kim@amdahl.UUCP (08/18/87)
[ 'Yo, 'bro, 'yo line is fried! ] <---(forgot who inspired this, but thanks!)
I happened on this on a local BBS over the weekend, and thought that a
few people out there might find it useful. Perhaps others would like
to contribute their own favorite hints and tips?
/kim
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How to digitize a picture... Hints and tips by Oran Sands
ojsands- Plink
The DigiView hardware and software make up a great product, so good in fact
no imitators have sprung up to challenge them. Perhaps the only Amiga product
that can make that claim. Many examples of the system exists on Plink and
local bbs's some good, some great and some not so good.
What makes for a better picture? What determines quality of the picture?
Well I'll let you in on what I've found out through trial and error and pure
dumb luck.
Start with the best equipment.
The software and hardware are fixed givens so make sure the equipment you add
is as good as you can afford (or borrow). The camera must have the following
attributes:
Interlace - 2:1 not random!
Internal Sync (unless you can feed horizontal and vertical drives to it ...
and if you don't know what those are, then stick with internal sync)
High Resolution - Perhaps the most important spec to check. The higher the
resolution the better the picture. The Amiga's horizontal resolution maxes
out at 704 pixels for the full screen. Using a camera with less than this is
underachieving. The better b&w cameras can easily approach 600 - 800 lines
of HORIZONTAL resolution (dont get confused with the scanrate of 525 lines
vertically). The extra investment will pay off. Your typical home color camera
has only 200 -250 lines of horizontal resolution. Try to find a good monochrome
camera if at all possible.
ALC - Auotmatic level control The human eye can adjust to light levels with
differences of a billion to one. Your camera should have a ALC of 100,000:1
or so if you're not using extra lighting.
Sensitivity - This will usually be low enough if the camera was built in the
last 5 years. 10 lux (10 footcandles) is usually fine.
Signal to noise ratio - The lower the better. The noise in the signal becomes
more apparent as the light level drops (also in the dark sections of an otherwise
well-lit picture.
Good glass - The lower the f/stop of the lens (a number like f/1.9 , f/2.5,
f/4.5 ) the more light the lens will pass to the camera alleviating the need
for more or brighter lighting. A zoom lens is helpful in framing up the shot
as you like it.
Etc. Use good cable and connections. RG-59 coax is proper spec for video
(75 ohm impedance). Try not to use adaptors if possible. Lights can be of
various types, shadowless types are preferable for shooting many things.
Harsh lighting can edge and shadow however and may be what you need.
Choose good pictures.
Although you may think the picture subject is great the picture itself may
not be suitable for digitizing. I've found some good rules of thumb for
choosing them. Stay away from pictures with soft focus, smoky looking-thru-gauze
type pictures ala Penthouse (did I hear a groan?) When you digitize a picture
you effectively reduce its resolution from 3000 lines to 704 (at best). In
short, you're ruining the picture!
Starting with a picture with no actual detail doesn't bode well for the final
product. Choose pictures with clear, sharp detail. The subtle shading of colors
in some pics can make life difficult for the software. Other than HAMs you've
only got 32 colors at most to play with. The softare will allocate the colors
the best it can. Don't ask it to work to hard. A good example is a picture with
flesh tones. These colors are perhaps some of the worst to try to emulate.
A great deal of complex coloration exists in flesh. It can really drive the
program nuts. Pictures with a limited range of colors are good to use. If
your pictures a nude scene you'll need all the colors to portray your subject.
If the background's green or blue (both colors not found in flesh tones) the
software must allocate colors to them to the detriment of your nude (less
colors to go around).
Use small pictures!
I know this sounds strange but try and follow me. A printed picture has an
effective resolution of say.. 3000 lines per square inch. It follows that the
larger the picture the more detail information there is to try to reproduce.
So the smaller the image, the less to reproduce, the less to try to represent
in the digitized image. The software can do its best if its not being asked to
reproduce subtle detail. Almost all the pictures I've circulated started out
no bigger than 4x6 inches.
Use pictures!
Digitizing live pictures can be very difficult. The reason is that regardless
of how close you get to a real object an infinite amount of detail still exists
unlike with printed pictures. There will also be an almost infinite amount of
color shading which will drive the software crazy.
Summary:
Use clear, sharp pictures
Use small pictures
Limit the amount of colors
The software almost always creates a black and a white. use this to your
advantage. Trim or mask off sections of the picture that contain non-essential
colors or subject. Mask off with either white or black paper. This will allow
the software to use its black and white on the background and not have to
waste other colors to represent the unnecessary sections.
Light at a 45 degree angle or there abouts. Look for reflections on the picture
or the detail of the texture of the paper. The texture of the paper can cause
the software to see subtle differences in the colors and again wasting colors.
Use enough light. The program will optimize the the monochrome image (the second
pass of the scan , from top to bottom). Once again, don't make them program work
too hard. If you have enough light the software won't diddle with the brightness
and co ntrast any more than necessary. Even with a perfect image the program
will still do somke correction. Look at the histogram. It shows your signal
and the program's version of it. They should be as similar as possible.
Don't leave the image alone. Use the color controls to adjust the pic. I find
the image always needs a few increases on the brightness control. Check out
the dark areas where you know there are details but you can't see them. Get
familiar with the controls and what they do. Don't adjust several at a time.
You'll get a result and won't know what did what to the picture. The sharpness
control provides edging on details. This can be great or a nuisance. Make small
adjustments at first. Keep increasing a little at a time.
If the picture has mostly reds but they look weak compared to the other colors
increase just that color. Remember that many of the other colors may have a red
component and will go somewhat reddish however. Play around, have fun!
Use a image manipulation program such as Butcher, FPIC etc. to further adjust
the picture. Butcher's ability to merge colors can help free up colors for use
as other things. Such as text in a paint program such as DpPaintII. Using
Dpaint II can be a godsend. Use it to paint out those annoying staple holes
(Playboy readers disregard). If the background is a solid color check it out
carefully. You'll find that its probably a mixture of several similar colors.
Paint out the background so it really is solid. This will reduce the image file
size dramatically!! If you're up- or down-loading it helps. Many of my pictures
have had backgrounds removed, objects moved, entire sections repainted to remove
random pixelization. Be creative.
Don't allow youself to beat a dead horse. All my pictures are good because I've
thrown away twice as many that never quite made it to their potential. I've got
a Countach picture I've been working on for two months and its still not quite
right! Keep at it and have fun. Digitizing can produce some awesome images
and it keeps us off the streets. I'd rather be an artist like Sachs but I'll
settle for good images however they come about!
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--
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