No, they are not smaller just because the IR channel is not included. I
have converted many raw files to dng without using Vuescan. The Adobe
convert to DNG software converts any raw file to dng and strips out any
metadata that is used by the proprietary raw camera format that will never
be used.
http://www.mosaicarchive.com/2013/05/01/the-raw-truth-about-dng/
The .DNG format, while retaining all the original image data, does dispose
of some of the metadata that accompanies raw files, but does not affect
image quality, such as camera settings and focus points. That means that a
.DNG file will be about 15% smaller than an identical raw file. However,
the image quality of the photographs themselves are identical. This helps
improve the one big drawback of shooting in raw – the larger file size of
these formats compared to .JPG or .TIFF.
Part of this data is contained in another file which accompanies raw files,
called a .XMP file. This folder contains information about editing
performed on the photograph. Occasionally, they can become dislodged from
their partner files, leading to trouble. This processing information is
stored within .DNG files, eliminating the need for a separate .XMP.
Another advantage of importing as .DNG files is that they contain a
checksum safety feature that easily and quickly identifies a corrupted
file. This is called embedded file verification.
Tina
On Tue, Jan 14, 2014 at 6:53 PM, Moose <olymoose@xxxxxxxxx> wrote:
> On 1/14/2014 2:27 PM, Tina Manley wrote:
> > I'm scanning at 4000 dpi, the highest actual dpi of the LS5000. My scans
> > end up about 150MB. I reprocess them through Vuescan for the filtering,
> > especially Digital ICE or Vuescan's infrared cleaning, saved as DNG, and
> > the size is reduced to about 110MB.
>
> On 1/14/2014 2:53 PM, Jon Mitchell wrote:
> > ... My experiments seem to show that when you ask VueScan to
> > save the file as RAW, it saves this as a TIF anyway - so what is the
> > difference in just saving it as TIF (assuming I leave all the Colour &
> > Filter settings alone) ? Is the "RAW" TIF, as the name implies, just the
> > RAW data from the scanner - but the non-RAW TIF has had some adjustments
> > done ?
>
> OK, folks, easy there, it all makes sense.
>
> When you ask VS to save as RAW, it sames not three, but four channels, RGB
> plus IR.The data is saved as linear scanner
> output, without applying gamma correction or any other adjustments.
>
> The files are ordinary TIFFs in format, but look very dark until gamma
> corrected and they contain that fourth channel.
>
> That, Tina is why your DNG output files from reprocessing VS RAW files for
> IR and other adjustments are smaller, they
> become only three channel, not from some inherent efficiency of DNG.
>
> My 4000 dpi scan RAW TIFFs are mostly in the 160 MB range, and the TIFF
> finished scans about 120 MB.
>
> Unless I'm just scanning a couple of frames, I always scan to RAW. That
> requires no real attention, but the scanning is
> very time consuming. I can just set it going and do other things. Once I
> have the RAW files, I 'scan' them in VS,
> setting exposure, white and black points, etc. and applying dust and
> scratch removal.
>
> If one doesn't come out quite right, 'scanning' it again only takes
> moments, not minutes, as with a physical rescan.
> Depending on one's available storage and OCD rating, the RAW files may be
> deleted after processing. I tend to keep them
> until I have finished all processing of the images in PS.
>
> Scanning For Moose
>
> --
> What if the Hokey Pokey *IS* what it's all about?
> --
> _________________________________________________________________
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>
>
>
--
Tina Manley
http:// <http://tina-manley.artistwebsites.com/>www.tinamanley.com
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