Inkjet Printing by Brian Smith LRPS Print Quality Factors • Colour Rendition – Colour Casts – Neutral Greys – Saturation – Smooth tones • Brightness & Contrast • Sharpness • Other.
Download ReportTranscript Inkjet Printing by Brian Smith LRPS Print Quality Factors • Colour Rendition – Colour Casts – Neutral Greys – Saturation – Smooth tones • Brightness & Contrast • Sharpness • Other.
Inkjet Printing by Brian Smith LRPS Print Quality Factors • Colour Rendition – 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 – – – – – 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 Base Paper PE coating 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 Dyes, Pigments & Gloss Dyes are absorbed by the coating, direct reflection, glossy appearance is maintained Pigments stay (mainly) on the surface & cause diffuse reflection 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! – 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 Printing Software Photo Editor Application Printer Driver PC/Operating System Colour Management • Non-managed printing – 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 Photoshop/Elements Printer Driver PC/Operating System • Print 6MB photo at 250 ppi • Resampled to internal resolution (600 ppi) • Data (35MB) transmitted via USB connection • Outputs ink droplets at 2400 dpi 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 Qimage Qimage Printer Driver PC/Operating System • 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 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…