Digital cameras have sometimes artefacts in their images.
My LX5 produces a black cross.
“Silent Tim” discovered this phenomenon. He had postprocessed
an underexposured night picture made at iso 80. He placed his cross-picture
on the panasonic talk forum of dpreview.
My LX5 can also reproduce this phenomenon. But I never saw this phenomenon in a real picture, although I assume that is always (not visible) present.
If you want to see it, take an underexposured picture at iso 80. The
underexposure (ev) should be -3 or less. And in post-processing you
can make it visible with a gamma correction.
At higher iso values the ghost-image is hardly visible by the noise.
I see that the ghost-image is present at the start of the exposure.
At longer exposure-times the photons will cover the whole picture and
then the ghost-image is no longer detectable.
So if the exposure-time increases it you will no longer detect the ghost
image.
On a LX5 picture there is an area (the ghost-image) that is less exposed then its surroundings. I estimate that the underexposure of the ghost-image is constant about 0,5% of the maximum intensity.
The shape of the ghost-image depends on the diaphragm f.
It can be a star (f2.0), a star in a cube (f2.2, f2.8, f3.2) or a black
cross (f2.5, f3.5 and higher).
I don’t understand this influence of the diaphragm on the shape.
Although this blackcross phenomen the LX5 is in my opinion still a superb camera.
