Red and blue dots on 600d

This is normal and is not a problem.

These are generally referred to as "hot pixels". The pixels at these positions are stuck and always "on" at a maximum saturated level. It is normal to have several of these and even my 5D mkIV has many. There are two general ways to remove them so that you don't see them:

A) The camera can map out the hot pixels. Remove the lens and cap and put the camera into manual sensor cleaning mode. The mirror will flip up and shutter will open. Let the camera sit and wait 30 seconds and shut the camera off. Take another dark frame and see if the hot pixels are gone.

B) Some software, such as Adobe Lightroom, will remove them as well if you are shooting in raw. This is useful if new hot pixels show up since you last mapped them out: if I'm shooting raw I still don't see them in LR.

Regards,

Mike

Cagri12 wrote:

I took a picture with lens cap on and 30 seconds and there are a lot of red,white and blue dots it only happens when i shot long exposures but does it a big problem?

It's not unusual for a long exposure.
FWIW, these are not stuck at maximum value; simply over-active.

Black images aren't a good choice to test for "hot" pixels.

If you see problems in any of your normal photography then it's worth looking into.
I can help you perform a reasonable test.
Contact me by email or Private Message (PM) if you'd like that.

bclaff wrote:

Cagri12 wrote:

I took a picture with lens cap on and 30 seconds and there are a lot of red,white and blue dots it only happens when i shot long exposures but does it a big problem?

It's not unusual for a long exposure.
FWIW, these are not stuck at maximum value; simply over-active.

Black images aren't a good choice to test for "hot" pixels.

If you see problems in any of your normal photography then it's worth looking into.
I can help you perform a reasonable test.
Contact me by email or Private Message (PM) if you'd like that.

I can't see any problem at my normal photography and after I put the cam to manuel cleaning mode there aren't much left so it's ok for me.

Thanks, everyone, for your help.

Cagri12 wrote:

I can't see any problem at my normal photography and after I put the cam to manuel cleaning mode there aren't much left so it's ok for me.

Thanks, everyone, for your help.

Are you referring to sensor cleaning when you say "manual cleaning mode"?  Because that has nothing to do with noise, stuck, or hot pixels.

Aoi Usagi wrote:

Cagri12 wrote:

I can't see any problem at my normal photography and after I put the cam to manuel cleaning mode there aren't much left so it's ok for me.

Thanks, everyone, for your help.

Are you referring to sensor cleaning when you say "manual cleaning mode"? Because that has nothing to do with noise, stuck, or hot pixels.

On some cameras doing a manual cleaning (or two in succession) also causes the firmware to detect and map out "hot" pixels.
So yes, it does make sense to mention.

bclaff wrote:

On some cameras doing a manual cleaning (or two in succession) also causes the firmware to detect and map out "hot" pixels.
So yes, it does make sense to mention.

This not stated in the manual.  And if true, what happens when some is physically cleaning the sensor?  The sensor will be exposed to all kinds of lights and colors.  How will it know which pixels to remap?

Aoi Usagi wrote:

bclaff wrote:

On some cameras doing a manual cleaning (or two in succession) also causes the firmware to detect and map out "hot" pixels.
So yes, it does make sense to mention.

This not stated in the manual. And if true, what happens when some is physically cleaning the sensor? The sensor will be exposed to all kinds of lights and colors. How will it know which pixels to remap?

It's a well-known "secret" "back door".
This has nothing to do with physically cleaning. Only asking the camera to self-clean.

bclaff wrote:

Aoi Usagi wrote:

bclaff wrote:

On some cameras doing a manual cleaning (or two in succession) also causes the firmware to detect and map out "hot" pixels.
So yes, it does make sense to mention.

This not stated in the manual. And if true, what happens when some is physically cleaning the sensor? The sensor will be exposed to all kinds of lights and colors. How will it know which pixels to remap?

It's a well-known "secret" "back door".
This has nothing to do with physically cleaning. Only asking the camera to self-clean.

Well I just tried your method on a 70D and the results are inconclusive. There was no change. Maybe the 70D doesn't have this feature?  Manual cleaning option on Canon cameras is for physically cleaning the sensor, as stated in the owners manual.

mdmarqphoto wrote:

I remember reading about this fix when I bought my 70D, and a quick Google search results in many links that say this does indeed work, including several people in this thread:

https://www.dpreview.com/forums/thread/3539961

Interesting.  I guess my 70D doesn't think it needs to remap itself, or thinks there are not a large issue with hot pixels.

I tired it too and didn't see much difference.  It must be very subtle.