Re: filmscanners: RE: filmscanners: VueScan clipping & flat images

[Arthur Entlich <artistic@ampsc.com>]

Jawed Ashraf wrote:


> 
>>>The LS40 and LS4000 (used with Nikon Scan) do.  It's what
>>>
>>happens when the
>>
>>>auto-exposure kicks in (I believe) which changes the brightness of the
>>>"lamp" (there's logic for why I could be wrong - I'll let somebody else
>>>argue the point).
>>>
>>No, they don't.  As Ed explained, they change the exposure time not the
>>brightness of the LEDs.
>>
> 
> I believe you're misquoting Ed.  He responded to the opposite effect, in
> response to someone who suggested what you're saying.  I'm fairly sure he
> was quite specific that the LED brightness changes.  The manual says the
> brightness changes, too (apparently - can't be bothered trying to find the
> manual).  (Can't find this message from Ed, either - damn - must try
> harder.)
> 
> Unless you mean that there is no connection between Nikon Scan's
> auto-exposure algorithm and LED brightness.  I have to say if that was the
> case, it would seem to be missing out on a key feature of the scanner
> (variable lamp brightness!).  Oh well.
> 
> Jawed
> 


Boy, this thing has grown legs... I was the person who indicated that 
Nikon's manual states that the brightness of the LEDs is altered.  Ed 
came back with information that the info is not correct, and that the 
CCD exposure time is altered instead, in spite of what Nikon's manual 
states and he was able to prove this via his monitoring of the command 
flow between the scanner and software adjustments.

I've quoted myself and Ed below.

Art


> In a message dated 11/21/2001 8:07:15 AM EST, artistic@ampsc.com writes:
> 
> 
>> Nikon might be approaching the limits of linearity in the LEDs.  They 
>> also need to be able to have a range of brightness available to them for 
>> the "analog exposure" they offer.
> 
> 
> No, Nikon scanners don't vary the brightness of the LEDs.  The
> "analog gain" option in NikonScan only changes the CCD exposure
> time.  I've traced the commands that NikonScan sends to the
> scanner, and the field it changes is definitely the CCD exposure
> time field.
> 
> In addition, the scan speed is proportional to the "analog gain"
> setting, which it wouldn't be if NikonScan were only changing
> the brightness of the LEDs.
> 
> Regards,
> Ed Hamrick
>