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Using Photographs as Artwork

The NEHOC system [both screen printing and PRINT GOCCO] will print photographs onto fabrics,  paper, wood, ceramics & many other items. This information sheet deals with using a photograph that has been scanned into a computer.
 
For details on using a manual Dot Screen click here . .
 

Update for CS5 Photoshop: Overlaying a dot screen is no longer located in the Printer Options Box as described on this page. Halftone Patterns are now incorporated into the program, enabling live changes to be viewed and aplllied.
Access the 'screens' option through the menus Filter > Sketch > Halftone Pattern

For other version of PhotoShop, check your versions Help Menu's and search for Halftone Pattern.


 
When printing a photograph you must break the photo down into a range of fine dots that when printed combine to form the picture [similar to newspaper print]. If a straight copy of the photo is used without creating a dot screen over the photo then you will receive no grey scales and the photo will print as one solid blob with no definition.
 
There are a number of different factors to take into consideration when using photographs as artwork as there is no 100% rule you can input and follow each time - every photograph is different in tone & contrast so you must adjust your setting to match.
 
Some photo's can handle a high level of definition, whilst others will require a coarser screen. The level of final detail also depends on the item that you are printing - paper will handle a high definition whilst fabrics/ ceramics are more absorbent so ultra fine detail may be lost[ depends on the design].
 
The following information should be used as a general guide - your final results will be a matter of personal preference and computer experience [plus the abilities of the computer program/ printer options].
 
Step 1
Open the image in PhotoShop or another suitable graphic design program that enables you to manipulate images. Convert the photo to grayscale as this helps to gauge contrast more accurately.
 
Step 2
Adjusting & manipulating the photo can be done using two common methods:
 
Method 1: The most commonly used method is by overlaying a dot screen over the design using PhotoShop's 'Screen' setting in the Print With Preview or Print options Box.
 
This Screen feature is not available on low end versions of the program and where the printer selected is not capable of overlaying a screen.
 
Most laser printers and postscript printers are suitable for screens, however many early inkjet printers are not capable of this option.
 
From the Print options box, select Screens [top left button in the advanced options area at the base of the box right] this will open up the Halftone Screens option box where the adjustments can be made.
 
You will notice that the dots change size depending on your setting.  Set a lower line frequency, your dots are big - set a higher line frequency, your dots are small. Some people like the look with the really big dots.
 
For fabrics the frequency range is generally between 40 [large solid areas] and 65 for fine detail. On paper using 135Mesh or PRINT GOCCO Print Masters frequency may vary between 45 and 70.
 
Angle can be changed where ever required and may alter the depth of the design depending on the frequency. When starting out change only the frequency to begin with until you have a better understanding of the line changes on your design.
 
The normal setting for shape is round as this helps to limit bleed, however any shape may be used.

It really comes down to what you envision your print as being - you may need to print out several variations using different settings [make sure you document the setting on the back].  If you're inclined to experiment, then pick 2 different ones to flash and print then compare.  You'll learn a lot just by doing this 1 experiment.

Or, you can make 4 small printouts from the laser printer with 4 different PhotoShop settings, fit them all onto the same screen to flash. Then you'll have 4 different results to compare with.
 
Method 2:  The opacity setting for the layer can be adjusted and set to around 60% percent, as this gives you an overall lighter image [less dense with dots in your laser printer output]. Regardless of what you set this to, the dots are always the same size, there are just more or fewer of them.
 
Changing the level/ opacity of the design works well when printing cards/ paper, however when printing absorbent items like fabrics, this method is not as effective.
 
Opacity may not always provide the grey scales required to give a photograph depth on some items, hence method 1 is most commonly used.

 
* Additional technical comments supplied by Shu-Ju Wang as posted to GOCCO-Printers List

 

 

Printable and Unprintable Images: FIRST IMAGE: Printable dot (highlight): Must be larger than one mesh opening plus 1.5 thread diameter to allow for printability regardless of the position of the dot on the screen. SECOND IMAGE: Unprintable dot (highlight): Blocked by threads or too small to be supported by screen. In this example, the angle of the dots relative to the mesh increases the problem. THIRD IMAGE: Printable dots (shadow): Can be as small as one mesh opening but will only print when positioned over an opening. Positioning of dots cannot be predicted or controlled. FOURTH IMAGE: Unprintable dots (shadow): The size and angle can render whole areas of the image unprintable or printable with moiré.
Though moiré can never be completely eliminated, higher mesh-to-dot ratios can reduce the incidence of global moiré. A minimum ratio of 3.5:1 is recommended, but results improve significantly at a ratio of 5:1 or higher. So at 3.5:1, a 65-line/in. halftone would require the use of a 230-thread/in. fabric (3.5 threads/line x 65 lines/in. = 227.5 threads/in.), and, at a 5:1 ratio, a 75-line/in. halftone would require a 380-thread/in. screen (5 threads/line x 75 lines/in. = 375 threads/in.).

 

 

 

 

 

 

 

 

 

 

 

 


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