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Hot Spots, Dead Pixels and Photography

posted by thesaint, Dec 24, 2006 9:33 AM — 9 comments

* Set your aperture to 8, slow your shutter speed down to around 5 seconds, leave the lens cap on and take a photograph.

* Open the image in Photoshop, you should see a large black photograph with no detail – obviously as you had the lens cap on.

* Increase the contrast of the photo until you start to see small, bright dots appearing across your image. There may be none, but on my 8 week old Canon 5D, I found 4 – so I imagine you’ll also find a few.

* Copy your hot spot image on top one of your award winning photographs. Now all you need to do is adjust the transparency of the hot spot image so that it acts like a map highlighting all the hot spots, hidden within the original.

Using this method you’ll eventually get used to where are your hotspots are in your image and will be able to edit them out when processing your images.

Remember to go through the above steps every now and then, you will pick up more and more dust spots along the way and you’ll need to know where they are.

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1. posted by surely, Dec 31, 2006 6:56 AM

great useful tip,cheers!


2. posted by omar_franc, Dec 31, 2006 9:37 AM

this information will come very handy, THANK YOU


3. posted by surely, Jan 1, 2007 7:36 AM

so,I did the test and I was quite disappointed at the end.now I wonder if the disappear when you have your censor cleaned?
any ideas,or do we have to learn to live with them?


4. posted by surely, Jan 1, 2007 7:52 AM

just a small addition,from what I got from google search it is suggested that
Make sure you close the viewfinder so no light can enter the camera via the viewfinder while doing the test.


5. posted by thesaint, Jan 2, 2007 11:43 AM

@3Yes they are removed when you have your sensor cleaned, unless of course they are dead pixels. But even these can be repaired sometimes.

@4 Thanks for the tip!


6. posted by zdeso, Jan 19, 2007 1:29 PM

thanks,
I found 6 small "dead" pixels on my canon, it can be seen only on
Av "0.8, Tv 8.0, but pixels cant be seen on other shutter speeds, but i think it is dast on chip and only one dead pixel :-(


7. posted by StarLight, Feb 10, 2007 8:14 PM

hello theSaint and others,

You can download a small utility to help check for bad pixels here:

http://www.starzen.com/imaging/deadpixeltest.htm

greetz,
StarLight


8. posted by rwetzlmayr, Aug 12, 2008 7:04 AM

Headsmacking suggestion, indeed. Thanks!


9. posted by StefanG81, Jan 2, 2010 10:29 AM

@ StarLight

That software tells me I have 3 dead pixels on one image, and roughly 1300 dead pixels on another. I.e, pretty worthless.

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