Monday, June 24, 2013

Tones: Highlights

For examples relating to adjusting tones for highlights, the following photo comes to mind for two reasons. One being the snow, which can add many challenges for tones. The other is for pointing out the effects of highlights when they are found along the edges of the composition - and with realizing that unless there are some printed tones, then the highlight color in the image will be the same as that of the paper. Unless an outlining border is added to the photo, it may create an odd silhouetted shape with its background.

As noted on the Tonal Adjustments & Shadows post, clipping (loss of tonal detail) can occur when scanning photos. In this instance though, maybe the scan captured all that was in the original photo, and the loss was from when the photo was taken with the camera being too flooded with light from the snow. Either way, most of the image is with highlights consisting of white (0% black) pixels. 

The main adjustment, above, was with the darkening of all highlights. The lightest tone for any of the pixels is now at about 6% black. This should (depending on press tolerances and stock selection) print as a very light gray (almost white) - yielding a silhouetted rectangle shape (of the complete photograph) onto its paper background. Though it may seem odd to make gray something (snow) that was pure white, the result is that the snow still appears as being white and we now have a bit of contrast with all of the photo to its background.
     Adjustments were also made to decrease the shadow tones found in certain areas (such as lower left of the shot), and to darken the mid/light tones in others (namely for the snow areas, and select areas of the children). Care was taken to not over compensate so as not to lose the character of the original photo. 

Friday, June 21, 2013

Tonal Adjustments & Shadows

Family photo, Kutztown, PA., early 1900s.
This old photo is typical of many which have very high contrast. When scanning, there are limits to how much detail can be captured in the darkest and lightest areas areas of an image (due to limitations of the scanner). 

The view of levels shows a high population of very dark pixels to the far left of the chart (above). This "peak" found just along the edge of the chart is where clipping has occurred with loss of tonal detail. 

Another way of showing this loss of tonal detail is to show just the pixels that are 100% black (above). This photo though, can still be adjust for optimum quality for print production. 

The above images was with gray levels adjusted to make the darkest areas of the image to be at about 90% gray (rather than 100%). For the lightest areas of the photo, the levels were adjusted to make them a bit lighter (to compensate for the overly dark highlights in the original). To bring out some of the tonal details in other areas, dodge and burn tools were used, in selected areas, to add contrast and to darken some of the shadows and midtones. In particular, this was to make more noticeable the tonal detail found in the buildings on the right side of the street, some of the roof tops, steeple, hills in the distance, etc. Final touch was to add a bit of sharpening to add some clarity.    
Different programs can be used for making these type of adjustments to images. Hopefully what is described here will allow you to make similar refinements using the paint or photo editing program of your choosing.

Thursday, June 20, 2013

Sharpen Filter

    The labeling of this photo editing trick is a bit odd. The term "unsharpen mask" is a term from days when film was shot and darkrooms were used for processing and printing photographs. The name is misleading though I am sure there was a reason for it at the time. Rather than for making something look more "unsharp" (more blurry and out of focus), it is actually for adding more clarity - to make more "sharp" - with details more pronounced rather than less.
     Another fascinating aspect of this trick is that it was evident at a much earlier time as seen in the artwork of Spanish Renaissance painter El Greco (a favorite of mine). Rather than having one area of color align cleanly with another area of a different color, the division between the two can appear more distinct (when seen from a distance) through the use of thin bands of different tones and opposing colors. The result being the illusion and perceiving of added clarity - lines of division between areas becoming more pronounced rather than less.
Original scanned photo lacking focus and clarity.

With a limited amount of sharpening added. Though subtle, 
there is some added clarity. 

With an extreme amount added. Though drastic in its effect, this example does show how different bands of varying tones are added to bordering areas of shades (such as on porch roof, end of stairs, wall areas around windows, etc.).   

Another before and after example, enlarged.  
     There is obviously a limit to how much clarity can be artificially added. Those TV programs showing photo editing tricks being used for reading license plates from blurry photos take from miles away, are just a bit too good to be true! This being said, this type of "sharpening" is a handy tool and trick to have for improving clarity with images.
(Image: family photo, corner store in Sinnemahoning, PA.)

Moire Patterns

Challenges working with patterns and problems with moire (moiré) patterns

      The image above shows halftone dots (black, red and blue) overlapping at skewed angles. Depending on the angles, certain visual patterns appear that are often unpredictable and can cause problems. These are called moire patterns, as is evident in the overlapping areas of blue and red dots. The splotchy and uneven blending of blue and red is caused by the how at times blue dots are beside the the red, and at other times they are on top of each other allowing the white to be seen in the voids.
     Prior to going too far with a discussion on moire problems, maybe an explanation is needed for the term halftone which is the process of turning continuous tone images into rows of dots. The original photo in this example (below) consists of gradations of grays (continuous tones). Where cameras may recognize shades of gray and colors when capturing images, printing is limited to using only the full strength (100%) of the color of the ink or toner being used. If black ink is used, the illusion of grays come from using a variety of sizes of small spots of black - as a pattern of halftone dots. For print production, this type of conversion is necessary. Desktop printers, such as some laser printers, also show images as halftone dots. (Other laser printers may use very thin horizontal bands of color rather than dots. Inkjet printers, I guess it could be said, also prints with "spots" though this is very different as they are spread in a much more random and seemingly unorganized way.)
     Aside from overlapping of halftone patterns, there are many other instances where moire patterns may appear, and at times, may cause problems. The photo (below) shows an unwanted pattern appearing in the areas of brick with "whitish" looking areas that appear to curve upward like multiple little "smiley faces." This too is a moire pattern and is caused by two conflicting patterns. One is with the pattern of rows of red bricks with layers of white mortar between them. The second is with the rows of pixels being used for this digital image. (See Image Types for more on bitmap images.) The overlapping of these two patterns means that in some areas the pixels are being used to mostly show the mortar (appearing more white) and at other times mostly showing the brick (being darker and more red).

    In print production, one of the most common instances of moire problems comes from trying to print images that have already been converted to halftone dots. Examples would be with scans of printed pieces (such as photos from newspapers, magazines, printouts from laser printers, etc.). Subsequent posts will be more specific to how to avoid this from happening. One tool though that may be needed, when photo editing, relates to sharpening of images (see Sharpen Filter).

Image Types: Vectors & Bitmaps

    Prior to getting too involved with describing the many different types of files used for images, it may be good to first identify two major types of images. One being vector type images, and the other being "bitmap" type images. These are considerably different from each other.

    Bitmap images consists of an arrangement of pixels "mapped" onto a grid. The digital photo above, to the left, consists of 63,960 individual pixels arranged on a grid (246 pixels wide by 260 pixels high). Each pixel is defined with its own color value. The image to the right is of a small detail from the photo (the very small sign to the right midway down the road) greatly enlarged to show the arrangement of pixels. These types of images can be saved as many different files of types, and can be refined using "photo editing" and "paint" programs.

     Vector images on the other hand are very different in how they are defined. Rather than being pixels on a mapped grid, these are defined as an arrangements of points (of theoretically no size) connected by lines and curves (of theoretically no widths) on a two dimensional plain (as in x and y coordinates) or in three dimensions (with the added z coordinate). The good thing is that math needed for defining these images is something that is done behind the scenes for you (by the program you may be using). The first example (above left), shows just the points and curves that make up a drawn object, all of which would be invisible until line characteristics (such as width and color) are added, as seen in the second example. The third example shown (on the right) is with a fill color also being assigned (filling in the voids with green).

     Another example of vector images can be found with font characters. Each letter of the alphabet is actually a small vector image. The letter "A" is shown, in the center example, with all of the line and fill characteristics removed. All that remains are the individual dots with connecting lines and curves. The example to the right is with colors re-assigned (using red for the lines with fill of green).
     In addition to programs that are specific to vector images (often called "illustrator" programs), there are many other programs that will provide some tools for also working with these types of images.
     One of the main advantages of vector images over bitmap images is that they are not size dependent. They are scalable. These images can be enlarged to whatever size is needed (without loss of quality). Another advantage is that the colors can be very specific to select areas of the image. This makes it more adaptable to those types of printing where colors are limited, and for types of printing where gradients and shades of color are not an option. For this and other reasons, logo designs, and files used for printing logos, very often need to be in a vector format.
    In time, we wish to expand on much of what has been introduced here. For now though, hopefully this will provide a branching off point on the subject of images, with an understanding of two common - but totally different - ways that images are defined.


     In time, we hope to provide some useful information on various graphics related topics. Having been involved with working on many print and web publishing projects for various authors and organizations, many interesting challenges occur which often get clouded by the technical nature of what is involved.
     Initially I would like to quickly consider the word "publish" - and to loosely define this as act of "making something available." Limits are not being placed on what this could mean. The content - that which is being "made" - could be anything such as a song, a sentence, a picture, a video, etc. And the means that this is "make available" to others - may vary.
      Often though, for us, projects end up being physical books with various characteristics. For this reason, many of the first topics that we hope to cover will relate to print production and some of the challenges involved with preparing something for publishing. Topics may related to: printing methods (such as offset printing with inks verses digital printing with toners); image characteristics and refinements (too many to list briefly here); prep of text (typesetting as it relates to writing, editing, and proofreading); etc.