What are the RGB values of a Kodak colour card if correctly exposed ?

[DBenz01]

Hi,

If I were to take a technically correct exposure of a pair of Kodak cards, one being the colour card, the other the greyscale one, what RGB values should I see for the Grey upper portion of these cards, and also for the individual colours ?

I have tried to photograph some paint chip colour charts to establish their RGB values for PC sim use, and had in the photo the kodaks as well. I took incident light readings (light source onto subject) using a luminos light reading disc that fitted the lens thread diameter, quickly set camera to manual given the suggested reading and took the shot, but feel the result is a bit dark, and photographing adjacent subjects immediately afterwards made them also darker than they were.

I have one shot that is visually pretty close to the kodaks, but wish to know what tweak to exposure in raw converter will get the kodak bang on ! Knowing the rgb value I can tweak and measure and tweak a bit more until kodaks are at best. Shots will also be adjusted for colour imbalance but having taken them about 1pm light shouldnt be too far out, however I will click the grey pipette on the grey to adjust , but again if I know the rgb value for that grey I can see if that adjustment was ok.

DBenz

 

[Iliah Borg]

Hi,

If I were to take a technically correct exposure of a pair of Kodak cards, one being the colour card, the other the greyscale one, what RGB values should I see for the Grey upper portion of these cards, and also for the individual colours ?

The card in question, is it Q13/Q14 or IT8.7?

What RGB colour space do you have in mind?

The whitest patch on Q13/Q14 is approximately L*=96.5, or close to G=245 in gamma 2.2 RGB colour spaces.

The whitest patch on IT8.7 is close to L*=92, or 231 RGB.

That is all you need if you are shooting in raw and your conversion procedure is accurate. Exposure is set for the highlights, and with even light and good conversion all other values simply fall in place.

 

[Mike_PEAT]

Just do a internet search for your card and add the words RGB VALUES (one I found):

 

[Iliah Borg]

Just do a internet search for your card and add the words RGB VALUES (one I found):

You need to know whom to trust. Internet is full of misinformation.

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[Michael Fryd]

Just do a internet search for your card and add the words RGB VALUES (one I found):

The correct RGB value will vary depending on the colorspace you are working in.

The RGB values shown in the above for Blue, Cyan, Green, Yellow, etc., seem to be for some idealized pure color, as opposed to the desired value for the color target.

 

[Iliah Borg]

Just do a internet search for your card and add the words RGB VALUES (one I found):

The correct RGB value will vary depending on the colorspace you are working in.

The RGB values shown in the above for Blue, Cyan, Green, Yellow, etc., seem to be for some idealized pure color, as opposed to the desired value for the color target.

Unfortunately, it is not just that, "idealized pure space". This "space" is a figment of imagination. Everything is wrong with that illustration, everything. Starting from the fact that "M" is definitely in Zone V.

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[DBenz01]

Hi,

I am referring to the Q13 8 inch long, and I am working in AdobeRGB1998 on camera and in Photoshop.

https://www.bhphotovideo.com/c/product/26662-REG/Kodak_1527654_Color_Separation_Guide_and.html

So I just wish to ensure the greyscale is correct and the exposure is correct. Thats what the cards are for. So there must be a way of suing them and checking against target figures (RGB) . Click on the grey area with grey pipette in RAW converter and it eliminates the colour cast from a blue sky or an evening light etc. Then adjust exposure slider until the grey RGB value matches that of the values if the correct exposure had been used.

but we as yet havent established what that grey value is in RGB !

The colour values will sort themselves out if the picture is adjusted to correct colour balance and greyscale. However, I ask of the colours though because my grey tops to these two cards appears a bit lighter to another set of these I have, that set being a more recent purchase, but I have mislaid them. All are kept in their sleeves, so having used the earlier set I need to double check the colours match target RGB after assuming the grey is how it should be.

I dont find by the way that the white first 'cell' of the greyscale looks 100% white, its not dirty, just never struck me as pure brilliant white.

and now I find this article:-

http://lists.apple.com/archives/colorsync-users/2008/May/msg00065.html

which has maybe what I need, assuming if I enter those LAB values I get a unique set of RGB appear in pshop.

also note mention of variance in the printing standard, Kodak, you surprise and dissapoint me !

So what would be a better chart to use ?

DBenz

 

[Iliah Borg]

I am referring to the Q13 8 inch long, and I am working in AdobeRGB1998 on camera and in Photoshop.

If you are shooting JPEGs, no practical chance the values will fall in place. That is primarily because in-camera JPEG engines are not for reproduction, they apply rather drastic tone curves. You choose your poison here - either get "M" patch at around 110-120 (cards are not calibrated, my cards are around 115 at that patch); or get the "A" patch to around 243 (all numbers are for green channel).

In case you shoot raw, 2 problems - first one is even lighting and no flare, second - the tone curve your raw converter applies.

Here are numbers, measured from the card with a spectrophotometer and converted to Adobe RGB:

A - 243

1 - 217

2 - 194

3 - 178

4 - 157

5 - 142

6 - 128

M - 115

8 - 104

9 - 93

10 - 84

11 - 75

12 - 68

13 - 61

14 - 55

15 - 50

B - 45

17 - 41

18 - 37

19 - 34

 

[DBenz01]

Hi,

I am shooting RAW files on a Canon EOS 70D. I only ever shoot RAW.

you have lost me there. what do those numbers refer to, a different card ?

I google A patch and dont find a card with grey and colour squares on it I can place in shots.

I have the Kodaks in my photos and just need to ensure they match their theoretical look in AdobeRGB. I have taken 100's of pics over the years I need to use them to adjust those pics.

DBenz

 

[Iliah Borg]

what do those numbers refer to, a different card ?

Q13 consists of two cards, gray scale and colour separation. The numbers refer to gray scale card Q13. Is it the colour control portion of that card that you want? That one is not designed for exposure control, it is for old CMYK separation process. I can give its numbers for AdobeRGB, of course:

Name R G B

"Light_Blue" 243.473 240.670 229.074

"Blue" 113.479 100.212 151.237

"Light_Cyan" 232.292 237.325 222.258

"Cyan" 39.255 157.842 200.724

"Light_Green" 222.769 227.829 192.470

"Green" 83.448 156.321 78.440

"Light_Yellow" 246.280 236.952 163.699

"Yellow" 248.129 222.480 52.150

"Light_Red" 234.436 201.450 155.827

"Red" 191.807 67.359 70.052

"Light_Magenta" 242.981 222.436 193.704

"Magenta" 186.805 24.702 90.269

"White" 247.637 245.723 237.539

"Light_Brown" 195.278 184.085 132.714

"Brown" 106.988 89.230 80.456

"Light_Gray" 233.699 231.318 215.430

"Black" 53.318 50.971 50.392

"Gray_Surround" 156.484 155.715 148.961

I google A patch and dont find a card with grey and colour squares on it I can place in shots.

On your link

https://www.bhphotovideo.com/c/product/26662-REG/Kodak_1527654_Color_Separation_Guide_and.html

"A", "M", "B" are rather visible.

 

[DBenz01]

Hi , thanks, those numbers will do for me

gives the the grey area rgb as well as the colour squares,

If I deliberately alter the exposure slider in RAW mode and the photo contains the Q13 greyscale, the segments 18 19 and 20 dont immediately go all black and fuse together, if I brighten the shot and drag exposure higher, segments 1 and 2 dont become one white area, so I am wondering how can one use Q13 to correct for exposure, simply slide that slider until the grey is the rgb value for the Q13 grey I presume., having first neutralised any colour cast by using pipette on the grey.

DBenz

 

[DBenz01]

Hi, Iliah Borg your numbers when I create the rgb mix in photoshop colour palette with e.g. light blue 243 240 229 I get a pale cream and nothing like the light blue on the kodak card, the blue values also are a notably paler blue, cyan green look nearer though light cyan is a pale green with those numbers.

cant use them as such, whats going on ?

:-(

DBenz

 

[D Cox]

Hi, Iliah Borg your numbers when I create the rgb mix in photoshop colour palette with e.g. light blue 243 240 229 I get a pale cream and nothing like the light blue on the kodak card, the blue values also are a notably paler blue, cyan green look nearer though light cyan is a pale green with those numbers.

cant use them as such, whats going on ?

You have the numbers in reverse order.

 

[Iliah Borg]

Hi, Iliah Borg your numbers when I create the rgb mix in photoshop colour palette with e.g. light blue 243 240 229 I get a pale cream and nothing like the light blue on the kodak card, the blue values also are a notably paler blue, cyan green look nearer though light cyan is a pale green with those numbers.

cant use them as such, whats going on ?

Must have typed in the wrong order, and the card may have faded too, sorry.

Here is from a known good one, amend the table:

Light Blue 236, 242, 243.

Blue 114, 100, 162

Light Cyan 222, 238, 236

Cyan 0, 159, 214

Light Green 213, 229, 203

Green 0, 158, 78

Light Yellow 242, 238, 171

Yellow 250, 223, 34

Light Red 239, 202, 164

Red 214, 69, 76

Light Magenta 243, 223, 205

Magenta 212, 27, 98

White 240, 247, 252

Light Brown 193, 185, 139

Brown 110, 90, 85

Light Gray 227, 232, 228

Black 52, 51, 54

Gray Surround 151, 156, 158