Re: Why So Many "RAW" Formats?

TheRealSteve <steve@xxxxxxxxxxx> wrote:
On Tue, 10 Feb 2009 05:05:53 -0900, floyd@xxxxxxxxxx (Floyd L.
Davidson) wrote:

TheRealSteve <steve@xxxxxxxxxxx> wrote:
On Mon, 09 Feb 2009 20:34:10 -0900, floyd@xxxxxxxxxx (Floyd L.
Davidson) wrote:

C J Campbell <christophercampbellremovethis@xxxxxxxxxxx> wrote:
On 2009-02-09 17:30:14 -0800, floyd@xxxxxxxxxx (Floyd L. Davidson) said:

ray <ray@xxxxxxxxxx> wrote:
On Mon, 09 Feb 2009 07:30:15 -0800, Matt Ion wrote:

Bob Williams wrote:
Seems like every Camera manufacturer has one or more of his own
versions of a RAW image format. And many (most?) versions are
proprietary.
RAW, by its very definition, is not an "image
format" but simply the raw
data straight off the camera sensor. Thus any change in the sensor -
including going to a higher resolution - results in a different RAW
output.
raw data files, as any other files, have a format.
But it is not an "image format".

Sure it is. It stores an image. There is no intrinsic difference
between a RAW file and any other image format -- it is all 1s and 0s
storing an image. In fact, Nikon calls the NEF files an "image format"
and compares them to JPG and TIFF.

Nikon Electronic Format is *not* a raw image format.
Nikon often refers to "NEF raw image data", but near as
I can tell they never call NEF a "raw image format".
That is true because, if for no other reason, NEF is
used for many very different types of raw data.

And there *is* an intrinsic difference between a data
file that contains raw sensor data and an image file
which contains the data for one specific image. The raw
data file *must* be interpolated to produce an image,
and there is no one single way to do that, which means a
raw data file's data can be interpolated many different
ways. It is not data for one image, but rather data
from which an infinite number of very different images
can be made.

By your definition, there is no such thing as an image file. Even
jpegs will look very different on each monitor they're displayed on or

That has nothing to do with it. A JPEG format image
defines just one image. It might well display
differently, and it can also be edited... but it is
still just one image. There is no single image defined
by the raw data from a DSLR sensor. It is a set of data
that defines many images, not just one. And there are
many ways to get an image from the data too.

It defines one image just as much as a jpeg file defines one image. Of
course, neither one defines just one image. For instance, there is no
definition in a jpeg file for what values at each pixel equate to what
luminosity. So a single jpeg file defines an infinite number of
images

That is not true.

on each printer they're printed on. That's because processing,
including interpolation among other processing, *must* be done to a
jpeg in order to produce an image you can see on any specific medium

There is no interpolation necessary with a JPEG image.
And the processing to convert a JPEG image to some other
format is well defined to produce a *single specific*
image. Granted that it might no always actually produce
exactly the same image, but the difference is an *error*!

No it's not an error when you get differences, because there is no
single defined way to do a conversion of a jpeg file to an image.

There are multiple ways, but each is *supposed* to
regenerate the original image. The difference between
the original and what is regenerated is "error". For
example, that is one reason that JPEG is called a
"lossy" format.

and there is no single way to do that, which means a jpeg file's data
can be interpolated many different ways.

False. JPEG data is not interpolated.

It is if you don't print or display it at it's native resolution. But
it's not just interpolated. It's also converted to light at a certain
amplitude and wavelengh at each pixel. And there's no single way
defined to do that.

If you resize it, the data is interpolated. But of
course that is also making an entirely *different* image
that the JPEG data described. (Differences in pixel
values are the error discussed above.)

Each pixel in a JPEG is encoded into a single set of RGB
color values. That data is not used for multiple pixels
except within blocks of identical pixels.

And how do those RGB color values get display as a image? Undefined.
If you turn up or down the brightness of your monitor, you're looking
at a different image from the same jpeg.

See "error".

Raw sensor data is not a one to one relationship with
image pixels. The value eventually calculated for any
single pixel location is *interpolated* from multiple
sensor locations (and multiple pixels, each of which
might be different, use data from any single sensor
location).

Raw sensor data is a recording of an image.

No, it is recording sensor data.

There's many different
ways to interpolate it to form a different image.

At which point yes you do have an image. And those are
save to image formats such as TIFF, PPM, JPEG, etc.

But it's still an
image. It just wouldn't look like the final result you see printed or
display. Just like a film negative is an image that doesn't look like
the final result printed.

But a film negative is just one image. The same as JPEG
is just one image.

But raw sensor data is not just one image. It is data
from which many different images could be generated.

In fact, a raw file is even more an image file format than a jpeg file
because it is an actual photograph, i.e., a recording of photons that
struck a specific area over a specific time. Once you start messing
with that via whatever processing you choose, you're getting further
and further away from a photograph although it's still an image.

That is silliness.

Silly, but true.

If you believe that then there is no point in discussing
technical details of digital imaging with you.

Also by your definition, a film negative is not an image because it
must be printed to create an image and there's an infinite number of
ways any single negative can be printed. But I contend that a film
negative *is* an image format, just like a raw file.

Correct, a film negative is an image.

By admitting that a film negative is an image, you're being internally
inconsistent with your ascerting that a raw file is not an image file.

Not even close.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.