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post #21 of 38 Old 02-19-13, 05:00 PM
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Re: Munsell N5

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Jason McKelvey wrote: View Post
This is what I came up with:

Colorant---BL---CL---FL---KXL
OZ--------3----0----0----7
384th-----54---176--64---0
Nope. Think base 384 math. You're not converting the mantissa back into 384ths

Do you really need a gallon of N5 paint or is this simply an intellectual exercise?
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post #22 of 38 Old 02-19-13, 05:02 PM
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Re: Munsell N5

Quote:
Jason McKelvey wrote: View Post
This is what I came up with:
Got it.

Colorant---BL---CL---FL---KXL
OZ--------3----0----0----7
384th-----208--176--64--32
BINGO!
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post #23 of 38 Old 02-19-13, 06:01 PM
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Re: Munsell N5

Harpmaker, I just realized that you are the one who took the Kodak credit card to the paint store. How do you know that it was truly neutral gray? I have purchased many 18% gray cards by various manufacturers and none of them match color wise.
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post #24 of 38 Old 02-19-13, 07:14 PM
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Re: Munsell N5

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Jason McKelvey wrote: View Post
Harpmaker, I just realized that you are the one who took the Kodak credit card to the paint store. How do you know that it was truly neutral gray? I have purchased many 18% gray cards by various manufacturers and none of them match color wise.
The N5 paint that results from this formula is more neutral than my Kodak Gray Card, I only used the Gray Card to get close. I then used color theory and a spectrophotometer to get the paint more neutral by trial and error. IIRC it took me three tries to get the final mix to it's current level of neutrality.
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post #25 of 38 Old 02-19-13, 09:59 PM
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Re: Munsell N5

You rock dude. I'm so glad there's forums like this and guys like you to take it to the next level for guys like me thanks a lot!
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post #26 of 38 Old 02-20-13, 01:16 AM
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Re: Munsell N5

Thank you very much sir!
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post #27 of 38 Old 07-22-13, 06:00 PM
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Re: Munsell N5

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Harpmaker wrote: View Post
The N5 paint that results from this formula is more neutral than my Kodak Gray Card, I only used the Gray Card to get close. I then used color theory and a spectrophotometer to get the paint more neutral by trial and error. IIRC it took me three tries to get the final mix to it's current level of neutrality.
Hi,

I am acquiring a grading suite for colour correcting video, and have been trawling the web for info about neutral gray paint and where to get it, with surprisingly confusing results. You guys seem far more knowledgeable than those that are on the colour grading forums so I thought I'd ask you. First off I will show you what I am trying to achieve with the walls:

Attachment 43188
Attachment 43189

The first priority is that they are neutral (in L*a*b* colour space, a* and b* being between -0.5 and +0.5). Secondly, as I'd rather have 2 shades on the go instead of a rather bland 1, rather than have just 50% gray (in terms of lightness, not reflectance) I'd like to have two shades equally far apart from 50%, say 25% and 75% (thereabouts is good enough).

Addressing the first point:
a) research suggests that if I go to a custom paint mixer and ask for nothing but black, it won't actually be a neutral black; similarly for white
b) taking an 18% gray card for colour matching won't get me neutral either
c) I have a Gretagmacbeth Eye1 Display 2 spectrophotometer, but can this be used to assess neutrality? So far I've only used it for monitor calibration, by placing it directly on the monitor surface - but they emit their own light. How are you using your probe, is it designed to assess more than monitors?
d) If my Eye1 is of no use I plan to buy a WhiBal white balance card (which is certified neutral), then take a photo of the (dried) paint with the WhiBal in frame (using a single light source), correct the image so that the WhiBal is displayed in my software as being neutral and compare to the walls using both a vectorscope and the digital color meter you get in Mac OSX
e) Once I've seen how bad things are, is it a particularly complex trial-and-error process to get to within acceptable levels of neutrality? If this was video and it was too yellow I'd just add some blue, but I don't know if paint works that way
f) I could just take my WhiBal to a paint mixer and have them match that, but then presumably when I ask them to make it darker things will go awry again

Addressing the second point:
Research suggests that mixing white and black paint in a ratio of 1:1 won't actually get me a gray that is perfectly in the middle, rather I will get a shade of gray heavily biased towards black. Therefore trying 1:3 and 3:1 for 25% and 75% is similarly futile. Is this true? The exercise on this webpage suggests I'd be fine going with the simple maths: http://kaplanpicturemaker.com/ccc_pa...-i_assignments

---------------------------
Now, the lightness value of a WhiBal is in fact 75 so that would sort that one out, but then I'd still need to get the 25% shade. This assumes that I would like the look of 25% and 75% of course, the shades in the images look like they may be more around 50% than that.


Any insights or rebuttals to anything I've said above would be most welcome
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post #28 of 38 Old 07-23-13, 08:28 AM
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Re: Munsell N5

The attachments didn't show up. It may be because you didn't have 5 posts at the time or because you posted a bit too quickly after your fifth post.

a) In our experience, this is correct.
b) This is going to be hit or miss. Generally speaking, the equipment at most paint stores isn't that accurate as it has no real need to be that accurate. It just has to be close (within a dE of 3) for paint. You could get an accurate match but if you did it 9 more times, 7 of the 9 could be unacceptable.
c)You can use your i1pro to measure paint. We use a variety of programs to do it. I use BabelColor and/or CalMAN normally. But those cost money. You should be able to use the free software from X-Rite to get simple readings. I know that I used it for awhile but it does require some conversion as I believe it uses D50 as the standard. Harpmaker probably knows of some free software that escapes me right now. He'll chime in if he does.
d) No need as the i1pro will work.
e) When dealing with just paint, you are correct. It can be tough sometimes though, especially when you throw in something much more complex such as aluminum.
f) It may be tough getting that 25%.

Have you looked into the GTI Neutral gray paint? It's my understanding that that is what the pros use. It's a little bit expensive but if you're looking for accuracy, I'd think it should be there. I know that they make a N8 or a N7 paint IIRC. If you really want the darker gray as well, what I would do would be to add 'Mars Black' (Liquitex and Golden sell this in an artist acrylic) to the GTI paint until you get it as dark as you require - double checking for neutrality along the way.


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post #29 of 38 Old 07-23-13, 05:46 PM
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Re: Munsell N5

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c)You can use your i1pro to measure paint. We use a variety of programs to do it

Have you looked into the GTI Neutral gray paint? It's my understanding that that is what the pros use. It's a little bit expensive but if you're looking for accuracy, I'd think it should be there. I know that they make a N8 or a N7 paint IIRC. If you really want the darker gray as well, what I would do would be to add 'Mars Black' (Liquitex and Golden sell this in an artist acrylic) to the GTI paint until you get it as dark as you require - double checking for neutrality along the way.
I'll look into those programs but I think you have the wrong idea about which probe I have. I have this one:

http://www.xrite.com/product_overvie...Specifications

and I'm guessing you have this one:

http://www.xrite.com/i1basic-pro-2

I'm going to do some more research but I think i might be out of luck. Can you just hold your probe up to a wall then or do you need a sample on a piece of paper? And how far away do you hold it? And I'm guessing that ambient light isn't a factor.

I'm going to try one of the attachments again:

Munsell N5-dr2.jpg

As for GTI that looks very helpful thanks, I can get it in N8 in the UK, I'll do more digging though to see if I can get N7. Wouldn't have guessed you could mix artist paint with wall paint successfully
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post #30 of 38 Old 07-24-13, 09:14 AM
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Re: Munsell N5

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mintgreen wrote: View Post
I'll look into those programs but I think you have the wrong idea about which probe I have. I have this one:

http://www.xrite.com/product_overvie...Specifications
I just saw where you said you had an i1pro spectro. I missed the Display 2 part. You have a colorimeter, not a spectro.

Quote:
mintgreen wrote: View Post
I'm going to do some more research but I think i might be out of luck. Can you just hold your probe up to a wall then or do you need a sample on a piece of paper? And how far away do you hold it? And I'm guessing that ambient light isn't a factor.

I'm going to try one of the attachments again:

Attachment 43203

As for GTI that looks very helpful thanks, I can get it in N8 in the UK, I'll do more digging though to see if I can get N7. Wouldn't have guessed you could mix artist paint with wall paint successfully
A close N3 match would be S7500-N and a close N2.5 match would be S8000-N. You should be able to find a paint store that knows how to mix these up. If you need verification, you can send a sample to Harpmaker or myself and we can get a reading for you.


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