Gradation curve and Histogram

flatbed scanners for Epson

norris_watkins
SilverFast Beginner
Posts: 20
Joined: Mon Nov 07, 2011 8:16 pm
Scanner: Epson V700
SilverFast Product: SE Plus

Gradation curve and Histogram

Postby norris_watkins » Thu Jan 19, 2012 4:29 am

( Im using Silverfast Plus 8.0 on an Epson v700 scanner )
1. What exactly is being shown on the histogram ( Is it teh input or teh output after applying all teh settings.
If its the input, then nothing we do should have an effect on teh histogram ( Assuming that Silverfast does not change the actual scanner exposure as a result of changing any settings )
If it is the output - after applying the settings like AACO - then it shoudl change against things like AACO, shadow/highlight sliders etc

2. Why doesnt teh gradation curve change when AACO is enabled ? ( AACO amplifies the shadows correct ? ) ( Isnt AACO same as Gamma ? )

LSI_Morales
SilverFast Master
SilverFast Master
Posts: 1430
Joined: Mon Oct 22, 2007 9:33 am

Re: Gradation curve and Histogram

Postby LSI_Morales » Tue Jan 24, 2012 10:21 am

Hi norris

It is the input histogram

norris_watkins wrote:If its the input, then nothing we do should have an effect on teh histogram ( Assuming that Silverfast does not change the actual scanner exposure as a result of changing any settings )


Not completely true, actually the content of the scan frame determines the info in histogram, if you change the scan frame or choose a different part of the image or a completely different scan frame, then the histogram will be different.

SilverFast Ai Studio has an output histogram.

norris_watkins wrote:2. Why doesnt teh gradation curve change when AACO is enabled ? ( AACO amplifies the shadows correct ? ) ( Isnt AACO same as Gamma ? )


Because they are two separate filters.

Cheers
Alejandro Morales

LaserSoft Imaging
Media manager, Software testing

norris_watkins
SilverFast Beginner
Posts: 20
Joined: Mon Nov 07, 2011 8:16 pm
Scanner: Epson V700
SilverFast Product: SE Plus

Re: Gradation curve and Histogram

Postby norris_watkins » Tue Jan 24, 2012 11:05 pm

Thank you Morales :
So what is being shown in Histogram is the Input Histogram correct ?
The Gradation curve seems to be acting as a 'Transfer curve' ( the curve that defines the relationship between input and output ).
But then settings changes like AACO ( which boosts the shadows ) does not have any effect on Gradation curve.
( Setting AACO should have boosted the lower part of teh curve, if it were acting as a Transfer curve )
Similarly changing Shadow point and Highlight point also do not have any effect.
( changing them from 0 and 255 should have respectively made the curve stick to teh lower and upper limits )

So it is not a curve that defines teh relationship between Input and Output.
If true, then what it Gradation curve ? ( what are its X axis and Y axis ? )

LSI_Morales
SilverFast Master
SilverFast Master
Posts: 1430
Joined: Mon Oct 22, 2007 9:33 am

Re: Gradation curve and Histogram

Postby LSI_Morales » Wed Jan 25, 2012 9:04 am

Hi there,

Think of those filters as being in different layers (the gradation curve as well), that is the reason why those changes are not reflected in the gradation curve.

Kind regards
Alejandro Morales

LaserSoft Imaging
Media manager, Software testing


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