Have a high mileage 5D MKIV and just noticed patches of red dots when I zoom in on raw photos in Photo Pro software. Just checked the previous shoots and those are fine, so it's definitely a new issue.
I've tried cleaning the sensor manually without success. Any ideas? or is this a trip to Canon service?
What is your exposure information for the shots showing red dots, ISO in particular? These red pixels from "hot" pixels are likely at high ISO and/or long exposure settings. Maybe a camera setting was accidentally changed causing it to use a higher ISO creating more color noise.
You are welcome Phil and with a sudden and large increase in hot pixels it sounds like it is time for Canon service. If the camera was stored/used in very hot conditions that will also cause an increase in sensor noise but it would have to be unusually hot to cause a sensor to suddenly start showing more noise.
Google hot and stuck pixels to see more about this issue.
Chasing hot/dead/stuck pixels can sometimes be a pointless excercise because they can show up in different positions with each shot.
My old 50D suffered with quite a few and I tried the supposed "manual remapping procedure" which worked for me at the time (but it may have been a coincidence). Here's how it's done:
Make sure you have a fully charged battery.
Remove lens & fit body cap.
Activate "manual sensor clean" in the camera menu.
Leave for 30secs to 1 minute.
Turn off camera at main switch.
That's it, dodgy pixels should now be gone.
Some people say that this works, others say it's a myth but it seemed to work for me some time ago and you have nothing to lose. Apparently it only works for still photography and does nothing for pixel problems with video.