Richard Ociepka wrote:
> Michael Wong wrote:
>
>> I have found there may be saved as RAW file by Nikon Scan & Vuescan. Is
>> there any benefit for these RAW files?
>>
First of all, I don't know that opening them in anything other than
VueScan is useful, as any other converter won't know what to do with
them. What they are is the direct output of the scanner, without any
processing by VueScan at all other than to put them in TIFF format for
storage. He calls them RAW, as they are in some ways like a camera RAW
file, being the unprocessed scanner output. But they are quite different
too, as they don't know anything about the color and exposure parameters
of the film that was scanned.
As far as I know, their major advantage is in workflow. When scanning a
roll of film, I scan to RAW first. That goes quite quickly, as VS
outputs to file as it scans, so there is no processing overhead time,
just one mechanical scan after another. Once I have the film all
scanned, I then "re-scan" from the RAW files, previewing as a batch,
making any adjustments needed to the previews, then scanning to ordinary
TIFF and/or JPEG as a batch. The scanning, processing, writing takes
time, but happily goes on in the background while I am doing other
things, on the computer or elsewhere.
I find this much more efficient than adjusting each preview from the
film directly, then waiting while VS does the full resolution scan, the
second scan for IR channel, the image and dust removal processing and
writing the files before I can go to the next frame.
The other advantage is that I can go back and "rescan" any frame or
frames with different settings if I want to change something. So if most
of the shots are under similar lighting and exposure, I may just set
parameters for the first frame, which sets the default settings for all
later frames, and do the batch scan without looking at each frame. If
one or another frame needs different settings for best results, I can
easily rescan from the file. I keep the RAW files until I'm completely
finished working with that roll, then discard them. If I'm not entirely
satisfied with any frames, and think changing the scan may help in the
future, I keep those RAW files.
> The ability to adjust the color temperature, saturation and contrast.
>
Weeeelll... Yes and no. No more ability to do so than in processing a
TIFF file in ACR, PS, etc. It's not like a RAW file from a camera. The
RAW converter can read from the camera file the color temperature the
camera used in taking the shot, tell you what it is and allow you to
adjust it directly to a known different temp.
With a film scan, the scanner has no way to know what the color temp of
the film was. So if you open a scan output file in ACR, for example, it
can let you adjust color temp relative to whatever is in the scan, but
not to a specific temp. You still need a reference of some sort.
Shooting a WhiBal or other black-white-gray reference will allow
adjustment pretty close to true color, but is only good for that.
Creating film icc profiles(s) allows you to ignore color temp. Scan
using a daylight profile and you get the color effect of other light.
Magic hour light, for example, will come out correctly warm. If you want
to correct light to look like daylight, make a profile for that light.
So you may shoot at sunset, under mixed artificial light, etc. and it
will look like daylight. With multiple profiles for different light with
the same film, you can very easily adjust white balance when scanning
from RAW files.
I don't know of any way to take film and accurately end up with a file
that you can simply slide the color temp slider on to hit a specific
temp. BUT - using icc profiles is actually more accurate. Camera sensors
are highly color linear, so simply adjusting a slider works well. Film
is not as color linear. The curves of the different color layers are not
exactly the same, so correct balance at mid tones may not, and usually
doesn't, guarantee correct balance in shadows or highlights. Building a
table of corrections at many points of color, an icc profile, is the
best way to color correct film.
Film and digital are very different technologies and simply require
different techniques for optimal color management.
I've posted this many times, but I think it's such a good illustration
of the value of color profiles for film. The first or top image in each
pair is the output frm VueScan using Neutral WB setting. Perfectly
decent scans that may be fairly easily adjusted in an editor. The second
image of each pair is exactly the same except that I used an icc profile
in the scan process. There has been absolutely no editor processing
other than to downdample for web display. As you can see, not only is
color corrected for WB, but the tonal curve is corrected.
This is the biggest time saver I know of in film scanning. Many, often
most, images are ready to print/display without further work. AND it
corrects the color better than anything else.
Moose
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