What are the factors affecting image sharpness in radiography?
(i) The size of the X-ray source (target or the focal spot) smaller the focal spot lesser the image unsharpness. (ii) The distance between the X-ray source and the recording surface which is the film (larger the distance lesser the unsharpness). (iii) The distance between the film and the subject being radiographed.
Radiation source as small as possible 0 The sharpness (detail) of images seen on a radiograph is influenced by the size of the focal spot (area in the target where x-rays are produced). The smaller the focal spot (target, source), the sharper the image of the teeth will be.
Obviously the optical quality of the glass elements within a lens determines a great portion of how sharp a lens is, but there are a surprising number of elements that factor into the sharpness of the image. Camera movement, shutter speed, aperture, ISO, filters, and tripods all have a role to play.
Radiographic quality depends on radiographic density, contrast, and geometric factors that affect detail. This chapter will define diagnostic image characteristics and explain how to obtain them (Fig. 5-1). Figure 5-1 Radiograph of a seashell showing contrast, density, and detail characteristics.
The important components of the radiographic image quality include contrast, dynamic range, spatial resolution, noise, and artifacts.  We will discuss these components briefly. Dynamic range: The dynamic range is the range of various X-ray intensities that can be imaged by the detector.
The shutter speed you use is a big factor in how sharp an image is. This is particularly true if you're handholding your camera. Humans aren't perfectly steady. Even when standing still the simple act of breathing causes movement.
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Last week, we looked at three common factors that can lead to a loss of image sharpness: the optical design/assembly of a lens, missed focus, and subject motion. This week we're going to look at two more: camera shake and depth of field.
Sharpness is a combination of resolution and acutance, where the first one is the size in pixels and the latter is a contrast of a photo. Meanwhile, the resolution depends on lens characteristics, acutance is different for every person.
Sharpness is one of the most important image quality attributes for a camera. Often, the sharpness and resolution of a camera system are confused and used interchangeably. In this post, I hope to sort out some of the confusion.
Will improve the sharpness of a radiographic image?
Source-to-object distance: The greater is the source-to-object distance, the smaller is the penumbra, resulting in a sharper image. Object-to-receptor distance: The greater is the object-to-receptor distance, the larger is the penumbra, resulting in a less sharp image.
Five observers read the radiographs. The first experiment showed that, when the film density is kept constant, the higher the kVp, the lower the resolution and image contrast percentage; also, the higher the mAs, the higher the resolution and image contrast percentage.
- Color Accuracy.
- Chromatic Aberration.
Factors that Affect Radiographic Contrast: Scattered radiation will increase the image noise and decrease the radiographic image's contrast. Radiographic collimation can reduce the amount of scattered radiation and improve the radiographic contrast.
For bitmapped images, the two characteristics most often associated with clarity are pixels per linear unit (often colloquially expressed as "dots per inch") and bit depth ("bits per pixel" or "bits per color channel").
Kilovoltage. Kilovoltage is the primary contrast control factor, but radiographic contrast is influenced by a number of other factors as well. These include the nature of the subject, the characteristics of the film and or the image receptor, and the amount of scatter radiation impacting the image receptor.
Focal length affects the sharpness of your photo as longer focal lengths have reduced depth-of-field. Read: What is Depth of Field. For example, if you have a very shallow depth-of-field, everything immediately in front and behind your in-focus subject will appear blurred.
This is the difference in the bright and dark areas of the image. If the contrast is high, the image looks lively; conversely, if the contrast is low, the image looks flat and monotonous. This is the image's clarity. The higher the sharpness, the more distinct the subject's contours will be.
The sharpness of the image on a display depends on the resolution and the size of the monitor. The same pixel resolution will be sharper on a smaller monitor and gradually lose sharpness on larger monitors because the same number of pixels are being spread out over a larger number of inches.
Image sharpness can be measured by the “rise distance” of an edge within the image. With this technique, sharpness can be determined by the distance of a pixel level between 10% to 90% of its final value (also called 10-90% rise distance; see Figure 3).
What is the difference between sharpness and resolution?
Higher resolution images create sharper images because of a higher pixel count. However, if a high resolution image is “soft” or out of focus, you just have a really big unsharp photo. So in short, high resolution doesn't = sharpness.
Image resolution is typically described in PPI, which refers to how many pixels are displayed per inch of an image. Higher resolutions mean that there more pixels per inch (PPI), resulting in more pixel information and creating a high-quality, crisp image.
Depending on what TV you have, you should set your sharpness to 0% or anything under 50%. If you notice a halo appearing around objects or if the image is too grainy, your sharpness setting might be too high. You will also notice that motion looks more natural when your sharpness settings are correct.
If you want an objective way to measure sharpness, the Edge-On-Up Sharpness Tester will give you accurate and repeatable results. Rather than test by cutting hair or paper, the Edge On Up uses a certified testing media and gives an actual number that can be used to compare edges.
As I noted in the introduction, a lack of sharpness can be due to the aperture, shutter speed, or ISO settings. In the case of aperture, if your depth of field (the area of the image that's in sharp focus) is too shallow, you might find that your subject isn't sharp, as seen in the image above.
Shutter speed is an essential basic setting to ensure the maximum sharpness. If your subject is moving and you're not using the right shutter speed, your image will be blurred. For instance, to take sharp photos of birds in flight, sports, and other fast-moving subjects, you'll need to use a fast shutter speed.
In photography, acutance describes a subjective perception of sharpness that is related to the edge contrast of an image. Acutance is related to the amplitude of the derivative of brightness with respect to space.
A photograph's exposure determines how light or dark an image will appear when it's been captured by your camera. Believe it or not, this is determined by just three camera settings: aperture, ISO and shutter speed (the "exposure triangle").
Sharpness is the clarity and detail of an image, affected by the lens, focus, and motion. Both noise and sharpness can be compromised by long exposure night photography, because you need to use high ISO settings, wide apertures, and slow shutter speeds to capture enough light.
Results: Image sharpening significantly affected spatial resolution and noise. Conversely, dynamic range and contrast resolution were not significantly affected by image sharpening.
How does aperture affect image sharpness?
If the aperture is wide open, a greater number of the photons will pass undisturbed. But at small aperture settings, most of the photons will have to pass close to the aperture blades, resulting in increased deviations from the actual path. The increased deviations create images that are less sharp.
- Is the amount of radiation required to produce a radiograph of standard density. A faster film will require a shorter exposure time to produce the same density resulting in less exposure to the patient. Image sharpness / detail - the clarity of the edge or the outline of a structure.
An increase in kVp extends and intensifies the x-ray emission spectrum, such that the maximal and average/effective energies are higher and the photon number/intensity is higher.
Higher kVp increases the penetrating power of the x-ray beam and results in less absorption and more transmission in the anatomic tissues, which results in less variation in the x-ray intensities exiting the patient. As a result, images with lower contrast are produced.
Changes in mAs affect radiation dose, signal-to-noise ratio (SNR), and contrast.  Increasing mAs produces more electrons in an X-ray tube and subsequently increases the amount of radiation exposure.  High mAs will increase SNR but will decrease image contrast.
Particularly when smaller images are enlarged, they can get blurry and of low quality. In often cases, when images are taken, the lens is not properly focused on the subject. Hence, images get out of focus, blurry, and pixelated. All of this can significantly reduce the quality of the image.
General characteristics of imagery, such as resolution, scale, tone, and contrast, are described in this chapter. Resolution concerns the minimum separation between two objects—that is, the distance at which the objects appear distinct and separate in an image.
There are four primary image quality factors. They are: contrast, IR exposure or density, distortion, and recorded detail.
Differences in absorption results in contrast. Type of irradiated material influenced by atomic number and tissue density. When differences in atomic number or density of adjacent tissues is great, there is high contrast. When differences are minimal, there is low contrast.
The sensitivity is the measure of the resolution of the image which can be obtained on a radiograph. The sensitivity is affected by exposure parameters (voltage, amperage, time and source-film distance), subject sharpness/ unsharpness, image contrast/ film density, film quality and processing technique.
What are the 5 radiographic densities?
1. The five basic radiographic densities: air, fat, water (soft tissue), bone, and metal. Air is the most radiolucent (blackest) and metal is the most radiopaque (whitest).
- Circle of confusion (COC)
- Aperture of the lens.
- Lens focal length.
- Focus distance (distance between lens and subject)
Sharpness. Sharpness is arguably the most important single image quality factor: it determines the amount of detail an image can convey.
Resolution, noise, and artefacts are the main parameters of image quality.
Various factors affect the diagnostic quality of radiographs: overexposure, underexposure, and poor positioning (these three factors can be controlled by the radiographer or medical imaging scientist); motion by the patient (from the patient's condition); and processing conditions and x-ray machine (equipment) ...
Sharpness. The unsharpness or blurred edges seen on a radiographic image is termed: Penumbra. The geometric characteristic that refers to a radiographic image that appears larger than its actual size is termed: Magnification.
If the contrast is high, the image looks lively; conversely, if the contrast is low, the image looks flat and monotonous. This is the image's clarity. The higher the sharpness, the more distinct the subject's contours will be. This is the depth of the colors in the image.
In the first article in the series, we looked at three common factors affecting image sharpness: the optical design of a lens, missed focus, and subject motion.
Two fundamental factors contribute to the perceived sharpness of an image: resolution and acutance. Acutance describes how quickly image information transitions at an edge, and so high acutance results in sharp transitions and detail with clearly defined borders.
Lighting, more than any other parameter of a photograph, is what will dictate how sharp your image looks.
What are the factors affecting image quality?
Sharpness, distortion, vignetting, Lateral Chromatic Aberration, noise, and dynamic range are the principal factors that can be measured at this stage. Most of these measurements can be clearly classified as good/bad.
Image quality is not a single factor but is a composite of at least five factors: contrast, blur, noise, artifacts, and distortion, as shown above. The relationships between image quality factors and imaging system variables are discussed in detail in later chapters.
shutter speed would be around 1/125th of a second with a standard lens or mid-range zoom lens on the camera. Unless you have extremely shaky hands, that will give you a sharp picture most of the time. The shorter the time that the shutter is open the sharper the photo will be.
In practical terms, resolution describes the sharpness, or clarity, of an image or picture. It is expressed in terms of the number of pixels that can be displayed both horizontally and vertically. Resolution is an important factor to measure the visual quality of digital images, photos and videos.