Technology and Vision

Even the briefest study of photography leads to the conclusion that the greater ability to express, and the expanded modes of expression are intimately tied to the evolution of the ways and means of taking and making pictures. While the subject of the image is often a child of its age, an expression of the attitudes and social mores of its times, the mechanics of camera, film and printing is often as much a part of the image as the idea communicated in the image itself. Though new ways of seeing are at the core of the evolution of photographic art, the defining principles of that vision are greatly determined by the equipment and chemicals used to manifest that vision.
Arguments have been made that portraits made in the first thirty years of photography surpass in beauty, charm and revelation of the human spirit those made today. Perhaps those images were even more startling to their contemporary viewers than most photographs are to us today, if only because the medium was nowhere near as prevelant as it is now. Yet the revelation of character in today's fine portraiture, with all the layers of meaning we bring to the image, could only be achieved with today's equipment used by today's photographers.
Just as with the early photographs, admittedly viewed through the filter of the ravages of time, the images created today are subject to the matrix of vision that is bounded by our ability to manifest that vision. That is why with each progression in technology there is so much more visual expression to explore.
Photography emerged within the context of the industrial revolution, with its concommitant alienation and dehumanization. Yet it was also the darling of the age of discovery, and grew alongside other profound changes in the visual arts. The vigor with which it grabbed the human imagination can be traced to its serving both masters so well. Essential to its understanding is that it addreses most directly the very human need to communicate through images, and plays upon the human ability to empathize with abstract forms. Thus, the mechanical serves the artistic, which in turn creates communication on virtually every level of visual perception.
The linkage between the art and craft has its roots in those people who pioneered modern photography. Many of the early explorers were artists seeking new and more efficient ways to create images from nature. Many were men and women who were grounded in the scientific method of discovery, yet who were also practising artists, or associated with circles concerned as much with aesthetics as they were with experimentation.
Photography sprang from a time when the lines between science, art and craft were not so clearly drawn, and when curiosity went beyond pre-packaged solutions to meaningless problems.

An Occassional Glossary: F.G

F-NUMBERS: A series of numbers designating the apertures, or openings at which a lens is set. The higher the number, the narrower the aperture. For example, f/16 is narrower (by one stop) than f/11--it lets in half as much light. An f-number range might be f/2.8, f/4, f/5.6, f/8, f/11...To find the next aperture in a narrowing series of single full stops, multiply by 1.4. F-numbers are arrived at by dividing the diameter of the opening into the focal length of the lens, thus a 10mm diameter opening on a 110mm lens is f/11. Alternately used with f-stops.

FAST: A term used to describe a film or sensor setting with a relatively high light sensitivity, a lens with a relatively wide maximum aperture, or a shutter speed, such as 1/8000 second, that will freeze quick action.

FILE FORMAT: An arrangement of digital information that may be particular to an application or generally adopted for use by a wide range of devices. Image formats in wide use include JPEG and TIFF. Raw format is proprietary to each maker, and often each camera by that maker.

FILL-IN FLASH: Flash used outdoors, generally to balance a subject that is backlit. Can also be used to control excessive contrast, add light to shadows, or brighten colors on an overcast day.

FILTERS: Any transparent accessory added to the light path that alters the character of the passing light. With film, filters can alter contrast, color rendition, or the character of the light itself (diffusion, diffraction, etc.) In printing, variable contrast filters are used to evoke different contrast grades from variable contrast black and white paper. In computer imaging software, a set of instructions that shape or alter the image information. In digital processing, filters are algorithms or a set of actions that change the character of the original image. Filters in digital are often "plug-ins", which means they work within the architecture of the main image processing program.

FILM: A compilation of light sensitive silver salts, color couplers (in color film), and other materials suspended in an emulsion and coated on an acetate base.

FINE GRAIN: Usually found in slow speed films, a fine-grained image is one where the medium of light capture and storage, the silver halide grain, is virtually invisible in the print or slide. With high, or coarse grain films (usually very high speed films) the texture of the grain becomes part of the physical reality, or weave of the image.

FIXER: The third step in black and white print and film processing; the bath removes unexposed silver halides.

FLARE: In lenses, internal reflections and/or stray light that can cause fogging or light streak marks on film. In general, zoom lenses have more potential for flare than fixed-focal-length lenses; in either case a screw-on lens hood helps reduce the problem.

FLASH: The common term used to describe the burst of light produced by passing electrical current through gas in a glass tube.

FLASH MEMORY: A special type of RAM memory that can hold data without electrical current. It is used in memory cards, the removable "digital film" used in digicams.

FLAT: Low in contrast, usually caused by underexposure or, in film, underdevelopment. Flat light shows little or no change in brightness value throughout the entire scene.

FLATBED SCANNER: A scanner that uses a linear CCD array for digitizing prints and film. Generally, the image is placed on a glass plate and the array moves past the artwork.

FOCAL LENGTH: The distance from the lens to the film plane or sensor that focuses light at infinity. The length, expressed in millimeters, is more useful as an indication of the angle of view of a particular lens. A shorter focal length lens, such as a 28mm, offers a wider angle of view than a longer one, such as 100mm.

FOCUS: Causing light to form a point, or sharp image on the image sensor or film.

FOCUS LOCK: In autofocus camera systems, a button, lever, or push-button control that locks focus at a particular distance setting, often used when the main subject is off to the side of the frame or not covered by the autofocus brackets in the viewfinder.

FORMAT: The size of the film, thus the camera that uses such film. Large format refers to 4x5 inches and larger; medium format uses 120 or 220 (6cm wide) film. Smaller formats include 35mm and 24mm. In computer imaging, the file structure, or "language" that can be understood by the device. The film analogy to format in digital terms would be more akin to sensor size and megapixel count.

FRAME: The outer borders of a picture, or its ratio of the height to width. The individual image on a roll of film. Also, to compose a picture.

FRAME GRABBER: Usually refers to a board that can digitize and process video signals to a single frame. Mac's Grab utility is a frame grabber, but can also be used to select certain areas of the monitor for capture.

GAMMA: A value that defines contrast of a photograph or electronic image. Gamma curves are key elements of monitor calibration. Gamma can be altered in black and white printing by working with various contrast grade papers. Gamma can be changed in an electronic image by working the curves in processing programs.

GAMUT: The range of colors available in an image or printer.

GIGABYTE: One billion bytes, or 1000 megabytes.

GRADE: With black and white printing papers, the built-in contrast of that paper, or the contrast evoked in variable contrast papers when printing through variable contrast filters. The lower the grade number the lower the contrast.

GRAIN: The appearance or echoes of the silver crystals in film in the final negative or positive image. The larger the area of the grain in the film emulsion, the more sensitive the film is to light; the more sensitive it is to light the "faster" it is. Larger grains are manifest in the image as mottled or salt-and-pepper clumps of light and dark tones, usually apparent in very fast films on visual inspection, in slow films upon extreme magnification. Grain is most easily seen as non-uniform density in areas sharing the same tone (such as a gray sky.)

GRAY SCALE: The range of tones, from bright white to pitch black that can be reproduced in a film and print.

GROUND GLASS: A specially prepared glass used as the focusing screen in cameras.

GUIDE NUMBER: A number that relates the output of electronic flash when used with a particular speed film or ISO setting on a digital sensor. The higher the guide number, the more the light output. Guide numbers, or GN, serve as a way to calculate aperture when shooting flash in manual exposure mode. Dividing distance into guide number gives the aperture: For example, a flash with a guide number of 56 (with ISO 100 film) would give a correct exposure at 10 feet with an aperture of f/5.6. With the state of today's automatic exposure flashes, guide numbers today are mostly useful for comparing the relative power of one flash to another and gauging the coverage a flash will afford. In most cases GN relates to the coverage when using ISO 100 film. It should be noted that some flash manufacturers will fudge the numbers by stating the GN at ISO 400.

Manipulating Light in Recording

Here's some follow-up on metering that to me makes mastering exposure worthwhile.
Moving light values around—it’s an odd idea, but one that allows you to make creative choices about how light is recorded. You can work to get as much visual information and tonal richness as possible, or you can eliminate certain values for graphic effects. Though it's usually best to go for the former, the ability to juggle recorded tonal values is a key creative element in photography that brings a personal touch to an often forgotten skill—seeing and interpreting light as you shoot.
One of the ways to begin the process is to shun the “matrix” or “evaluative” metering pattern. Not that there’s anything incorrect or faulty with that pattern; it’s just that we want to be able to direct the exposure system to read values as middle gray. Move on over to spot metering pattern.
If you spot meter off a bright area in a tonally-varied scene and do nothing, the bright areas will record as middle gray and the darker areas will be compressed down into darker and darker tones. Conversely, if you meter and expose for the darkest area in the scene the brighter areas record brighter on film and may be driven up into overexposure. Think of the tonal scale as working in lock step, with the ability to record a range of values as having a fixed spread that can be moved up and down the grayscale “spectrum” of brightness values.
Once this idea becomes real to you the path toward being able to manipulate light should open. You can, as mentioned, read only from a bright value and record that as middle gray, and have the darker areas lose detail and become dark tones. Or, you can read the bright value as middle gray and then compensate exposure by opening up two stops; thus the birghter value will record as bright with texture and visual information. Or, you can open up three stops and have that value record as bright, textureless tone. (For example, plus two would keep the texture of wood in a brightly lit white picket fence; plus three would give you pure, driven snow.)
Conversely, you can read the significant shadow value and have it record as middle gray, which will make the brighter values record brighter still (or perhaps become overexposed.) You can also read the dark value as middle gray, close down two stops to have detail recorded in that dark value. Or, or you can use that same reading, close down three stops and just get a deep tone with virtually no visual information. In these ways you control what is recorded with detail, and what records as dark or bright tones without detail. Compensation is not limited to working with two stops--you can manipulate values by one stop, or by half stops if that serves your purposes.
The above assumes you are working in an autoexposure mode, like aperture priority. If you prefer working in manual so much the better, as you can dispense with using the exposure compensation and exposure lock features on your camera.
All this gives you control over highlights and shadows, and how the scene you have in front of you will record. Once you grasp the concept of value and tonal manipulation you have a wide range of choices that allow you to shape the exposure in many ways.

Spot metering for the highlight in this shot "drives down" the darker values into deep shadow, or pure tone.

Image and text copyright: George Schaub

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Digital Image Quality Considerations

Today’s digital cameras range from simple point and shoot models to those used by pros. One of the keys to getting good images to print is the megapixel count of the sensor. Mega means “millions” and refers to the number of photo sites—or light and image gathering points—on the sensor. If you would like to make prints as large as 8 x 10 inches you will need at least a 6-megapixel camera. If you want to make larger prints—or get the best quality in your 8 x 10 inch prints—then a higher megapixel camera is recommended.

You might think that you can simply buy an older camera and get the megapixel count required to make great images and prints, but the key here is in the image processor. Older digital cameras tend to produce much noisier images with numerous image “artifacts” that can be quite detrimental to image quality. My advice is to avoid buying a used digital camera made prior to 2009.


You have a number of options when making photographs with your digital camera. For the best prints follow these guidelines:
If you have a camera that only allows you to photograph in JPEG format:
1) Choose the largest file size you can get. If you have a choice of various pixel resolutions choose the largest. This is generally indicated as “L” on the menu choice (with M or medium and B or basic also available.)
2) Choose the lowest compression ratio. Compression is a way for the system to gather more images on a given capacity memory card, but it tosses away information when it writes to the card and replaces that information with mathematical formulas, not “raw” image data. If, for example, you have a choice between Super Fine, Fine and Normal, or some such naming scheme, choose Super Fine.
3) Don’t “tweak” the image processor in the camera with contrast or sharpness settings. These are fine for special effects in the camera, but we can do better with the image information later in the digital darkroom.
4) Don’t use digital zoom. This actually crops into the sensor rather than getting optical information through the lens. Even if you use the largest available resolution (Large) and lowest compression you’ll lose information.

If you have a camera that allows you to choose between JPEG and Raw format, do the following:
1) Choose Raw. The only drawback to Raw is that you have to open and view and change the image file in special software, usually bundled with the camera that has a Raw mode option.
2) If you have a choice of pixel resolutions in Raw choose the highest pixel count.

Although the image resolution or file size is key when making prints, that’s just part of the equation. Exposure and lens sharpness and how the camera’s internal image processor converts the data from the sensor to digitized image information have a very important role to play as well.

When thinking about settings on your digital camera consider how file format and compression will affect results, and what the end use of the image will be. This shot was made in a coastal town in Maine using RAW file format on a Canon DSLR.

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Copyright: George Schaub 2011

An Occassional Glossary: C, D, E

Here's a bit more on the ongoing glossary project, C through E

Center-weighted Metering Pattern: In a metering scheme, an exposure system that takes most of its information from the center portion of the frame. Most center-weighted systems also take additional readings from the surrounding areas, but weight the reading towards the center.

Color Balance (digital camera): The setting in a digital camera that matches the available or artificial light to faithfully renders color.

Color Temperature: Described by the Kelvin scale, which is defined in degrees. It is used as a standard for judging the effect or color cast a certain light source will have on color rendition.


Continuous: The shooting mode that allows for continuous firing without lifting the finger from the shutter release button In tonality, a smooth range of tones from black to white. In autofocus, allowing shutter release regardless of whether subject focus has been attained.

Contrast: The relationship between the lightest and darkest areas in a scene and/or photograph. A small difference means low contrast; a great difference, high contrast. High contrast scenes may cause exposure metering problems; however, their “difficulty” can mean they hold the potential for more expression. In addition, combining bracketed exposures, HDR and tone curve compensation techniques can overcome high contrast challenges, Though contrast is often linked with scene brightness, there can be low contrast in a bright scene and high contrast in dim light. Contrast can also describe attributes of color, composition, and inherent qualities of film and sensors.

Correct Exposure: The combination of aperture and shutter speed that yields a full-toned image and the best possible representation of the scene. The constants in an exposure calculation are the ISO or sensitivity of the sensor and the brightness of the scene; the variables are the aperture and shutter speed.


Dedicated Flash: A flash that coordinates with the camera's exposure, and sometimes focusing, systems. Dedicated flashes may, among other things, automatically pick up the camera’s ISO setting, set the camera sync speed, and "tell" the camera when it’s ready to fire. Flashes dedicated to autofocusing cameras may also vary their angle of flash throw (coverage) according to the lens in use (even with zoom lenses), and emit autofocus beams that aid focusing in very dim light or even total darkness. For outdoor work, dedicated flashes may provide totally automatic fill flash exposure. In short, a dedicated flash can make flash photography as simple as automated natural light photography.

Depth of Field: The zone, or range of distances, within a scene that will record as sharp. Depth of field is influenced by the focal length of the lens in use, the f-stop setting on the lens, and the distance from the camera to the subject. It can be shallow or deep, and can be totally controlled by the photographer. It is one of the most creative and profound image effects available to photographers.

Depth-of-field Preview Button: A switch, button, or electronic push button on SLRs that allows the photographer to preview the depth of field of a selected aperture in the viewfinder. During composition the lens is wide open, thus the depth of field in the viewfinder is always that of the maximum aperture of the lens. DOF Preview is very useful for critical selective focus shots.

Dynamic Range: The ability of a sensor to record a certain range of light.

Electronic Flash: Known as a flashgun, strobe, or speedlight, a device consisting of a gas-filled tube that is fired by an electrical charge. It can be mounted directly on the camera hot shoe (which links the shutter release to the flash firing), or on a bracket or stand, and be connected to the camera via a sync cord or wirelessly through IR beams or radio signals.

Equivalent Exposure: Recording the same amount of light, even though aperture and shutter speeds have shifted. For example, an exposure of f/11 at 1/125 second is equivalent to an exposure of f/8 at 1/250 second.

Exposure: The amount of light that enters the lens and strikes the sensor. Exposures are broken down into aperture, which is the diameter of the opening of the lens, and shutter speed, which is the amount of time the light strikes the film. Thus, exposure is a combination of the intensity and duration of light.

Exposure Compensation Control: A camera function that allows for overriding the automatic exposure reading. The bias, or shift, can be set in full or partial stops. Used in difficult lighting conditions, when the reflective meter might fail (that is, dark or bright value dominance), or for deliberate under- or overexposure of a scene. Can also be used to bracket exposures.

Exposure Meter: Light-reading instrument that yields signals that are translated to f-stops and shutter speeds.

EV Numbers: A system of expressing exposure that combines apertures and shutter speed. Scene brightness translated to aperture and shutter speed values. For example, EV 15 at ISO 100 might mean 1/1000 second at f/5.6, or 1/500 second at f/8. EV numbers are often used as shorthand for the combined aperture and shutter speed value combinations and are used for making exposure compensation, when doing autoexposure bracketing or for readouts of exposure.

Very Selective Focus

There are a number of lenses that allow you to break the rules of depth of field. Because you can shift and tilt these lenses on an unusual axis not parallel to the image sensor, you can correspondingly tilt (up and down) and shift (side to side) the planes of focus in the photo. This technique is often used by large format, view camera photographers to attain unusually deep depth of field, where the shifts and tilts can be coordinated between both the front (lens stage) and back of the camera itself. Because the back of a DSLR is rigid there is less freedom of movement, and while specialty lenses can be used to create very deep depth of field, I use them for creating an almost angular plane of focus, thus a very shallow depth of field and “odd” focusing effects. What is most unusual is that these lenses allow you to turn the rules of depth of field on their head, if you will, by allowing you to have sharpness in, for example, one subject six feet away on the right side of the frame while another subject six feet away on the left side is quite unsharp.

While you can attain this effect via software, shooting with lenses that mount on your camera in the field is a much more visceral and engaging activity. I have used two types of lenses for this work-- “Lensbabys”, with various options for effects and operation, and a PC (perspective control) lens. Both are available for most every make of DSLR. They require manual focusing but usually can be used with automatic exposure, albeit with some occasional exposure compensation required.

PC lenses have a tilt and shift mechanism with various knobs and locks on the barrel. This allows you to tilt the lens to and fro and shift plus and minus. If you look at the back of the lens you will notice the rear element is recessed into the barrel. This so-called retrofocus-type construction allows the lens to be swung to and fro because the coverage of the lens circle exceeds the diameter of the sensor or film. Most of these pricey lenses are constructed so the tilts and shifts do not cause excessive vignetting, although you should watch for that with some more extreme movements.

You can play with the planes of focus in odd ways with one of the Lensbabys (www.lensbaby.com). This replaces the normal lens directly on your camera and allows you to shift the focusing planes so they are not parallel to the camera, something that is at odds with how we think about photographic sharpness. You do this by literally twisting or pressing down on one side of the lens; the bellows in the mount give way to make the lens surfaces sit at odd angles to the sensor. The lens can be shot wide open (usually about f/2.8) as supplied, or you can insert small diaphragms that create various aperture settings. I usually don’t use those stops as I want as shallow a plane of focus as possible.

Tools: PC (perspective control) lens or one of the Lensbaby models. Live View if available. Aperture priority or manual exposure mode. Manual focusing.

Depth of Field

The aperture setting determines the “thickness of the pipe” through which light flows, thus the volume of light and exposure. But as, if not more importantly it influences depth of field, thus plays a major part in creative focusing decisions.

You can think of depth of field as a grid of distance markers from the front to the back of your photo, sort of like a football field. When you make different aperture settings you are influencing how sharp objects at the ten, twenty, thirty yard lines, etc, will be. You are also influencing how sharp they will be in relation to the point or distance you actually have focus set.

Some settings will make the difference of sharpness between, say, the ten and thirty yard lines quite dramatic, and others will make it less so, and others will eliminate any sharpness difference between those distant points.

How can we control the fact that this image shows sharp foreground trees as well as the massive falls miles away? That’s the kind of control depth of field gives you. With a 24mm lens, exposure at ISO 250 was f/9 at 1/125 second.