Al Dykes wrote:
> If I shoot RAW and then in Photoshop, export it to a jpeg
> with the highest ssetting, how much information is lost?
>
> If I then bring that jpeg into PS and save it as a PSD, how much have
> I lost?
>
There is no general quantitative answer. It depends on the
amount of detail in the image, including subtle variations
in color.
Ockham's Razor wrote:
> In article <a7j423lutgag52d016inh7b3pirqb4dcke@4ax.com>,
> John Bean <waterfoot@gmail.com> wrote:
>
>> On 15 Apr 2007 11:57:47 -0400, adykes@panix.com (Al Dykes)
>> wrote:
>>
>>> If I shoot RAW and then in Photoshop, export it to a jpeg
>>> with the highest ssetting, how much information is lost?
>> Impossible to quantify. Depends on the contents of the
>> image.
>>
>>> If I then bring that jpeg into PS and save it as a PSD, how much have
>>> I lost?
>> None.
>
> But you do not get back anything you lost with the original JPEG
> compression.
You can do an amazing amount of adjustments to the RAW image itself in
recent versions of ACR and the release version of Lightroom. Using one
of those, you could quickly go back to the source image and start
afresh, or use the full image already adjusted to generate a new TIFF or
PSD.
In article <4mm423pmraljjjislh6p7gob25d3gm3tvl@4ax.com>,
Ed Ruf (REPLY to E-MAIL IN SIG!) <egruf_usenet2@cox.net> wrote:
>On 15 Apr 2007 12:57:08 -0400, in rec.photo.digital adykes@panix.com (Al
>Dykes) wrote:
>
>
>>What is "ACR". The initials escape me. "A" probably stands for Adobe
>>but I need to buy another clue.
>
>Adobe Camera Raw. The raw converter in PS. PSE and other Adobe products.
That's it. I use RAW in PS all the time. The initials drew a blank this morning..
--
a d y k e s @ p a n i x . c o m
Don't blame me. I voted for Gore. A Proud signature since 2001
Today, Al Dykes made these interesting comments ...
>
> If I shoot RAW and then in Photoshop, export it to a jpeg
> with the highest ssetting, how much information is lost?
>
> If I then bring that jpeg into PS and save it as a PSD, how
> much have I lost?
>
>
if a tree falls in a forest and nobody is there to see/hear it,
does it make any noise?
>>
> if a tree falls in a forest and nobody is there to see/hear it,
> does it make any noise?
>
This filosofical question has been answered by scientist. As science stands
at this moment the anwser is YES.
And allthough observers ALWAYS influence an experient, taking away the
observers does not take away the sound, but as with Schrodinger's cat one
can not say that the tree has fallen or not fallen until an observation is
made. So the tree might still be standing.
For the question of how much information is lost, one first has to anwser
how much information was there in the scene, how much information was there
in the 'raw format' and what of that information is lost. The amount of
information is at most equal to the amount of data, but often it is far
less, but it's very difficult to express how much information there is in a
picture.
Reducing a picture to only exactly 9 colors does reduce the data a lot in a
picture, and hardly any information is lost in the picture. (At least if the
consumers of the picture are humans). If the picture is used for coding
something then a lot of information is lost.
The coordinates (3) of a picture, the angles (3), the time, the
shutterspeet, focal length, focusdistance, aperature and format information
determine a picture completely. This is only a few bytes of information and
one only needs a time/travel machine to completely reconstruct the picture
from this information.
On Sun, 15 Apr 2007 20:41:39 +0200, ben brugman wrote:
>> if a tree falls in a forest and nobody is there to see/hear it,
>> does it make any noise?
>>
> This filosofical question has been answered by scientist. As science stands
> at this moment the anwser is YES.
> And allthough observers ALWAYS influence an experient, taking away the
> observers does not take away the sound, but as with Schrodinger's cat one
> can not say that the tree has fallen or not fallen until an observation is
> made. So the tree might still be standing.
>
> http://en.wikipedia.org/wiki/Schr%C3%B6dinger's_cat
>
> For the question of how much information is lost, one first has to anwser
> how much information was there in the scene, how much information . . .
According to the NYTimes, it loses all the information that's not
fit to print.
Al Dykes <adykes@panix.com> wrote:
>
> I know that you can't replace lost info and that saving a jpeg on
> itself is a Bad Idea.
Al, if you save with minimum compression, for instance Photoshop Q12,
very little information is lost. But the files are not very small.
The most efficient space/quality tradeoff is relatively high quality,
say around 94-96 on the IJG scale, with 4:2:2 chroma subsampling.
Most good digicams (Canon, Fuji) produce something like this nowadays.
You cannot write this combination with any version of Photoshop,
unless Adobe added 4:2:2 in CS3. You can do it with GIMP.
How much information does jpeg lose? 
Linear Mode
