So many thoughts. So little time.

Monthly Archives: March 2010

Fundamentals of Light, and the Photoshop L*a*b Color Space

Way back in 2005, rutt posted the best summation of how colors work as light I’ve ever seen, at DigitalGrin.com.

Rather than force you over there to read that post, I am replicating it right here, as it required a few edits for clarity.

“In order to understand the relationship of LAB, RGB, and CMYK, we have to understand that the colors are actually defined in terms of one another.

  1. Red is a primary in light.
  2. Cyan is the pigment opponent of red. It is defined as the pigment that reflects green and blue perfectly but no red at all. So in light, cyan is composed of equal parts green and blue, but no red.
  3. Green is a primary in light.
  4. Magenta is the pigment opponent of green. It is defined as the pigment that reflects red and blue equally, but no green at all. So in light, magenta is composed of equal parts red and blue, but no green at all.
  5. Blue is a primary in light.
  6. Yellow is the pigment opponent of blue. It is defined as the pigment that reflects red and green equally, but no blue at all. So in light, yellow is composed of equal parts red and green, but no blue at all.

Given these definitions, we can see why the pairs green, magenta and blue, yellow are called opponents. There can be no green at all where there is magenta, by definition. Shine a green light on a magenta surface and you see black; nothing is reflected. Magenta is defined in terms of what it doesn’t have, namely green.

[I edited the following part, as he was muddy in this section, contradicting later assertions – Terry]

To the extent that a color is created by combining magenta light [he is referring to the combination of blue light and red light] and green light, the color just gets grayer and lighter.

You can experiment with this in the RGB color space. To get yellow, set the red and green values to 255 and blue to 0. [You’ll see a very rich and bright yellow.] Now increase the blue. As you do so, the light does not actually become more blue, it becomes less yellow, paler and brighter. You cannot add enough blue to get a bluish yellow light. If you increase the blue all the way to 255, you get white light.”

[Note: In L*a*b mode, Lightness is expressed in the L channel, while in RGB lightness is expressed as separate values of red, green and blue — higher values meaning both brighter as well as more saturated color in RGB.]

I love the thought of there being a bluish-yellow light, as he suggests, or a greenish-magenta, or a cyanish-red! But then again, Alice Through the Looking Glass is one of my favorite books as well!! Such colors are impossibilities according to the definitions above.

For Further Reading:

See previous post, “Some Color Theory and Photoshop LAB mode – Warm-up for Full Article

Some Color Theory and Photoshop LAB mode – Warm-up for Full Article

This is an open-letter to a co-worker that I thought might make a nice warm-up to the full-blown Color Science and Photoshop LAB Mode article that is upcoming. Enjoy and watch for the article!

(Join the newsletter to be notified when I release those big things – this Color Theory one as well as an Actions tutorial video series and a full-on L*a*b series of videos are forthcoming!)

———————————————————————————->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Dear Libby,

The other day I mentioned colors used in the
L*a*b color mode and which were opposites.

Naturally, being an ART student, you countered me (a former graphic arts college
professor, yet!) in my definition of what opposite colors were. Well, you were right…
historically speaking at least. I didn’t have time to go into it then,
recognizing it as a near universal problem when addressing color science to
those trained in the traditional ways that Art schools portray the issue.

Check this article at Wikipedia to understand what I’m referring to!

http://en.wikipedia.org/wiki/Complementary_color

Art and design

Because of the limited range of colors that was available throughout most of the history of art, many artists still use a traditional set of complementary pairs,
including:
white and black
red and green
blue and orange
yellow and violet
The complement of each primary color (red, blue, or yellow) is roughly
the color made by mixing the other two in a subtractive system:
red complements (blue + yellow) = green
blue complements (red + yellow) = orange
yellow complements (red + blue) = violet
When two complements are mixed they produce a brown,
or, in the case of black and white, a gray.

Blue-Yellow-Red color wheel. Opposite colors are called complementary. ____________________________

What I described as opposites were the scientifically opposite colors according to how the eye sees color. Conveniently, these break down into the primary colors of light vs pigments. Those are called “additive” vs “subtractive”, as light “adds together” to make colors, while pigments “subtract out” to reflect only the remaining colors of light.
Light <=opposite=> Pigment
Red <==> Cyan
Green <==> Magenta
Blue <==> Yellow

Pigments add a “K” or blacK pigment for printing to save on color ink (not having to use three colors always to produce every shade of gray).

Light mixes so that equal percentages of Red, Green and Blue equals a gray. This handy fact is used in color correcting in RGB mode, making it easy when we KNOW that a certain color in a photo is supposed to be a shade of gray.

Ideal pigments would mix 33/33/33 to produce gray, but in reality, because it is so difficult to produce a “strong” enough Cyan, the breakdown is more like 36%-C/27%-M/27%-Y to produce a neutral gray.

A *very *simplified way of looking at this is:
Cyan pigment looks “Cyan” because it soaks up all the Red light and reflects Blue
and Green light, which mix in the eye to make Cyan to the brain.

Pigments are “light sponges” this way, soaking up certain colors of light and
reflecting whatever is not soaked up.

So, similarly, a “Red” pigment is soaking up all the Blue and Green light
and only is reflecting the Red light.

So, if you are following this as to pigments, Red, Green and Blue PIGMENTS (RGB being also the light primaries) soak up two light primaries each and reflect only one.

Cyan, Magenta and Yellow soak up ONE light primary and reflect TWO! Those
are mixed in the eye to produce the color we “see”.

As I say, this is *very* simplified, as I put it above, because the white
light spectrum is comprised of more than ONLY red, green and blue light when
viewed using a prism, but the subtractive principles apply because pigments
soak up a wider part of that spectrum than only red, green and blue light…

There *IS* an orange light *frequency*, etc., but in color science, which
has to do mostly with how the eye and brain SEES colors, the RGB light
primaries apply.

Your RGB emitting computer monitor produces a yellow LOOKING color, not light at a frequency corresponding to pure yellow light! When our eye sees an equal mixture of Red and Green, it “perceives” that as Yellow (ie., Not-Blue!!!! See below!)

Your monitor does not have Yellow phosphors, and emits no Yellow frequency light, but we “see” Yellow from the simultaneous Red and Green light that the monitor DOES emit. Wild, eh?

Technically, according to the “opponent process theory” the eye sees
Green/Not Green(magenta) and Blue/Not Blue(yellow)!!!) This is exactly what
the L*a*b color mode in Photoshop allows you to adjust. This is usually
stated as “yellow as opposed to blue” and as “green as opposed to magenta”
in L*a*b terms.

Chew that over! 🙂

However, that is only a way of abstracting things, so don’t fret too much! An increase in the a and b channel’s “warm tones” together in L*a*b produces that Red (stronger Magenta in a-channel mixed with stronger Yellow in the b-channel), and a decrease in both a and b channels (the cool tones) produces the Cyan (“Greener” in a-channel mixed with “Bluer” in b). But it’s good that you are starting to “get” the way the eye/brain actually sees via a “less or more” relationship than as literal detecting of specific frequencies like some kind of electronic sensor would!

In short, in L*a*b mode, positive numbers in the a-channel and b-channel designate the warmer colors of Magenta, Yellow and Red (both a & b positive), while negative numbers in the a-channel and b-channel designate the cooler colors of Green, Blue and Cyan (both a & b negative). A negative a-channel with a positive-b would mix Green with Yellow for that Yellowish-Green that we see most often in nature, while a positive a-channel with a negative-b would mix Magenta with Blue to produce Purple. So, that’s where the intermediaries come from, at least in the L*a*b model.

The eye actually does have cones that are preferentially sensitive to Red
light (the L, or “Long-wave” ones), as there are cones that are
preferentially sensitive to Blue light (the S, or “Short-wave” ones) and to
Yellowish-Green light (the M, or “Medium-wave” ones). These are referred to
as the “trichromatic theory<http://en.wikipedia.org/wiki/Trichromatic_theory>”.

We perceive the brightness of a color by the “spill-over” into at least one

other cone by that specific frequency exciting it as well. Wow! As it says
in the trichromatic theory<http://en.wikipedia.org/wiki/Trichromatic_theory>
page:
“For example, moderate stimulation of a medium-wavelength cone cell could
mean that it is being stimulated by very bright red (long-wavelength) light,
or by not very intense yellowish-green light. But very bright red light
would produce a stronger response from L (red-sensitive) cones than from M
(yellowish-green sensitive) cones, while not very intense yellowish light
would produce a stronger response from M cones than from other cones.

So, a combination of stimulated cones results in there being brightness and
intensity info. Cool.

Here’s the whole story as to the physiology of color perception:
http://en.wikipedia.org/wiki/Color_vision.
*
*
I love the L*a*b mode in Photoshop. As Dan Margulis puts in his opening to
Chapter 2 of The Canyon Conundrum, “The structure of LAB is frightening:
opponent-color channels; a zero in the middle of a curve; negative numbers
for cool colors and positive numbers for warm ones; colors that are well
outside the gamut of any output device. And outright imaginary colors, ones
that don’t and couldn’t possibly exist anywhere but in the mind. But there’s
logic behind the lunacy, and with practice the system is easy to use.

I agree!

Good further reading:

The “Don’t Panic!” thread at DigitalGrin.com, where rutt summarizes chapter 2 of Dan’s book and there is discussion afterwards. Excellent!

Sneak Peek – L*A*B Color Mode
Image Improvement Techniques

I’m busy working on a series of articles and videos I’ll release here soon on using the LAB mode for improving images (or L*A*B mode as some prefer to write it, myself included!)

A friend, Fred Vaughan, has agreed to allow me to use his beautiful photographs taken in Colorado and elsewhere in the western U.S. as my subjects.

Below is a sample done using just some fairly simple curves – all work being performed in the L*A*B color space!

By increasing color contrast (not merely by increasing saturation), we can bring out the natural coloration that the light presented to our eyes, and restore that which is lost by the static interpretation of the camera lens.

Before (Click image for full-screen versions – you can load both into separate tabs to A/B compare them):

Fred Vaughan Image - original

And after having the curves shown beneath the image applied (Click image for full-screen version):

Note how the vibrancy of the full daylight is restored from the above version where the camera had “flattened out” the color’s dynamic range.

Watch this space for some nice full tutorials soon! But in the meantime, please try some L*A*B mode moves on your own!

Fred Vaughan image - with LAB Curves

Lightness Channel – I added some brightness to the lower-mids to open up the dark trees in the middle background, adjusting the top to allow the light to appear to “shine through” the leaves
“A” channel – the lower part is made “steeper” to bring out the darker greens in the mountainside
“B” channel – the odd “hook” in the lower section removes some blue haze obscuring the mountain’s features

HutchColor offers great desktop background for Photoshop

I’ve used this desktop background for years! Over at http://www.hutchcolor.com/Images_and_targets.html, they’ve given public access to download many of their print-specific and monitor calibration-specific targets, images and tools.

One that is a standout is their desktop background, called “CMS 30 128.JPG” (36 K – RGB) (I cannot simply provide a link to the image download due to their own restrictions [which I honor], so go to the link above and get it!)

It looks like this (but is not this – go download it at the above link):

Install it as a desktop background and “tile” it, and it will provide a perfect, even gray, non-distracting background for your color editing work in Photoshop.

HutchColor is a family run business by the Hutcheson family. Check out all their Free and Cool featured stuff, of course, but please do take notice of the great Services and Tools they have that keep their business such a vital service to the printing and imaging industries.

I have no affiliation with them – those links are not affiliate links. I just think this company rocks and has done so for a long time. They’ve been doing this stuff for us for years, so kudos to them!

Rutt at Dgrin offers another gem – Dan Margulis Portrait Action

I mentioned a very prolific poster at DigitalGrin.com naming himself “rutt” (I believe John is his real name). He is a follower, as I am, of Dan Margulis. rutt has offered up his own “DanMargulisPortrait.atn” (link is often dead – see below) — a Photoshop action — in the thread  of the Chapter 16 of the Photoshop Lab Color book discussion thread on page 12 (!) of the thread posts. That chapter was the final chapter in Dan’s excellent book, and gave a neat “recipe” for optimizing portraits and any face shots you might have. Rutt’s photoshop action automates the process by stepping you through that same recipe’s moves.

The above is his link to the action from that thread. I’ve also put up a safety backup link on my server – “backup of DanMargulisPortrait.atn“, mostly in response to the fact that this link has died in the past!

As that link is pretty buried in there (I mean, page 12 – yikes!), I wanted to create at least a couple back-links pointing to the post  so Google might find it easier!

Read the thread and you will see some pretty nice results demonstrated there from using this technique!

That’s all – I really just wanted to share this with you quickly! Enjoy!

Black and White discussion at Dgrin turns up nice PS action!

So… I’m reading this great tutorial by rutt over at Dgrin (Digital Grin, folks!) called “B&W Conversion Workflow“, and I’m reading through it and see he has included a little Photoshop Action set. As rutt puts it:

“I have an action which aides to to getting to this point. Pick it up here.”

Brief and to the point.

So… I go and download this thing and put it in my Photoshop Actions folder, and load it into my actions pallette with Photoshop running to try it out it on a color photo.

And, lo and behold, this baby not only contains rutt’s two little actions, it also possesses a complete “realization” by Robin L. Holden, Sr. of Greg Gorman and Mac Holbert’s quite innovative B&W conversion action (… as described in the only PDF that exists in Greg’s “Learn” section — titled “Black and White Conversion Tutorial” — find that PDF at http://www.gormanphotography.com/Duotone.html – at his site under the “Learn” section.)

BTW – That’s THE Greg Gorman – one of the most amazing B&W photographers of all time presenting a how-to tutorial at his website on building a Photoshop Action to be used to create B&W shots from color ones!!!

And Who is this Mac Holbert, you ask?

Well! Just another one of the greats in B&W photography!

Interesting collaboration to produce a Photoshop Action, eh? Especially one converting color photos to black and white ones. I’d qualify these two as being pretty “picky” when it comes to quality assessments of B&W from Color conversions!

That rutt includes this “realization” action along with his own technique is a very generous offer. His own and the Gorman/Holbert techniques BOTH produce very nice results, and leave the adjustment layers there for finer tweaking after the actions are run.

I suggest you take a look at rutt’s post and at the PDF at gormanphotography.com, download the action set, and give both approaches a try! (Here’s an alternate download link at my server in case that link above breaks in the future: B&W Action DeLuxe!

CamStudio Settings to Keep Audio and Video in Sync

I just created this video after a bit of trial and error (and research!) that demonstrates how to set up:

CamStudio 2.6 Beta (official download link)

so that the audio and video stay in synchronization throughout the length of the video.
(Or download the Most Stable Camstudio 2.0 release)
Getting CamStudio to synchronize the video to the audio requires that
the “Playback Rate” in Video Options divides evenly into 1000 milliseconds,
with the result being placed in the entry that goes in the box above it, “Capture Frames Every”. This must be a whole number (no fractions).

This basically means that you have five options for playback rate/frames per second
(as CamStudio does not allow fractional entries in the “Capture Frames Every” box).

You must use, therefore, 40 milliseconds with 25 frames/sec, or
50 milliseconds with 20 frames/sec, or 100 milliseconds with 10 frames per second,
or, if you are a mad scientist, 20 milliseconds with 50 frames/sec or 25 milliseconds with 40 frames/sec.
The first two settings mentioned are plenty adequate for 90% of applications, though.

Any other settings will cause a lag to develop in the audio that will get worse and worse as time passes.

This helpful information came from the following two links as sources:
http://en.wikibooks.org/wiki/Screencasting_with_CamStudio
http://en.wikibooks.org/wiki/Creating_Screencasts

Though I’ve seen it often stated that you can use 15 fps with a
“Capture Frames Every” setting of 66, that still sums to 990 (15 X 66), as does 30 fps and 33 (30 X 33).

Those settings will slowly cause lagging to occur.

I haven’t tested whether it will matter sufficiently in a 10-minute-MAX
YouTube video yet, but it probably will be a problem even at that length.

The settings that multiply to equal 1000 are the best optimized ones,
as 1000 milliseconds is equal to 1 second, but 990 milliseconds is clearly not!

I hope people find that helpful, and try to create their own screencasts.

[Edit: 03/23/10] Although these settings keep the sound and video in sync, they are not the only important ones. It is important to also set your video display settings in Windows so that “Hardware Acceleration” is turned completely off to avoid mouse jitter issues and other problems. Open the Display Settings control panel (right-click on the desktop background and select “Properties”), then select the “Settings” tab. From there, select the “Advanced” button. Once in there, select the “Troubleshoot” tab, where you will find the “Hardware Acceleration” slider. Slide that all the way to the left and hit the “Apply” button. Don’t forget to set this back again when you are done screen recording. For recording Games and such, you may have to try setting the slider at higher settings for game functionality to be adequate.

Later, from a request in a comment at YouTube, I recorded this how-to describing how to get sound from the “Stereo Mix”, so you can record what you hear on your speakers (as well as the microphone if you have one!) I had the settings a little hot for this microphone, so pardon the occasional distortion…

For people using Realtek HD Audio Input and a few other audio cards, you will need to allow the stereo mix to appear (enable it) and then make it the active input:

1. Enter the Sounds and Audio Devices control panel.

2. Click on the “Audio” Tab at the top.
Click the Sound Recording “Volume” button.


You can also get to the this panel from the CamStudio
Options/Audio Options/Audio Options for Microphone “Volume” button:

3. In the Recording Controls panel, drop down the “Options” menu and select “Properties”


4. Make sure “Stereo Mix” is checked and click ok.

5. Then, in the “Record” Section look for “Stereo Mix” and select it as your input:

Keep the volume level on Stereo Mix pretty low so it doesn’t clip.(distort)

6. You now can use the regular Master Volume sliders to control the mix.
Remember, the Mic input here in the “Master Volume” control is usually muted by default, so if you are using the mic input, be certain to un-mute it! BTW – the sound from your media players, browsers, etc. is coming through the “Wave” input slider.

If you have trouble with this, there are excellent videos on the subject at YouTube.

“I don’t want to learn Photoshop!” optikVerve’s free offerings

OK, I live to show people how to get the most out of Photoshop.

I taught at the college level three semesters deep on Photoshop alone!
However, I realize not everyone is into the same journey as I am, and would
simply like to get some results from their own photographs they’ve taken with their digital camera!

There are plenty of Photoshop actions out there…

(do a Google search for “Free Photoshop Actions Download”),

as well as Photoshop Filters…

(do another Google Search for “Free Photoshop Filters Download”),

but maybe you don’t even own a copy of Photoshop. After all, it is rather
expensive! I still use Photoshop CS for everything at home and to make my
free actions and tutorials, though admittedly, at work we have CS4 installed.

There is a solution, and it is from the
remarkable optikVerve Labs, home of the FREE

VirtualPhotographer Filter plugin

for Photoshop CS4 and EARLIER.

(or Photoshop Elements, or Corel PhotoPaint, or IrfanView,
or PaintShop Pro, or any other program that can use Photoshop .8bf plugins).

But more importantly for those not owning Photoshop,
they are also the creators of the ALSO FREE software called

VirtualStudio

which includes not only the VirtualPhotographer plugin, but additionally
works with any and all plugins that you can find using a Google search for free plugins.
It can be installed on Windows 7, Vista 32-bit, Windows XP, 2000, ME or ’98 operating systems!!! WOW!!!

Look, folks, I love teaching Photoshop.

I generally target my tutorials towards people who are passionate about doing it themselves.

But still, I want to help everyone and anyone into making DY-NO-MITE pictures!
I want to encourage creativity, not put artificial limits on what you have access to here.
I’ll be posting plenty of other free things in the future as
I discover them (or as you folks bring them to my attention!) 🙂

Enjoy! That is the bottom line!