Brilliant! The Very Latest in Optical Brighteners

Transcription

1 #Color2018 Brilliant! The Very Latest in Optical Brighteners Peter Pretzer FUJIFILM North America Corp. Graphics Systems Division

2 The electromagnetic spectrum

3 Lighting affects color perception. Same office furniture. Same carpet. Same wall paint. Different lighting!

4 We have a standard for that. ISO 3664:2009 Graphic technology and photography Viewing conditions Describes conditions for viewing prints and transparencies

5 ISO 3664:2009 Viewing conditions Viewing apparatus Describes illumination at surface of viewing and surrounding surfaces; Positioning: light, image, viewer s eyes Surrounding chroma values: neutral Spectral conditions for illuminant Describes spectral power distribution and chromaticity

6 Spectral Power Distribution Example: relative power distribution of ten different phases of daylight For graphic arts: specific SPD between 300 nm and 780 nm in increments of 5 nm

7 D50 Describes the SPD of illuminant specified in ISO 3664.

8 ISO 3664:2009 Viewing conditions Color rendering index Accuracy of light at viewing surface: > 90 Ambient conditions Extraneous light from sources or reflected by objects and surfaces Walls, ceilings, floors, clothing Maintenance Time the viewing apparatus is expected to remain within spec Illumination (D50) and illuminance (2,000 ±500 lx / 2,000 ±250 lx)

9 How do I know? Measure viewing conditions with a compliant spectrometer and compare data to metrics described in ISO 3664:2009

10 The substrate is a color. L*95, a*0, b*0 L*95, a*0, b*-4 L*95, a*1, b*-10 Three different shades of paper, all G7-aligned, resulting in a shared, neutral appearance.

11 The substrate is a color. Paper previously whitened with titanium dioxide TiO2 is an effective absorber of UV light But expensive!

12 Principles of optical brightening agents Today, paper is brightened bleached and dyed. OBAs are colorless or slightly colored organic compounds that, in solution or applied to a substrate, absorb ultraviolet light and re-emit most of it between 400 and 500 nanometers as blue fluorescent light. 2 Re-emission in visible blue 1 Absorption of invisible UV and edge of visible blue energy

13 Principles of optical brightening agents Remember this?

14 Metamerism Metameric failure is when two samples appear to be the same color but have different spectral reflectance curves. Common causes: Different dyes Different pulps Different fillers Different levels of fluorescence

15 Confluence of ISO 3664 and OBAs Papers in older lighting conditions (minimal or no UV) The same papers in ISO 3665:2009 viewing conditions (higher UV) Same papers in high UV lighting conditions for exaggerated effect

16 Confluence of ISO 3664 and OBAs Substrates with OBAs fluoresce under standard lighting conditions. Substrates with higher amounts of OBAs fluoresce even more. Substrate with no OBA Substrate with high OBA ISO 3664:2009 (Current color viewing standard) Differences in UV energy in lighting and OBAs in substrates compromise consistency. ISO 3664:2000 (Previous color viewing standard)

17 Proofing Evaluating color on different press substrates and what appear to be similar proofing substrates with various amounts of OBAs under two different lighting conditions.

18 Proofing Proofs and press sheets need to have similar white points and levels of OBA

19 Proofing & paper choice Proofs and press sheets need to have similar white points and levels of OBA. If not, this

20 Proofing & paper choice Proofs and press sheets need to have similar white points and levels of OBA. If not, this can become one of these.

21 What about spot colors? Same ink, coated vs. uncoated paper

22 What can we do about all of this?

23 Appropriate viewing conditions Do what you can to standardize your lighting and surroundings for appropriate viewing conditions. Don t forget about ambient conditions!

24 Appropriate viewing conditions For non-standard conditions, try to match what your customers need.

25 Measuring devices Measure in M1 whenever and wherever possible. Calibrate your devices regularly. Use the appropriate aperture for the printing condition.

26 Align to CRPCs: ISO For non-standard conditions, try to match what your customers need.

27 SCCA Calculate a new RPC data set from an existing one. Example: Start with CRPC6. Plug in the new white point. Calculate new press aims or a new data set for proofing or digital matching source profile. Communicate new aims to all involved in supply chain.

28 Proofing L*95, a*0, b*-2 GRACoL 2006 L*95, a*0, b*-4 GRACoL 2013 L*96, a*1, b*-10 High OBA E.g. GRACoL_CRPC6_SCCA_96_1_-10 Use appropriate paper! If printing on high OBA paper, a standard GRACoL proof may not be accurate enough. Create a new, white pointadjusted data set and find a proofing stock of sufficient brightness. You can always make it yellower but not brighter/bluer. Use if paper color difference is > E or higher.

29 Proofing & printing Test your materials.

30 Validation/verification Validate whenever possible