Multi-exposure test reports

[Jossie]

Good evening,

on the SilverFast webpage on ME there are two test reports provided. Unfortunately they are for SilverFast6, which I do not have. I have looked into these reports and they only state at the beginning that "For scanners that offer different exposure times multiple images are scanned with at least one image at each exposure time." Is the functionality of ME in SF6 the same as in SF8, i.e. two exposures are taken, one with standard exposure time and the second with the exposure time doubled (which is the case for SF8 and my DD6000)? Is this the same for all scanners or are there differences from scanner to scanner?

Hermann-Josef Röser

[LSI_Ketelhohn]

Multi-Exposure is the same in SilverFast 6.6 and SilverFast 8 and all scanner models.
It is always one normal and one high exposure image.

Kind regards,
Arne

[Jossie]

Good morning,

thank you very much for the clarification. This means, that the ME-exposure has twice the exposure time than the standard exposure for all scanners. This is what I measure for my DigitDia6000.

On the LSI-Webpage on ME there is a report published, which states a gain in density due to ME for the Nikon LS-5000 of 0.7 and for Nikon LS-9000 of more than 0.8.

How does one reconcile these values with the following simple thought experiment: Assume the ME-scan is made through an ideal neutral density filter, which cuts the photon flux in half for all wavelengths. This will make the ME-exposure be identical to the standard scan (modulo noise, of course). The neutral density filter will thus give directly the gain in density due to ME. According to the definition of density this hypothetical filter must have a density of log(2) = 0.3, which should be the theoretical maximum gain achievable, independent of the scanner.

Hermann-Josef

[LSI_Ketelhohn]

Dear Mr Roeser,

You probably assume the two devices are using the same sensor, which unfortunately is not true. The achievable density is of cause depending on the used sensor.

Kind regards,
Arne