Monday, July 30, 2012

Pencil Not So Basics

Although most of the posts on this blog pertain to digital subjects, having used a pencil for much longer than I've used a mouse, track pad or graphics tablet, I decided to author a post about the pencil. 

Pencil making began in the mid 17th century in Germany, Nicolas-Jacques Conté (1755-1805) was the first to patent the present commercial process for mass manufacturing pencils in 1795 in France. The name Conté should be familiar to illustrators because of the Conté crayon or stick. Conté compressed and fired powdered natural mined graphite, finely ground clay and water to create long thin cylindrical or square rods. The graphite content determined the softness of the pencil while the clay content determined the hardness. The Faber Company, one of the first pencil manufacturers, now familiar to us as Faber-Castell, began producing pencils even before the Conté Process was invented.
Graphite raw material.
Clay raw material.

The Pencil

Using Nicolas Conté’s process, pencils are manufactured in a variety of softness and hardness called “grades”. Although differing from Conté’s, by the end of the 19th century, a number/letter grade system was recognized and is now used by most European and American pencil makers for artist and drafting pencils. And even though there is no lead metal in the graphite in pencils, the grades are also called leads.

The grades are as follows:
9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, 7B, 8B, 9B

Tonal scale of pencil grades.

H stands for “hardness”.
B stands for “blackness”.
F stands for “fine or finest”.
A 9H lead is hardest, producing the lightest mark. A 9B lead is the softest leaving the darkest or blackest mark. Although not documented the F grade most likely began with the German manufacturers where it is “feinste”.

Not All Pencils are Created Equal

Another simpler number system is also in use in the US. It ranges from #1 to #4 with the most common being the #2 pencil with yellow coated wood and an attached eraser, Although the #2 is equivalent to an HB in hardness its best use is for simple handwriting. It is important to note that the quality of these pencils differs significantly from artist and drafting pencils. I have seen many an art student struggling to draw with one of these pencils, only to be limited by its poor quality of graphite/clay mixture and mistakenly thinking a #2 pencil should be darker.

In the Too Much Information Category

An older way of classifying pencil grades was by the use of multiple letters. Primarily used by pencil manufacturers in England, it went like this. Hard pencils were stamped with an HHHH, HHH, HH, etc., while soft pencils were labeled BBBB, BBB, BB, etc.

How to Use Pencil Grades “The Bicycle Analogy”

So now we come to the real purpose of this post. We all know that if we use a light touch, a 4B lead can make a mark equivalent to an HB, or a 2B lead can make a mark as dark as a 6B. So why are there so many grades of pencils? Here’s why.

I’ll use “the bicycle analogy”. Professional cyclist’s bicycles come with a range of gears that allow the cyclist to be most efficient in all circumstances. The goal is to pedal at a steady rate. In cycling its called “cadence”. A cyclist uses a higher gear to get more speed and distance using a consistent amount of energy from pedaling on a level surface. They downshift to a lower gear to go up inclines, which causes a loss of speed and distance but keeps pedaling rate and energy expended as consistent as possible to the level surface situation.

Lead samples.

Now think of pencil grades the same way, except this time instead of pedaling rate, think in terms of the hand pressure used to make a mark. Every artist draws in a way that is natural for him or her. Some artists have a light touch while others are “heavy handed”. The idea is to use the pencil grades to provide the different tone variations in a drawing without having to drastically stray from your natural pressure. So, a heavy handed drawer can have difficulty if they try to use a 3B pencil to get some lighter subtle tones, whereas by switching to an F grade pencil those desired tones can be achieved with ease, and without the need change their natural pressure.

So does that mean an artist always needs to have all 20 grades of pencil at hand? Of course not, however they are at your disposal for nearly any circumstance. Engineers and draftsmen tend to use H grades for mechanical drawing and hand plotting. Illustrators tend to use the B grade pencils, but they can also use H grades to do light preliminary sketching. H pencils can be so light that they won’t disturb the illustration as it proceeds to finish.

How a Pencil Works

It’s obvious and yet it may not be. When you use a pencil to create a drawing, you are making marks on paper by applying some pressure and moving the pencil across the surface. As you do, lead is transferred from the pencil to the surface of the paper. The pencil begins to wear down because you are using the lead to create an image. So that’s the obvious part. What is not so obvious is that while you are moving the pencil across the surface of the paper, friction is created by the movement of the pencil, heating up the tip of the lead. The faster you move the hotter the tip becomes, so when you are blackening in a large solid area or hatching, the tip of the pencil heats up. The heat actually hardens the tip of the pencil, which in turn causes the pencil to resist transferring lead to the paper surface. Alternatively, the pencil tip, which is now harder, begins to “burnish” or polish the graphite that is on the surface of the paper, so dark dense areas begin to shine.  The heat can also warp the surface of the paper depending on the paper structure. And, if you want to darken the darks in a your drawing, paper accepts graphite better than graphite accepts itself, so it is difficult to layer graphite over an area where the surface of the paper is saturated with graphite. It’s best to use a soft grade pencil to apply dark graphite to the paper rather than trying to go over a dark area to make it even darker. (More on paper in a future post.)

Closeup example of pencil work burnishing itself and warping the paper.

One Last Thing

Have you ever been frustrated when sharpening a pencil, only to find that when you take your pencil out of the sharpener, the tip is broken? So you repeat the sharpening, only to find yet another broken tip, and so on. The natural inclination is to blame the sharpener, but it could actually be the pencil that’s to blame. It’s fairly easy to damage a pencil. If you drop one, it may look just fine, but the impact could have cracked the lead inside of the wood sheath. Much the same as when a carton of eggs is dropped. The carton looks just fine, but the eggs inside are broken. And who’s to say how the pencil had been treated during shipping or by the retailer. If this happens it may be time to switch to another pencil.


The point of the story, no pun intended, is to consider which pencil grade is appropriate for a desired effect and frequently sharpen your pencil. You can also rotate the pencil tip to expose fresh lead. By sharpening and rotating you will allow fresh exposed lead to transfer to the paper and also improve the line and tone quality of your drawing. 

Tuesday, July 24, 2012

Digital Raster Image Resolution


PPI – Pixels per inch
DPI – Dots per inch
LPI – Lines per inch
Bit Depth – The number of bits used to define each pixel


PPI "pixels per inch" is the number of pixels per line per inch in a digital image. Image size is determined by establishing a horizontal and a vertical value for an image. For example, the display size on this monitor is currently set to 1920 x 1080. The file size for a color image is determined by multiplying the horizontal and vertical pixel dimensions, then multiplying by the “bit depth”, then dividing that number by the minimum color bit standard of 8.

Pixel magnification at 1600%

DPI is the number of “printed” dots of ink per line per inch. DPI is the resolution of a printed illustration and is referred to as "dots per inch". Some sources consider PPI and DPI to be interchangeable. However, since PPI exists in a digital environment and DPI does not, I prefer to use them separately. A higher the DPI results in an image with greater detail provided the PPI of the original file is of an equivalent higher resolution.

LPI is used by printers and publishers in their production specifications when they convert continuous tone or digital images for commercial printing. Commonly referred to as “line screen”, halftones and color separations are classified using LPI. For instance, The Wall Street Journal prints images using a 100-line screen. Travel & Leisure Magazine is printed at 133lpi or uses a 133-line screen. Although printed images appear to the naked eye to have continuous smooth tones, they are made up of finite dots and spaces, which become visible under magnification. See below.

CMYK screen pattern magnification.

Halftone screen pattern magnification.

Bit Depth is the number of “bits” used to define a pixel. The number of bits per pixel determines the number of grey scale or color tones that can be represented in an image. A 1 bit per pixel image has two tones, black or white (2 to the power of 1). An 8 bit per pixel image has 256 tones (2 to the power of 8), and a 24 bit per pixel image contains 16.7 million tones (2 to the power of 24).

Managing Resolution

So how can you be sure that you’ve created your illustration at the proper resolution? Here are three simple principles to always keep in mind.

Principle #1 Think Ahead.
Always check the production specifications for any publication, printer, website, or output device before you assign a size or resolution to a new document.

Additionally, try to anticipate all possibilities you may want to use your illustration for in the future. For instance, you may want to use a web image you created at 72ppi for an 800 x 600 display space in an offset printed promotion that requires a 400ppi at 100% file. Many sources provide blanket recommendations for file size, such as “always use 300ppi at 100%”, but this could turn out to be insufficient. This brings up another rule of thumb.

Principle #2 Think Large.
Digital file size can be very changeable as long as the only way you change a files size is down, or make the file smaller.

Changing a files size is referred to as “resampling” and artists, designers, printers, etc. all resample to comply with display and production specifications for publishing images. It’s important to understand the distinction between resampling and “resizing”. Resampling is changing the number of pixels in an image i.e., the file size. Resizing is changing the size an image will print without changing the file size/number of pixels.

Original image: 3" x 4" at 300ppi, or 3.09M.

Resized image: 9" x 12" at 100ppi, still 3.09M.

When you decide to resample an image down or reduce its size, programs such as Adobe Photoshop, discard data to reduce the file. This works because the data that was discarded was there in the first place. And unless you retain an original version of your file, the data that is discarded is permanently gone. Now, to increase the size of a file, you have to add data to it, but there isn’t any true data to add, so the software program will fabricate the missing data. This nearly always results in a visually perceivable quality loss.

Resampled image: 3" x 4" at 200ppi, now 1.37M.

Principle #3 Think Twice.
The rule of thumb when converting PPI’s to DPI’s or LPI’s is to think two to one. In other words, a publication using 150dpi or line screen will require a digital file that is at least 300ppi at 100% of the image dimensions. This applies when creating a file that will be converted to a color separation and printed on a commercial printing press.

Also, don’t forget Principle #1. I recently ran across a magazine that used a 150-line screen for images but required all files to be 600ppi at 100%. So if a file was created at the ratio of two to one, there was a chance it would be rejected by the publication. And remember Principle #2; “sampling up” would not be an option.

Halftones, Duotones, and Tritones

The resolution needed for halftone, duotone, and tritone printing varies from the resolution needed for a CMYK continuous-tone or “contone” image. Here’s a way to understand why. Consider that a contone image at 300ppi is made up of a 300ppi cyan channel, a 300ppi yellow channel, a 300ppi magenta channel, and a 300ppi black channel. So in essence, for an image setter, the 4-color image channels will combine to have 1200ppi in total. Since a halftone is a monotone image, and a duotone or tritone is a combination tone image, they contain less than four channels. So they have less density and require a higher resolution to make up for it. Here are recommendations for file resolutions.

Halftone (Monochrome)
1200ppi at 100% image size. (1200ppi x 1 color = 300ppi x 4 colors)

Halftone image.
Duotone (Two Color)
600ppi at 100% image size. (600ppi x 2 colors = 300ppi x 4 colors)

Duotone image.
Duotone swatches.
Tritone (Three Color)
400ppi at 100% image size (400ppi x 3 colors = 300ppi x 4 colors)

Tritone image.
Tritone swatches.

Laser and Inkjet Output

Photo-quality ink jet printers use DPI resolution for classification purposes. Most printers print in thousands of dots per inch. 1200 to 4800dpi printers are typical. Good quality image prints can be achieved with files that have 140-200ppi resolutions at 100%, and high quality image prints are possible with 200-300ppi resolution files. Laser printers are generally thought to be higher resolution than inkjet printers.

Tuesday, July 17, 2012

Digital Type Sizing Explained

So, why isn’t type true to its classified size? For instance, why is 24 point size type less than 24 points in height? And for that matter, why is any size or any style type font less than its classified size? And, on top of that, why do different fonts in the same point size differ in height? Understanding why, makes it a little easier to deal with the frustration of using letterforms that have to visually conform to a finite layout dimension in an illustration. 

It all has to do with historical type production and practice before the digital, and even the photographic type environments came along. Printing type was originally produced as wooden or metal letterforms that were used to print documents on a printing press. The letterforms could be arranged or “composed” into manuscripts, and then taken apart and reused. Printing presses used a considerable amount of pressure to transfer an image, or make an “impression” of the type onto printing paper. And, in order for this to occur without causing damage, the raised letterforms were affixed atop a supporting “body” of metal. An engineered “body” below the letterform was required to reduce the stress the printing press exerted on the letterform. Thinner font styles required a larger body to be used, while heavier fonts could get by with a smaller body and less support. As printing presses became more sophisticated, the relationship of size between the letterform and it’s supporting body also became a decision made by the type designer based on the intended use of the font and the aesthetic appearance the designer desired.

So, in keeping with tradition and the conception of users, printers, and designers regarding the appearance of a specific font in a particular size in both photographic and digital type, designers and transcribers, adopted a virtual approach to sizing type rather than an absolute one. In other words, even though it wasn’t needed, an imaginary bounding space was adopted for translating non-digital fonts into the digital environment.

The following letters are all set to 72 point. The rectangle around the letterform indicates the cast body the type was affixed to for usage, which shows why all the fonts shown are classified as 72 point, and in turn why although the letters vary in height, they are all classified as 72 point.

Letterforms set digitally at 72 point.
Letterforms and letterform bodies overlapped for comparison.

Comparing Type Size

Depending your size needs when applying type to an illustration, type can chosen using different standards. The three examples of typestyle comparisons below show fonts sized using three different priorities. The first example shows two fonts chosen for the same capital letter height, but having different “waist” heights, i.e., the height of the lower case letter "x". The second example shows fonts chosen for the same waist height, but differing cap heights. And the third example shows two fonts used to make equivalent ascender/descender heights, but differing cap and waist heights.

Type with equal cap heights, unequal waist height.

Type with equal waist height, unequal cap and ascender/descender heights.
Type with equal ascender/descender height, unequal cap and waist height.

So, there is more than one criterion that can be used to determine the visual size of a typestyle. Some situations require an illustrator or designer to rely on the height of capital letters to make decisions about selecting a typestyle while other uses rely on the waist height or lower case to determine the selection a font. 

Tuesday, July 10, 2012

Document Units of Measure

There are several options when it comes to selecting a unit of measure to use for a digital document. Selections include inches, centimeters, and millimeters, which are fairly straightforward and familiar. However, some units of measure are less familiar. Other options include “points” and “picas”. These units are mainly familiar to typographers, graphic designers, printers, and digital publishers. The "pixel" is another option offered and is essential for raster-based sizing and operations.

Historical Background

Point systems were developed by typographers and adapted and reinterpreted by type foundry companies. Although the point was invented prior to Fournier, the French typographer Fournier is generally credited with creating a functional point system in the mid 18th century. Another typographer, Didot, adapted Fournier’s system to the existing French Royal inch unit of measure, also in the 18th century. It wasn’t until the late 19th century that the American point system was proposed. It was based on the American inch. In the early 1980’s when the computer publishing revolution began, and due to the already established, universal use of the point as a unit of typographic measure, it was adapted as the main unit of measure for the Postscript language for digital typography and production. The pica was retained as a unit of measure for page layout.

Definition of a Point

Since there have been several definitions and varying measures that were classified as points, the information provided below will mainly focus on the “Postscript” point system. The Postscript, or computer point system, is a streamlined version of prior point systems and is easier to work with in the digital environment.

Point Pixel, and Pica

A “point” is a unit for measuring the size of letterforms, and line spacing
1 point = 1/72nd inch (Postscript point to true inch)

Highlighted area shows the number of points in an 8.5"x11" document.

A “pixel” is a two-dimensional, square unit for measuring area
Pixel stands for "picture element".
1 point = 1 pixel (on a 72ppi display) 72 pixels = 1 inch
1 point = ½ pixel (in a 144ppi document) 144 pixels = 1 inch, and so on
Although a comparison has been made here for reference, points and pixels are 
distinct, in the same way that a square foot differs from a linear foot.

Highlighted area shows the number of pixels in an 8.5"x11" document.

A “pica” is a unit for measuring aspects of page layout, text width, spaces, etc.
12 points = 1 pica
6 picas = 1 inch

Highlighted area shows the number of picas in an 8.5"x11" document.

These units of measure work very practically and efficiently in a digital environment because they allow document size, layout considerations, and typographic information to be determined using whole numbers.

Tuesday, July 3, 2012

Commercial Printing Processes

An understanding of printing processes is very important for any illustration commission, particularly for digital illustrations. With digital art, it is the illustrator or graphic artist who must create their illustration to be “print ready”. Even for non-digital illustrators, it is still important to know about printing processes. After all, the final outcome for an illustration or graphic design is the reproduced published image, not the original.

Letterpress Printing

Letterpress printing is perhaps the oldest form of commercial text printing in the western world, and although not nearly as popular today, it was the mainstay of producing publications for 900 years. It originated in China and it’s use dates back to the 11th century A.D. It migrated to Europe in the mid-15th century A.D.

Also called “relief printing”, type and images on a raised surface accept ink, which is then transferred directly to the printing paper. Because of the direct contact of the paper to the printing surface, the raised images appear in reverse, or “wrong reading”. Pressure is used to force ink to be transferred from the raised surface to the printed page. For this reason, letterpress prints presents a slight indentation when closely examined or touched.

Non-commercial application: Wood Block Printing and Linoleum Cut Printing.

Ink is transferred from a raised surface. © 2012 Don Arday

Offset Printing

Offset printing, also called planographic printing or lithographic printing, is now the most widely used method of printing. Lithographic printing was invented toward the end of the 18th century A.D. and gradually grew in popularity toward the last quarter of the 19th century A.D.

Lithography first employed the use of a thick flattened stone. The printmaker or artist would draw directly on the stone with a grease pencil or brush. Open areas could be kept clean with a solvent. The greasy areas would attract and hold the ink while water in the porous open areas of the stone repelled it.  In traditional lithography the printing paper contacted the stone directly, so as was the case in letterpress printing, images had to be drawn in reverse or “wrong reading”.

Commercial offset printing uses very thin zinc or aluminum plates that are coated with a light sensitized emulsion. Imagery can be photographically or digitally transferred on to the printing plate. Hardened areas of emulsion attracted ink while unexposed areas are washed away to repel ink. The printing paper does not come into contact with the printing plate. Instead the ink is “offset” onto a rubber blanket that then transfers the image to the printing paper. Hence the title offset printing.

Non-commercial application: Stone Lithography.

Ink is transferred form a resist surface. © 2012 Don Arday

Gravure Printing

Intaglio printing dates back to the 7th century A.D. in China and its forbearer, wood block printing, dates back to the 3rd century A.D. A more commercial form of gravure began to appear in the 17th century A.D. Gravure became even more widely used when it was combined with photographic processes in the 19th century A.D. The black elements on US paper currency including the finely webbed lines are an outstanding example of gravure printing.

Also called “intaglio printing”, or “engraved printing”, gravure involves having type and images cut or etched into a metal plate. The printing areas are the recessed parts of the image. Ink is then forced into the recessed areas and cleaned off of the raised surfaces. The printing paper is then pressed down onto the plate to draw the ink out of the recesses.

Non-commercial applications: Intaglio Printing, Engraved Printing, and Etched Printing.

Ink is transferred from a recessed surface. © 2012 Don Arday

Screen Printing

Some sources date “stencil printing” back as far as the 27th century B.C. However, the use of silk to form the stencil was developed in the 10th century A.D. in China. It was popularized and perfected in Japan in the 15th century A.D. And around that time it was adopted in Europe.

Silk fabric is stretched around a frame to become the substrate for the stencil. The applied stencil contains solid areas and open areas. Ink is then forced through the silk by a squeegee. The open areas of the stencil allow the ink to move through the silk to be transferred to a printing paper or fabric. The silk material comes available in a variety of densities. Very fine silks can be used to produce astonishingly fine detailed prints. Stencils can be photomechanical, digital, hand-cut, or even drawn or painted directly on the silk.

Non-commercial applications: Fine Art Screen Edition Printing and Mono-Print Screen Printing

Ink is transferred through an open surface. © 2012 Don Arday