How I test the sharpness of a lens

Again and again people ask me how exactly I test the sharpness of lenses. This is why in this post I am going to explain my test method.

For all tests, the camera is mounted on a tripod, I use release the shutter via wifi and if possible I use the electronic shutter. This ensures that the result is not influenced by vibrations.

I always use the camera with the highest resolution available to me and if possible a high-res mode. In case of shallow depth of field, I take several pictures and refocus for every shot to make sure there are no focus errors. The samples I use for my reviews are always 100% crops at base ISO.

I always refocus on the image borders to test their sharpness. If I suspect a significant field curvature, I test it separately.

I have been asked if the post cards I use as my test subject are sharp enough. If they are the limiting factor you are going to see the pressure grid.

Here is an example what this looks like:

Example of the lens outresolving the post card, the pressure grid is visible.

If you do not see the pressure grid, the post cards were sufficient as the test subject.

If you still have doubts, take a look at my comparion between the Olympus M.Zuiko 25mm F1.2 Pro and the Olympus M.Zuiko 12-40mm F2.8 Pro. Although this are expensive lenses and part of Olympus Pro line, the difference between the maximum aperture and F/5.6 is clearly visible.

Even if a different subject would show a difference at F/5.6, honestly, there is a point where a lens is just sharp enough. I am interested in real photography and I do not think that there is a picture that would suffer from the amount of sharpness that those two lenses display in my test.

If you have any more questions about how I test the sharpness of lenses just leave a comment!

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