You are looking for an LS-30 equivalent of the "Kodachrome" setting on
and LS-40/50 or LS-4000/5000. Stephen is telling you that not only
doesn't that work (it leaves a blue cast) but that his AG settings on
the "Positive" setting give better results - something which is
completely the opposite of what you have been looking for and which does
not correlate with any of the comparative "Kodachrome" scans which you
have been shown.
This is based on a sample of 1 (the images you sent me - the first
lot) so it's to be taken with a boulder or salt...
With that caveat out of the way, the main difference between LS-40/50
(and friends) and my LS-30 seems to me to be the darkness of my scans.
The blue cast appears to be very similar in both (relatively speaking)
in the sense that there is a (severe) lack of red and (over) abundance
of blue.
I am not assuming anything of the sort! I am assuming that both of you
are attempting to obtain a scanned image which has an equivalent density
to the original slide. Stephen quotes a variance of +/-0.3EV to achieve
this, whilst you quote a variance of +/-0.5EV. However you both quote
an average difference which is of the order 2.1EV - a difference which
simply cannot be bridged by the variances you both quote.
Not quite sure I follow that. If I understand you correctly the
variances (+/-0.3EV and +/-0.5EV) refer to the difference in our
individual channel corrections, while average difference refers to
master settings (2.1EV) i.e. the difference in "darkness". Is that
right?
Now, again, if I understand correctly, you're saying that such major
average difference (2.1EV) is (theoretically?) inconsistent with the
variance (+/-0.3EV and +/-0.5EV). Is that right?
I did some tests whereby I varied the master AG gain but this did not
affect the ratio of individual channel AG adjustment (let's just say I
was not able to spot any difference). Not knowing the theory I had to
arrive at this empirically and my worry was that boosting master AG
would unravel everything and affect the ratio of individual RGB
channels - and upset the balance - but apparently it doesn't.
Too easy - except it ignores the fact that your scanner works fine with
E-6 type slides, negatives and monochrome film. Blaming your scanner
implies that it somehow magically detects your Kodachrome slides from
other media and then adjusts its own exposure *equally* on all 3
channels to achieve a 1.3EV error. If the firmware is that smart you
really ought to spend all the time you have disassembling it, because
the algorithm could win you a fortune at the races!
Well, it was your explanation that different LEDs may have different
chromatic responses and that's why the LEDs in my scanner may not be
able to react to Kodachrome as they do to other slides or negatives,
or indeed why LEDs in other scanners may react differently to KC.
Stephen's results do confirm there are differences between LEDs (he
doesn't need to boost master AG as much as I do) but there are also
similarities (in terms of color balance) which is what I have been
focusing on.
BTW, in my particular case this is all somewhat academic because I
have moved on to other avenues and methods but it's very interesting
theoretically.
Don.
