In order to quickly carry out a test, whether or not the purchased illuminant flickers too much, there are several possibilities which can be used without any measuring means at any time.
In addition to the two tests described below, there is more information about light flicker on Wikipedia and in this flicker blog by Wolfgang Messer, which unfortunately only serves as an archive.
Of course, optical light flicker can be precisely measured by the service of Der Lichtpeter.
In contrast to the eye-open-close-test shown below, the rod test (also referred to as "fan test") applies to each light source, since the light source is evaluated during operation and not shortly thereafter.
For this purpose, a thin bright object is used (usually a white, thin rod of approx. 15 cm length, the back edge of a knife, the side edge of a check card or the outstreched index finger, in the pictures it is a folding rule). This bright object is moved back and forth under the light source at a small distance, so that the object is illuminated by the light, preferably with a dark background.
! Caution: Do not move the rod between the lamp and the eye (danger of glare) !
The direction where the light comes from the lamp should be approximately the same as the direction of view. In the pictures here the light comes from the left, lights up the rod which has a dark
background (book) and the camera also looks to the right.
To put it bluntly: light and eye look in the same direction.
The illuminated back and forth moved object is to be observed.
The left picture shows the object as a tail, which is perceived only when the illuminant has little or no recognizable flicker. Here, the object is illuminated at any time on its way from one side to the other, i.e. at any time there is light.
The right picture, however, shows the object only as a fan with dark phases in between. On its way from one side to the other, the object is temporarily not illuminated, i.e. the light is temporarily not present, which is nothing more than an expression for flickering: the light sometimes is but sometimes not present. The stronger the light-dark contrast, the stronger the optical flicker.
This test is possible in Europe (mains frequency 50 Hz) and a camera with 24 fps, e.g. that of a smartphone, in order to detect the most common 100 Hz flicker.
To do this you just have to call the camera app and keep the camera very close to the light source, no filming, no picture taken.
If there is flicker, dark to black bars run through the image.
The darker and / or wider the bars, the stronger the flickering.
However, the significance is very dependent on the distance, which is why the rod test provides a better statement.
New smartphones have Kamara apps with them
1. a so-called "anti zebra stripes" mode, this must be switched off.
2. a special mode for manual setting of shutter speed (S) and sensitivity (ISO).
If you set this to S = 1/1000 and ISO = 2000, the flicker can be traced back exactly to the place of origin even at greater distances.
This test is an additional one you can make.
Caution Warning! :
The direct view into a operated lamp is dangerous for the eyes!
1. Close the eyes and align them to the light source (approx. 50 cm away).
2. Switch on the lamp (eyes remain closed!)
3. After 3 seconds turn off the lamp and at the same time (not before!)
open the eyes and observe the LED filament.
If no afterglow (min. 1 sec... 2 sec.) can be detected when switching off, then you might have the certificate to own a flickering illuminant, otherwise you may not have bought the worst
This test is only valid for filament lamps, because they usually have no high-frequency switching regulators implemented. Lamps with high-frequency switching regulators do not afterglow, but also hardly flicker.
On the other hand, this test does not certify a flicker-free lamp, but only that the flicker can be acceptable.
Der Lichtpeter doeas not accept any responsibility for any damage (particularly to persons or things) caused by incorrect or correct handling of this test.