Inkjet Printing by Brian Smith LRPS

Print Quality Factors Colour Rendition Brightness & Contrast Sharpness Colour Casts Neutral Greys Saturation Smooth tones Brightness & Contrast Sharpness Other Faults

Test Evaluation - colour Rich Blues Gradients Skin colour and smoothness Shadow separation Sky Blue, and highlight detail Natural hues Bright Reds Neutral monochrome Sharpness Texture in all colours

Test Evaluation - mono Maximum black Smooth gradient Neutral mid-grey Highlight contrast & detail Shadow separation Full tonal range visible and neutral

Print Rendition Causes of poor prints Poor image Printer faults Wrong or incompatible paper & ink Software

Printer Faults Misaligned heads Clogged nozzles Depleted cartridge(s) Mechanical malfunctions Pizza wheel marks Scratches (paper thickness?) Paper curl Ink deposits from rollers

Papers & Inks Paper type Inks Matte Glossy & Lustre/Pearl Swellable vs Micro-Porous Cotton Rag Baryta (Fibre) Inks Dye Pigment OEM vs Compatible

The need for coated paper Inkjet coating PE coating Base Paper Uncoated media Uncontrolled ink spread Bleed & strike-through due to porous substrate Lower density due to absorption Poor fade resistance Cockle Coated media Controlled ink spread High resolution Large colour gamut Stays flat Better fade resistance

Pigments stay (mainly) on the surface & cause diffuse reflection Dyes, Pigments & Gloss Pigments stay (mainly) on the surface & cause diffuse reflection Dyes are absorbed by the coating, direct reflection, glossy appearance is maintained

Inkjet Inks Generalities Dye based inks Bright colours Quicker fading Sensitive to oxidizing Glossy media available Colours vary more with different papers Low water resistance after printed Pigmented inks Less bright colours Fade resistant Wide range of Matte surfaces Fewer glossy options available Good weather resistance

Paper vs Ink problems Colour! Poor contrast (D-Max) Banding Metamarism Wrong profile or driver setting? Poor contrast (D-Max) Banding Metamarism Blotching (slow drying) Gloss differential Bronzing

Why is monochrome so difficult? Because making grey by mixing C+M+Y is extremely difficult

Printer Ink Sets C+M+Y+K – normal printing & consumer inkjets C+M+Y+K+Lm+Lc - Photo inkjets C+M+Y+PK+MK+Lm+Lc+Lk - HP Vivera C+M+Y+K+Lm+Lc+Lk+Llk - Epson K3 Ultrachrome C+M+Y+K+Lm+Lc+Lk+Llk+Red+Blue – Canon ChromaLife More inks deliver wider gamut

Ink Starts Two blacks Three blacks

What’s the solution? Use the printer’s default monochrome settings Use monochrome (low chroma) inks Use special (extended grey) ICC colour profiles Use “grey balancing” software Use a RIP (raster image processor) Use a printer that has 2 or 3 black inks

Photo Editor Application Printing Software Photo Editor Application Printer Driver PC/Operating System

Colour Management Non-managed printing Colour Managed Assumes sRGB files Colours controlled by driver Colour Managed By driver OR printing software Double profiling typically gives a magenta cast Built-in profiles for manufacturers papers only Custom profiles are more accurate Demo: Print Drivers

Resolution dpi – dots per inch (e.g. 2400: Canon, HP, 2880: Epson) - internal to printer ppi – pixels per inch (e.g. 300, 360) – determines how large your print will be. 300 ppi is an industry standard for commercial printing (e.g. magazines) 240 ppi is easily sufficient for high quality inkjet printing

Print Size Consider a 6MB image: 3000 x 2000 pixels At 300 ppi -> 10” x 6.6” print At 200 ppi -> 15” x 10” print If you actually want a 12” x 8” print, then print at 250 ppi. In all cases, the image itself is unchanged.

What actually happens Print 6MB photo at 250 ppi Resampled to internal resolution (600 ppi) Data (35MB) transmitted via USB connection Outputs ink droplets at 2400 dpi Photoshop/Elements Printer Driver PC/Operating System

Resampling (upsizing) Printers have a native resolution: Epson = 720 ppi Canon & HP = 600 ppi Printing at exact multiples can give higher quality 180 or 360 for Epson 150 or 300 for HP, Canon Resample: Photoshop, Genuine Fractals etc. Use Qimage

Qimage Print 6MB photo as 12x8 Resampled to printer driver resolution (600 ppi) Apply sharpening etc. Pass through (35MB) image data Data transmitted via USB connection Outputs ink droplets at 2400 dpi Qimage Qimage Qimage Qimage Qimage Qimage Qimage Qimage Printer Driver PC/Operating System

Sharpening Images to be printed MUST be sharpened a little to compensate for ink diffusion Over-sharpening is easily achieved, and harshly judged Demo: Examples

Summary Tips If you find colour management complex, stick to an unmanaged workflow: Use sRGB colour space Use manufacturers papers and inks Find the right driver settings, and stick with them Managed workflow offers more options, but more pitfalls Limit the range of papers you use, and learn their characteristics Have custom profiles made for non-OEM papers Don’t keep changing your workflow – consistency in results comes from consistency in approach Do a nozzle check before an important print run Print a test image periodically…