Resolution

SR
Posted By
Stephen_RH
Jan 13, 2004
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258
Replies
5
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Closed
This is one of the most basic things one must know, but I am just beginning to use Photoshop again after a couple years and I am drawing a blank.

How can I calculate out what resolutions I should use for an image? For example, if I am printing an 8×10 magazine cover, what resolution should the image be?

Once I have that figured out, how could I then use a formula to determine what resolution I should scan in a particular sized image at so it can be a large enough size for the project?
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RK
Rob_Keijzer
Jan 13, 2004
Stephen,

I’m not the expert on this, but I’ll tell you what I know. Allways scan/shoot/paint with the highest amount of data obtainable from the input device. whether the final is going to be a print or a desktop icon.
Never reduce in a camera or a scanner, do that in the process or afterwards. CF-cards an RAM-chips can be used more then once.

About the printer: I woul allways save an image at a higher res than the printer can print (inkjet).

But again, during editing keep the most data in the image.

Rob
L
LenHewitt
Jan 13, 2004
Stephen,

if I am printing an 8×10 magazine cover, what resolution should the image
be?<<

On a general note 300 ppi at the finished size will be safe. However, the REAL answer is 1.4 x the linescreen frequency (lpi) that the magazine will be printed at.

Assuming a 175 lpi linescreen then (175 x 1.4) or 245 ppi at the final size will be fine. In that case a 10" x 9" image would need to be 2450 px by 1960 px.
SR
Stephen_RH
Jan 13, 2004
I’m really embarrassed to ask for any more help out of such knowledgeable people, but I have a really ignorant question to ask.

What is the linescreen frequency (lpi)? Thanks for working it out for me Len, really helps (and I’ll be able to figure it out in the future), I’m just not certain what the lpi is and how to know what it should be.
JS
John_Slate
Jan 13, 2004
If you look real close at a printed piece you will see dots. The dots are arranged in rows and columns (or lines). The linescreen or LPI (also referred to as screen ruling) is the number of lines of dots in an inch.
L
LenHewitt
Jan 13, 2004
Stephen,

When jobs are printed by offset Litho (as most things are, although some very high volume jobs MAY be printed by Photo Gravure), a linescreen is applied to break the image up into a series of non-overlapping dots so the individual inks (Cyan, Magenta, Yellow and Black) form a rosette pattern – put a lens on any printed material and you will see the screen.

The finer that screen (the higher the lpi) the better the reproduction will be, but will also require higher quality paper.

Common linescreen frequencies are 80 lpi for Newsprint, 133 lpi for low-quality general printing (usually B&W only these days), 150 lpi (general colour jobs) or 175 lpi for better quality 4-colour jobs. Fine art repro is often done at 200 or 225 lpi.

and how to know what it should be.<<

Only the printer or the magazine publisher will be able to tell you what the job will be printed at in the case of a Magazine. If YOU were having the job printed yourself, YOU would tell the printer at what linescreen frequency the job was to be run at, and you would also specify the paper it was to be printed on.

Normally publishers will provide a "Mechanical Data Sheet" that specifies such things as image resolution, formats, bleeds, page-sizes etc.

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Give your photos a professional finish with sharpening in Photoshop. Learn to enhance details, create contrast, and prepare your images for print, web, and social media.

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