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Red and Blue Dots
scootog
Registered Users Posts: 92 Big grins
I was recently taking a series of nite shots. As I scrolled through the pics I noticed a red star that didn't move with the rest. I zoomed in and found a red dot with an adjacent blue dot. I noticed this some years ago with a cheap camera. I just thought it was a flaw in the sensor. Does anyone have an idea whats going on?
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Yep! I sure do! to a certain extent it is indeed caused by a flaw in the sensor, but it is not unexpected, and it is very normal for digital cameras.
What you are seeing is points on the sensor where a small amount of heat has built up, when this happens, that area will show the red and blue that you see.
The reason you notice it in the star pictures and not in other pictures, is because the sensor is active for a longer period of time, and so it has more time for the heat to build up.
There is something else unique about these spots, on your camera, they will be in the same spot every time, and using the same shutter speed and ISO, they will be the same brightness every time.
Because of this, there is a solution, and most DSLRs have a feature called "long exposure noise reduction". typically how this feature works, is after you take a long exposure, the camera automatically takes another picture for the exact same length of time, with one difference, the shutter is closed, and then it uses data from the second picture to cancel out the dots.
it looks like you have the Canon t1i? it should have the feature, it will be listed in your custom functions, under the image category, by default it is set to auto, but by turning it on you can force it for any photos longer than 1 second.
There are other options that you can do on the computer afterwards, but this option is the simplest, with the downside being that your longer exposures take twice as long.
If you have anymore questions, feel free to ask!.
Have a great day!
Ben
AdventureSportRider
Glad I could help!
Ben