DIP9 Default save settings

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Guest

When I edit a photo in DIP9 and hit save DIP9 seems to reduce the size of the
photo on disk notably but from what I can tell the resolution, size etc. of
the picture is no different. Can anybody shed any light on what is
happening? Surely I am loosing somthing?

Thanks!
 
This is true with DIP9, as I found out just like you have, and indeed there
is no lost in resolution (provided you selected highest quality when saving)
..
I contacted DIP9 support about this issue and the long and short of it is
that DIP9 uses a much more efficient algorithm to save .jpg files than your
camera, resulting in a much smaller file size, but no change in resolution.

In fact if you open this smaller file made by DIP9 and edit it with another
photo editor (Photoshop or the newer DIP10) and you save the file, it will
be just about the same file size as your original file size from your
camera.

In the newer DIP10 this size reduction will not take place as in DIP9.
 
The size of the JPG depends on the resolution and on the amount of
compression.
The latter basically means (for JPG format) that the maximum amount of
colours is reduced to a visibly still acceptable one, but less. This way less
bits per pixel are needed than with full colour (8x8x8).

PIP9 is not more efficient. The efficiency is detemined by the JPG standard.
It just compresses more. One should be able to tell PIP9 what amount of
compression to use or have it stuck with the orginals file compression.
Common is 90% and 80% colour reduction leading to file sizes of only 10%.

The way this works is best explained to search for information on sRGB or
Adobe colorspaces.

Considering this and the fact that it is not clear how PIP9 does a resize
(with or without resampling) this looks like a good program but onder hood it
is as good as basic freeware.
 
You are asking the same question I asked myself when using DIP9 for the
first time. I wish I still had it on my computer to try it again but it is,
in digital time, obsolete.

But here is my answer.

1. I have an original JPG format file of ,say, 1000 x 1000 pixels (and we
will call this resolution) and the file size is, say, 1 MB.
2. I edit this file with DIP9, save it and now the file size is 0.5 MB. How
can this be? Did DIP9 discard pixels? No, this new file is still 1000 x 1000
pixels. So, as you mentionned, what is the other option? More compression
and lower quality file. But no, I selected highest quality. So now I am
worried about the quality of this new file. Maybe DIP9 highest quality is
not good. I will get a poor print.
3. So I do an experiment. I print an original file at 8 x 10 and I make a
copy of this file and then open the copy with DIP9 and add a single letter
on top of this picture so I know I edited it, then I save it and print it. I
can't see any difference. I ask my wife to look at the two prints and she
can't see any difference. Well maybe on this picture. But what about
selecting a picture with a lot of straight edges. Lower compression quality
will show jagged lines on straight edges, typical of low quality jpg
compression. No. This is not happening. So what is the answer?
4. I e-mail DIP9 support and tell them in details what is happening. I get
an answer that this is impossible. I answer back that I am ready to e-mail
my original picture and the DIP9 edited picture with the single letter added
on it and they can do the experiment. They accept. I get back the answer. I
am correct, the original file size dropped from 1 MB to 0.5 MB when they did
the same editing I did. But I should not worry about this because the
resolution (pixel size) was not changed and the JPG compression quality is
the same on the edited file as on my original file.
5. OK. So pixel size is the same (I can see this from the file properties)
and compression quality is the same (there is no way for me to actually
confirm this as I can confirm pixel size), how can the edited file size
decreases by 50%? So I e-mail to DIP9 support again and ask how can this
happen. Waited two or three days and the answer came "we have a more
efficient algorithm to save jpg files" than your camera does and with a
follow up phone call about such.
6. Well, maybe. What I can tell you is such file size change is not
happening with DIP10 or DIP2006 when you edit. If you have DIP9 and want
better for editing, Microsoft usually releases a new version in
August/September. I don't know if such will happen this year but John Inzer
will probably post an alert if a new version comes up.
7. I do not believe that information on sRGB vs Adobe RGB is the answer
here. These are color spaces and nothing to do with jpg compression.
Obviously interesting to learn about such thing as color space but even if
you have a camera capable of saving a jpg in Adobe RGB color space, if you
don't have a printer capable of accepting such the results will be terrible.

In the end, we all use a variety of photo editing softwares because they
each have some particularly good features.
For example, for cropping to a particular print size I love:
www.faststone.org

For my wife's computer, I love:
www.picasa.com
She does not have to search for anything. Just start Picasa, go to Time line
display and she is in business.

I think that as you work with photos you will come to the same conclusions.
Each photo editing software has good and not so good features.
 
Can you run a check on the two version of your photo using
Irfan view, Information, Numer of unique colors.

Seems like the camera JPG more colors (1 MB) then
after saving with PIP9 (500 kB). As the amount of pixels stays the same
the amount of colors must be less (otherwise no drop in filesize).

I'll bet you'll find a difference in there. Just did it with a file and found
quality = size= 800 kB colors= 138571 (camera's original, JPG fine
90%)
quality = 50% size= 150 kB colors= 130025 (no visible impact)
quality = 10% size= 70 kB colors= 44472 (visible loss in quality)

The less colors we have in the JPG the less bits we need to store.

Seems like this goes with a tripple power. Hence a sincere drop in file size
for only a small loss in colors amount.

Use of what color space is not important. It was just an example that
the amount of colors is a variable for file size as is amount op pixels.
 
I agree with you without having to do the experiment.
JPG compression is done on colors and when you select a lower quality it is
very difficult to see as you wrote "a visible impact" unless you print. Even
if you print, how good is your printer so you can really see a difference.
My own approach is to save at the highest quality and not worry about file
size because storage is now so cheap and there is no telling what we will be
able to do with photo files in the future.
However, as I wrote in my previous message, I was not happy about DIP9 doing
this file size reduction. DIP10 does not do this and DIP2006 (real name is
Digital Image Suite 2006) does not do this.
 
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