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What 3 things can sensitometry measure?
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Sensitometry
Chapter 9 Fosbinder
| Question | Answer |
|---|---|
| What is sensitometry? | The study of the relationship between from the amount of intensity from tube and amount of density on the film |
| What 3 things can sensitometry measure? | 1. Speed 2. Exposure Latitude 3. Contrast |
| What will always be on the film? | Chemical Fog |
| Equipment is needed for sensitometry? (2) | Penetrometer or Sensitometer Densitometer |
| What is a penetrometer? (Step wedge) | Piece of aluminum with varying densities in the shape of a step wedge. Step 1- black (X-rays pass through, thinest step) Step 11- white |
| What is a Sensitometer? | A device that is designed to expose a reproducible, uniform, optical step wedge onto a film. |
| Which is more effective, a penetrometer or Sensitometer? | Sensitometer |
| What is a densitometer? | A device used to numerically measure the amount of blackness on the film after processing. |
| What is the light transmit formula? | The amount of light that is actually transmitted through the film. it x 100 io ***only have to recognize formula*** |
| What Optical Density? | The numerical calculation of transmitted light through a film to incident light originally striking the film. Log10 (io) (it) OD ranges 0-4 0 = white part of the image 4 = black part of an image **only have to recognize formula ** |
| What is the relationship between optical density and light transmittance? | Increased optical density (more black) = decreased light transmittance Decreased optical density (more white) = increased light transmittance OD increases by .3 and decreases light by 1/2 OD decreased by .3 and increases light by double |
| What is a sensitometric curve? | A graph demonstrating how a film respond to a series's of increasing exposures. |
| 5 Parts of the sensitometric curve? | 1. Toe 2. Threshold 3. Straight-line region/ slope/ gamma 4. Average gradient 5. Shoulder |
| What is the toe of the curve? | Bottom of curve, low density/underexposed, never at zero because of base + fog |
| What is base + fog? | Film has a tint added to the base, fog is present due to processing chemicals. Acceptable range of B+F is between 0.1-0.2 optical density |
| Where do you find base + fog on a film? | On any blank unexposed part of the film. |
| What is the threshold of the curve? | Area where the curve begins to turn upward. |
| What is the straight line region (slop/gamma)? | Area of the diagnostic and useful ranges in density. Found between the threshold and the shoulder. |
| What is the optical density range on a graph? | 0-4 |
| What is the useful range of optical density on a graph? | 0.25-2.5 |
| What is the diagnostic range of optical density on a graph? | 0.5-2.0 |
| What is the shoulder of the curve? | The point on the curve where the maximum density have be produced. Most amount of black. (Dmax) |
| What is average gradient? | A line drawn on the slope representing the densities found within the image. Normal average gradient diagnostic range = 0.25-2.0 about the B+F measurement |
| What is solarization? | The point on the curve beyond where the maximum density had been produced (Dmax) |
| What are the 3 film characteristics determined by the curve? | 1. Film Speed 2. Film Contrast 3. Exposure Latitude |
| What is film speed? | The films sensitivity to radiation, and indicated the amount of optical density produced for a given radiation exposure. |
| What is a speed point? | The point on hype sensitometric curve that corresponds to the optical density of 1.0 + B + F |
| What is the speed exposure point? | The point in the x-axis that corresponds to the speed point on the y-axis which indicated the intensity of the exposure needed to produce a density of 1.0 + B + F regardless of the shape of the curve. |
| What is film contrast controlled by? | The design and manufacturing of the film components and effects of processing. |
| If the graph has a high contrast, what will the slope look like? | More vertical. |
| If the graph has a more horizontal slope what type of contrast will the film have? | Low |
| How do you find the slop of a curve? | Rise Or Y2-Y1 Run X2-X1 High number = steep slope = high contrast Low number = long slope = low contrast |
| What is exposure latitude? | Refers to the range of exposures that produces optical density within the straight line region of the curve Horizontal slope = wide latitude = low contrast, lots of grays Vertical slope = narrow latitude = high contrast! more black and white |
| What is optimal density? | It is achieved when radiographic densities are produced that lie within the straight-line region of the curve thus maximizing the amount of information visible. |
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Aborys88
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