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renatoa
03/25/2024 12:38 PM
coffee drink, Ramper?

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Roast Color Nerdy Stuff
HarryDog
So I ordered the Pro version as it is slightly better $125 cad,
I did find two others that might be of interest.
Pro Version
https://www.aliex...fp1HA8N7nd


https://www.aliex...AfEZCYIWpC

https://www.aliex...ANzMmVXU3K
 
oldgrumpus

Quote

HarryDog wrote:

So I ordered the Pro version as it is slightly better $125 cad


Excellent! Please keep us up to date!!
Clever Coffee Dripper
Grinder: Macap M4
Roaster: Completed drum roaster project photos shown here:
Photos https://goo.gl/ph...Da6K4wfqw5
Videos https://www.youtu...Bd1NrdpSUH
 
HarryDog
Hello Everyone, I'm looking for the paper that has the CIELAB readouts corresponding to the Agtron roast levels. Tom from Sweet Marias eluded to it in his video, wondering if anyone has seen it?

Thanks.
 
renatoa
Actually you can build your own roast level chart, based on your taste.
The more important is that you have a reproducible way to measure, and establish some references, not the value of references.
Is like the roasting, is not important that you have FC at 195 or 205 degrees, what matters is the speed you arrived there, and how you drive the roast from that point forward.
 
HarryDog
I agree, if it works I will be able to sample and create results that can be used. I was wanting to compare to the standard readings made by Agtron and get my hands on one of the cards just to read/test them. I don't live in the US so it's maybe Taiwan to get a card, Sweet Marias won't sell the card by itself. More hassle and cost then the cost of the meter?
 
renatoa
This white paper could give an idea of the degree of... nerdiness... Shock
https://support.h...l_1_14.pdf
 
HarryDog
Thank you renatoa, I read an article from Hunter labs testing at 640nm before but not at 880nm wave length, I think the first meter is a unit that Hunterlab uses or sells? The second I don't know.

The meter I ordered has a range or 400-700nm should be an ok test device. Not sure if I can set that wave length or how it works.
Thanks again.

Why is this equation R² = 0.9715 on the graph and what is the relation to the data on the USPRO graph?
I guess it's part of the calculation of the Agtron value.
Edited by HarryDog on 02/04/2023 10:55 PM
 
renatoa

Quote

R-Squared (R² or the coefficient of determination) is a statistical measure in a regression model that determines the proportion of variance in the dependent variable that can be explained by the independent variable. In other words, r-squared shows how well the data fit the regression model (the goodness of fit)

www.toppr.com/gui...d-formula/

In our case, the 0.97 value of R², means a very close fit to a proportional (linear) relation between the two wavelengths used for tests, shown also on the graph.
All data tell us that using any wavelength to evaluate of Agtron will led to an acceptable error, in the 3% ballpark.

Nerd enough ? Grin
Edited by renatoa on 02/08/2023 1:32 AM
 
HarryDog
I think I get the general idea, Thanks.
 
oldgrumpus

Quote

renatoa wrote:

Nerd enough ? Grin


NO! Just kidding!! I didn't think this thread would go "over the top" but my expectations were too low. Amazing indeed.

All joking aside, I'm learning way ABOVE what I expected to... and that's a very good thing!
Clever Coffee Dripper
Grinder: Macap M4
Roaster: Completed drum roaster project photos shown here:
Photos https://goo.gl/ph...Da6K4wfqw5
Videos https://www.youtu...Bd1NrdpSUH
 
HarryDog
So the Pro Colormeter came in and I have been doing some testing.
The test with the milk bottle forget that as it was a fail, the bottom glass is raised and has some texture on it and was no good.
I did find a glass with a flat bottom and these tests were fairly consistent. The reading inside the glass was about 40% the actual reading of the bean but it was consistent in the tests.

Reading Whole Beans, this was an issue if attempting to read a tray of beans from a roast, the reading varied an easy 2 points.
Now reading the round back of the whole bean was very close each time. I tested 10 random beans from a roast and was surprised they were so close. I have not tested ground beans yet.

I want to get my hands on a RoastRite card but no luck yet, don't really want the individual cards at 100USD + Shipping + Tax or Vat as that's crazy. Looking for one in North America that is not 2x the price of the meter. I only found one place that had stock and the price was ok but shipping was stupid. Most shops won't sell the card by itself either, shipping/importing the beans is a bit high.

I did get one card with beans in a kit and read that for fun, how accurate I don't know but this file is what the meter read next the the Roast name and then the color the app came up with and the true readings from Google.

Looks like PDF's are not allowed, loaded pictures!
HarryDog attached the following images:
chart3.jpg chart2.jpg chart1a.jpg

Edited by HarryDog on 02/18/2023 11:11 AM
 
oldgrumpus

Quote

HarryDog wrote:
...and the true readings from Google.


I think I understand most of your post but not sure what this means or how you confirmed from Google.
 
HarryDog
The app will provide a color to match the read of the card or coffee, I was using the CIElab color space, I then used the reading of the point in the color space that is represented by the color the app thinks it is and confirm with a Google search.

So for Blonde the meter reads this.
Blonde #725239 L=37.64 a=10.41 b=19.91
Google tells me #725239 is this
CIE-lab L=37.6757 a=10.0296 b=19.8914

So this looks like a close read but I don't know the value of the original card.
So the info the Meter and app is giving me can be confirmed with the Google search.

I can't tell you how accurate this is as I don't know the original card color space reading?

For what it's worth the info from the meter and app look to be confirmed by the info on the Color Hex site. When I visually compare the color it looks the same as the card.

I think the Meter and app would be a good tool to identify roast level on a budget. During a roast you would need to pull a bean to get a good read.

Hope I'm clearer with this as I'm no expert on color space but have played with some of this years ago.
 
HarryDog
Just did a roast.
Sumatran
#4e3d35 L=27.38 a=5.82 b=7.62 401.5 F (Full City) according to the chart.
HarryDog attached the following image:
sumatran2-19.jpg
 
renatoa
If would be mine, according to graph, this would be medium roast.
 
renatoa
Is the color really relevant? ... not enough to read the darkness only ?
How many hues could have a "coffee brown" to change the judgment, compared to a monochrome image ?
In colorimetry, brown is an mix of red and green. The coffee brown seems to be an equal balance of the both, I am unable to see any red or green hue in a coffee bean roasted of any degree. Many decades photographer eye...

The guy from Roast Vision sell for 300 his device made using a $5 pulse oximetry sensor, able to distinguish only 36 levels of gray... not even fifty Grin
And SCA quote him as innovative... Shock
Edited by renatoa on 02/20/2023 6:29 AM
 
HarryDog

Quote

renatoa wrote:

If would be mine, according to graph, this would be medium roast.


The Color chart I have, I have no idea how accurate it is but putting the beans on the card they are Full City to Dark.
The Chew taste test dark!

Now the artisan log shows my temps and I think they are low, using my guess at temps Medium?

Using the meter? Because they are positive numbers.

L= lightness
a= (red-green) or redness
b= (yellow-blue) or yellowness

So using the meter reads of the chart I have, the only one I have.

L- 27.38 (How light or dark) puts it at Full City
a=5.82 (How Red) puts it between Full City and Full City+
b=7.62 (How Yellow) puts it between Full City and Full City+

How relevant is the color? I don't know but visually using the chart I put the beans in between Full City and Full city + and I think the meter reading backs that up. Based on eating a bean (Blindfolded) I would say it was a Dark roast.

I'm sure some beans will present darker or lighter then others and the Sumatra is a darker earthier tasting bean?

Do you think I went wrong with comparing the bean to my created color chart?
 
ACEMBL
I’ve been keeping an eye on progress with this thread. Very interesting indeed. Within the visible spectrum Renatoa is spot on with the red green thing, it’s often used in agriculture for detecting ripeness of fruit and veg although not so good for brown.

From a little research it seems the best data might be found in the NIR range so I’ve ordered some bits to make a cheap colour spectrometer. There’s a chap on YouTube with instructions and code on GITHUB.

There are also some nice cheap, visible and NIR spectrum sensors on Sparkfun - plenty to ‘waste time’ on.
 
renatoa

Quote

HarryDog wrote:

Do you think I went wrong with comparing the bean to my created color chart?


No idea, especially on the chew test...
For my roast I am using mainly the weight loss to judge their roast level, regardless of any color and taste.
But weight loss judgment is valid only if related to greens humidity, else...
If you want an evaluation during roast, then color seems the way to go. For me is development time.
 
HarryDog
With my current roaster it's not so easy to check the beans during the roast so just checking after as one more data point.

Weight loss is 16.98%, so the sweet maria chart puts this at Burnt?
Other sites put this at high end of Medium.

What are some trusted numbers for roast levels based on temp and or weight loss? A site I should consider correct values to use as guidelines?
 
renatoa
17% loss is definitely FULL ! Shock You are good at chewing beans Grin
My roasts are mostly around 14%

Trusted number depends on your green moisture, is it in the 10-11% ballpark, at best ? Or 8-12%, at the worst...
My actual greens is 9.8%, measured in the shop at the moment of buy.
Depending on the storage conditions, you can experience severe loss, even 1% per week during summer and open bag.
 
HarryDog

Quote

ACEMBL wrote:

Within the visible spectrum Renatoa is spot on with the red green thing.


That's only part of it but yes. Info from the wiki.

The CIELAB space is three-dimensional and covers the entire gamut (range) of human color perception.
L* is the lightness value
a* axis is relative to the green–red opponent colors
b* axis represents the blue–yellow opponents

This link is a color representation of my result on this roast.
https://www.googl...=%234e3d35
 
renatoa
For those non familiar with the figures above...
CMYK is the color mode intended for printing with ink, i.e. reflected light, i.e. subtractive color model.
RGB is the color mode intended for screen displays, i.e generated light, i.e. additive color model.

CMYK should be used when evaluating real beans color (in the trier for ex.), under a neutral white light.
RGB should be used when looking on a display, a picture of those beans, taken under ideal conditions of exposure and white balance.
 
ACEMBL

Quote

HarryDog wrote:

Quote

ACEMBL wrote:

Within the visible spectrum Renatoa is spot on with the red green thing.


That's only part of it but yes. Info from the wiki.

The CIELAB space is three-dimensional and covers the entire gamut (range) of human color perception.
L* is the lightness value
a* axis is relative to the green–red opponent colors
b* axis represents the blue–yellow opponents

This link is a color representation of my result on this roast.
https://www.googl...=%234e3d35


Oh I agree CIElab is a good way of describing what’s seen. I was mainly pointing out the fact that the main change is observed in the red green axis. However, from what I’ve read (allowing for some companies not sharing their IP) most sampling equipment uses selective NIR wavelengths for the ‘agtron type’ scales as theres greater quantifiable difference across the roast range.
 
HarryDog
Yes from what I have read 880nm wavelength is used on some Agtron type units (Much more separation), I think I seen this on a spec sheet for an Agtron model as well. If I see that again will post the info, I just can't say for sure.

I was scanning that info to see what color space would be best to use on this cheap meter. So far samples of Hunterlab and CIElab were close. I just thought CIElab would be better at sampling more yellows? Then Hunterlab that expands in the blue area, but claims to be more uniform. Probably just a toss up.

Renatoa posted that paper from HunterLabs comparing 640nm to 880nm.
Edited by HarryDog on 02/20/2023 9:43 AM
 
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