Thursday, May 17, 2012

How Good is My Ancient Sun Workstation Monitor?

In my last post I mentioned an unexpected  advantage of upgrading my desktop--the discovery that  I now had a video driver specifically for my Sun workstation monitor.  Major result--my monitor colors looked brighter and more vivid.  Minor result--a software switch between my manual screen layout--squished in with black borders so the aspect ratio of  a square image is exact--and the driver's more open layout that fills the whole screen.

I began to wonder if I could go from 'this looks better'  and come up with some tests where I could say 'this is exactly how much better" the colors appeared.  Something like I'd attempted after I bought my first digital camera and wanted to reverse engineer how digital cameras worked. Then I photographed a fan of paint cards and compared the swatches to the colors I saw on my monitor.  With mixed results if I remember correctly.

A decade later I now understand why my naive first attempt at color management ended a bit off.  Somewhere in the house is an extra thick tome on the complexities of  eyeball, brain, camera, scanner, printer, press and monitor color processing.  Someday I might even finish reading it. During my last attempt my brain seized up when I hit the complexities of mating CMYK processing with the ink spread on various paper grades during high speed offset printing.

But I did manage to retain a few key facts. The first is color calibrate your monitor. If that is off everything that follow will be meaningless. To correct gross problems you can fiddle with your monitor controls  and attempt to match images you find on the web. But to calibrate accurately you have to buy hardware.

I invested in a Pantone Huey--at the time $99 at my local we-stock-everything craft store.  The Huey has its quirks.  The software in the box dated from the Win 2000 era and did not install on my newer OS.  Once I located the upgrade, more of a hassle to find than it should have been, I couldn't make the 'adjust the contrast and brightness control so the top right circle... etc etc' part of the setup work. In the end I set them to 75% and clicked next. Despite these quirks, the Huey did cleaned my obvious color management problems. Still I never did discover how accurate the color matches were

So I was thinking of getting out the camera and repeating the paint card experiment when I discovered .  Which, not surprising, is a site with a data base of paint swatches. They even provide the RGB numbers used to create the swatch and CMYK numbers to print the color cards. Below is an example of what you find there

So all I had to do was collect some paint card.  Unfortunately finding them in stores I happened to pass while doing grocery shopping didn't work out well. Walmart's ColorPlace wasn't in the data base. Home Depot's Glidden had only one swatch on line that matched the cards I took.  In the end I made a trip to Sherwin Williams. It has a swatch for every paint it sells. This combined with larger than normal paint cards printed on thicker than normal paper stock makes it my recommended store for swiping your cards. 

With cards in hand I download a swatch.  And I hit my first technical problem.  Monitors blasts out light. The paint cards, on the other hand, reflect light. Depending on the light quality (intensity, color temp and all that jazz) they will, more often than not, look different than the monitor swatch.  After holding card by the monitor I could say the swatches sort of looked the same. but that wasn't the accurate one-to-one comparison I wanted.

After some fiddling I discovered if I opened the curtains of a window to the left of monitor and angled the card up or down to catch more or less light I could match the intensities.  But I still ended up with a so-so color match.  Close but hardly perfect like in the photo below.

I must confess to spending far too much time fiddling with controls while the answer to the problem stared me in the face.  Quick question. What is causing the green cast on the swatches of the lighter blue paints?  After all Sherwin Williams wouldn't mix a little green pigment in with its expensive blue paints.

All I had to do was carry the card to the window, twist it first to face the window light and then away, to watch it switch between slightly greenish and pure blue. The Wisconsin clear sky sunlight had started out pure. But once it was reflected off the green leaves that shade the patio below the window it had a greenish component.

Problem solved. Color cast in the light.  Factor that out and the match between real object and monitor image colors becomes almost perfect.  Some days life is good.

Or close to good. Measured with Gimp, the RGB numbers on a swatch are what says they should be.  Measure with RawTherapee using its neutral profile, one that is supposed to display an image exactly as shot, and the numbers end up 5 to 9 units lower  So after I post this I should be a good RT user and also post a bug report.


The  RGB 5-9 off bug is when I save a swash snip in png format. When saved in jpg format the numbers are off by 1.

And not surprising when you think about it, the green colorcast that had me twirling about mentally yesterday depends on the time of day and where the sun is in the sky.  Around noon when trees are in direct sunlight the reflection off the leaves is a problem.  But earlier this morning when I repeated the test and the sun was much lower in the sky the match was so close I could hardly make out the seam where the card touched the monitor swatch.

Ain't color management tricky ... but fun.

1 comment:

  1. Part 2 more or less

    In the feb 2013 section