Darkimages of Watec and Mintron (25°C)

www.mondatlas.de: Version 10. Oktober 2003
Martin Elsässer


The dark-images of the two cameras were taken at very high temperatures of 25°C. (comparison at cold temperatures) The displayed images are the average of very many individual frames. Both cameras were set to their maximum sensitivity settings, with maximum gain and exposure time, 10sec for the Watec and 2.5sec for the Mintron. The settings of the used framegrabber were not changed.

Darkimage of the Watec, inverted
Darkimage of the Mintron, inverted: uneven background brightness towards the left edge. Only half line resolution.


The displayed histograms were generated from the above darkimages (not inverted). The histogram of the Mintron shows the increased and widenend floor, resulting from the artificial "brightness" on the left side .

Histogram of the Watec dark image
Histogram of the Mintron dark image


The following two cross-histograms of the cameras were generated from the full number of dark-images and demonstrate the amount of noise of the two cameras at different levels. An ideal cross-histogram would look like a thin line. The ideal cross-histogramm for dark-images would actually be a single point. A broadening of the line shows the degree of noise at a certain level of brightness. The differing size of the images results from the fact, that the brightest pixels in the image-series differ between the two cameras.

Cross-histogram of the Watec-dark-frames, quite thin (little noise) and not as high as with the Mintron, so the hot-pixels are less hot then with the Mintron. Cross-histogram of the Mintron-dark-frames, clearly wider (more noise) and higher, so the Mintron has "hotter" pixel, despite the shorter exposure time.


long-exposure comparison