How do scanner drivers works exactly?

[Benoît-Nicole Morrissette]

I have a CanoScan Lide 70 scanner with the corresponding ScanGear 12.0 driver.
In the driver interface, there are options to adjust the brightness and contrast
of the images. Are these operations done in software OR does the driver
adjust the intensity of the scanner's LED's?

I ask that because if it is done in software only, i can do it with
PaintShopPro, PhotoShop or any other picture processing software
with much better control over the process. If it is done in hardware
then it is another story because changing the intensity of the LEDs
do change the pixel information returned by the driver and that is what
i want to do ( i have old photos, either too dark or too light...).

Any idea?
Thanks,

Benoit-Nicole...

 

[CSM1]

I have a CanoScan Lide 70 scanner with the corresponding ScanGear 12.0
driver.
In the driver interface, there are options to adjust the brightness and
contrast
of the images. Are these operations done in software OR does the driver
adjust the intensity of the scanner's LED's?

I ask that because if it is done in software only, i can do it with
PaintShopPro, PhotoShop or any other picture processing software
with much better control over the process. If it is done in hardware
then it is another story because changing the intensity of the LEDs
do change the pixel information returned by the driver and that is what
i want to do ( i have old photos, either too dark or too light...).

Any idea?
Thanks,

Benoit-Nicole...

Exposure in scanners is done the same way it in done in digital cameras, you
adjust the time the camera (sensor) is gathering light or data.

The intensity of the light source (LEDs) is not changed.
There is both a software and hardware component to getting the correct
exposure.

Here is a good explanation of how a scanner works.
http://www.howstuffworks.com/scanner.htm

 

[Barry Watzman]

Re: "I ask that because if it is done in software only, i can do it with
......"

No you can't.

If the settings don't allow the full dynamic range, then there will be
"clipping" (either in highlights or lowlights). Once that happens, the
information is lost forever and can never be restored. Granted, you can
change the brightness/contrast/gamma subsequently AS LONG AS THE
ORIGINAL SCAN WAS NOT CLIPPED. But if you don't set these parameters
when the original scan is done and transferred, then clipping is LIKELY.

 

[gowanoh]

The argument about whether to make adjustments in the scanner driver or in
post-scanning image processing software is an old one with many opinions.
I believe for most purposes scanning should transfer as much picture
information as possible and processing should be done in a program such as
Paintshop or Photoshop.
This is analagous to shooting jpegs with a dSLR or shooting raw. If the data
has been compromised your ability to use it later is restricted.

 

[Barry Watzman]

But if you don't do the settings right in the scanner driver, then you
won't "transfer as much picture information as possible".

 

[Roberto]

But if you don't do the settings right in the scanner driver, then you

won't "transfer as much picture information as possible".

That was the original concept behind Veuscan (originally Viewsmart --
a third-party driver that would get more of the picture from the
original HP Photosmart than the manufacture-provided driver.

 

[mp]

In an ideal situation, you should use the tools provided by the
scanner software. It definitely gives image editors more continuous
data from which to derive a final image.

Some basic functions that you should do include:

1. Basic color correction. Get it close
2. Basic "brightness" You understand the image will always appear
less bright if you are printing the final output right?
3. A little unsharp masking.

With that said, most scanning software is simply not up to the task,
nor is there any semblance of color savvy workflow in the average
desktop to take advantage of what a scanner has to offer anyway so
it's a moot point.

-Vuescan and Silverfast are two (best) options for scanning software.

I will make the bold statement that anyone that still believes
photoshop is the only tool for the job and/or the old hack "scan at
maximum optical resolution then downsample" is outdated and
uninformed.

MP