The image analysis algorithm used in FoCal has been specifically designed to provide a consistent measure of sharpness and minimise the effects of small movements (e.g. vibrations) and small changes in light level. However, there are things you can do when choosing a test location that will improve the reliability of the results from FoCal.
FoCal will operate best if there is as little movement as possible. Bear in mind that the are you choose can have a bit impact – ground level on a concrete floor is likely to be much more stable than on a suspended first floor. For the duration of the test, it’s best to not jump around near the camera too!
Testing outdoors is perfectly acceptable – indeed it is often necessary to ensure a large enough distance between the camera and the target as the focal length of the lens increases.
As mentioned above, minimising movement is critical so when testing outside it’s important to pick an area sheltered from any wind that might disturb the camera or the target.
Lighting on the target must be stable, so it’s best to test on either a day with no clouds or a day with an even cloud cover – passing clouds changing the light level on the target will almost certainly affect FoCal’s ability to produce an accurate result.
Continue on to The FoCal Target