Spectrophotometer Directly gives the final result of Delta E report, Delta E report Determines whether the sample is Yellower, Redder, Bluer, Greener, and the depth of Value, Chroma, Hue of labdip. The Given Value of delta e by Spectrophotometer advises the difference of labdip from standard (DEcmc). This value having tolerance 1.00. This is the standard value for any colour difference but difference beyond will reject the sample and supplier needs to do give new labdip option. In the given below images it shows that Colour difference is 0.66 Bluer than the actual standard so this much difference can be accepted by buyer.
Procedure for evaluation through spectrophotometer as follows:-
1) First fed the Colour Standard into The Machine and saved the reading which determines depth of Hue, Chroma, and Value of standards.
2) Condition the labdip for a minimum of 30 minutes before measurement.
3) Fold the samples to be viewed to sufficient thickness to make them opaque, typically two to four layers. The sample is opaque if it does not allow light to pass through. Make sure to measure the face side of fabric.
4) Remove the sample from the instrument, re-fold, re-position and measure it. Shift the location 90degress and/or direction of the sample at each measurement to optimize surface reading. Do not read the same location.
5) Take a total of 4 measurements.
6) After all are measurements completed, the instrument will provide DELTA E (DE) reading for comparison.
How To Calculate Delta E – MIS
Below explains how to calculate Delta E based on Hue, Value, and Chroma. 2 samples are measured below
Fig- Delta e Report.
DEcmc =Colour Difference
DL* =Difference between Standard and Labdip Value- Light/Dark. (+ = lighter, – = darker)
DC* = Difference between the standard and lab dip Chroma – bright / dull
DH* = Difference between the standard and lab dip in the overall hue
Da* = Difference of tone between Redder and Greener. (+ = redder, – = greener)
Db* = Difference of tone between Yellower and bluer. (+ = yellower, – = bluer)
Formula for calculating Colour difference (DEcmc):-
Identifying Colour Differences Using CIE L*a*b* Coordinates.
Delta E value will ranges from 0-100, as we discussed already acceptable delta e value for textile is 1.00,
Below table will shows meaning of delta e values:-
|Delta E values||Perception by human eyes|
|<= 1.00||Not Visible by human eyes.|
|1-2||Visible through very close observation by standard observer|
|2-10||Visible at glance|
|11-49||Colours are similar than opposite colours (ex. Black vs White)|
|100||Colours are exactly opposite to each other|
After Getting Pass report of Delta, Supplier will send the labdips to Customer/Buyer. Once buyer has received the labdips they will also evaluate all the labdips option by visually as well as by instrumentally, and select one option which is looks closer to Standard.