E-10 |
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Manual |
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Focus |
E-10 |
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Manual |
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Focus |
The problem manifests itself in a strange way. If you auto focus and look through the viewfinder, it looks in focus. If you change to manual mode, play with the focus a little and then refocus manually, again it looks in focus. But it's not. If you switch back to auto focus and let the camera focus, it actually changes and still looks in focus. I haven't seen this, but that is how I understand from what I've seen written.
How can you tell if you have the problem? How do you know it isn't just camera shake or a bad eye? Even with the best camera it is easy to be in too much of a hurry and not get the focus exact.
Somebody has come up with a test that's as scientific as I've seen.
Next you set up a little still life, as follows. This still life is boring and you aren't going to frame it, but it will help you detect a problem with your camera.
Here is how I set up the "still life".
I taped a piece of paper to box so one side and the bottom are flush against an edge. I set the box up on a counter so that the paper is standing up perpendicular to the camera.
I then placed a ruler next to the sheet of paper. It should be just slightly angled from parallel to the direction of view so the lines and numbers are visible. Make sure that a well defined mark on the ruler is at the same distance from the camera as the paper.
Make sure this still life is well lit. You may want to put a light on the side at a steep angle to highlight a little bit of the grain of the paper.
Put the camera pretty close to the arrangement and zoom in on it a bit to ensure you have a shallow depth of field (dof).
Place the focus point on a letter that is very close to the point on the ruler closest to the paper.
Take several shots with auto focus and manual focus. You might want to use the remote to be doubly sure you don't shake the camera (remember to close the view finder if you do). Purposely take it out of focus before you take your manual focus shots to ensure you are doing the focus and not just verifying the auto focus.
Also, when you do the auto focus, look through the view finder and make sure it looks in focus to your eye. Adjust the diopter if you have to.
When I did the test I took several shots at each of a variety of distances and zoom settings.
On your computer look at the shots at 100% (looking at the actual pixels). Try 200%. The letter you were focusing on should be crisp. So should the mark on the ruler that was the closest to the paper.
If there is a problem with the manual focus, all of the auto focus shots will be clear, but the manual shots will not. More than that, the manual shots will be off in a very consistent way. Look at the ruler and figure out where the focus point is located. Is this the same point for all of the manual shots taken at that distance/zoom level? If it is, the problem might be your camera. If the point of focus is different in every shot, you might want to practice manual focusing with this camera and then try again.
This is a sample at 100%. I focused on the letters closest to the ruler. The 6 was the closest point on the ruler to the paper.
My camera evidently does not have this problem.
Here is a full image that shows the setup and the septh of field.
Now, when I'm in the field and in a bit of hurry……
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