scanner and Photoshop skills?

alex8735 wrote:
I would be glad to help. This can easily be done in Photoshop...the
quality of the result just depends on how good the scanner is. Just
mail ) me the scans and I will se what I can do.

A panaorama stitching tool is not necessary because it is only required
to get rid of lens distortion which does not occur in scans.

Excellent. My scanner should get here sometime next week; I'll send out
the scans shortly thereafter. You want the highest-density scans
possible, in original bitmap rather than JPEG form? Those are going to
be some big files; the scanner claims 1200 dpi, and some of the
pictures are full pages.

Johan Larson

High resolution is always good. The files do not necessarily have to be
bitmaps. Best quality jpeg files should not have any visible quality
drawbacks....but I don't mind big files either.

For the best possible scans you should scan in the nativ resolution of
the scanner (no interpolation to higher or lower resolutions). Any post
processing by the scanner or its software should be turned off (like
color correction) because Photoshop is better at it;-)

If you plan to publish on the web, you need not bother with the great
size of files your scanner's full resolution will produce. 72 dpi is
about right for the end product you will need although since you are
going to edit in Photoshop maybe scanning at 150dpi and then scalling
down in photoshop will produce better end results.

In any case, you will be scaning from magazines and if you consider
that the top limit for any such source will most probably never exceed
300dpi (which is the max that wil have been used at the printer's
originally) you should not really concern yourself with more than that.

I would only use higher resultion than this if I were scanning a high
quality original photo print or negative.

wrote:
alex8735 wrote:
I would be glad to help. This can easily be done in Photoshop...the
quality of the result just depends on how good the scanner is. Just
mail ) me the scans and I will se what I can do.

A panaorama stitching tool is not necessary because it is only required
to get rid of lens distortion which does not occur in scans.

Excellent. My scanner should get here sometime next week; I'll send out
the scans shortly thereafter. You want the highest-density scans
possible, in original bitmap rather than JPEG form? Those are going to
be some big files; the scanner claims 1200 dpi, and some of the
pictures are full pages.

Johan Larson

Re resolution: The most important point is that you're scanning a
printed picture, i.e. a screen. Depending on what you intend to do with
your scan, there is a big chance that the result will show an unsightly
moiré pattern.

If your scanner software has an "unscreen" feature (the name of this
function varies with the software), then check it and insert the screen
frequency (probably 150 lpi for a magazine). With some programs, this
function works as advertized, sometimes it does not. If it does and you
don't want to enlarge the picture, there's no point in scanning with
more than 300dpi (or even 72 dpi for monitor display).

If your scanner software doesn't have this function, then things can get
tricky. Usually you'll get the best the results scaning with very high
resolution and downscale afterwards. This approach requires a bit try
and error.

For post processing it is important to have a high resolution. This has
nothing to do with the final result which of course has to be smaller
to fit the screen in the end.

By the way, screens do not have a fixed resolution of 72dpi. Most
screens nowadays will be running near 100dpi but this depends on the
resolution set by the user. The term dpi only really applies to
printing.

I am quite sure that National Geographic prints at a higher resolution
than 300dpi (my printer at home does 600dpi).

I still recommend not to use any kind of scanner demoiré features
because scanner software usually is not as good as Photoshop. Each
post processing step takes information from the original leaving less
options for the guy putting it all together in the end.

alex8735 wrote:
I still recommend not to use any kind of scanner demoiré features
because scanner software usually is not as good as Photoshop. Each
post processing step takes information from the original leaving less
options for the guy putting it all together in the end.

I guess the ideal scenario would be a raw-output mode for the scanner,
and a free Photoshop plugin to read the output files.

Johan Larson

alex8735 schrieb:

For post processing it is important to have a high resolution.

Agreed. However, it's all a question of economics. There's definitely no
point in scanning an entire magazine page with 1200 dpi, which will
create something like 500 MB of data, then sending this data through a
modem line, then working on this huge file, only to have it downscaled
at the end to something which will be displayed as a 15cm x 10cm picture
on a web site. Scan as needed.

I am quite sure that National Geographic prints at a higher resolution
than 300dpi (my printer at home does 600dpi).

For line art, high resolution is crucial. I can even tell the difference
between 600dpi and 1200dpi.

However for half tones (aka pictures), there's no use to set the
resolution higher than twice the printed screen frequency. Note: This is
the *theoretic* maximum of data that can be reproduced when you
rasterize a picture! Practically, with most pictures, even a factor 1.4
will yield perfect results.

Now as most magazines print with a screen of around 150lpi, the raw
material is never higher than 300dpi. (Art reproduction is a different
story because they use finer screens. And FM rasters are yet a different
story altogether.)

I still recommend not to use any kind of scanner demoiré features
because scanner software usually is not as good as Photoshop.

Replace "usually" by "sometimes", the I agree. Again, it's a question of
economics: If you want to demoiré in Photoshop, you indeed need a high
resolution scan.

Stefan