My camera do not show up in Finder

Most experienced users never connect their camera to their computers, they remove the card plug it in and import their photos into their preferred app such a Photos, Lightroom, PS Elements, etc....

You can also use Image Capture to import them too directly from the card.

Brand and model of camera?

What if you take the card from the camera and put it into a card reader?

Can Image Capture see it?

It is much more simple to remove the card from the camera and then use the card port on the back of your iMac.

It came up after half an hour!!

Reformat your card with the camera.