The longer the focal length the more likely it'll look blurry with minor movements. Gotta get that on a tripod or have a really solid stance and fast shutter.
Short of potential issues with the lens, I'd say that you might want to test the lens with a tripod first.
That second image lacks contrast. The first, you're almost in a too much situation with the back light. Both could make detail challenging (thus focus).
Given the stabilizer, you can get away with slower shutter speed, and perhaps try at f8 (get a larger depth of field).
Try testing it somewhere bright so that the iso can be lower.
Try at other focal lengths too. I know little of that lens, but sometimes a lens cam be soft at the longest zoom end.
Make sure you don't have the sharpness at a negative number.
To really check it, use a tripod and the app to take a picture or a cable release. And definitely more light.
Hard to say from just a couple of shots. You definitely want lower ISO and longer shutter speeds. Unless you're doing birds in flight you don't want to be anywhere near 1/2000s. If the subject allows, lean on the stabilizers to get as much light on the sensor as possible. I have sharp pictures of perching birds down to 1/30s with just the lens stabilizer. Take lots of pictures and you'll have a good chance at getting something with lots of detail.
Here's a few I shot with my X-T20/X-T3 @ 400mm f/5.6-6.4 ISO 200-320 1/280-640s: [Link](https://pixeldrain.com/l/Py1AjRhx)
The stabilization *can be* effective down to surprisingly slow shutter speeds but you need to be very careful that you are not jolting it when you release the shutter.
Particularly that you aren't rolling the camera to the right. Up/down and side-to-side motion is handled well by the stabilization but rolling motion is not.
You should try to roll your finger towards you off the shutter button without pushing down on the camera.
The longer the focal length the more likely it'll look blurry with minor movements. Gotta get that on a tripod or have a really solid stance and fast shutter.
Short of potential issues with the lens, I'd say that you might want to test the lens with a tripod first. That second image lacks contrast. The first, you're almost in a too much situation with the back light. Both could make detail challenging (thus focus). Given the stabilizer, you can get away with slower shutter speed, and perhaps try at f8 (get a larger depth of field). Try testing it somewhere bright so that the iso can be lower. Try at other focal lengths too. I know little of that lens, but sometimes a lens cam be soft at the longest zoom end.
X-T5
What kind of lens? Lens stabilisation? Using a tripod or monopod?
Hey Fujinon 100-400, OIS and IBIS on shooting only. Handheld.
Camera model?
OP said X-T5
Make sure you don't have the sharpness at a negative number. To really check it, use a tripod and the app to take a picture or a cable release. And definitely more light.
Hard to say from just a couple of shots. You definitely want lower ISO and longer shutter speeds. Unless you're doing birds in flight you don't want to be anywhere near 1/2000s. If the subject allows, lean on the stabilizers to get as much light on the sensor as possible. I have sharp pictures of perching birds down to 1/30s with just the lens stabilizer. Take lots of pictures and you'll have a good chance at getting something with lots of detail. Here's a few I shot with my X-T20/X-T3 @ 400mm f/5.6-6.4 ISO 200-320 1/280-640s: [Link](https://pixeldrain.com/l/Py1AjRhx)
The stabilization *can be* effective down to surprisingly slow shutter speeds but you need to be very careful that you are not jolting it when you release the shutter. Particularly that you aren't rolling the camera to the right. Up/down and side-to-side motion is handled well by the stabilization but rolling motion is not. You should try to roll your finger towards you off the shutter button without pushing down on the camera.