EOS Rebel t3i and 75-300mm lens

The camera and lenses are only about 6 months old.

I have a 75-300mm lens that I was taking pictures at my daughters Beach volleyball game.
All was fine until at the end of the day, the lens would not auto focus lock on and would not take any more pictures - it would just zoom in and out. Every now and then it would take a bad picture and read on the display the connection between the lens and camera was bad. I also noticed that looking through the camera or looking at the display with this lens on it looked really dark--inside or outside. I cleaned everything and put in a fresh battery. Same problem- Dark viewing and autofocus will not target lock on. If I take it off auto focus it will take a picture but it is still dark even outside.

I changed lenses to my 18-55mm and everything is perfect on that lens.
Like I mentioned. This lens was bought with the camera six months ago and probably only has 200-300 photos taken with it. Any help on what the problem is?

If lens was bought with camera I'm assuming new and therefore under warranty. Send it to Canon.

This is also what the lens is doing...see top right there ss a ring on the top right of every photo...what causes this?

Looks like the lens has something loose inside; send it back for repair or replacement.

Honestly, the 75-300 is not one of Canon's better efforts. You would be better off with Canon EF-S 55-250

Thanks for the tip on the Canon EF-S 55-250. I put it in my wish list on Amazon to take a look at a possible buy...

As others have said it is still under warranty as long as you have the original receipt from within the last year, send it to Canon for repair.

As has been suggested, send the lens in to Canon for warranty repair. When it comes back, sell it and get the EF-S 55-250 mm IS lens!

thanks all- I have sent an email to canon to send the faulty lens in for WARRANTY Repair...and will look at the EF-S 55-250

75-300 is a dog!!