multisampling as compared to single sampling

[Guest]

just wanna clarify one point>>>multisampling is an absolute nessecity but not really better than single sampling...
>>>if the neg is properly exposed, not under exposed, single sampling is all that is needed
>>>many times i tried repetitively that multi sampling makes a more blurry image
and less noise image at the same time
>>>multisampling is best used for under exposed film
>>>ever wonder why most mega dollar scanners and drum scanners don't ever need multisampling?
>>>multisampling is best for slightly under-exposed film
>>>u can never have drum scan quality or 1200dpi or 2700 to 4000 dpi by multisampling
>>>hope this could help, don't take my word, try urself and see

[President_LSI]

Multi-Sampling and its benefits

The main purpose for Multi-Sampling is noise reduction. Scanners that are not using very costly electronics or are not so carefully desinged, produce noise with their CCD and AD-converters.
Noise will come up especially when the light falling onto the CCD is low (when there are dark areas in an image). This noise is statistical in its nature which means it is randomly distributed.
Multi-Sampling is taking several samples of the same image (acquire several scans or CCD-lines) and average them. Since the noise will always be in different spots of the image, it will be cancelled out throught the avaraging process.
Multi-Sampling realisation:

1. Multi-Sampling (repetition) of the whole scan and realisation in software (this requires the scanner to be mechanically precise enough, so each scan aligns perfectly with the next one. Only very few scanners are precise enough. We have inplemented that method in SilverFast Ai for fe scanners.

2. Multi-Sampling on a single scan-line
A single stationary line of the CCD in sampled several times and averaged. This is the best method, because the mechanical precision of the scanner is not relevant, also the process is faster.

Why don't high-end scanners need it?
Most high-end scanners either have this procedure inside (without telling) or they are using other technolgy such as a 'Peltier'-element to cool down the CCD or in the case of a drum scanner with a photomultiplier, there just is no noise being produced.



<font size=-1>[ This Message was edited by: President_LSI on 2002-01-26 18:52 ]</font>

[defiantm]

I just puchased an Epson Perfection 4990 PRO with SilverFast Ai 6. I spotted the Multi-Sampling button and became very exited. I tried the feature and to my dissapointment it made the images blurry. I looked online to find out why and found this topic. Can you please make an update for SilverFast Ai 6 that would allow you to set the option of how the image is Multi-Sampled? Your software is already the best I have ever used and being able to perform a Multi-Sampling on a single scan-line would make it the ultimate in scanning software. Please let me know if you will, or if it is even possible.

Thank you for your time,
Justin Moore

[President_LSI]

Multi-Sampling for Epson Perfection 4990

Dear Justin,

Multi-Sampling for the Epson 4990 will not be possible on a single scan line since the manufacturer does not allow such a command to be established. However we will come up with a new intelligent multi-sampling procedure that will compensate for the mechanical deviation between sampling scans. So there will be no blurring effect!
The good news is: This new function will be available in SilverFast Ai STUDIO or SF SE Plus versions. Will be released shortly!

best regards (':wink:')

Karl-Heinz Zahorsky
President
LaserSoft Imaging

[LSI_Leschke]

Multi-sampling with auto-allignment is available now.

http://www.silverfast.com/show/silverfast-multisampling/en.html