Archived posting to the Leica Users Group, 2010/04/28
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Bob Adler
http://www.rgaphoto.com
On Apr 28, 2010, at 8:29 PM, Tim Gray <tgray at 125px.com> wrote:
On Apr 28, 2010 at 07:05 PM -0700, Bob Adler wrote:
You can't edit with Camera Raw if it isn't a Raw file. You can certainly do
non-destructive edits on a .tif file (using LR or CS# layers), but my
understanding is that a .tif file is created by software interpreting the
sensor output (either scan or camera).
Go to the File>Open menu in Photoshop. Highlight your tif or jpeg. Change
the Format popup menu to 'camera raw'. Play with your file in Camera Raw to
your heart's content.
A Raw file is simply the sensor output without any software interpretation
(other than the obvious firmware interpreting the RGB value to give photon
strengths received).
That is true. The difference between camera chips and scanner chips is that
cameras use Bayer filters over the sensor. I'm sure we all have some
concept of what that is, so I won't get into it. So the raw data of the
sensor is a mosaic of RGB values. But it's not full color yet. Cooking the
raw file interprets the raw data and demosaics it, giving us our RGB output
file. It's during this process that you can set the white balance, since
you demosaic the data differently depending on the chosen balance.
Most scanners do not use Bayer filters. They read R, G, and B values for
every single pixel. There is no interpreting of the data to get an image
like there is for a raw file. So while you can store it in a DNG, the data
isn't raw. It's the same as would be stored in a tiff - RGB for every
pixel. You can call it raw if you want, but it's already 'cooked'. You can
store it how you want, but you gain no advantage.
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