MTF Test Chart – Final Destination

All good things come by three – this seems to be true for test charts as well. After the unusable Forex chart and the large batch of paper charts with compression artifacts, I’ve got some great news:

The third run of test charts is now suitable for providing accurate MTF measurements!

A Few Details

The new test charts are printed on 200g/m2 matte paper and exhibit very high edge acutance.

In order to allow the testing of optical systems from wide (around 20mm) to very long focal lengths (up to 600mm), I ordered three different chart sizes: A2, A1 and A0.

According to my calculations, a printed test chart has to be at least A2 to allow for reasonably accurate MTF measurements.

Just to illustrate, when testing a 600mm lens with a 35mm imaging system, the required distance to the test chart is around 10 meters. Therefore, a big – or to be more precise: a long - studio is required to test such an imaging system.

In any case, even if I would have preferred to work with charts smaller than A2 in order to reduce the working distance when testing such long focal lengths, this wouldn’t have been feasible as the accuracy and validity of the results would have suffered.

As I’ve written before, the bigger the test chart, the better, as the impact of aliasing effects present on the test chart (inevitable) then carry less weight.

Way Ahead

Although it does not sound like much, the solution of the test chart issue is a big step in the right direction.

I’ve already got a long list of things I want to test besides lenses. For example, have you ever wondered how much a UV filter reduces the resolving power of your highßend lens? Well, I certainly have and now I can measure it and share the results with the world.

Stay tuned!