Tips, Tricks and Other Good Things To Know

Contents

Why can't I get good blacks like yours?
What's so important about the number 256?
RGB Values In Black And White digital printing
Does BO printing use the light black ink in 7-ink printers like the 2200?
Why do the other inks get used up?
How do I convert digital camera images to black and white?
A fun bit of computer science (not enough to hurt)
Film and paper Aspect Ratios

Why Can't I Get Good Blacks Like Yours?

The most common reason is that an image may look black on screen but not be really black. Technically, black means an RGB value of zero (0,0,0). If it's not 0 it's not black. These printers are incredibly sensitive. I have moved a point on a curve by 1 RGB unit and observed a subtle difference in the print. The drivers do everything by numbers and algorithms. If a number changes somewhere, then they respond by adjusting the dot pattern a tiny bit. We shouldn't underestimate the sensitivity of these systems.

We must be careful to ensure that anything we want to be black in a
print is truly black in the image. When I go over black areas
carefully while looking at the densitometer on the Info Palette (see "RGB Values" below) I am often surprised to find that areas that look black are
often anywhere from 3 to 6 or more. These areas will look weak in
the print. So use whatever technique you wish, but get those values down to 0 and you'll get good blacks.

What's so Important About The Number 256?

In computer lingo a piece of data, such as a letter, is called a "byte", and is represented by a collection of 8 values from the binary math system. In other words, a byte contains eight Ones or Zeros. These 8 numbers are called "bits". When we are limited to 8 bits, there are only 256 possible combinations of Ones and Zeros. Therefore, any symbol system or language is limited to 256 characters. Every letter, number, punctuation mark or symbol is represented by a value between 0 and 255. For example, in the standard character set, the letter "a" is #97 and the letter "A" is #65. This system carries over into other aspects of computers, such as colors.

RGB Values In Black And White Digital Printing

In computer graphics, colors consist of a combination of three values from the Red, Green and Blue parts of the spectrum (sometimes called "channels"). Each of these three channels has a range of intensity that is expressed in a scale of 256 values, from 0 to 255. Any particular color is a combination of these three values. This is called the RGB system. For example, a light pastel yellow can be made up of the RGB values 240, 240, and 170 (lots of red and green, not so much blue).

The important thing for us to know in black and white printing is that whenever all three RGB values are the same, we will have a grayscale tone somewhere between black and white. Pure black is RGB 0,0,0. Pure white is RGB 255,255,255. Middle gray is RGB 128,128,128. Since all three numbers are always the same, we often express grayscale values by referring to just a single number: black is 0, white is 255.

Grayscale values are also expressed as a % value, where black is 100% and white is 0%. Both systems are useful. The % system is easier to comprehend when referring to a range of values or a position on a contrast curve. For example, we might say a curve "drops off steeply at 95%".

However, when we are working with an image in PhotoShop the RGB system is much more precise because the range from black to white is divided up into 256 values instead of 100 values. Each percent represents 2.56 RGB units. In a digital print we can see the difference in a change of values as little as 1 RGB unit, but we can't express that in the % system.

PhotoShop provides us with a densitometer in the Info Palette. This can be configured to display the pixel values in RGB units. Click on the round arrow button to open the menu and choose Palette Options. In the window, set First Color Readout to "RGB Color", then OK to save. Now when the pointer is moved over the image, each pixel's RGB value is displayed in the palette. We can know the exact value of any pixel in the image.

Does BO Printing Use the Light Black Ink In 7-ink Printers Like the 2200?

No. In black only printing only ink from the black cartridge is used.

Why Do The Other Inks Get Used Up?

During printing, the print head pauses periodically to do brief nozzle cleanings. Each time, a tiny bit of each color ink is squirted onto the parking pad. Also, whenever we do a cleaning cycle to clear a clogged nozzle, a considerable amount of ink from each cartridge is used. Over time the other colors will be used up and need to be replaced.

Another thing to consider: A cleaning cycle is performed whenever we turn on the printer. In order to conserve ink, many people leave their printers on all the time, just to avoid these cleaning cycles.

How Do I Convert Digital Camera Images To Black And White?

There are lots of ways to do this, from brainless to highly complex. This is my version of a technique I found on the internet somewhere a few years ago (unfortunately I don't remember where I saw it or who posted it, but I offer my thanks to whoever it was). This is my favorite version because is fairly quick and easy and gives a great amount of control.

1) Create a Hue/Saturation adjustment layer but leave at default values for now.

2) Create a Channel Mixer adjustment layer and click the Monochrome box.

3) Adjust the RGB sliders to something suitable. Every image is different but a good starting point is Red 60%, Green 40%, Blue 0% (they must total 100%). The blue channel often contains the most noise so be careful about introducing too much of that. You can then adjust the over all brightness by using the Constant slider (but most of the time I leave it alone). Click OK when you are done.

4) Double click on the Hue/Sat adjustment layer to open the adjustment window. Adjust the hue slider and you can make the image to look more like Tri-X or some other film, or simulate the affects of a filter. Click OK to save.

5) Flatten the layers and change the mode from RGB to Grayscale. Now you are ready to begin the real work.

For real quick jobs I use an abbreviated version without layers - simply open the Channel Mixer window, set sliders to Red 60%, Green 40%, Blue 0%, click the Monochrome box and close, and change to grayscale mode. This works fine most of the time.

A Fun Bit Of Computer Science (Not Enough To Hurt)

Because machines can't think, emote or rationalize (thank goodness), computers must operate by logic. In terms of pure logic, something is either true or it isn't true. How do we make a machine that can process and store information by means of pure logic? The answer is a combination of mathematics, electronics, and magnetism.

Mathematics - In mathematics we can represent pure logic with a binary system, a system that uses only two numbers, 1 and 0, where 1 represents True and 0 represents False.

Electronics - Early computers used vacuum tubes, which were later replaced by the transistor. A tube or transistor is like a switch which either does or does not allow electric current to pass through it. A switch is either open or closed (a binary system), so it provides us a way to represent logic and mathematical concepts in the real world, to create data.

Magnetism - Magnetism allows us to store and retrieve electronic data. When a particle of metal is magnetized, it is polarized either North or South (another binary system). Hard drives, floppy disks and backup tapes contain microscopic magnetic particles who's polarization can be manipulated. This gives us a way to convert electronic binary data to a physical substance that can be stored and retrieved later.

Magnetic storage devices are delicate and data can be easily destroyed by magnetic fields, physical trauma (such as being dropped) and other things. Storage technologies like the CD use lasers to burn holes or "pits" in a non-metallic substance. Each particle is either a pit or not a pit. This gives us a binary storage method that is not affected by magnetic fields and is more durable.

To summarize, logic is a purely mental concept. Mathematics allows us to express logic in a way that is quantifiable and repeatable, but still conceptual. Electronics allows us to reproduce logic and mathematical concepts in the real physical world to do useful work and create data. Magnetism and laser technologies allow us to store and retrieve the data.

Film and Paper Aspect Ratios

There is actually nothing very standard about the standard film and paper 
sizes. The aspect ratio, or the ratio of the long and short dimensions of the
rectangle, varies widely among the various film formats and paper sizes.
Films, for example, range from the long aspect of 35mm film cameras (which
has carried over to digital SLR models) to the pure square formats used by
many cameras.

There is a correspondingly wide range of opinions among photographers about
which aspect ratio is more preferred.  Some, for example, prefer the longer
aspect of 35mm/DSLR images, while others prefer the shorter aspect of other
formats.  

Some conflict arises when it comes time to make a print from an image.  Most
of the standard artistic photo paper sizes, such as 8x10


My understanding is that 35mm is/was originally motion picture film,
so I suppose that aspect was for theater screens.  I have never liked
the 2:3 ratio for photos, it always seemed too long.  My favorite
camera for years was a Pentax 6x7 which was closer to the ratio of
photo papers.  With 35mm I always had to compose while remembering how
much would have to be cropped.  But I also often felt that the 8x10
ratio was a bit too fat.  

I have really come to love the 3:4 ratio of digicams.  It's right in
between the two extremes.  I don't know how the industry decided on
3:4 for digicams but I'm glad they did.  The photos look great and
they fit nicely on 8.5x11 paper.  Unfortunately, standard frame and
mat sizes are still 8x10/11x14, so framing at 8.5x11 is still a custom
job.

I like to reduce the various ratios to a single aspect number, derived
by dividing the short side by the long.  It makes it easier to
mentally sort them. Here they are in order, for various films and papers:

Size               A#
----------------------
35mm/DSLR 2:3-----.66
4x6---------------.66
13x19-------------.68
5x7---------------.71
645 (41x56mm)-----.73 (image size from a Mamiya 645 contact sheet)
digicams 3:4------.75
8.5x11------------.77
11x14-------------.78 
6x7 (55x70mm)-----.78 (image size from a Pentax 67 contact sheet)
8x10/4x5----------.80
6x6--------------1.00