QCLlaser

The ASHA QCL can be used to assist with treatment planning, prioritization of goals, counseling, and documentation of outcomes. The ASHA QCL may be used to supplement other measures of impairment or functional communication. It is an ideal complement to the ASHA FACS. The average time to complete the scale is 15 minutes.

Semiconductor laser

"Full Stops" are noted in bold, above. If you think these numbers are strange... be glad we traditionally round them off to only two significant digits. It could be worse. Strictly speaking, f2.8 should be f2.823427...

Where do they get those particular numbers?!  f-stop values have to do with the area inside of a circle – the circle within your open aperture that allows light into the camera.  Note that every-other number is different by a factor of about 1.4. Note that 2.0 is approximately 1.4x1.4    So 1.414 is the square root of 2, which is related to the fact that when you open your aperture by a full stop, you double the amount of light allowed in.

Aperture is measured, or described in "f-stops". The smaller the "f-stop", the larger the aperture. Its odd at first, but that's the system.

Qclscientific

(in the diagram, above, the max diameter of the lens is "D", which is similiar to the max aperture of the lens — though the aperture will always be somewhat smaller than the lens.)

At large apertures the f-stop is a small number and each successive stop is only a slightly larger number. As apertures get smaller, the f-stop number gets larger and the numeric gap between f-stops gets larger.

Aperture is one of the three corners of the "exposure triangle" — the three settings or controls that your camera offers to allow you control over exposure. (for the other two, see Shutter Speed and ISO)

Go up a Half Stop or a Third of a Stop... The "in between" partial stops are even less consistent mathematically than the whole stops. Between the largest apertures, you may have approximate half steps — f/1.4 to f/1.8 is not actually a half stop, but its close enough. At smaller apertures, rough 1/3 stops are common — between f/11 and f/16, you have f/13 – f/14. The steps are not actual 1/3 steps, but, again, its close enough. Photographers adjust freely up and down in fractional stops to improve their exposure — but they are usually not calculating aperture or percent change in illumination. They are just adding or removing exposure to lighten or darken the image — aperture adjustments become rather intuitive eventually, rather than being precisely calculated. Its more fun that way, after all.

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Funding support for developing the ASHA QCL came, in part, from Grant H133G970055 awarded to ASHA from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research.

Quantum dot laser

The ASHA QCL emerged from a widespread need for a reliable and valid instrument designed specifically for assessing the quality of communication life for adults with communication disorders. Quality of communication life is defined as the extent to which a person’s communication acts—influenced by personal and environmental factors, and filtered through a person’s own perspective—allow meaningful participation in life situations.

"An example of the use of f-numbers in photography is the sunny 16 rule: an approximately correct exposure will be obtained on a sunny day by using an aperture of f/16 and the shutter speed closest to the reciprocal of the ISO speed of the film; for example, using ISO 200 film, an aperture of f/16 and a shutter speed of 1/200 second. The f-number may then be adjusted downwards for situations with lower light." (WikiP)

Aperture literally means Opening or Hole. A camera's aperture is a hole of varying size that influences how much light exposes an image — light passes through the opening in order to get to the image sensor (or film). The bigger the hole (the larger the aperture), the more light reaches the sensor. The smaller the hole (the smaller the aperture), the less light reaches the sensor.

Stops  f-stops and common fractional stops:  f/1 – 1.2 – f/1.4  - 1.8  - f/2.0 – 2.2 -  f/2.8 – 3.2 — 3.5 – f/4.0 – 4.5 –  5.0 — f/5.6 – 6.3 – 7.1 – f/8.0 – 9 – f/11 – 13 – 14 – f/16 –18 – 20 – f/22 – 28 – f/32 — f/45 — f/64 — f/90 — f/128

Quantum well

"Diagram of decreasing apertures, that is, increasing f-numbers, in full-stop increments; each aperture has half the light gathering area of the previous one." (WikiP)

When purchasing lenses, the larger the aperture (the smaller f-stop) the better – and it will cost more. Most intro consumer zoom lenses have a maximum aperture around 4.0 or 4.5. A professional zoom lens may have a maximum aperture of 2.8 — such a lens will cost several times more than the consumer zoom lens. A decent 50mm prime less may have a maximum aperture of 1.8. A professional quality 50mm prime may have an aperture of 1.2 and cost a thousand dollars more than the f/1.8 lens. The size of the actual glass lenses in the f1.2 lens are much larger and are much more costly to manufacture.

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This podcast discusses of the essence of aperture – one of the core technical concepts that controls exposure.  In the podcast, he compares aperture to turning on a faucet to fill a bathtub; the wider the aperture, the less time it takes to “fill” an image with light; the more open the faucet, the less time it takes to fill the tub with water. Filling the tub is like exposing an image until it becomes fully white. To be more accurate, each and every pixel in your camera's photo-sensor is such a bathtub or a bucket — if no water (light) gets in, that pixel is black. If the bucket fills with water (light), that pixel is white. Also, how aperture is related to depth of field is discussed (the depth of the region that is in focus).  The wider the aperture, the narrower your depth of field.  The smaller the aperture, the deeper the field of focus.

The ASHA QCL captures information about the impact of a communication disorder on an adult’s relationships; communication; interactions; participation in social, leisure, work, and education activities; and overall quality of life. It is intended to provide information about the psychosocial, vocational, and educational effects of having a communication impairment. The ASHA QCL was found to be a valid measure of the quality of communication life for use with adults with neurogenic communication disorders (i.e., aphasia, cognitive communication disorders, and dysarthria).

Add Two Stops... From f/5.6 to f/11 is two stops — your exposure has 1/4 as much light as before. Note that the number 11 is roughly 2x 5. From f/11 to f/22 is up two stops — 1/4 as much light. And, obviously, 22 is 2x 11.

That’s not fully explained…I know. The "up" and "down" jargon gets frankly confusing because f-stops increasing means aperture decreasing. Its just one of the hazards of photography.

Every full stop, the aperture doubles.    "aperture doubles" means that the lens allows twice as much light in. So, if I change aperture from f/11 to f/8, f/8 allows twice the light in as f/11. When the aperture is closed by a full stop (via a higher f-stop),  ½ of the light is allowed in.  So if a switch from f/2.0  to f/2.8, f/2.8 lets ½ of the light in that f/2.0 lets in.

Go Down a Stop or Open Up a Stop And, conversly, every time the f-stop decreases by a factor of 1.4, the aperture is twice as large — twice as much light exposes the sensor. If you change your aperture from f/16 to f/11, you've gone down a stop and double the amount of light reaching the sensor... your image will be lighter. If you adjust your apertuure from f/5.6 to f/4, you've opened up by a full stop; twice as much light gets through. From f/22 to f/16 is down a stop and double the aperture.

Add a Stop or Closing Down a Stop For the photographer, every time the f-stop increases by a factor of 1.4, the aperture is half as large — half as much light exposes the sensor. That is, if you change the f-stop from f/1.4 to f/2.0, you've added "a stop" — you've reduced your exposure by half. If you change from f/2.0 to f/2.8, you've added a stop. From f/5.6 to f/8 you've added a stop. Etc.

Note that each lens has its own max and min aperture (lowest f-stop and highest f-stop).  These aperture variations are one of the key distinctions in lens design, lens capability and, of course, lens price.