Howtek D4000 level manipulation @ analog stage?

[zhengjdc]

Hi, I am currently owning a Howtek D4000 drum scanner with Silverfast Ai 6.6 and there is something puzzled me for a while, it's about the analog amp inside Howtek D4000, is it being access by Silverfast?

I have tried scanning with 48bit HDR color, which automatically turning off everything regarding color management, and got a very dark image (understandable). The following step I did is to do a level/histogram/curve adjustment inside Photoshop 5.1, however, the result seems to be very noisy, despite I was editing it with photoshop 16bit color mode.

Since the result wasn't very satisfactory, I did the other way around... I adjusted level, histogram & curve ALL inside of Silverfast, then I scanned with 48bit Color (NOT HDR), the picture looks much better than the one did with 48bit HDR Color.

This just puzzled me... as I presumed, Silverfast did all these Histogram/level/curve adjustment all at digital level, so theoretically, the result should be NO different than doing such adjustments inside Photoshop, but the result spoke otherwise. Thus I can only assume that Silverfast indeed did all these level settings at analog stage, for my particular scanner--- Howtek D4000, it did all these at the Log amp stage (before A/D conversion took place).

Can someone confirm me this?

Thanks

[LSI_Ketelhohn]

Dear customer,

adjustment of the image data befor the A/D Converter is not possible.
Manipulation of electronic devices is always digital.

The difference probably is caused by the different color spaces used and the skipped highlights/shadows adjustment.
The 48bit HDR image stays in the scanners internal workspace which can not be read by Photoshop.
Depending on your settings Photoshop will assume a standard color-space.
But because this was never correctly rendered the assumed colors will be wrong.
In addition this will also result in a compression of the color information and therefor a loss of dynamic range.

SilverFast however is designed to work with device specific color-spaces and will create a correctly rendered image with a standard color-space and correctly set highlights and shadows.

kind regards,
Arne Ketelhohn.

[zhengjdc]

Very appreciate your reply. But I think I need to point out something:

I also own an Epson scanner v700, the epson scan software has the ability to adjust the exposure time somehow which results a better looking image, and its level setting indeed adjust the analog gains of the v700.

Same goes for Howtek D4000. The result was sooooo drastically better which I don't believe it's been manipulated at a digital level.

I wonder whether silverfast utilizes any Howtek software modules such as those inside Trident which indeed adjusts the analog gains. Maybe Silverfast doesn't have direct access to the internal of scanner but the modules(or whatever) it utilizes indeed was doing all the work there?

Thank you (dunka)

[LSI_Ketelhohn]

I also own an Epson scanner v700, the epson scan software has the ability to adjust the exposure time somehow which results a better looking image, and its level setting indeed adjust the analog gains of the v700.

Same goes for Howtek D4000. The result was sooooo drastically better which I don't believe it's been manipulated at a digital level.

The MultiExposure function operates the scanners hardware to achieve higher exposure values directly through the sensor.
This is an analog function but the resulting image is processed digitally by our advanced algorithms.
There is no image processing taking place with analog image data.
Access to this information is not even possible with most devices (e.g. the V750).


kind regards,
Arne Ketelhohn.