Color Measurement - SP 60 Sphere Spectrophotometer - How do we input the L*a*b*

pmwong

Involved - Posts
#1
Hai,

Hopefully someone might be able to help on this. We had a new customer, one of our criteria is to check on the color after spray. We are using one called SP 60 Sphere Spectrophotometer. Although we have a Spectrophotometer manual to follow, some of us still have query how do we input the L*a*b* into the spectrophotometer? we have try but still unsuccessful.

Has anyone able to provide any info e.g how to key in this data into the spectrophotometer or how to set up a color check criteria?
 
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Jim Wynne

Staff member
Admin
#2
pmwong said:
Hai,

Hopefully someone might be able to help on this. We had a new customer, one of our criteria is to check on the color after spray. We are using one called SP 60 Sphere Spectrophotometer. Although we have a Spectrophotometer manual to follow, some of us still have query how do we input the L*a*b* into the spectrophotometer? we have try but still unsuccessful.

Has anyone able to provide any info e.g how to key in this data into the spectrophotometer or how to set up a color check criteria?
L*a*b* is data the output of the spectrophotometer. Why do you want it to be input? If you're talking about using a reference value, it's a function of the software that should have come with the device, I think. Have you checked the help file in the program? Your best bet in the end, though, is to contact the manufacturer of the spectrophotometer, first through their website.
 

ScottK

Not out of the crisis
Staff member
Super Moderator
#3
I have used X-Rite Spectrophotometers in the past.

If I have understood your question it looks like you want to input a standard into the machine. This would be used for calculating differences and Delta E

Here is the manual for the SP60 series:
http://www.xrite.com.cn/documents/manuals/en/SP62-500_SP60_Series_Operators_Manual_en.pdf

The chapter I believe you want is Instrument Operation: Standards Mode starting on page 5-1.

From here you can input a standard, the go to QA Mode and the machine will calculate differences and delta E for you.
 
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CarolX

Super Moderator
Super Moderator
#4
Jim Wynne said:
L*a*b* is data the output of the spectrophotometer. Why do you want it to be input?
Jim - not true - color measurement values are expressed in terms of "L", "a", and "b". The color measurement devices measure the color of your sample, compare to what the standard is, and derive a deviation value called Delta E, which encompases all the variations from the L*a*b values. As I understand, a Delta E value of less than 1 is not visable to the human eye.



pmwong - we entered our values by measuring the customer approved standard. This was for a hand held unit.
 
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Jim Wynne

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#5
CarolX said:
Jim - not true - color measurement values are expressed in terms of "L", "a", and "b". The color measurement devices measure the color of your sample, compare to what the standard is, and derive a deviation value called Delta E, which encompases all the variations from the L*a*b values. As I understand, a Delta E value of less than 1 is not visable to the human eye.



pmwong - we entered our values by measuring the customer approved standard. This was for a hand held unit.
This is all correct, but you can't have Delta E without LAB values (called tristimulus data). Thus LAB values are spectrophotometer output--Delta E is a post hoc calculation in the software.
 

CarolX

Super Moderator
Super Moderator
#6
Jim -
I think we are trying to say the same thing. Yes, your L*a*b are an output, but most measurment units will allow you to input your standard values to allow for quick calcuations of deviations from standard. I guess I read into the question - the poster is probably trying to set-up his unit to output the Delta E number.
 

Jim Wynne

Staff member
Admin
#7
CarolX said:
Jim -
I think we are trying to say the same thing. Yes, your L*a*b are an output, but most measurment units will allow you to input your standard values to allow for quick calcuations of deviations from standard. I guess I read into the question - the poster is probably trying to set-up his unit to output the Delta E number.
We are definitely saying the same thing. LAB output values have to be based on comparison to a standard, which is usually the customer's color "master." Thus the OP's question apparently relates to how to input master values. With many (if not most) devices, this is done by "shooting" the master and then storing the values obtained, then "shooting" the sample. The software then computes the LAB and Delta E values.

For those who aren't familiar with color measurement, there's a good explanation here, as well as a Delta E calculator.
 

ScottK

Not out of the crisis
Staff member
Super Moderator
#8
Jim Wynne said:
We are definitely saying the same thing. LAB output values have to be based on comparison to a standard, which is usually the customer's color "master." Thus the OP's question apparently relates to how to input master values. With many (if not most) devices, this is done by "shooting" the master and then storing the values obtained, then "shooting" the sample. The software then computes the LAB and Delta E values.

For those who aren't familiar with color measurement, there's a good explanation here, as well as a Delta E calculator.
When I was doing color measurment we didn't shoot a sample but manually entered the target L*a*b* numbers, which were part of of the product spec.
That's my interpretation of the OP's question.

Don't know if the X-Rite unit he's specifiying can make a spec out of sampled data or not.
 
R

ralphsulser

#9
Jim Wynne said:
We are definitely saying the same thing. LAB output values have to be based on comparison to a standard, which is usually the customer's color "master." Thus the OP's question apparently relates to how to input master values. With many (if not most) devices, this is done by "shooting" the master and then storing the values obtained, then "shooting" the sample. The software then computes the LAB and Delta E values.

For those who aren't familiar with color measurement, there's a good explanation here, as well as a Delta E calculator.
I agree with Jim. At one company I worked at for 10 years we used to use this type equipment for color measurements of a "sample" compared to a "master standard" supplied by the customer. The McBeth unit had an input for a "standard", then a second step to input the sample to measure L*A*B* in DE units. This was for Boeing supplied master color standards. Initially the max DE was 1.5, then a few years later reduced to 1.0. The aircraft interior norm was 1.5DE.
 
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Jim Wynne

Staff member
Admin
#10
Discordian said:
When I was doing color measurment we didn't shoot a sample but manually entered the target L*a*b* numbers, which were part of of the product spec.
That's my interpretation of the OP's question.

Don't know if the X-Rite unit he's specifiying can make a spec out of sampled data or not.
I think you're probably right.
 
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