Histogram puzzle...

[Don]

But Don, as I keep telling you, NO scanner with the Dmax and bit depth
limits of the LS-30 can cope with the density range and dynamic range
that slide film (let alone Kodachrome slide film) can reproduce.
Consequently it is inevitable that you will run into "problem slides"
which are beyond the capabilities of your scanner. This is not a new
discovery you have made. It has been well known for a very long time
and is actually very well documented. When this was among the best
desktop available it was just an accepted fact of life that some slides
just did not scan at all well.

I'm not trying to get the equivalent of an LS-50 scan but the best an
LS-30 can do. And my original scans were miles from that humble goal.

For example, turning off ICE and NCM alone has improved things
immensely. Had I done that at the beginning I wouldn't have even known
Nikon had problems with Kodachrome (aside from the blue cast).
Frequent rebooting of both NS and LS30 has removed the erratic
response.

And last but not least, by modifying Analog Gain directly I can even
get difficult slides to scan to, what I consider, acceptable results
regarding dynamic range. The only thing left is to streamline cast
removal so it doesn't depend on my imperfect judgement but is based on
something objective.

Speaking of which, can I bother you for another test/favor? Actually,
it's not just for me but others who expressed interest in this thread
would benefit too.

Could you scan a slide (preferably Kodachrome but failing that any
slide will do). ICE and NCM off, everything at neutral. I'm actually
after two scans, one as "Positive" and the other as "Kodachrome". I
just want to see the difference between the two. I'm aware of
everything you wrote previously but I have never seen such a head to
head comparison for myself.

Do you have access to a site where you can post this? I think TIF
would be better but to keep the file size in check please use a really
low resolution, 500 ppi or so.

Thanks as always!

Don.

 

[Don]

In which case I suspect that, strange as it may sound to you, setting
NONE is giving you the real data from the scanner since the histogram
quantisation demonstrably results from processing the limited bit depth
you have to begin with. The lack of the visible effect with bilinear
interpolation on suggests that some interpolation is still being
performed, even at the optical resolution. It's difficult for me to
prove this because I do not have access to an LS-30, s it is just a
suggestion. The bottom line is that any workflow which enables you to
produce a smooth histogram after applying gamma 2.2 to an 8 or 10 bit
per channel image must involve noise addition or resolution/bit depth
trading because there simply is not enough information there to begin
with.

No, I understand that explanation, and it actually makes perfect
sense. What I found weird was that, previously, Bilinear setting would
produce spiky histograms, and now it doesn't! I attribute that to NS
not initializing the scanner, so I now reboot frequently, and over the
last few days haven't had any more erratic responses like that. It
appears I managed to turn off "Nikon's random exposure generator"...
;o)

Coincidence. Gamma 1.2 v 0.8 and 1.1 v 0.9 are only symmetrical in an
exponential form. In terms of luminance at most levels there is no
symmetry.

I thought it was probably a coincidence, but it was just something
that struck me as curious.

Don.

 

[Kennedy McEwen]

Speaking of which, can I bother you for another test/favor? Actually,
it's not just for me but others who expressed interest in this thread
would benefit too.

Could you scan a slide (preferably Kodachrome but failing that any
slide will do). ICE and NCM off, everything at neutral. I'm actually
after two scans, one as "Positive" and the other as "Kodachrome". I
just want to see the difference between the two. I'm aware of
everything you wrote previously but I have never seen such a head to
head comparison for myself.

My ISP's news server crashed and has slowly been backfilling some
articles, so I have just managed to read this.

If you email me directly from a valid account then I will send the files
on to you, There are three files at 400ppi, normal scan (NCM, ICE etc.)
Kodachrome and Positive, each around 1.4Mb - so you need to be able to
accept at least 6Mb, allowing for mail encoding.

 

[Don]

If you email me directly from a valid account then I will send the files
on to you, There are three files at 400ppi, normal scan (NCM, ICE etc.)
Kodachrome and Positive, each around 1.4Mb - so you need to be able to
accept at least 6Mb, allowing for mail encoding.

Thanks as always Kennedy! The email is on the way...

Don.