[Ham-Computers] RE: Editing A Photo (long)

Sun, 9 Jun 2002 17:31:27 -0700

Oooooooh, tough one.  To make an informed decision requires some knowledge
of the different picture formats and some definitions.

Compression - "Squeezing" the image in a way to reduce the filesize.
Although the filesize is smaller, the picture will be restored to it's
original size before a program manipulates it or shows you the image.
Similar to the way .ZIP files work for data files.  Compression can be
"lossy" or "non-lossy".

Non-lossy - a format where the image is saved without losing any picture
information... the picture in the file is, for all intents and purposes, an
exact copy of the original.

Lossy - a format where the image is "compressed" to create smaller
filesizes, but at the cost of some picture information.  Depending on how
much info the picture started with (resolution and colors) how much
compression is used, the resulting file either look great or look extremely
pixelated.  Proper use of compression is extremely important when using
lossy file formats.  Opening a image and subsequently re-saving it will
create generation loss much like analog audio copying.  The more you open
and re-save, the worse the picture gets.

Scaling - the ability to re-size an image without distorting the picture too
much.  Some formats "scale" well - you can resize the picture and not notice
too much difference in the picture.  Other formats don't scale well and will
create scaling artifacts such as pixelation.  The quality of scaling also
depends on the program used to re-size the image (can't go wrong with
Photoshop!)

.BMP - BitMaP - A "bitmap" of the image.  The image is stored "full size" in
a "raster" format.  Basically, this means that every bit is saved in the
file along with the color information. For example, a picture that's 800x600
in size in 24-bit color will result in a file that's 1,440,000 bytes in size
(800x600x24).  BMP's generally don't "scale" very well.

.GIF - Graphics Interchange Format - Another "bitmap" format.  Created
originally by CompuServe, it uses non-lossy compression to achieve smaller
filesizes (not much).  The original format was 8-bit and newer .GIF's
formats support 24-bit color and "animation".  These are the animiated
pictures you often see when surfing the web.  Doesn't scale well.

.JPG, .JPEG, .JFIF, others - Joint Pictures Expert Group - a format created
by a group of photo experts.  It uses lossy compression to achieve greatly
reduced filesizes.  Most common picture format found on the web.  Scales
well.  .JPG files can also be saved in a "progressive" format.  This format
is "interlaced" and resulting image comes across much like horizontal window
blinds being opened.  Popular with websites since the full size of the
picture is sent almost immediately, but only "slivers" show up at a time;
however, not all programs support progressive .JPG files and will choke if
you try to open them.  And, always remember that .JPG is always a lossy
format - even choosing minimum compression (some programs erronously call it
"no compression") results in some loss.

.TIF - Tagged Image Format - The "preferred" format for archiving and
professional printing.  The original format is non-compressed, so filesizes
are huge.  Some programs allow non-lossy .TIF compression with
LZW-compression being the most common.  LZW is not very efficient (only 10%
to 20% smaller file), but it does help.  Be aware that not all programs
support compressed .TIF files - for example, many commercial printing
presses will not accept compressed .TIF files.  Also, many programs also
don't recognized compressed .TIF files.  It scales well and is the absolute
best format to save pictures in if you have the storage space available.

.PSD - PhotoShop Document - Photoshop's native format.  It uses no
compression and can compare with the .TIF format.  Only difference is that
it's optimized for Photoshop and .PSD files will load faster than .TIF files
in Photoshop.

There are also many other formats, but these are now the most common.

Now, to answer your question, .BMP or .JPG - well, either or neither!  If
you're doing some serious photo editing and will be printing it or sending
it to a commercial photo finisher for re-printing, then .PSD or .TIF would
be preferred.  In your case, since you'll be restoring some pictures, I
would suggest .PSD while you actually work on the pictures.  If you're going
to send them to a photo lab for re-prints, save a copy in non-compressed
.TIF format and give it to the lab.  For e-mail, reduce the picture to
800x600 in size and use .JPG with moderate compression.  Be aware that these
800x600 pictures may not print very well.  And, to reduce the size of the
final archival image, you can use .JPG with light compression.  You won't
lose much detail, but the file size will typically be chopped by at least
1/2 (I would still prefer to save it in .PSD or .TIF)

When scanning the pictures, make sure you scan them at 300dpi or higher.
You will also want to scan the Polaroid in full size (in inches) - don't
reduce it when scanning as many scanning programs default to.  It will
result in a larger file to save, but it will produce better quality images
as the program will have a better representation of the original picture.
If you scan at a lower dpi, then Photoshop will need to "interpolate" (aka,
add information) when it doesn't have enough info about the picture.

And, finally, what version of Photoshop are you using?  The full package is
quite "heavy".  There are a LOT of tools and many are not user friendly.
Adobe recently released a new version called "Photoshop Elements".  They
took the most commonly used Photoshop tools and modified the user interface
to make it easier to use without all the bells and whistles used by
professional editors.  For example, Photoshop doesn't have a "one-touch"
red-eye reduction tool; you needed to use color "pick-up" tool to get the
right color, then the airbrush tool to replace the red with the new color.
Photoshop Elements has a tool specifically for red-eye.  Also has tools for
easy scratch and dust removal, and more.  "Photoshop Elements" be the
version you should get.  It runs for about $100... *MUCH* less than
Photoshop at $700 and more useful for the average home user.

Good luck and let me know if you have any other questions!

  - Aaron Hsu, NN6O
    (athsu)@unistudios.com
    (nn6o)@arrl.net

-----Original Message-----
From: Duane Fischer, W8DBF [mailto:[email protected]]
Sent: Sunday, June 09, 2002 4:06 PM
To: [email protected]
Subject: [Ham-Computers] Editing A Photo

When editing a photo that has been scanned, must it be saved as a .bmp or
may it
be saved as a .jpg?	

The software I have to edit a photo with is Adobe Photo Shop Deluxe.	

The goal is to recover color and detail from color Polaroid shots taken in
the
late sixties.	

If this software is inadequate to accomplish this task, please suggest
software
that will permit a skilled user to make these editing changes. 	

thank you.	

Duane W8DBF	
[email protected]	

P.S. Yes, I am totally blind. No, I am not doing the editing! (patented
Fischer
smirk). I want restoration here, not reconsruction!  

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