New Canon 100D not focusing correctly

Hello Simon57,

In my opinion the first photo with the red car is perfectly in focus. Look at the text on the passenger door. The focus is there. There is some ghosting and flare. The Sigma 18-200mm is not the sharpest lens and while it was OK on your previous camera, the increased resolution of the 100D shows its weaknesses. Also, look at all the chromatic aberation - it subjectively decreases sharpness but can be corrected in post. You can also try to turn on the chromatic aberration correction in the 100D, but I'm not sure if it works with third-party lens. 200mm at 6.3 is the extreme end of this lens and it is where it performs the worst. Your best bet would be to close the aperture down to f/8 on the sigma, if shooting at 200mm.

In the second photo things are a bit trickier. There is evidence of back focus and there is also motion blur. Your equivalent focal length is 480mm. If you want pixel sharp image at that range with a high resolution sensor, you need to double the shutter speed to at least 1/800 in my opinion. Also, keep in mind that when the car is moving towards you, if the camera acquires and locks focus slightly before the shutter is pressed, the car would be out of the focused area. After all the 100D is not a performance sports camera and there is a reason higher end models exist.

I also own 100D and my telephoto lens is the first generation Canon 55-250 IS. I've had some great shots and some disappointing ones, as this lens is also famous for its softness. That is why I am looking forward to upgrading to the STM edition.

To me it seems that your camera is working fine, so your best bet would be to know your gear, its strong and weak points and work around them