What are these purple pixels on my Canon 60D and how do I get rid of them?

Question

I bought this used Canon 60D for a reasonable price, however, I get these purple pixels in the top right of my image. Even though I can work around it, it is very annoying. I've tried a lot of ways to fix it, like manual cleaning. I am trying to find another alternative than having to send my camera to Canon, as I don't have too much money to spend on repairing or a new one.

https://i.stack.imgur.com/UKTqo.jpg

Thanks in advance for any help!

Here's a full image.

Here's a crop of the affected area.

Answer 1

It's near impossible to tell exactly what the spots in your picture are. It is fairly easy to look at them and eliminate what they are not: hot or dead pixels.

Due to the sharp outlines and well defined irregular shapes of the different spots it is fairly safe to say that they are on or very close to the actual sensor itself, and not on top of the stack of filters that lie directly in front of the sensor. If they were on top of the entire sensor stack at the very wide aperture with which the example image appears to have been taken they would be very blurry and indistinct, rather than sharply defined. They might even be an effect of some sort of internal sensor damage that affects the readout of the sensor.

It's just a guess but I think it may be possible your camera might have attended a "color run" or similar event in the past. When colored powder got into the camera someone tried to clean it. In the process some magenta colored powder seems to have been moved under the sensor stack into the surface of the sensor itself where it is now trapped between the sensor and the filters that cover the sensor. The fact that the problem area is very close to an edge supports this theory.

You might try to reduce the effects of the spots by following the procedure outlined in your EOS 60D Instruction Manual (pp.231-32) for recording and applying dust deletion data. Once you do that the camera will apply the dust deletion data to jpegs produced in-camera when that option is selected in the camera's menu.

If you save the raw data files and want to automatically apply the dust deletion data when editing on your computer you can use Canon's Digital Photo Professional to convert the raw files. Version 4 of DPP is quite good, includes more features, and has a more user friendly interface than the previous versions. I prefer using DPP to convert the raw files from my Canon cameras. It seems to me that the colors can be more finely controlled than with third party tools such as Lr/Ps or DxO.

Since the spots all seem to be a rather uniform magenta in color, you might also try to reduce the magenta by using the Hue/Saturation/Luminance (HSL) tool included in many photo editing applications. If the photo you're editing has no other instances of magenta in the frame you can reduce the saturation for magenta to zero and then adjust the luminance value to blend it in with the surrounding area.

If that doesn't work you can try to manually repair each spot with a "healing" type of tool that converts spots to the average color of the surrounding area. Most such tools allow you to specify the size of surrounding area from which the color is averaged.

Ultimately I don't think you'll be able to totally remove the effects of these artifacts without replacing the sensor.

Answer 2

These are irregular shapes and my guess is that they are not pixels, but drops of some purple liquid. If you set your camera to the cleaning mode, remove the lens and inspect your sensor with loupe and a flashlight. When you try to locate the spot on the sensor, don't forget that the image is recorded upside down.

Answer 3

Edit: see comments

These look like "hot" or dead pixels. It's quite common for sensors to develop a small number broken photosites during their lifetime - these will commonly show up as single pixels of a very bright single colour, or sometimes as a completely black pixel - no amount of cleaning will solve this problem.

The RAW-JPEG conversion done in some camera models will remove these by interpolating the values from surrounding pixels, and the same can be done in many RAW processing applications during post-processing. This can mostly be done automatically (e.g. in darktable, you can add the "Hot Pixels" plugin to a profile, and then apply this to all images - it will automatically detect the dodgy pixels and hide them).

The only way to get rid of them for all images is to replace the sensor with a working one - whether this is worthwhile in a second hand camera is questionable given how easy the issue is to fix in post-processing.

The fact that your sensor has developed several close together suggests that it was caused by damage to the sensor rather than sporadic failure.