LaserSoft Imaging

In NegaFix's expert dialogue is the auto-tolerance slider. Either in Ian Lyon's tutorial or in the SF manual it states that this slider affects the strength of the negative mask. What does this mean?

When one looks at the expansion histogram, it appears that the slider levels something out, like white balance. From just playing with it, I find that I typically like the slider moved about 1/3 toward the right. But this is really a finger-in-the-wind way of using this tool. Can someone give me a little more insight as to what is going on?

Thanks,
Joel W.

Joel,

In NegaFix's expert dialogue is the auto-tolerance slider. Either in Ian Lyon's tutorial or in the SF manual it states that this slider affects the strength of the negative mask. What does this mean?

Exactly what it says. Each negative film has coloured mask (for historical reasons it's usually referred to as the orange mask). With many modern films the mask can be purple and all shades of YUK!. When Auto is selected SilverFast will set the end points of the histogram so that the highlight and shadows pixelsjust clipped and no more. Using the "Auto Tolerance" slider you can crop the endpoints tighter and thus remove even more of the mask colour. Usually this isn't necessary. Actually if you press the Reset button the image will likely turn a bluish colour (inverted orange/yellow). This shows how the image would look if the highlight shadow endpoints were left untouched.

When one looks at the expansion histogram, it appears that the slider levels something out, like white balance. From just playing with it, I find that I typically like the slider moved about 1/3 toward the right. But this is really a finger-in-the-wind way of using this tool. Can someone give me a little more insight as to what is going on?

It is NOT finger in the wind. Negative type films are a first order pain in the butt when it comes to how exposure and developement latitude cause the film base characteristics to alter. Get either wrong and the mask density/colour goes to pot. There is NO perfect setting so LaserSoft give us the facility for refining it to "our" liking. The auto setting is designed to just clip the initial pixels and no more. The Auto-Tolerance simply allows us to clip more pixels. Clip too many more pixels and contrast will increase and highlight detail will be lost, etc.

Ian

PS: I added a section to the tutorial yesterday that deals with increasing decreasing saturation of specific colours within NegaFix. The web version is complete. The PDF still needs to be uploaded. I think it should answer your other question



<font size=-1>[ This Message was edited by: ilyons on 2002-01-20 22:54 ]</font>

Thanks for the explanation about auto tolerance and the image masks. The language that I find confusing is "strength" of the mask. It's hard to know whether this means that the effect of the mask is stronger when the slider is pulled to the right, or weaker. I still don't really know, but I think I understand your explanation.

I don't uncheck auto before moving the slider. I usually drag the slider all the way to the right to see the effect and then drop it back to 75% and then 50% before usually settling for 25-30%. Is this correct?

After doing this and closing the NegaFix expert dialogue, I usually try the Image Auto-Adjust button but find that it often does very little. I'm wondering if on a great many images it is really doing something quite similar to the auto tolerance slider? There are so many ways to do the same thing in Silverfast, I thought this might be another example.

Another thing I've found I like to do even after selecting the Auto-Adjust button is select the histogram button and move the sliders in from either end to 4 and 96. I then check and adjust the curves a little and perform the scan. The histogram adjust gives me a little room to play with the image in Photoshop, where I almost always do a little levels and curves adjustment.

Does this workflow seem sensible?

Joel W.

On 2002-01-20 23:39, jdub wrote:
Thanks for the explanation about auto tolerance and the image masks. The language that I find confusing is "strength" of the mask. It's hard to know whether this means that the effect of the mask is stronger when the slider is pulled to the right, or weaker. I still don't really know, but I think I understand your explanation.

All the way to the right is maximum strength. At the left it is at a point were the mask colour is eliminated without clipping the highlights to maximum white. As you move the slider to the right (increase strength) you clip more and more highlight end pixels. These become maximum white and so cannot be orange

I don't uncheck auto before moving the slider. I usually drag the slider all the way to the right to see the effect and then drop it back to 75% and then 50% before usually settling for 25-30%. Is this correct?

Yes - ideally we should never need to uncheck Auto. Some films due to age or awful processing might need the Auto to be unchecked. Once unchecked we can pull the vertical bars towards or away from the end of the histogram to remove the mask (it will appear blue because we are looking at a positive)

After doing this and closing the NegaFix expert dialogue, I usually try the Image Auto-Adjust button but find that it often does very little. I'm wondering if on a great many images it is really doing something quite similar to the auto tolerance slider? There are so many ways to do the same thing in Silverfast, I thought this might be another example.

At its most simplistic level you would be correct. However, NegaFix works on the negative and gives us nearly perfect positive. Auto Adjust typically will have very little left to do, but the other tools such as gradation curves, hue/saturation, etc. can still be used to further refine the image.

Another thing I've found I like to do even after selecting the Auto-Adjust button is select the histogram button and move the sliders in from either end to 4 and 96. I then check and adjust the curves a little and perform the scan. The histogram adjust gives me a little room to play with the image in Photoshop, where I almost always do a little levels and curves adjustment.

Does this workflow seem sensible?

If it works then it is sensible. I use different workflows for different images. there is NO one way and NO absolute way in SilverFast or Photoshop. Each user will find a workflow that suites them and that is beauty of such software - also why it cost more than some folk think fair.

<font size=-1>[ This Message was edited by: ilyons on 2002-01-21 00:02 ]</font>

Indeed, Ian, it seems to work extremely well for me. I don't know if I'm ready to give up on slides, but SF renders negatives so gorgeously I will doubtless shoot more C-41 in the future.

I look forward to checking out your updates to the tutorials tomorrow (a holiday for us in the USA).

Best regards,
Joel W.