4800dpi b/w scanning - how much RAM do I need?

  • Thread starter Thread starter Dot Net Developer
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Dot Net Developer

Hi,

New to scanning on PC.

Want to achieve the following -

Scan in (poor) image (b/w mode) at 4800dpi, then manipulate (inside
editor) & save on to PC.

Problem - only got 1gb memory, and things grind to a halt.

Would extra 1gb of RAM solve problem? (Don't really understand how
much memory is truly required for resolution mentioned above.)

(Sure, I can drop res to 2400, but source image is poor and want to try
to get best results possible.)

Thanks, regards, dnw.
 
Hi,

New to scanning on PC.

Want to achieve the following -

Scan in (poor) image (b/w mode) at 4800dpi, then manipulate (inside
editor) & save on to PC.

Problem - only got 1gb memory, and things grind to a halt.

Would extra 1gb of RAM solve problem? (Don't really understand how
much memory is truly required for resolution mentioned above.)

(Sure, I can drop res to 2400, but source image is poor and want to try
to get best results possible.)

Thanks, regards, dnw.
Click to expand...
Read the scantips.com web site for lots of information on how
to do what you wish.
There is little point in scanning at high resolution if you are
going to downsize later anyway. The rule of thumb is use 300dpi
for a finished inkjet printed image (some people use 240) and
then multiple this by the degree of enlargement (say you want
to make an 8x12 from a 35mm original = 8X). So for my example
8X300 = 2400dpi for the scan.

I also have some scanning tips on my web site which may be of
use to you. Follow the tips link on the home page.
 
Dot said:
Hi,

New to scanning on PC.

Want to achieve the following -

Scan in (poor) image (b/w mode) at 4800dpi, then manipulate (inside
editor) & save on to PC.

Problem - only got 1gb memory, and things grind to a halt.

Would extra 1gb of RAM solve problem? (Don't really understand how
much memory is truly required for resolution mentioned above.)

(Sure, I can drop res to 2400, but source image is poor and want to try
to get best results possible.)

Thanks, regards, dnw.
Click to expand...

You might want to do a test and see if 4800 is really giving you a
better scan. You should be able to crop a small area to be scanned,
say 1/4 of a full frame, and scan at both 4800 and 2400 ppi and see if
there really is any differance in what you get.

Scott
 
Yep - tried that, and did see small improvement @ 4800, but using the
recommended scantips website (thanks) I realise that even if I upgraded
to 2gb RAM, it wouldn't be enough.

Regards, dnw.
 
Dot Net Developer said:
Yep - tried that, and did see small improvement @ 4800, but using the
recommended scantips website (thanks) I realise that even if I upgraded
to 2gb RAM, it wouldn't be enough.
Click to expand...

What format are you scanning?

If you set things up carefully (and don't use layers), most photo editors
(Photoshop and Picture Window Pro, at least) can be persuaded to operate at
RAM speed as long as you have twice as much RAM as the image plus a bit for
OS and the software itself. (Of course, even "RAM speed" can be painful;
just loading a large scan can take a age.)

An 8-bit scan of 6x7 requires (3 x [(4800 x 2.2 x 4800 x 2.7) = 137 MP] =
411 MB. So 1 GB of RAM would be OK for 6x7 at 8 bits, but you'd need 2GB if
you wanted to scan at 16 bits.

Oops. I just goofed. Since you are scanning B&W, you only have to store one
or two bytes per pixel, so you are home free. Since 4x5 = 461 MP at 4800
ppi, 1.5GB would be plenty for 8-bit scans of 4x5. This assumes that you can
persuade the scanner to scan to and save a monochrome, single-channel image,
though.

Persuading Photoshop to operate reasonably requires setting the number of
saved history states to the smallest possible value. In Picture Window Pro,
you have to manually delete intermediate images.

If you've got the RAM and the time, scanning at 4800 ppi and downsampling to
a more reasonable resolution can have advantages. You can apply noise
reduction more aggressively at 4800 ppi without losing significant detail,
and the scanner does scrape out a slight bit more detail, even though it's
usually not visually significant.

David J. Littleboy
Tokyo, Japan
 
Hi,

I'm scanning A4 paper, which I think is causing a problem in terms of
RAM required.

My rough calculations make A4 @ 4800 with even 2gb a show stopper.

Once scanned, I also require the b/w image to be upgraded to greyscale.

I think I might upgrade my RAM from 1gb to 1.5gb, and then scan @ 2400,
and I think I'll be OK. Also, I am stuck with paint shop pro for the
time being, which I don't like.

Thanks, regards, dnw.

Dot Net Developer said:
Yep - tried that, and did see small improvement @ 4800, but using the
recommended scantips website (thanks) I realise that even if I upgraded
to 2gb RAM, it wouldn't be enough.
Click to expand...

What format are you scanning?

If you set things up carefully (and don't use layers), most photo editors
(Photoshop and Picture Window Pro, at least) can be persuaded to operate at
RAM speed as long as you have twice as much RAM as the image plus a bit for
OS and the software itself. (Of course, even "RAM speed" can be painful;
just loading a large scan can take a age.)

An 8-bit scan of 6x7 requires (3 x [(4800 x 2.2 x 4800 x 2.7) = 137 MP] =
411 MB. So 1 GB of RAM would be OK for 6x7 at 8 bits, but you'd need 2GB if
you wanted to scan at 16 bits.

Oops. I just goofed. Since you are scanning B&W, you only have to store one
or two bytes per pixel, so you are home free. Since 4x5 = 461 MP at 4800
ppi, 1.5GB would be plenty for 8-bit scans of 4x5. This assumes that you can
persuade the scanner to scan to and save a monochrome, single-channel image,
though.

Persuading Photoshop to operate reasonably requires setting the number of
saved history states to the smallest possible value. In Picture Window Pro,
you have to manually delete intermediate images.

If you've got the RAM and the time, scanning at 4800 ppi and downsampling to
a more reasonable resolution can have advantages. You can apply noise
reduction more aggressively at 4800 ppi without losing significant detail,
and the scanner does scrape out a slight bit more detail, even though it's
usually not visually significant.

David J. Littleboy
Tokyo, Japan
Click to expand...
 
Dot said:
Hi,

I'm scanning A4 paper, which I think is causing a problem in terms of
RAM required.

My rough calculations make A4 @ 4800 with even 2gb a show stopper.

Once scanned, I also require the b/w image to be upgraded to greyscale.
Click to expand...

Well there is your problem, scanning a either paper or a print at much
past 300 ppi normally is not needed and adds little to any detail you
are going to pick up. If I am scanning a very sharp print I might scan
at 600 ppi but that is rare most of the time it is at 300 ppi.

Can you really see any more detail in a 4800 ppi scan over a 600 ppi
one?

Scott
 
The paper to be scanned is very old and faded and I need the best
quality possible.
 
Dot said:
The paper to be scanned is very old and faded and I need the best
quality possible.
Click to expand...
Re-reading an earlier post I see you talked about upgrading to gray
scale after you have scanned. You can't really do this, you have to
scan in gray scale right from the start. If you are scanning in the
mode where you get either black or white and nothing in between then
you will never get a good scan of a faded document.

Just what is it you are scanning and what are you going to with the
scan once you have it?

Scott
 
Dot Net Developer said:
I'm scanning A4 paper, which I think is causing a problem in terms of
RAM required.
Click to expand...

Ah, there's your problem. There really isn't any more than 600 ppi of
information on paper, so even scanning at 1200 ppi would be overkill.
Once scanned, I also require the b/w image to be upgraded to greyscale.
Click to expand...

You should scan in full color and then determine which of the RGB channels
captured the image best.

Try a 600 ppi scan in 24-bit color. The 24-bit color will probably make more
of a difference than moving from 600 to 1200 ppi.

David J. Littleboy
Tokyo, Japan
 
Dot said:
Hi,

I'm scanning A4 paper, which I think is causing a problem in terms of
RAM required.

My rough calculations make A4 @ 4800 with even 2gb a show stopper.

Once scanned, I also require the b/w image to be upgraded to greyscale.

I think I might upgrade my RAM from 1gb to 1.5gb, and then scan @ 2400,
and I think I'll be OK. Also, I am stuck with paint shop pro for the
time being, which I don't like.

Thanks, regards, dnw.
Click to expand...


OK if a 4x5 scan is at 4800 ppi is 1.5gb, then an A4 scan would be 4X
of that or 6gb really an excercise in futility. Scan at 300 ppi and in
crease your contrast via the curves function in your scanning software,
you could try 600ppi but any more than that would seriously bog down
your system as you have been finding out. Trying to bring up the
contrast in the scan will help the image and then use Photoshop to do
more enhancements.

Tom
 
Thanks for all replies. Sorry, bit rushed atm due to extra workload.

Hope this email will clarify what I am trying to achieve -

Source ~ A4 sheet, it's b/w, it has text only on it, handwritten text
and printed text. The handwritten text is very difficult to read.

Scanning ~ currently @ 2400dpi. Save as b/w bitmap. After saving, I
then use paint shop pro to upgrade image to greyscale because I need to
add in gray colored graphics - they need to be gray rather than black
unfortunately.

Printing ~ Then, I print on mono laser @600dpi, although I may be able
to obtain inkjet with higher dpi.

Problems ~ Firstly, 1gb machine grinds to halt if scan @ 2400. If scan
@4800, PC tips over because of the strain! Secondly, as source is very
faded, really want to preserve as much of the detail as possible in
this whole process, as resulting output print is very hard to read.

Many thanks, regards, dnw.
 
Dot said:
Thanks for all replies. Sorry, bit rushed atm due to extra workload.

Hope this email will clarify what I am trying to achieve -

Source ~ A4 sheet, it's b/w, it has text only on it, handwritten text
and printed text. The handwritten text is very difficult to read.

Scanning ~ currently @ 2400dpi. Save as b/w bitmap. After saving, I
then use paint shop pro to upgrade image to greyscale because I need to
add in gray colored graphics - they need to be gray rather than black
unfortunately.

Printing ~ Then, I print on mono laser @600dpi, although I may be able
to obtain inkjet with higher dpi.

Problems ~ Firstly, 1gb machine grinds to halt if scan @ 2400. If scan
@4800, PC tips over because of the strain! Secondly, as source is very
faded, really want to preserve as much of the detail as possible in
this whole process, as resulting output print is very hard to read.

Many thanks, regards, dnw.
Click to expand...

With even 2400 ppi you are driving your machine into vitrtual memory,
you are still looking at 1.5gb images which are huge. Your printer will
be happier too if you keep the res to 600 ppi. While it may look better
on ther screen if the final print is at 600ppi then that is you maximum
res. Scanned some documents yesterday with physician's hand writing on
them, used 200ppi and the results were quite legible. Also you want to
look at the text at 100% to check the legibility. text may look choppy
when compressed on the screen.

Tom
 
Dot said:
Thanks for all replies. Sorry, bit rushed atm due to extra workload.

Hope this email will clarify what I am trying to achieve -

Source ~ A4 sheet, it's b/w, it has text only on it, handwritten text
and printed text. The handwritten text is very difficult to read.

Scanning ~ currently @ 2400dpi. Save as b/w bitmap. After saving, I
then use paint shop pro to upgrade image to greyscale because I need to
add in gray colored graphics - they need to be gray rather than black
unfortunately.
Click to expand...

The problem is that there is no good consistent terminology for some of
this stuff and so it is very possible that I am not fully understanding
what you are doing. It sounds like you are scanning in a mode with no
gray levels, either all black or all white. If this is the case then
it is very hard to capture faint writing in this mode, you would be
much better off scanning in a gray scale mode at much lower resolution.
Even 300 ppi should be more then enough when scanning in gray scale,
which my scanner calls B/W photo.

Just to be clear this is what you scan should look like the top of this
image not the bottom
http://www.pbase.com/konascott/image/69870853

When scanning in gray scale if you can see the writing on the paper you
will be able to see it in the scan.

Scott
 
Scott said:
The problem is that there is no good consistent terminology for some of
this stuff and so it is very possible that I am not fully understanding
what you are doing. It sounds like you are scanning in a mode with no
gray levels, either all black or all white. If this is the case then
it is very hard to capture faint writing in this mode, you would be
much better off scanning in a gray scale mode at much lower resolution.
Even 300 ppi should be more then enough when scanning in gray scale,
which my scanner calls B/W photo.

Just to be clear this is what you scan should look like the top of this
image not the bottom
http://www.pbase.com/konascott/image/69870853

When scanning in gray scale if you can see the writing on the paper you
will be able to see it in the scan.

Scott
Click to expand...
I agree with Scott here. I do a lot of scanning of old documents and
photographs for genealogical reasons, some badly faded. My technique is
to scan A4 at 300ppi, in color. A color scan of an A4 at 300ppi results
in an image file of about 25 megabytes. Since fading is predominantly
yellowish/brownish in color, the blue channel of a color image sees the
yellow darker than the green and red channels, thus minimizing the
fading, so I select the blue channel (Ctrl-3) in Photoshop) and convert
to gray-scale (Image/Mode/Gray scale). Some more work with Curves or
Levels will yield a high-quality result that will print and look well.

Your idea of scanning at 2400 ppi is really barking up the wrong tree.
Your problem is not definition, it is optimizing the recovery of faint
parts of the document. 300ppi is quite adequate and much easier to handle.

Colin D.
 
Thanks v. much 4 all replies.

Will redo my project this w/end with all this new info! :o)

Regards, dnw.
 
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