Why is the Canon 24TSE not sharp at infinity when set at f4?

Started Nov 4, 2012 | Questions thread
MirekE Contributing Member • Posts: 925
Re: Why is the Canon 24TSE not sharp at infinity when set at f4?
  1. Start with live view and 10x zoom to make sure that you focused correctly. If the LV focused images are sharp, but shots focused through viewfinder are blurred, it is likely that your focusing screen or AF confirm (or both) are off
  2. In the images, check if the image is blurred in general or if it is focused elsewhere. If it is focused somewhere else, the problem is likely your manual focusing, not the lens
  3. Try to shoot a wall that is perfectly parallel with sensor plane and check all corners. They should be all in focus or equally out of focus. If one corner is more defocused than others, the lens may be decentered and may need servicing/replacement
  4. Since your pictures are gradually worse as you open the aperture,camera blur is probably not your case, but make sure that your camera is absolutely stable during these tests (tripod and mirror lockup) or that you use very short exposure, like 1/1000s
  5. Don't use focus and recompose for these tests
  6. Infinity mark on the lens is not necessarily infinity. The hard stop of the focusing ring is almost certainly not at infinity, but behind. So these tests really need to be made via Live View, if you have not already done so
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