Re: filmscanners: Silverfast lamp lightness option

[michael smith <michaelasmith@earthlink.net>]

Dear Steve , thank you for your thoughtful work. Ill try it out for myself
as I have been curious too, but lazy(or at times just plain overwhelmed by
the steepness of the learning curve). Have you checked this with Ian Lyons?

   Regards, Michael Smith

> From: "Steve Greenbank" <steve@gccl.fsbusiness.co.uk>
> Reply-To: filmscanners@halftone.co.uk
> Date: Thu, 5 Apr 2001 16:02:57 +0100
> To: <Filmscanners@halftone.co.uk>
> Subject: filmscanners: Silverfast lamp lightness option
> 
> Reading Ian lyons very helpful tutorial "Silverfast 5 and the Polaroid
> SS4000 : Part 1 - Basic steps to IT-8 calibration", I found he used a value
> of 10 for lamp lightness. He noted that this allowed him to maximise shadow
> detail.
> 
> Sounds good to me, but how do I know what value would be good for my
> (mechanically) similar Artixscan 4000 ?
> 
> After a little thought I came up with the following technique:
> 
> I used IT-8 slide with the HDR option. I made an initial scan and used PS to
> check the RGB values in the grey scale area for rectangles "0" and "23"
> which I think should be pure white and pure black respectively.
> I found the white was well short of 255 in every channel. So I tried
> progressively higher values in lamp control until it became almost
> completely 255 in every channel. I then backed the lamp control off until
> the values were generally 255/254 in every channel. This by my reckoning
> maximised the bandwidth as the black was still showing RGB 0/1 or sometimes
> 2. I then recalibrated using the IT8 slide. I checked a before and after
> scan nd I do not appear to have introduced loads of noise.
> 
> My final value was 24 where as Ian ended up at 10.
> 
> Does my technique of arriving at the final lamp setting make sense ?
> 
> Can anyone suggest anything better ?
> 
> Any nasty flaws ?
> 
> Steve
>