Best Practices – Print Size Processes

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Posted By
Perianthal
Sep 20, 2006
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444
Replies
14
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Closed
My work is all created as direct digital capture on a flatbed scanner (scanner photography). I need to determine in my workflow, when and how best to convert my image into the final size for printing.

The options I am aware of are:
1 Setting the scanner at final size and enlarging during the scanning process. 2 Scanning letter size, then converting in CS2, using image size, but unchecking the resample box. 3 Scanning letter size, working with the file at that size and desired resolution, then creating new document at the final print size and copying and pasting into it.

For example,
I can scan an object at 720 ppi a letter size. My print shop requests the file arrive full size at 360ppi, so after I am done editing, I create a new document that is 17 x 22 and copy and paste it into that document. The result is full size at 360ppi.

An alternative is to scan at 360ppi but set the format to 17 x 22 at the begnning of the process.

Or another alternative would be to simply save as and use the image size pull down to convert directly.

I am anxious to know what consequences of each approach might be that are not immediately obvious. Will there be a negative impact by any of these procedures. Which approach is recommended?

Thanks very much!

Marsha

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CN
Cybernetic Nomad
Sep 20, 2006
I can scan an object at 720 ppi a letter size. My print shop requests the file arrive full size at 360ppi, so after I am done editing, I create a new document that is 17 x 22 and copy and paste it into that document. The result is full size at 360ppi.

Why not just use image size with resampling off?

An alternative is to scan at 360ppi but set the format to 17 x 22 at the begnning of the process.

It ends up being the same thing ie, the scanner scans at 720 ppi either way

Will there be a negative impact by any of these procedures.

As long as you don’t resample, no.

I find it best to scan at the scanner’s native resolution and resize in PS later
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Perianthal
Sep 21, 2006
Cybernetic Nomad,
Thanks very much for your response. May I ask what you mean by "scanner’s native resolution"? And why you feel it is best to use that?
~Marsha
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Bernie
Sep 21, 2006
The native resolution is also referred as the optical resolution

From wikipedia:

"The other qualifying parameter for a scanner is its resolution, measured in pixels per inch (ppi), sometimes more accurately referred to as samples per inch (spi). Instead of using the scanner’s true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher thanks to software interpolation. As of 2004, a good flatbed scanner has an optical resolution of 1600Β–3200 ppi, high-end flatbed scanners can scan up to 5400 ppi, and a good drum scanner has an optical resolution of 8000Β–14,000 ppi."

I feel it is beter because using it (or an even divider of it) avoids interpolation at the scan itself
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Perianthal
Sep 22, 2006
I looked up the PDF Information sheet from Epson for my 4990 scanner. It says that the optical resolution is 4800 dpi (I assume they mean ppi). Are you saying then, that to avoid all types of interpolation I must scan below 436 ppi which produces a letter size document of the dimensions 4796 ppi x 3708 ppi to stay below the 4800 ppi threshold?

And that if you then want a larger image than letter size, it is better to use upsizing in Photoshop or other interpolation software than increasing the data directly from the scanner- even if there is some interpolation?

I’m really over my head on some of this, but seems that capturing the most data initially is more logical.

Am I still missing something?

Thank you for your insights, I do a ton of scanning and want to be sure I approach it most effectively.
L
LenHewitt
Sep 22, 2006
Perianthal,

You seem to be confusing pixels per inch with pixels.

If you wish to scan at the optical resolution of 4800 spi then a letter-size page would produce an image 8.5 * 4800 by 11 * 4800 or 40,800 x 52,800 pixels which you would probably find way larger than you want to work with.
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Perianthal
Sep 22, 2006
That was my interpretation too at first, but the more I read the data sheet the less convinced I was. You are correct, that scanning using the setting of 4800 would make a file of several gigs, and no, even though I’d love that, my computer wouldn’t.

Here is the description from Epson:

"Maximum Scan Area
8.5" x 11.7" (216mm x 297mm)
Optical Resolution
4800 dpi
Hardware Resolution
4800 x 9600 dpi maximum with Micro Step DriveΒ™ technology Maximum Resolution
12,800 x 12,800 dpi with software interpolation
Effective Pixels
40,800 x 56,160 pixels (4800 dpi)
Color Depth
48-bit internal/48-bit external*
Grayscale Depth
16-bit internal/16-bit external*
Optical Density
4.0 Dmax
Scaling (zoom)
50% to 200% (1% step)"

It looks to me that if you scan anywhere near 4800 you will exceed the 12,800 x 12,800 – and they say that uses "software interpolation"

I don’t understand the difference between that and what they call "effective pixels" the 40,800 x 56,160 is much more like what you would get if you scan at 4800.

Thank you again for taking your time to address my left field concerns!! ~Marsha
DM
Don_McCahill
Sep 22, 2006
Nope, you are still mixing up pixels and dpi. The 12,800 is dpi, not total pixels. Software Interpolation means that the scanner, while scanning at 4800 dpi, will interpolate up to 12,800. This means it will physically scan at the lower number, but then split those dots up using interpolation … looking at the surrounding dots and deciding what value to give each of the smaller dots.

You can scan a total size of at least 30,000 x 30,000 in Photoshop. (There is a 300,000 x 300,000 optional format as well, but I’m not sure if you can scan to it.)

That said, you really don’t want to scan anything at 4800 dpi, except perhaps transparencies or things for scientific purposes. (Perhaps something very small that will become very large, like a postage stamp that you want to make a poster of.)

This is the way you do it. You take the final dimensions you want: let’s say 8×10. You take the resolution you want: for print 200 or 300 dpi is usually good enough (let’s use 300). Then you take the size of the item you are scanning. Let’s say it is a 4×5 postcard.

You will need to scan the postcard at 600 dpi to get a scan with sufficient resolution to provide the 300ppi image you want to end up with. This is what was meant earlier, when someone said it is best to scan at the final resolution you need, so no interpolation is necessary in Photoshop.
GS
Gustavo Sanchez
Sep 22, 2006
My print shop requests the file arrive full size at 360ppi

Full size – 360 ppp… uh… That’s is way too much for most prints.

But it’s your print shop…
JJ
John Joslin
Sep 22, 2006
Marsha

The Epson scanner software which opens in Photoshop when you select File > Import > Epson… will do exactly what Don correctly recommended.

You don’t even have to think. πŸ™‚

Just for future simplicity.
L
LenHewitt
Sep 22, 2006
Marsha,

As Don says, that 12800 is the maximum spi that the scanner will produce which is 4x the optical resolution. It does this increase by software interpolation and is nothing whatsoever to do with the maximum number of pixels that the scanner can produce at it’s optical resolution. – The maximum number of pixels the scanner can produce will be 12800*8.5 by 12800*11.5 or a grand total of:

112640 x 147200
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Perianthal
Sep 24, 2006
Thank you to all who have answered. I apparently am unable to ask my question well enough to get to the information I am seeking. I’ll keep reading and hopefully get a clearer undertstanding.
Thanks for trying,
~Marsha
JJ
John Joslin
Sep 24, 2006
Re-reading your original post I think you want your Option 1.

If your scan software after selecting File > Import > Epson… looks like this (partial view):

<http://imageshack.us>

just put 300 in the "Resolution" box, and the desired output size in the "Target size" box, and you should get what you’re after without bothering about what’s under the hood.
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Perianthal
Sep 24, 2006
In your example above, how big can I set the target size before scanner interpolates?
JJ
John Joslin
Sep 25, 2006
As I see it, if you are aiming for a required size and resolution, those settings should give you the best possible result without needing to think about the native resolution of the scanner.

Edit: The figures in the boxes in my illustration were not related to your particular case. Do your preview scan and work from there to get yor target result.

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