Post Re: Hot Pixels
What software do you have available to process your RAW images? If you have Photoshop you can automate the process fairly easily, and you can find lots of tutorials showing how to do that. After Effects probably takes the prize for the easiest way of doing it... you import the RAW sequence directly and hot pixels are removed automatically via ACR during import.

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Fri Sep 23, 2011 3:07 pm
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Post Re: Hot Pixels
No, I'm working with PSP8 and Windows Movie Maker right now. I also have the Canon suite that comes with the cameras. That works well for adjusting the images, but I'm not sure you can do dark frame subtraction automatically. I've barely gotten into this and just messing around for now. I can take care of it in PSP, most likely, but I have to convert to 16-bit TIFFs. Not sure how tough it will be but it has the ability to do batch processing and record scripts. If not, I'll live with the pixels until I get some software, cause I ain't applying a dark frame to a few hundred images by hand! :o


Fri Sep 23, 2011 10:10 pm
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Post Re: Hot Pixels
You can do it with Digital Photo Professional from the Canon suite. It has a stamp tool, and once you have stamped out offending hot pixels in one image you can save a "recipe" that you can copy to the rest of the images. Not as easy as having them removed automatically, but not too bad either (unless you have a LOT of hot pixels). And while you're in DPP you may want to add more to that recipe than just removing hot pixels - do white balance, curves, noise reduction etc. Unlike a lot of junk software that comes with miscellaneous devices, DPP is actually a pretty good tool for RAW editing. Check it out.

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Fri Sep 23, 2011 11:13 pm
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Post Re: Hot Pixels
flyvholm wrote:
You can do it with Digital Photo Professional from the Canon suite. It has a stamp tool, and once you have stamped out offending hot pixels in one image you can save a "recipe" that you can copy to the rest of the images. Not as easy as having them removed automatically, but not too bad either (unless you have a LOT of hot pixels). And while you're in DPP you may want to add more to that recipe than just removing hot pixels - do white balance, curves, noise reduction etc. Unlike a lot of junk software that comes with miscellaneous devices, DPP is actually a pretty good tool for RAW editing. Check it out.


Thanks! I've been using DPP to adjust the quality of the images and have used recipes for that. I didn't see the stamp tool. I've only got a couple of noticeable hot pixels. So its not a big deal. they only show up in night sky lapses. They really stand out since they are still and all the other little points of light are moving.

I wonder if I could figure a way to apply a dark in DPP?


Sat Sep 24, 2011 8:05 am
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Post Re: Hot Pixels
I don't think there's any way to do that, but for just a few pixels the stamp tool probably works equally well in practice.

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Sat Sep 24, 2011 3:24 pm
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Post Re: Hot Pixels
I asked Tom this question when I was shooting sRAW with my 5DMK2. He responded with sRAW burns in hot pixels. At first I was reading it in the wrong context, like sRAW produced more hot pixels than full RAW, but later he replied saying that ACR automatically removes hot pixels and to my surprise it does, or at least sure looks like it does.

Do a test if you have LR3 or ACR with Photoshop. Shoot sRAW, 30 seconds, ISO 1600 with the lens cap on. Then shoot RAW with the same settings. Post them to jpeg from LR3/ACR with minimal edits and see for yourself.

-Roy

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Thu Jan 19, 2012 7:38 am
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Post Re: Hot Pixels
flyvholm wrote:
You can do it with Digital Photo Professional from the Canon suite. It has a stamp tool, and once you have stamped out offending hot pixels in one image you can save a "recipe" that you can copy to the rest of the images. Not as easy as having them removed automatically, but not too bad either (unless you have a LOT of hot pixels). And while you're in DPP you may want to add more to that recipe than just removing hot pixels - do white balance, curves, noise reduction etc. Unlike a lot of junk software that comes with miscellaneous devices, DPP is actually a pretty good tool for RAW editing. Check it out.


I don't think you can save edits from the stamp tool into a recipe. I've tried and it just doesn't seem to work. It does save color/brightness/contrast/sharpening type of edits, but nothing from the stamp.

But I sure as heck wish it did! I'm cleaning up hot pixels in hundreds of images and it's a real waste of time to have to do it one image at a time. In DPP you can select all the images, open the stamp tool, make a bunch of edits using the stamp tool in the first image, and then copy those to the next image. You can continue to go through each image one at a time and do this.... but with full size raw files, it takes about 6 seconds per image to load, paste, then move on to next image. Doesn't sound bad until you've got 500+ images to deal with.... I sure wish canon would add some sort of batch processing for the stamp tool. It could be added to the recipe, or even within the stamp tool a button that says "apply to all selected images" would be freaking awesome...

If anyone has a better method (on a mac, not windows) to manually stamp/clone-out hot pixels then apply those exact edits to any number of raw images, please let me know.... preferably with free/cheap software... A workable method in DPP (or possibly gimp) would be best!

Thanks,
Rob


Sun Apr 29, 2012 3:30 pm
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Post Re: Hot Pixels
Like MotleyPixel said, if you shoot RAW doesn't the 5DM2 somehow flag or mark hot pixels? I feel like whenever I shoot in RAW and JPEG I can import the JPEG time lapse into After Effects and there will be hot pixels and then I can import the RAW sequence and the hot pixels will be gone. I even think there's a brief second where the hot pixels are shown and then they're automatically taken out/fixed.

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Tue May 01, 2012 10:08 am
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Post Re: Hot Pixels
I had a similar problem with my 60D but I was able to fix it using the method described in this link, it won't fix the footage you already have but it will prevent problems in the future.
Hope this helps.

http://cheesycam.com/fixing-random-hot-or-dead-pixels/


Thu Jun 14, 2012 5:40 pm
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Post Re: Hot Pixels
I recently had a 'dead' hot pixel located close to centre of frame ...... damn obvious.
I had tried the technique described in drewsdepictions link several times with no success ....... then a couple of weeks ago it just disappeared!
I was resigning myself to a trip to Canon Service and getting ready to do a bit of re-touching on recent material.
The heavens move in mysterious ways - as most night-sky Timescapers know. ;)


Thu Jun 14, 2012 8:46 pm
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Post Re: Hot Pixels
you can clone the pixels out in a frame in lightroom and apply that and/or the rest of the camera raw adjustments to the rest of the images (camera raw will remove most hot pixels from a frame as well) there is no control and the higher you crank the clarity the more hot pixels are left.

I am reprocesing a ton of shots from 06-07 right now and found if i let lightroom remove the hot pixels, export jpgs or tiffs, reimport into lightroom then adjust with the modern tools and sliders i get way better results. takes twice as long and 3-4+X the hard drive space but i have been able to pull off some miracles on shots that i never even processed because i though they were trash back then

download the fully functioning demo of lightroom (works for 30days) its indispensable software for working on images nothing comes close to the level of processing you can do with LR4.. also get LRtimelapse (free plugin)

oh if you have a shot on a dolly or panning and tilting head you cannot clone the same stamp on every frame. you will see it in the final video becasue the motion of that clone/repair will have a different motion than the rest of the shot.

t


Thu Jun 14, 2012 11:14 pm
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Post Re: Hot Pixels
I resume this interesting topic just to ask if anybody found a method to clean sRAW and mRAW files. I really prefer to use this format instead of full RAW because of the smaller size on the card and hard disk.


Tue Jul 30, 2013 4:45 am
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