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Photography Question 
Pam Kliment
 

printing color too red


I take a lot of shots with pavement in the background; manhole covers, etc. Sometimes the prints are coming out well, then all of a sudden, they turn reddish.
I do all the printer maintenance. I have calibrated my monitor so what is on the monitor really looks like it did in real life. I have a trusty old Canon i960. This red b usiness is really a problem
thanks


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2/26/2008 8:37:02 PM

 
Alan N. Marcus   Hi Pam,
Inkjets print by spraying three colors plus black. The three colors are known as the subtractive primaries. These are Cyan – Magenta – Yellow. Their counterparts are the three additive primaries Red – Green – Blue.

These three subtractive primaries are the only ones that work under conditions where dye is laid down on paper. Furthermore, the dyes are transparent, meaning the viewing light is able to transverse the dye, and strike the white paper underneath, reflect backwards towards the observer and in the process make a return transit through the dye. What I am trying to tell you is the light makes two transits through the transparent dye thus it need not be too heavily laid down.

Now we view under white light conditions. This is satisfied when the viewing light source emits nearly equal amounts of red – green – blue – light.

Thus white light falls on the paper. Areas with no dye reflect white light back at the observer.

Yellow dye areas allow red and green light to transverse and red + green is returned to our eye. Red + green = yellow. The yellow dye absorbs blue light energy; blue light is prevented from reaching the observer. Should the yellow ink be reduced in quantity or nonexistent, the print appears too blue.

Magenta dye areas allow red and blue light to transverse and red + blue is returned to our eyes. Red + blue = magenta. The magenta dye absorbs green light energy, green is prevented from reaching the observer. Should the magenta ink be reduced in quantity or nonexistent, the print appears too green.

Cyan dye areas allow green and blue light to transverse and green + blue is returned to our eyes. Green + blue = cyan. The cyan dye absorbs red light energy; red is prevented from reaching the observer. Should the cyan ink be reduced in quantity or nonexistent, the print appears too red.

If perfect shades of cyan + magenta + yellow were available, the location where they overlap would appear black as each stops one of the three additive primaries thus all thee are stopped and the absence of light results in black. However no one has discovered the proper colors of subtractive primaries thus we must apply black to make up for this deficiency.

Of the three subtractive primaries yellow is the best followed by magenta, cyan is very poor meaning it can’t filter out red with efficiency. To solve and improve this dilemma two shades of cyan are supplied. Some printing systems utilize two shades of magenta.

Your red condition is due to the fact that your printer ran out of cyan ink.

Took me too long to arrive at this expiation!. That’s why I call myself a dispenser of marginal technical gobbledygook. Furthermore after years and years designing photo printers and teaching this stuff – I couldn’t resist.

Alan Marcus, Anaheim, CA
ammarcus@erathlink.net



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2/26/2008 11:54:15 PM

 
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