I enjoy taking pictures of birds so not long ago I splurged and bought the Canon 100-400 L II lens for my Canon T3. I've taken several hundred shots with the new lens and about 5 of them have been crisp and sharp. Normally when birding I hand-hold so I understand that there will be some camera shake for a lens that heavy. Today I used a tripod and got similar results - not sharp. My camera was set up with AI Focus and 800 ISO. I turned off the Stabilizer on the lens and set the focal length to Full. Below are some of the results (no PP). Note that I typically crop bird pics at least 50% but I swear that doing so with my 55-250mm lens got better results. When cropping (and to a lesser extent on these uncropped) I notice vertical branches in the background appear ghosted - that is two parallel unfocused lines instead of one unfocused line. Please let me know what I can do to get crisper pics. Thanks

Your subject is way too small and shrouded in an AF confusing fog of branches, leaves and weeds ! If you have a "protective filter, take it off. Do a focus test and calibration ! - on an unshrouded subject - oops, no fo-cal on a T3 - but you still need to TEST and send to Canon if need be. Use the focus center spot ONLY. Your expectations and technique are out of whack !

Finally, hand holding at 250mm is MUCH easier than at 400mm ! The ONLY time I recommend hand holding @400mm is for BIF.

1. too far away - I too had to learn a long lens didn't mean that I could be in the next county
2. shutter speed way too slow (1/100 on the first pic), you need a minimum of 1/400 and better yet even faster
3. a lot of camera movement so for hand held use at least 1/800 SS and off a good solid vibration free tripod at least 1/400 or 1/640
4. IS should be turned off only on the tripod or at SS above about 1/500 or higher
5. never use AI Focus, the little bitty processor is trying to decide between One Shot and AI Servo so the shutter often clicks
while it is focusing. Most high end cameras don't even have AI Focus as a choice, more than a few I know are wondering
why Canon put it on the 7DII. Set the camera for the shutter to not fire unless exposure is locked. At least for the first shot in a burst. It will slow things down or even keep the shutter from firing but it is better than a shot taken while the lens is focusing.
6. open that shutter up to f/8.0, f/7.1 or even f/5.6.

My usual setup for birds is 1/1000 SS, f/8.0 and ISO on auto. In shade or poor light or slow birds I will drop the SS to 1/640 or so. I will open the f-stop to f/5.6. For fast birds (like hummers or BIF) I go up to as fast as 1/2000 and open the f-stop to the max. I have my ISO limited to either 3200 or 6400 depending on which body I am using. Knowing I will need to use noise reducing software unless the light was real good. (Yes fast birds/SS and an f-stop for great depth of field will drive even sunlite shots to high ISOs.

Either my 6D with the 100-400L mk II or my 7DII with the 100-400L mk II (sometimes with the 1.4x III extender).

AI Focus is not good, use AI Servo and set up Back Button Focus if you have not. Learn to use BBF.
Use a single focus point.
I try to shoot at 1/2000 shutter speed if hand holding at 400mm. I usually use Tv mode for sports shooting. If you don't stop the motion the DOF doesn't matter in my view. Get a DOF calculator app for your phone and play with it to understand what DOF you will get at various apertures, focal lengths and distances. You may be surprised how small the DOF can be at 400mm at f/4 or f/5.6 even.
You will need to determine how high an ISO your camera can tolerate and set that in the menu system as an upper limit if you use auto ISO.

Best,
Todd Ferguson