DMAX Question

[Pavel Dvorak]

Yes, hardware is the cause, but VueScan is the problem. Namely:

Misalignment does happen with all scanners because scanner mechanics
just aren't capable of such high precision i.e. going back to exactly
the same place as during the previous pass. This can be ameliorated
afterwards by sub-pixel alignment in software.

The problem with VueScan (one of many) is that is makes empty claims
without taking this into account. Since no sub-pixel alignment takes
place the end result is a blurry mess. As outlined earlier, you can
get much better results by simply applying a small amount of Gaussian
Blur to dark areas.

To see how different exposure are blended by professional software
check:

http://www.ict.usc.edu/graphics/HDRShop/

Version 1 is free. It has its shortcomings (8-bit input/output,
clipping) but it's definitely worth a try.


I'm not familiar with that scanner but are you sure you're not
*single-pass* multiscanning?

I am sure. The scanner feeds the frame through repeatedly.

(I'll try the test you suggest below.)

If it is a genuine *multi-pass* multiscan, then it depends on how you
do the tests. There are mathematical models to do this properly, but
even with a simple visual test you need to follow some basic
guidelines. For example, examine the *two* images at maximum
resolution, overlapped and then toggling between the two. This will
clearly show the amount of misalignment and areas where this is most
apparent. Only then can you go to the combined image and examine
(again at maximum resolution) the areas where the misalignment is most
apparent.

But it could very well be that the blurring doesn't bother you, in
which case you can just ignore all of the above.

The specified scanner resolution is only 2720 ppi, so any misallignment may
not be so obvious as with a 4000 ppi scanner.

Pavel

 

[Gordon Moat]

I believe that FS2710 simply does not have enough dynamic range, or low
enough dark current, to do dark slides. At least in my experience.

I will agree on that. It seems the best actual from the FS2710 is about 3.2
(roughly) DMax.

On
occasion, I intentionally overepxose slides that I intend to scan. It
works, a kind of, and is not that objectionable with today's oversaturated
films.

Pavel

Another option is to manually alter the exposure in the scanner settings,
then scan once to get shadow details. That causes the highlights to blow out,
which means doing another scan to get those. Then careful work in LivePicture
or PhotoShop can be used to combine the results. I have one example of that
at:

<http://www.allgstudio.com/gallery/corporate/Amtrack_LAoldyard.jpg>

However, once I tried SilverFast, I found I could get almost the same result
in one scan. I should point out that I had my scanner modified by an
electrical engineer friend of mine, though I think anyone with an FS2710
should be able to get good results. This is a very underrated scanner.

Ciao!

Gordon Moat
A G Studio
<http://www.allgstudio.com/technology.html>

 

[Bart van der Wolf]

SNIP

The specified scanner resolution is only 2720 ppi, so any
misallignment may not be so obvious as with a 4000 ppi
scanner.

Correct, it's a hardware repositioning accuracy issue. There may also
be an additional CCD blooming issue with the longer (over)exposure.

Bart