Post-Processing RAW vs Post-Processing TIFF

In message <BAPId.1169$>,

Oh, great; that all we need - outr cards being filled in the background.

8-bit TIFFs lose lots of highlight precision, and usually clip some of
the top of the dynamic range if they are made to be immediately
viewable. They are about 50% bigger than RAW, even if they use the LZW
compression (and have less and less-precise information).

For Bayer-sensor cameras, RAW is it; really. If they find better ways
of losslessly compressing RAW, great, but keep your TIFFs.
--

 

No.

The truth is that a so-called "six megapixel"
digicam has 1.5 million red sensors, 1.5 million
blue sensors, and 3 million green sensors.

It's not really "six megapixels" at all, but
it's now become standard practice to rate
and specify digicams this way.

[Foveon sensors are another story...]

The RAW file needs only to encode six million
digital values -- ie., the readings from these
six million sensors. Reconstruction into
RGB "pixels" is done within the RAW converter.

If the file were in TIF format, you'd need
18 million encoded values -- assuming you're
calling this a "six megapixel" image.

JPG is actually somewhat appropriate for
encoding digicam images, but is not nearly
as flexible as RAW. That is, with RAW,
you can reinterpret the six million sensor
readings at will. With JPG you must live
with the effects of the original interpretation.


rafe b.
http://www.terrapinphoto.com

 

Speaking of TIFF, why don't more cameras offer a TIFF option for

Tiff is about 300% larger than low ISO RAW for 8 bit files with my Canon dSLR
cameras. 16 bit tiffs would be about 600% larger.

 

No. Lossless compression just doesn't work
that well for most photographic images.

To the extent that there's a lot of sharp
detail in the image, the compression gets
worse (ie., less effective.)

Try it for yourself with WinZip. The
compression will vary quite a bit depending
on the nature of the image -- but typically
isn't much more than 15-20%.

JPG, on the other hand, is specifically
optimized for images and to take advantage
of the nature of human vision. So while it
is regarded as "lossy" (and it is) the
compression is terrific, and the actual
losses (in practice) can be made almost
negligible.


rafe b.
http://www.terrapinphoto.com

 

In message <>,

It *is* six megapixels, because light levels are recorded at six million
different 2D locations in the focal plane. A pixel does not equal R + G
+ B.
--

 

You will NEVER convince him, EVER!

You and I will sit here KNOWING that the Bayer system works really well
(better than anything else tried for digital, so far) and that it aproximates
the way the human eye works, but pixel peepers around wont be satisfied, EVER

If you gave them a million dollars, they would complain that it is GREEN &
WRINKLED.

 

In message <>,

You mean 300% larger or 300% as large? The former means 4x.
--

 

In message <>,

Gather them together, and we'll see if any of them can tell the
difference between two foveon images in Lab mode with the 'a' and 'b'
channels pixelized to two pixels, at normal viewing magnifications.
--

 

Actually on my camera (Olympus E-1), TIFF takes more space than RAW, and there
are other cameras where RAW saves even more due to being compressed (it isn't
compressed on the E1). However, TIFF is still subject to a lot of problems
that JPG has (in camera processing possibly losing details, clipping of dynamic
range from 12-ish bits to 8). All that is avoided by using TIFF instead of
JPG, is any artifacts caused by the JPG lossy compression.

 

Not at all, I've made the same arguments
myself several times, right down to the
explanation of the a and b channels in
Lab space. I fully appreciate the cleverness
of the Bayer sensor.

Even so, by the time I'm screwing with
the image in Photoshop, every pixel has
to have a Red, Green and Blue coordinate
(or some set of coordinates in whatever
type of color space I'm using at the time.)

A "pixel" in terms of my 10D's Bayer sensor
isn't the same thing as a "pixel" in
Photoshop. The point of my explanation
was to explain the relative sizes of TIFF
vs. JPG vs RAW files.

So save your uppercase shouting for
someone else, OK?


rafe b.
http://www.terrapinphoto.com

 

Perhaps the firmware for COMPRESSED tif files is prohibitive.

Compressed 8 bit-channel tiff's using LZW or ZIP are generally still larger
than RAW files. Plus you have the problem of opening them, many (maybe most)
software apps won't open LZW compressed tiff files.

I once tried compressing 16 bit-channel tiffs and they just don't compress well
with LZW or ZIP, some of the "compressed" files were actually larger than the
uncompressed ones and none had savings of even 10%. So for 16 bit files you're
still looking at about 6x the memory space compared to RAW.

RAW is the way to go, you can generate your tiff later, several different ways
if need be, and it's much smaller on the cameras I've used.

 

Tiff is about 300% larger than low ISO RAW for 8 bit files with my
Canon dSLR

MB per 8 bit/channel tiff (for those easily confused by %'s).

 

I am chagrined, however, the common claim of 6, or 8 megapixels for a Bayer
camera is generally accepted to mean 6 or 8 megapixels of luminance
information, nowhere on any of the packaging, manuals, or advertising do any
of the (Bayer) manufacurers claim that these cameras give 6 (or 8) million
RGB pixels..Except for Fuji, where the picture size and pixel count is
accomplished by magic dwarves living inside the camera. (but they still dont
claim anything about RGB pixels.

People who spend the bucks to buy a digital camera should have done enough
research to understand this BEFORE buying the camera, not after.

 

The "vast majority" of digicam users don't
know or care about such subtleties, just as
the vast majority of film camera users
don't know or care about how film or
cameras work.

Of much greater concern is that many
digicam users don't know anything at
all about the need to archive their
images, and will be in for a rude
surprise somewhere down the road.

Those who know the difference between
RAW, TIF and JPG are already ahead of
the game, at least they're asking the
right questions and know what a file is.


rafe b.
http://www.terrapinphoto.com

 

Had a look at your website.. nice stuff.

bably agree as to vast majority.. though my feelings on the subject are
probably less helpfull than yours. I tend to feel if they dont investigate
before spending money, then they dont qualify for free help.

I guess Im just a grumpy old curmedgeon.

 

Another problem is that there are so many variations on TIFF - even a
simply freeware app like IrfanView gives you the option of saving with
no compression, or using LZW, Packbits, JPEG, or ZIP compression...
PMView Pro also offers the option to apply horizontal differencing for
LZW compression, the choice of "White is zero" or "Black is zero"
photometrics, selectable encoding strip sizes (4k, 8k, 16, 32k and
single-strip), and the use of either Intel (LSB-first, PC-standard) or
Motorola (MSB-first, Mac-standard) byte ordering...

All of these have different uses and different benefits and drawbacks
depending on specifics of the image. You can'e expect the camera to
always choose the right one. And some software doesn't support some
forms of compression (I tried loading a TIFF into my Avery label
software and it complained that it didn't support LZW compression -
resaving the file without compression allowed it to load).

 

As long as we're wishing for features...

What I'd really like to see is a camera that can talk to a USB storage
device. The cameras already do FAT file systems and already do USB.
If you could have the camera transfer pictures from the flash card to
a USB hard disk then people wouldn't have to spend hundreds of dollars
on devices that do the same.

 

There's not much difference... there are portable
devices for well under $200, including 20G or 40G
hard drive, which will read a CF card and copy
it to the hard drive. Several examples here:

<http://www.mydigitaldiscount.com/>


rafe b.
http://www.terrapinphoto.com

 

Kibo informs me that (Dr. Joel M. Hoffman) stated that:

No. TIFF is far less space efficient than RAW. Try converting a RAW file
to 16 bit TIFF yourself, & you'll find that the TIFF file is much,
*much* larger than the original RAW file.

 

Don't understand marketing, do you? Grin.
They have to make PROFIT, you know.