ADJUSTING COLORS WITHOUT MAKING COLOR SEPARATION

In this first part of the lecture material you'll find instructions to adjusting colors of designs aimed to be digitally printed, so for designs with unlimited amount of colors.


Working with unlimited amount of colors:

You can use unlimited amount of colors with digital prints.

You can also begin the work and make the repeat on a computer using unlimited amount of colors, even if you are going to separate the colors later. This suites for example for painterly designs.

Working with unlimited amount of colors: In Edit –> Preferences –> General, change Image Interpolation to e.g. Bicubic Automatic (see image below). When using tools, you can have Anti-alias ticked. You can also adjust values like Feather, draw with soft-edged brush or use stamp, filters etc.




Changing colors in multicolored image

There are many possibilities in Photoshop to adjust colors of a multicolored image. Some tools work better for some designs, so try different tools if you are not happy with first!

When making the color changes with Adjustment Layers, the original coloring is kept safe.

see image below: the icon marked below the Layers panel is one place where you'll find Adjustment Layers. If you want the Adjustment Layer to effect only to one layer, select that layer and press the icon with alt pressed to have Window opened where you can tick on Use Previous Layer to Create Clipping Mask (these layers have arrows pointing downwards and have white mask visible)



The following three Adjustment Layers suite for roughly changing the colors into right direction – tuning to exactly correct tones can be done later with other tools. Colors can be changed from the entire design, from separate layers or by creating a selection.

  • Try: Layer –> New Adjustment layer –> Hue/Saturation. Adjust Hue in Adjustment window to change the colors. You can adjust all the colors in design, or e.g. only blue or magenta tones. (in image below: on the left side the original pattern; on the right side all colors changed (Master selected) with Hue/Saturation)


  • OR: Layer –> New Adjustment layer –> Color Balance. There you can adjust the amount of colors in different tone ranges. (in image below: on the left side the original pattern; on the right side midtones are changed with Color Balance)

  • OR: Layer –> New Adjustment layer –> Selective Color. This is maybe the most versatile of all Adjustment color tools. In Selective Color window, select first the tonal range you want to modify (yellows or neutrals for example) and blend the color by decreasing or increasing the amount of cyan, magenta, yellow or black in it. Relative creates more subtle adjustments than Absolute, so try them both. (in image below: on the left side the original pattern; on the right side blues are changed to more green by increased the amount of yellow and decreased the amounts of cyan and magenta, Absolute selected)


Replace Color is a suitable tool for tuning the colors into exactly right tones. It does not suite well for changing the colors completely. Replace color cannot be found in Adjustment layers list and you will need to make copy layers and merge used Adjustment layers before using Replace Color. In Image –> Adjustment –> Replace Color select first the color range to be modified. Add more tones in selection with Add to Sample Eye dropper (+). Increase Fuzziness to expand selection. To change the selected tones into the exactly right tone, click Result swatch. (in image below: purple shades are selected with + Eye dropper and some Fuzziness, then the exact brown color is selected from Swatches panel as the Result color)



Try also other Adjustment tools either in Image –> Adjustment, or in Layer –> New Adjustment Layer.


Adding monochromatic tone to an image

One option is to use only one tone in the design.

Do Layer –> New Adjustment Layer –> Black & White. In the first window that opens click ok (check that Use Previous Layer to Create Clipping Mask is selected). In Adjustment window, define how the image will be desaturated – which colors will be converted into darker and which into lighter tones of gray. Tick Tint. Click the color swatch next to it, and select a color for tint. If the result is too light, adjust the desaturation. Try presets like Darker, or Maximum black, or even drag all color sliders into the left, dark end of them.

OR: Do Layer –> New Fill Layer –> Solid Color. In the first window that opens click ok (check that Use Previous Layer to Create Clipping Mask is selected). In the second, select color. Color now covers the image entirely. Change Blending Mode of Fill Layer into Color. To change the color of Fill layer, double click the symbol of color in Layers panel. 

OR: Do Layer –> New Adjustment layer –> Hue/Saturation. Tick Colorize, and tone the image by dragging the sliders. This method is not as precise as the other methods. 


Example designs with digital prints and their colorways

images on top: Color Gradient design (Petra Haikonen, repeat size 100cm*320cm)
images on bottom: Sound Marble design (Petra Haikonen, repeat size 50cm*70cm)





COLOR SEPARATION

In this second part of the lecture material you'll find instructions of making color separation for surface designs in Photoshop. First we'll go through how to reduce the amount of colors of a file with Indexed Color mode, and then there are instructions of how to make raster images and use Bitmap mode.


Most important color modes:

  • Image –> Mode –> Bitmap: black and white pixels without any other tones. Flattened layers. Only some of the tools can be used in this mode.
  • Image –> Mode –> Grayscale: allows the use of most tools and functions, also layers
  • Image –> Mode –> RGB: the default color mode that allows all tools and functions and layers
  • Image –> Mode –> Indexed Color: optimum for working with color separation. Allows the use of some tools and functions, but not layers.



Working with reduced amount of colors:

For most common textile and surface design production methods (screen prints on fabric, paper or ceramics, woven and knit fabrics), you need to use limited amount of colors.

Working with reduced amount of colors in Photoshop: When possible, work in Indexed Color mode. Often it is not possible, because layers, filters. etc. cannot be used in Indexed Color mode.

If it is not possible to work in Indexed Color mode, use usually RGB mode. Adjust how Photoshop treats the image when scaling and transforming: In Edit –> Preferences –> General, change Image Interpolation to Nearest Neighbor. When using selection and drawing tools, never tick Anti-alias and put zero in functions like Feather or Dither. When drawing, use hard edged pencil instead of soft edged brush.

Color separation can be made both for a ready pattern, or for separate elements before building the pattern. Though notice that if you first do the color separation, then be sure not to use tools in repeat making that add any new colored pixels to the pattern, e.g. Anti-alias or Feather with selection tools.


Prepare the design for color reduction

Before color reduction, consider if you want the design to be neat and clean with solid color areas, or if you want to keep it structured and painterly. When clean result is desired, various tools could be used to smooth the design before color reduction (try following to dublicate layers):
  • Small amount of blurring can be used for smoothing the design, e.g Surface, Smart or Gaussian blur (0,5–1 px). Surface Blur blurs only the surface, preserving sharp outlines. Blurring can help you for example to reduce the structure of the paper from the sketch. Note that if you want to use the structure as an effect, you do not need to blur it. (see image below: original painted sketch, Surface Blur, and colors reduced to 8) 

  • Increasing contrast can also help in similar way. Do e.g: Layer –> New Adjustment Layer –> Levels or Layer –> New Adjustment Layer –> Curves
  • Also some of the filters can help to clean the design for color reduction. They could be used e.g. to clean a pencil drawing into neat lines or a painting into neat color areas. Try e.g. Filter –> Filter Gallery –> Sketch: Graphic or Stamp, or –> Artistic: Watercolor, Dry Brush or Cutout. (see image below: original painted sketch, Dry Brush Filter, and colors reduced to 8)



    • Also Layer –> New Adjustment Layer –> Posterize can be used. (see image below: original painted sketch, Posterize (Levels 2 in here), and colors reduced to 8)


    Save the progress file before color separation!


    Separate colors by converting the image into Indexed Colors

    Do: Image –> Mode –> Indexed Color. About the appearing window:
    • Select –> Palette: 
      • Local Perceptual (takes in color palette main colors human eye can see in the image)
      • OR Local Selective (same as Perceptual, but combined with web colors) 
      • OR Local Adaptive (counts all colors in image and takes in color palette the ones that appear most often) 
      • OR Palette: Exact, if you already have exactly the desired amount of colors in the image.
      • OR Palette: Custom for separating the colors directly into Custom colors. Click Load to load your swatches. (Note: this method works well, if you adjust the colors close to your custom color palette prior to color separation.)
    • Select as much colors as needed for the design to look good (usually less than 20). You can reduce the amount even more later on.
    • Select usually: Forced: None (For black and white sketch you could select Forced: Black and white)
    • Dither: noise or diffusion would make fine pixel mesh on the edges of color areas (instead of neat and clean edges) If that is not wanted, select: Dither: None
    • Ticking Transparency makes a transparent background behind the image and adds transparent to one color. (When you clear or erase part of the image, you will see the transparent background underneath). Usually untick Transparency


    After reducing the colors open: Image –> Mode –> Color Table, and change very similar colors to exactly same colors. Click a color, and select new from the design (or e.g. an exact tone from color palette or Swatch Library (see image below)). You can select several colors at once, if they are next to each other in color table. 
    • If you would find it easier, you could of course also change the colors using Magic Wand and Edit –> Fill, or Paint Bucket


    Change design to RGB mode (Image –> Mode –> RGB), and then back to Indexed Color  mode (Image –> Mode –> Indexed Color). Photoshop should now suggest the right amount of colors (Exact -> ). Note that if Transparency is ticked, then that increases the amount of colors by one. You should usually end up with 2–8 colors.




    Some tools for working with colors in the design:

    Cleaning the design: You may have undesired stray dots of colors somewhere in the design. Select all of that color with Magic Wand. Now you can paint over the stray dots without affecting other colors in the design. OR Select the area with stray dots using e.g. Lasso or Quick Mask. Then take Magic Wand and use it in Intersect with Selection mode. Select the stray dots inside the selection with Magic Wand. Do Edit -> Fill, and fill with the desired color.


    Expanding the color area (e.g. if some lines in the design are too narrow): Select the color with Magic Wand. Do Select –> Modify –> Expand, 1 pixel or more. Fill the area with color: Edit -> Fill -> Use color. (see image below with dark red color areas are expanded by 1 pixel)



    Cleaning large areas in this manner can be time consuming. It would be most often faster to adjust the design before color reduction using e.g. filters. Keep the original version without color separation saved so you can always go back to it to make the color separation again.


    Make files for exposed screen

    Select each colour (in RGB colour mode) with Magic Wand and separate them to own layers. 

    Consider the appearance of colour layers from the perspective of (hand) printing: fix e.g areas that would be too difficult to align by drawing or filling. 

    Change the colour in each layer to black

    Save layers as separate files: File – Export – Layers to Files (TIFF).

    Check that resolution is 720 ppi and the file contains only black (0,0,0) and white (255,255,255)

    Save the file to TIFF from Bitmap mode, no layers.


    Example designs with colors reduced with Indexed Colors

    image on top left: flower print with 4 colors (Petra Haikonen, repeat size 150cm*64cm); image on top middle: surface print with 2 colors (Petra Haikonen, repeat size 50cm*21,333cm); image on top right: surface print with 2 colors (Petra Haikonen, repeat size 50cm*64cm); 
    image on bottom left: woven jacquard with 6 colors (Petra Haikonen, repeat size 60cm*80cm); image on bottom right: woven jacquard design with 2 colors (Petra Haikonen, repeat size 60cm*40cm)




    CREATING RASTERS AND BLACK AND WHITE BITMAPS FOR PRINTING SCREENS  ETC


    There are many tools in Photoshop for separating colors of a design into only black and white. These tools can be used for making a color separation for all monochromatic images. To use these tools for color images, convert the design first to Grayscale. If there are several different tones of color in the design, start by separating each tone on its own layer. (See: Making color layers in digital prints instructions)

    There is a color mode in Photoshop that can include only black and white called Bitmap mode. These black and white bitmaps are often used when making files for exposed printing screens. In addition to this, they can be used easily also in Illustrator.

    All methods mentioned here suite for Grayscale mode: First convert the sketch into Grayscale: Image –> Mode –> Grayscale. 


    Basic method for separating colors into only black and white:

    Do Image –> Adjustment –> Threshold. Drag the slider to have more black or white in the image.

    To use the file for exposed screen (or in Illustrator), convert it in Bitmap mode: Image –> Mode –> Bitmap, use: 50% Threshold

    See image below: left original sketch in Grayscale; second added contrast with Levels adjustment layer; third using Threshold adjustment layer; forth converting to Bitmap)





    Adding a raster into design by converting to Bitmap

    To better preserve tonal, e.g. watercolor look of the sketch, you could use raster. You could use raster with just one print color, but also with two or even more colours. As described above, then two layers are needed - and when working with screen printing, also two screens would be needed.

    Before adding raster, check that the size of the design is as desired, and, if you are making printing screens, chance the resolution to 720 ppi

    First, whiten the image and increase contrast between shadows, middle tones and light tones. Use Image –> Adjustments –> Levels. A raster screen file should contain some areas of solid colour (black) and some areas without any colour (white), because printing with a screen full of raster would easily result in smudgy print. Drag the black slider right to blacken the darkest areas in the design, and drag the white slider left to whiten the lightest areas. Print dye droplets spread a little while printing, and thus the print result will look darker than the screen file. To avoid too dark results, lighten middle tones = drag the grey slider left. A good screen file looks lighter than the desired end result, but has some areas of full black and pure white.

    Little bit of blurring can be added to smooth the image.



    Note, that with the lightest tones exposing really tiny raster might be difficult.

    Save the Grayscale image as a new file.


    Adding raster to image by converting to Bitmap


    Bitmap – Diffusion Dither ("pixelated" outcome)

    Do Image –> Mode –> Bitmap – Method: Diffusion Dither

    The size of the raster depends on output resolution, for hand-printing use 40-80 ppi.

    Input = the image resolution (720 ppi), Output – the size and density of pixel dots (40–80 ppi)

    Rasterized image has to be scaled back up to resolution 720 ppi:

    If you want the pixels to stay square shaped, change the resolution in bitmap-mode.

    If you want to soften the pixels and make them more round; change the colour mode to Grayscale (size ratio 1). Scale the image: Image –> Image Size –> Resample Image – Bicubic. Then reduce the colours to black and white in returning to Bitmap mode: Image –> Mode –> Bitmap – Threshold 50% (output 720 ppi)




    Bitmap – Halftone Screen (traditional dotted raster in diagonal lines)

    Do Image –> Mode –> Bitmap – Method: Halftone Screen

    Input = the image resolution (720 ppi), Output = use 720 ppi

    Frequency: the distance of lines. With hand-printing try 20-30 lpi. For the best quality use lpi that goes evenly to the image resolution (e.g. with 720 ppi, use 18/20/24/30..lpi)

    Angle: with several colour rasters printed on top of each other use different degrees angles (e.g. 30 degrees more in each colour layer raster).

    Shape: try different shapes. With screen printing on textile usual shapes are round and ellipse



    Preparing the screen print file

    Check that resolution is 720 ppi and the file contains only black (0,0,0) and white (255,255,255)

    Save the file to TIFF from Bitmap mode, no layers.


    Viimeksi muutettu: maanantaina 25. huhtikuuta 2022, 10.51