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Still confused about RAW & TIF



 
 
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  #21  
Old December 4th 06, 10:31 PM posted to rec.photo.digital
Thomas T. Veldhouse
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Posts: 962
Default Still confused about RAW & TIF

Floyd L. Davidson wrote:
"Thomas T. Veldhouse" wrote:
Little Juice Coupe wrote:
The Raw file is the Raw data from the cameras sensor and in general doesn't
have any of the image camera processing done to it. Which means you can
change white balance after the fact without loosing image data, etc.


Changing these settings are just metadata values of the RAW file [like
changing the name ... it doesn't affect the actual image data] and these
values are applied during conversion to RGB (or whatever).


The Nikon D2x uses a 4 channel output sensor and does white
balance correction at the analog level *before* the image is
digitized.


Give me a reference to that please. I do NOT believe that to be the case ...
there is simply no "analog level" to apply white balance too.

A 16 bit TIFF formatted file is easily able to contain all of
the data available in a 12 bit NEF file.


I indicated that they would be similarily sized files for the same bit-depth.
They would.

--
Thomas T. Veldhouse
Key Fingerprint: D281 77A5 63EE 82C5 5E68 00E4 7868 0ADC 4EFB 39F0


  #22  
Old December 4th 06, 10:36 PM posted to rec.photo.digital
Thomas T. Veldhouse
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Posts: 962
Default Still confused about RAW & TIF

Scott W wrote:
The raw filewill me much smaller since its format is much more
efficient. Take a 8 MP camera, the in the raw file there are 8,000,000
pixels each of which needs only 12 bits of data, therefore and
uncompressed raw file should come in right about 12 MB, with lossless
compression this shrinks to between 8 to 10MB. A tiff file from this
same camera will have three colors / pixel (note the raw file only has
one per pixel) and it will use 16 bits / color or 48 bits per pixel
compared to 12. When I convert to 48 bit tiff files the resulting file
is right around 48 MB in size, which is why I don't like to keep the
tiff fills around.


Only if compressed will you see a difference [minus the metadata]. Data is
data. RAW is only smaller than TIFF for two reasons; the first is that
there is often compression applied (TIFF can also be compressed, but often is
not), and second is that typically RAW is 12-bit and TIFF is 16-bit. There is
no reason you can't have a 12-bit RAW (in fact, that is basically what you get
when you convert to DNG format as DNG format is based upon the TIFF format and
DNG is a true RAW file, preserving the linear data with or without lossless
compression).

--
Thomas T. Veldhouse
Key Fingerprint: D281 77A5 63EE 82C5 5E68 00E4 7868 0ADC 4EFB 39F0


  #23  
Old December 4th 06, 10:39 PM posted to rec.photo.digital
Scott W
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Posts: 2,131
Default Still confused about RAW & TIF


Thomas T. Veldhouse wrote:
Scott W wrote:
The raw filewill me much smaller since its format is much more
efficient. Take a 8 MP camera, the in the raw file there are 8,000,000
pixels each of which needs only 12 bits of data, therefore and
uncompressed raw file should come in right about 12 MB, with lossless
compression this shrinks to between 8 to 10MB. A tiff file from this
same camera will have three colors / pixel (note the raw file only has
one per pixel) and it will use 16 bits / color or 48 bits per pixel
compared to 12. When I convert to 48 bit tiff files the resulting file
is right around 48 MB in size, which is why I don't like to keep the
tiff fills around.


Only if compressed will you see a difference [minus the metadata]. Data is
data. RAW is only smaller than TIFF for two reasons; the first is that
there is often compression applied (TIFF can also be compressed, but often is
not), and second is that typically RAW is 12-bit and TIFF is 16-bit. There is
no reason you can't have a 12-bit RAW (in fact, that is basically what you get
when you convert to DNG format as DNG format is based upon the TIFF format and
DNG is a true RAW file, preserving the linear data with or without lossless
compression).

You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.

Scott

  #24  
Old December 4th 06, 10:46 PM posted to rec.photo.digital
Thomas T. Veldhouse
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Posts: 962
Default Still confused about RAW & TIF

Scott W wrote:
You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.


True ... but there are Red, Green and Blue pixels, each getting 12-bits of
linear data, which makes up one pixel [three colors] in TIFF. In fact, for
some reason, I believe Bayer sensors have two green pixels for every RGB pixel
in TIFF.

--
Thomas T. Veldhouse
Key Fingerprint: D281 77A5 63EE 82C5 5E68 00E4 7868 0ADC 4EFB 39F0


  #25  
Old December 4th 06, 10:47 PM posted to rec.photo.digital
Thomas T. Veldhouse
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Posts: 962
Default Still confused about RAW & TIF

Thomas T. Veldhouse wrote:
Scott W wrote:
You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.


True ... but there are Red, Green and Blue pixels, each getting 12-bits of
linear data, which makes up one pixel [three colors] in TIFF. In fact, for
some reason, I believe Bayer sensors have two green pixels for every RGB pixel
in TIFF.


I take that back ... I am sure green is probably just weighted doubly during
conversion.

--
Thomas T. Veldhouse
Key Fingerprint: D281 77A5 63EE 82C5 5E68 00E4 7868 0ADC 4EFB 39F0


  #26  
Old December 4th 06, 10:52 PM posted to rec.photo.digital
acl
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Posts: 1,389
Default Still confused about RAW & TIF


Thomas T. Veldhouse wrote:
Thomas T. Veldhouse wrote:
Scott W wrote:
You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.


True ... but there are Red, Green and Blue pixels, each getting 12-bits of
linear data, which makes up one pixel [three colors] in TIFF. In fact, for
some reason, I believe Bayer sensors have two green pixels for every RGB pixel
in TIFF.


I take that back ... I am sure green is probably just weighted doubly during
conversion.


No, there are twice as many green as red or blue on the filter array.
It looks like
RGRGRGRGRGR
GBGBGBGBGBG
usually.

  #27  
Old December 4th 06, 10:58 PM posted to rec.photo.digital
rafe b
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Posts: 169
Default Still confused about RAW & TIF


"Thomas T. Veldhouse" wrote in message
news
Your above statement isn't correct. There is no way to know which has
more
information based upon file format. Equal sized uncompressed TIFF and RAW
with the same bit depth should be similarily sized.



That's dead wrong. In general the TIF file will be
about three times larger.


rafe b
www.terrapinphoto.com


  #28  
Old December 4th 06, 11:00 PM posted to rec.photo.digital
acl
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Posts: 1,389
Default Still confused about RAW & TIF


Thomas T. Veldhouse wrote:
Scott W wrote:
You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.


True ... but there are Red, Green and Blue pixels, each getting 12-bits of
linear data, which makes up one pixel [three colors] in TIFF. In fact, for
some reason, I believe Bayer sensors have two green pixels for every RGB pixel
in TIFF.


It's interpolated. In reality, if you have an 8000000 pixel camera,
each of these pixels receives either red, green or blue light. Thus, 12
bits per pixel in the raw data (each pixel records one colour). What
conversion from raw to eg tiff does is, basically, to take these and
interpolate so that each pixel is assigned a colour (not just a value
for r, g or b, but one for each). Thus, an 8mp raw uncompressed file
will be around 12MB, while an 8mp 8-bit (per channel, as 8-bit usually
signifies) tiff will be around 24MB (and 48MB if 16-bit).

If you don't believe me, google for IRIS, download it and look at a raw
file. Or google for demosaicing, I'm sure you'll get lots of hits.

Whether the format is linear or not is completely irrelevant to the
size of the files; it only has to do with their interpretation.

  #29  
Old December 4th 06, 11:04 PM posted to rec.photo.digital
rafe b
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Posts: 169
Default Still confused about RAW & TIF


"Thomas T. Veldhouse" wrote in message
.. .
Scott W wrote:
You are missing the big reason, 1 color / pixel for raw vs. 3 colors /
pixel for tiff.


True ... but there are Red, Green and Blue pixels, each getting 12-bits of
linear data, which makes up one pixel [three colors] in TIFF. In fact,
for
some reason, I believe Bayer sensors have two green pixels for every RGB
pixel
in TIFF.



But the fact is, in a so-called "6 megapixel" camera,
there are only 6 million sensors, distributed between
Red, Green and Blue. Green gets 2X as many pixels
as either Red or Blue, so in this example, 1.5 million
(each) of Red and Blue, and 3 million green.

In the equivalent TIF file there will be 18 million
values (6 million per color.)

Each reading (in the sensor) may be up to 12 bits,
but the lossless compression will reduce the overall
storage by 20-30%. Thenet result for a RAW file
is roughly one byte per pixel.

It's the RAW converter program that does the
interpolation from RAW to TIF, and that's where
the file size gets tripled.


rafe b
www.terrapinphoto.com


  #30  
Old December 4th 06, 11:22 PM posted to rec.photo.digital
Scott W
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Posts: 2,131
Default Still confused about RAW & TIF


rafe b wrote:
"Thomas T. Veldhouse" wrote in message
news
Your above statement isn't correct. There is no way to know which has
more
information based upon file format. Equal sized uncompressed TIFF and RAW
with the same bit depth should be similarily sized.



That's dead wrong. In general the TIF file will be
about three times larger.

Well if the tiff file is 16 bits/color it would be about 6 times
larger. The loss using an 8 bit tiff instead of a 16 bit one is small
but sometimes it does matter.

Scott

 




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