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Author Topic: Colour print viewing filters  (Read 1077 times)
Jason DiMichele
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« on: March 21, 2014, 11:05:58 PM »
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Hey folks,

The other day I was making a number of prints from an art reproduction and was trying to tweak the colour as close as possible. I finally got to a very good match and the client was very happy with the result. However, although I've got a colour managed environment and using soft proofing, I had an idea that I thought may be beneficial. I was wondering if using colour print viewing filters would assist with quicker colour matching of slight colour variations than soft-proofing and then making test prints would. I originally thought of looking online to purchase some then realized that I had some good quality inkjet clear film and could print my own. I would be able to print the equivalent of -/+5,10,15, etc CC of Cyan, Magenta and Yellow filters. I could print a set with larger variations in order to narrow the colour correction down and then print a set of finer variation filters to get as close possible. Thoughts?

Cheers,
Jay
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Jason DiMichele
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« Reply #1 on: March 21, 2014, 11:17:02 PM »
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Well, the problem would be exactly how to create the correct tint and print them so that they would be accurate and meaningful. I agree that viewing filter would be useful but primarily for identifying the exact cast and tint correction. Looking at a color wheel, it's tough to determine if a color cast is a single color or a mixed color...that's where the viewing filter would be useful. Is the cast only red or is it red/magenta...and by how much?

Also, the question is are you going to use them to make corrections (adding filters and viewing the print while flicking the filters in/out) or identifying the cast (laying the filters on white paper to identify the cast ad amount)?

Color casts and color corrections can be difficult...so use whatever works!
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« Reply #2 on: March 21, 2014, 11:29:15 PM »
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I assume that you are talking about placing a color correction filter over your proof to try to make a visual match against the original?

It's an interesting thought, but I see a few shortcomings with that concept.  First, is that if you are viewing through a shiny material, it will be tough to make an accurate comparison, as the surface and reflections will be quite different.  Also, I have yet to see an inkjet film that maintains transparency, even with dye based ink, so I can't see how printing your own would be much help.  You could get color correcting lighting gel, like CTO for tungsten/daylight conversion, and it comes in various densities that are totally transparent.  I'm not sure that it would offer much more than a vague direction to lean the adjustment, though, as it wouldn't really be likely to have any correlation to what +5 of cyan (for instance) in Photoshop would give you.

More significantly, though, is that this approach would only seem to be useful for global color adjustments.  Aside from a minor global value adjustments that I make with curves, I rarely use adjustment layers for art reproduction that are uniform corrections to the overall hue of the file.  With an accurately set white balance, the focus for me in color correcting to match an original painting is in dealing with metamerism and quirks in the profiles and the sensor's recording of very specific parts of the spectrum.  I find that most of those corrections are specific to the paint and substrate in specific works.  

If I shoot a MacBeth Color Checker, it comes out perfect without the need for any adjustments.  A patch of oil paint that looks to my eye to be an exact match to the sky blue patch of the CC, though, may look more cyan or magenta.  It's really a case by case tweaking that I find is required, and often my adjustments are made with Hue/Saturation or Color Balance adjustment layers targeted to a very specific hue with a mask made using the Color Range tool in Photoshop.  I don't see how physical filters would be worth much for that type of issue, except perhaps as a learning tool to train your eye to see which direction a color needs to be leaned.
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Some Guy
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« Reply #3 on: March 21, 2014, 11:57:59 PM »
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I use the Lee Color Print Viewing Filters all the time.  Very similar to the old Kodak Wratten Color Viewing Filters.  http://www.bhphotovideo.com/c/product/287849-REG/LEE_Filters_VK3_3_Density_Color_Print.html

Works best with a neutral grey for the color selection and determination with the filters.  How much of the filter to apply to your RGB changes in your editor of choice is up for grabs though since they were for older color printing filter packs with chemicals.  Too bad there isn't a easy cross reference between them and the RGB numbers - or I haven't found one yet.  I know with something like Qimage, you can look at a filter of say a "Red 0.05" strength and maybe change the Qimage editor to Red 1.10 or so to see a change in the subsequent print.  Qimage has some odd numbers that go quite high for density values in the editor and not RGB related.

SG
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Ernst Dinkla
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« Reply #4 on: March 22, 2014, 06:11:29 AM »
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If I shoot a MacBeth Color Checker, it comes out perfect without the need for any adjustments.  A patch of oil paint that looks to my eye to be an exact match to the sky blue patch of the CC, though, may look more cyan or magenta.  It's really a case by case tweaking that I find is required, and often my adjustments are made with Hue/Saturation or Color Balance adjustment layers targeted to a very specific hue with a mask made using the Color Range tool in Photoshop.  I don't see how physical filters would be worth much for that type of issue, except perhaps as a learning tool to train your eye to see which direction a color needs to be leaned.

What I experience too. If a reproduction fails it is most often on one hue that can not be compensated by an overall color shift but has to be separated for special treatment.

I did use Pantone transparent patches from a guide that I think is no longer produced. Artists painted silkscreen film positives for me and in the printing process we discussed the next ink color based on the Pantone filtering of the first inks laid down. Not a typical CMYK process, 7 colors was not unusual. Worked quite well but there was no digital translation needed, I mixed the next transparent ink to be printed based on the selected patch color.
An example http://www.pigment-print.com/Jacques_van_Erven.htm

An interesting approach would be light of an RGB controlled LED spot surrounded by D50 light of equal strength so the eye can not adapt and by that observing the influence of the RGB selection. The last then correlating with RGB settings in Photoshop.

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Jason DiMichele
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« Reply #5 on: March 22, 2014, 10:15:33 PM »
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Well, the problem would be exactly how to create the correct tint and print them so that they would be accurate and meaningful. I agree that viewing filter would be useful but primarily for identifying the exact cast and tint correction. Looking at a color wheel, it's tough to determine if a color cast is a single color or a mixed color...that's where the viewing filter would be useful. Is the cast only red or is it red/magenta...and by how much?

Also, the question is are you going to use them to make corrections (adding filters and viewing the print while flicking the filters in/out) or identifying the cast (laying the filters on white paper to identify the cast ad amount)?

Color casts and color corrections can be difficult...so use whatever works!

Hi Jeff,

Thank you for your feedback. I suppose to determine if a cast was a mixed colour I could have a set of filters printed at half density so that I stack them on top of each other they would be the equivalent density of a single filter. Although the combinations of required filters may get out of hand, I suppose this is something that may work. I think the way I would use the filters would be flicking the filters in/out as I'm viewing the print.

Cheers,
Jay
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Jason DiMichele
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« Reply #6 on: March 22, 2014, 10:28:14 PM »
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Hi Colorwave,

Some great feedback, thanks!

I assume that you are talking about placing a color correction filter over your proof to try to make a visual match against the original?

Yup!

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It's an interesting thought, but I see a few shortcomings with that concept.  First, is that if you are viewing through a shiny material, it will be tough to make an accurate comparison, as the surface and reflections will be quite different.  Also, I have yet to see an inkjet film that maintains transparency, even with dye based ink, so I can't see how printing your own would be much help.  You could get color correcting lighting gel, like CTO for tungsten/daylight conversion, and it comes in various densities that are totally transparent.  I'm not sure that it would offer much more than a vague direction to lean the adjustment, though, as it wouldn't really be likely to have any correlation to what +5 of cyan (for instance) in Photoshop would give you.

With regard to viewing through a shiny material, I think the colour print viewing filters back in the day were on the shiny side weren't they? The inkjet film that I've got is InkPress Media Clear Film. They state that it is designed for overlays, colour keys, colour separations, etc and has a glossy finish, low haze, extremely clear, very smooth and utilizes a low ink load. The gels are an interesting idea. The method of determining the correlation of a gel would be difficult but if the Inkpress Media film worked well it would be relatively easy to determine the correction amount I think.

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More significantly, though, is that this approach would only seem to be useful for global color adjustments.  Aside from a minor global value adjustments that I make with curves, I rarely use adjustment layers for art reproduction that are uniform corrections to the overall hue of the file.  With an accurately set white balance, the focus for me in color correcting to match an original painting is in dealing with metamerism and quirks in the profiles and the sensor's recording of very specific parts of the spectrum.  I find that most of those corrections are specific to the paint and substrate in specific works.  

Excellent point about colour corrections not often required globally. However, there is potential to use the filters for areas of the repro that aren't minute. As long as the area is large enough they could be used to determine cast corrections all over the print. For your workflow are you creating a camera profile? If so, is it a DNG or ICC profile? Are you using the MacBeth colour checker as you mention below to create the profile with?

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If I shoot a MacBeth Color Checker, it comes out perfect without the need for any adjustments.  A patch of oil paint that looks to my eye to be an exact match to the sky blue patch of the CC, though, may look more cyan or magenta.  It's really a case by case tweaking that I find is required, and often my adjustments are made with Hue/Saturation or Color Balance adjustment layers targeted to a very specific hue with a mask made using the Color Range tool in Photoshop.  I don't see how physical filters would be worth much for that type of issue, except perhaps as a learning tool to train your eye to see which direction a color needs to be leaned.

Definitely food for thought, thanks again! Smiley

Cheers,
Jay
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Jason DiMichele
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« Reply #7 on: March 22, 2014, 10:34:06 PM »
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I use the Lee Color Print Viewing Filters all the time.  Very similar to the old Kodak Wratten Color Viewing Filters.  http://www.bhphotovideo.com/c/product/287849-REG/LEE_Filters_VK3_3_Density_Color_Print.html

Works best with a neutral grey for the color selection and determination with the filters.  How much of the filter to apply to your RGB changes in your editor of choice is up for grabs though since they were for older color printing filter packs with chemicals.  Too bad there isn't a easy cross reference between them and the RGB numbers - or I haven't found one yet.  I know with something like Qimage, you can look at a filter of say a "Red 0.05" strength and maybe change the Qimage editor to Red 1.10 or so to see a change in the subsequent print.  Qimage has some odd numbers that go quite high for density values in the editor and not RGB related.

SG


Hi SG,

So when you use the filters, are you then just using them to determine a rough colour cast? Generally how many times are you tweaking in post processing and printing proofs with the use of the filters? If I was to make my own filters (or purchase some), there would have to be the benefit of it making the colour correcting much more efficient than multiple test prints. I suppose to determine what the correlation is you could print a step wedge?

Cheers,
Jay
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Jason DiMichele
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« Reply #8 on: March 22, 2014, 10:46:12 PM »
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What I experience too. If a reproduction fails it is most often on one hue that can not be compensated by an overall color shift but has to be separated for special treatment.

Hi Ernst,

What is your preferred method of corrected the various hues that need adjusting? Are you also using a method similar to Colorwave's? It almost seems as though the consensus is to not use the filters but to just be very careful with soft proofing and test prints. I do realize that there are some colours that can't be reproduced with inkjet technology, but I'm hoping that the filters may speed up the process even though there isn't a uniform global cast.

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I did use Pantone transparent patches from a guide that I think is no longer produced. Artists painted silkscreen film positives for me and in the printing process we discussed the next ink color based on the Pantone filtering of the first inks laid down. Not a typical CMYK process, 7 colors was not unusual. Worked quite well but there was no digital translation needed, I mixed the next transparent ink to be printed based on the selected patch color.
An example http://www.pigment-print.com/Jacques_van_Erven.htm

This process sounds quite interesting!

Quote
An interesting approach would be light of an RGB controlled LED spot surrounded by D50 light of equal strength so the eye can not adapt and by that observing the influence of the RGB selection. The last then correlating with RGB settings in Photoshop.

Now that would be cool. Almost as though you could soft proof through hardware. By continually moving the LED spot around you could make notes to which areas of the print would require which correction. Or to take it a step further (and perhaps overkill), you could have a hardware/software interface that would perform the proper adjustment when you signal an "OK" from the LED hardware. But maybe I'm dreaming. The eyes might no nutty after a while of using it as well perhaps. Smiley

Cheers,
Jay
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Jason DiMichele
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« Reply #9 on: March 23, 2014, 09:56:07 AM »
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I had an idea that I thought may be beneficial. I was wondering if using colour print viewing filters would assist with quicker colour matching of slight colour variations than soft-proofing and then making test prints would.
A good ring-around print would probably work better if I understand your problem. Remember that great old Photoshop plug-in "Test Strip"?
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Andrew Rodney
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« Reply #10 on: March 23, 2014, 11:36:10 AM »
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Hi SG,

So when you use the filters, are you then just using them to determine a rough colour cast? Generally how many times are you tweaking in post processing and printing proofs with the use of the filters? If I was to make my own filters (or purchase some), there would have to be the benefit of it making the colour correcting much more efficient than multiple test prints. I suppose to determine what the correlation is you could print a step wedge?

Cheers,
Jay


I just flip the Lee Print Viewing Filters (or the old Kodak set) in-and-out while looking at a neutral gray in a print, or even mix them for odd colors like "puke" yellow & green mix, or "burple" which is a blue and magenta mix.  They work well for those, and I use them in fine-tuning my work a lot.

In bright areas like skin, they don't provide as reliable feedback as a neutral gray so a step wedge may not work well with them.  Kodak used to promote that instruction when using their print viewing filter set.  Hard to get an exact handle as to how much color to add or subtract in the ink using them, but you get a general feel as to which way to go.  I believe I posed that to Lee long ago and they responded with the filters being a CC-type and no concrete answer to RGB numbers using them.  Wish there was a viewing set where 10 points RGB "Red" print-to-ink value was exactly a 10 point "Red" viewing RGB filter, but doesn't seem to be anything out there.

Sadly, using them is not an exact science, but seems neither is the ICC profiling either since monitors have huge Kelvin color casts around the screen and we generally only spot read one place on a monitor (i1 Profile Pro 2 has some ability to read 9 areas on a screen for Kelvin, but you cannot adjust those nine areas individually as can a factory calibration like Eizo does to their better screens and for big $$$ too!).  x-rite mentioned in one of their webinars that no two monitors are ever alike.  Even 10 labs using their own profiles hand me back 10 different looking prints, or one reprint handed back days later looks different from same lab.  Maddening!

At least for me, I get an idea using the Lee filter set if the print color has a yellow or a green cast and how much since the 3 filters on each card are stepped in density and I can overlap them in various ways.  Sometimes hard to distinguish which is at play and sometimes adding a blue and slight magenta both clean up the neutral gray respectively.  Stare at it long enough and you might find some other issues in shadows or highlights, and then you are back to wild crossovers in the RGB curves and tuning with the filters to null that.  I can burn through a box of paper easily trying to get one print where I want it:  Monitor and print are never exact no matter how much I profile and mess with it, and I use Qimage a lot for fine tuning that picky part (and I'm getting a feel I like my prints "warmer" too over the monitor!).

Good luck!

SG
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« Reply #11 on: March 23, 2014, 01:20:07 PM »
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A good ring-around print would probably work better if I understand your problem. Remember that great old Photoshop plug-in "Test Strip"?

Hi Andrew,

That's an interesting idea indeed! Maybe I will play around with printing a test. I guess the trick would be to make one ring with a more coarse variant and a few with finer tuned variations. Like I would have done if I print the square filters I think having both will allow me to narrow down the cast better. How large would you consider would be an appropriate circle size (both the inner hole cutout and the diameter/circumference) when I try the wheel filter?

Thanks for your input!

Cheers,
Jay
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Jason DiMichele
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« Reply #12 on: March 23, 2014, 05:46:41 PM »
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Hey SG,

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I just flip the Lee Print Viewing Filters (or the old Kodak set) in-and-out while looking at a neutral gray in a print, or even mix them for odd colors like "puke" yellow & green mix, or "burple" which is a blue and magenta mix.  They work well for those, and I use them in fine-tuning my work a lot.

In bright areas like skin, they don't provide as reliable feedback as a neutral gray so a step wedge may not work well with them.  Kodak used to promote that instruction when using their print viewing filter set.  Hard to get an exact handle as to how much color to add or subtract in the ink using them, but you get a general feel as to which way to go.  I believe I posed that to Lee long ago and they responded with the filters being a CC-type and no concrete answer to RGB numbers using them.  Wish there was a viewing set where 10 points RGB "Red" print-to-ink value was exactly a 10 point "Red" viewing RGB filter, but doesn't seem to be anything out there.

Those are some pretty funky colour names. lol. I've seen a lot of pieces of art that don't necessarily have any neutral grey in them. So your method may not work so well on those I'm assuming. About the issue of knowing the correlation of the CC value and how it corresponds to post processing, that's why I think that printing my own instead of buying some may work better because I will know which RGB values I used to print the filters therefore would be able to apply the appropriate values (plus or minus) to the image. That's my theory anyway. Sometimes things don't work out as planned! Wink

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x-rite mentioned in one of their webinars that no two monitors are ever alike.  Even 10 labs using their own profiles hand me back 10 different looking prints, or one reprint handed back days later looks different from same lab.  Maddening!

Yeah my two NEC PA241W's are slightly different even though they've both been calibrated with the same process and an i1Photo Pro 2 profiling package. I can understand that 10 labs may have different results based on their knowledge of colour management and the quality of their tools. but I'm a little surprised that the same lab wouldn't be able to produce the same print within days of each other. Unless they replaced the ink or paper (of the same manufacturer) that deviated from manufacturing tolerances.

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Stare at it long enough and you might find some other issues in shadows or highlights, and then you are back to wild crossovers in the RGB curves and tuning with the filters to null that.  I can burn through a box of paper easily trying to get one print where I want it:  Monitor and print are never exact no matter how much I profile and mess with it.

On the most recent repro I did the more I stared at the print and the original they almost started to look the same! lol. It's amazing how intelligent our vision system is with regard to adapting brightness, colour, etc. And yes, although one can get extremely close with a monitor and print match, it'll never be 100% exact. Just like when I'm trying to match a pigment inkjet print with an oil, pastel, etc original.. it'll never be 100% accurate (and it's known that some colours won't reproduce that closely at all).. my goal is to be able to come as close as possible while utilizing my time as effectively as possible. Knowing when good enough is good enough is a learned skill for sure! Smiley

Cheers,
Jay
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« Reply #13 on: March 23, 2014, 08:43:43 PM »
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Thinking more about this, wonder if one could print the complementary colors on their own inkjet printer in differing densities on clear inkjet film and use those for correcting the RGB in PS?

Eg:  Begin with printing the best RGB 128, 128, 128 you can and verify with the Profiler it is that, and then add 10 points of cyan to that and then subtract the 128 gray neutral, just so the thing will print a density and not some odd non-linear color thing by beginning with RGB of 0, 10, 10?  Maybe a density of 5, 10, 15, and 20 cyan RGB values for one viewing sheet?

At least you might know how much red RGB with the above to cancel that in PS.

My own experiments seem to not always follow that a -10 RGB red in PS will equal a -10 RGB red in the print, but may change a bit of the yellow and magenta as well for that -10 red.  Inks don't play nice together, and I had a incident where the black channel plugged solid and all I saw was strong cyan where the black should have been.  So black and cyan both mix together for my printer's Photo Black it seems.  Then again, I've bought OEM yellow ink from Canon and one was obviously orange, and the other cart more yellow.  Dunno.  Probably would need to do it with each printer and different ink too.

SG
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« Reply #14 on: March 25, 2014, 03:10:43 PM »
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Thinking more about this, wonder if one could print the complementary colors on their own inkjet printer in differing densities on clear inkjet film and use those for correcting the RGB in PS?

Eg:  Begin with printing the best RGB 128, 128, 128 you can and verify with the Profiler it is that, and then add 10 points of cyan to that and then subtract the 128 gray neutral, just so the thing will print a density and not some odd non-linear color thing by beginning with RGB of 0, 10, 10?  Maybe a density of 5, 10, 15, and 20 cyan RGB values for one viewing sheet?

At least you might know how much red RGB with the above to cancel that in PS.

My own experiments seem to not always follow that a -10 RGB red in PS will equal a -10 RGB red in the print, but may change a bit of the yellow and magenta as well for that -10 red.  Inks don't play nice together, and I had a incident where the black channel plugged solid and all I saw was strong cyan where the black should have been.  So black and cyan both mix together for my printer's Photo Black it seems.  Then again, I've bought OEM yellow ink from Canon and one was obviously orange, and the other cart more yellow.  Dunno.  Probably would need to do it with each printer and different ink too.

Hey SG,

Your thought about printing on one's own printer with varying densities, etc is the reason I started this thread. That's what I wanted to know is if it was worth me printing my own colour print filters. I don't think using the profiler to verify that the colour is dead on really matters because you would know the RGB values you used to create the filter and therefore would know how which values to use to process (once the relationship of how much adjustment on the monitor correlates with how much is required for the paper) with if the filter corrects the cast on the original. The values would all be relative.

A -10 Red adjustment won't be a direct match to that same -10 Red adjustment on the print, but it will be relative - it doesn't matter that a -10 Red on the monitor has as much or less impact as a -10 Red on the print as long as you know the value to change to make the print more colour accurate.  However, having the system calibrated as accurately as possible (for example using the custom white target in SpectraView for each paper you use) will help get closer.

You've purchased an OEM ink for your printer which was orange but should have been yellow? Not sure I've ever seen or heard of that one. lol. Not sure what you mean by needing to do it with each printer and different inks. Both of my printers use the same ink set and I'm using the same media on both (except canvas). With a properly profiled printer it shouldn't make that much of a difference. I only use OEM inks. If someone isn't using OEM inks then that opens a completely different set of problems. Unless using third party inks for B&W but I digress..

Cheers,
Jay
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Jason DiMichele
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