I have a problem with focus points through the camera viewfinder, and when I photograph through the digital screen it works perfectly.
It is a problem in canon EOS 80D
e.g. I am sure that the problem is with the viewfinder, because I tried using other cameras with the model and there was no problem with the viewfinder. I also tried using 3 other lenses, and I'm sure the problem is with the camera and not the lense.
I went the the shop where I bought the camera and the salesperson told me to enter the 4th settings (with a camera icon in orange), and in this menu enter C.fnII:Autofocus and try to play around with the numbers. I tried lots of numbers and it didn't help solve the problem.
Hope you can guide me
The problem is that through the viewfinder I get images with focus that is not where I placed it
Then for example when I photograph a person and want to focus on his eyes it focus instead on the hair for example
If you do not have a copy of the full User Manual, then I suggest that you visit the 80D support page at Canon Support. It would be the same page where you download all of the software to use with the camera.
The AF system is quite advanced, and far too complex to fully describe and [tutor] someone in user forums. There are lots of good and bad videos on YouTube describing the 80D AF system. The video linked below by Grant Atkinson is the first in a series he [goes] in depth on describing how the AF system works, [and what the menu settings actually do.]
You state that the camera produces in-focus images when you focus using the rear LCD but not when you use the optical view finder. Is that correct?
If so your camera might need to be adjusted.
But before we reach that as a final conclusion try some controlled tests with the camera on a tripod.
About 20 feet away focus on a stationary object and see if you can confirm your problem.
Focus on the object using Live View. Carefully switch off Live View. While watching the lens focusing ring and/or focusing scale carefully press the shutter button. Did the lens move? If so, OVF and Live View are focusing at different distances.
If the lens shifted towards infinity then the lens is back focusing; if towards lower distance it is front focusing.
See your manual for lens microfocus adjustment.
See this article: Canon-AF-Micro-Adjust-Guide.pdf (static-bl.com)