[filmscanners] Re: how to scan 'red' 'green' or 'blue' lights?

["Dieder Bylsma" <scanners@spacemoo.com>]

Hi all, just catching up on today's email, so I'm combining a few
email responses together.




At 08:51 -0500 03/01/20, Doug Franklin wrote:
>I've seen the same thing on the CanoScan FS-4000US, but only in the
>red.  I've never seen it happen to blue or green, but the "pure" reds,
>holy cow they're red.  And brake lights is one of the first places I
>noticed it.

yes, red seems to be easily super-saturated 'eye-popping' red on the
scanner, whereas in a print they are not. It takes a considerable
amount of effort to 'tone down' the red 'highlight' which has a
corresponding zero value in the other Green and Blue channels, hence
the 'pop'.



At 09:18 -0800 03/01/20, Paul D. DeRocco wrote:
>If I take you literally, you seem to be saying that the hot colors appear on
>the film, as well as the scan. If they're on the film, then they ought to be
>in the scan, too, and your problem may be that the printer gamut isn't large
>enough to represent the color.

my point and query is not whether or not the 'hot' colours appear on
the film, because quite clearly in looking at prints made at all
sorts of labs, using all sorts of films, the 'red' is never so
'saturated' as to be  65536:0:0 (RGB).


>On the other hand, you seem to be speculating about a problem in the
>scanner, suggesting that you may have intended to say that the hot colors
>that appear in the scan aren't on the film at all. If they're not on the
>film, and they're not on the print, then it may be that the monitor is
>miscalibrated. After all, when you look at a scan, you're looking at it on
>your monitor.

The value is not so far as I can see one of colour calibration. Raw
values taken courtesy of Vuescan show that brake lights are usually
'saturated' that way when I scan with my LS-4000.

>By the way, quite a few of my pictures have traffic or brake lights in them,
>and I haven't noticed any funny effects when scanning either Kodachrome or
>E6 slides on my LS-2000.

I'll have to run through my trannies and see if I can find one that
has brake lights in them and confirm that my observations (largely
based upon negs) carry 'true' for trannies.

At 16:20 -0800 03/01/20, Paul D. DeRocco wrote:
>When you say the colors are "over the top" do you mean that they're too
>bright, or too saturated? If they're too bright, and the scanner is
>clipping, they'll actually wind up undersaturated, because once the red
>channel reaches its limit, any further increase in brightness will only
>bring up the residual green and blue. If you're using Photoshop, it would be
>worth seeing if the red value is pinned at 255. If so, you might try
>rescanning while turning down the exposure in the scanner software, and then
>using Photoshop's Levels control to bring back the overall brightness
>without clipping off the top.

True'nuff, but red brake lights, in fact any 'red' light of any sort
usually comes through a scan like a red laser pointer in a dark room.
Hence my query about whether this is the case because of

light source in the scanner (diffuse/collimated)
type of light source (LED vs fluorescent tube)



>If the colors are oversaturated, but not clipped, then all I can imagine is
>that the scanner's negative to positive conversion just isn't very accurate.

I guess you could call it 'clipped' but there's a very sharp
'fall-off' where the colours are truly 'clipped' and after that they
are fine. As far as possible I'm dealing with 16 bit colour
acquisition/manipulation processes, be it with Vuescan or Nikonscan
or Photoshop



At 17:18 -0800 03/01/20, Frank Paris wrote:
>Nor me on my Polaroid SprintScan 4000. I was reading this post and was
>thinking, "Well, yes, a bright red light SHOULD appear bright red!" I
>couldn't figure out why anyone would complain about that. What am I
>missing?

The thing is that the 'red' is a type of red that just pops out of
the rest of the picture, very 'hot' red whereas all the other colours
aren't.

>BTW, any relationship with Anner Bylsma?

other than the name? no. :-)



At 19:39 -0800 03/01/20, Paul D. DeRocco wrote:
>I'm not sure what fluorescent red means, as compared simply to red. What RGB
>values do you get when you hover over the objectionable color in PS?

in 16 bit mode or 8 bit mode the approximate ratio is the same:

99.7% : 0.15% : 0.15% RGB which is just 'unreal' when the rest of the
picture doesn't have that type of saturation.




Dieder

----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body