Often described in millikelvins (mK, thousandths of a degree), NETD is determined by the thermal camera’s sensor sensitivity and the f-stop of the lens.Īn ƒ/1.0 Ge lens allows for 250% more infrared thermal energy to be transferred to the infrared sensor than an ƒ/1.6 lens. A thermal camera’s sensitivity is measured by its NETD (Noise Equivalent Temperature Difference). This increases the detail, contrast, and overall performance of the thermal infrared cameras, especially for surveillance where long-range detection, recognition and identification is desired in even in low contrast scenes. The lower the f-number the larger the aperture diameter, meaning more thermal IR energy is reaching the infrared sensor.
Lenses are typically specified with their maximum aperture (some lens apertures are internally adjustable) and max focal length/zoom power. An f/1.0 lens means the aperture diameter is equal to the focal length, whereas an f/2.0 lens would mean the aperture diameter is half of the focal length. You want to photograph a basketball game, and need to stop fast action.An f‑number (ƒ/#) or f‑stop refers to the ratio of a lens’s focal length to its aperture’s diameter (lens opening vs focal length) and indicates the amount of IR energy (heat) coming through the lens to the infrared sensor. Focus may be a problem, so you need to set your camera for maximum depth of field. You want to photograph people on the street, and know that you have to work quickly. You wish to lower your shutter speed to 30, to add a swirl of colored movement in a Zumba class. Your light meter indicates a shutter speed of 250, f/stop 8.
F STOP ON CAMERA ISO
Choosing the ISO number you indicated above, what will be your new shutter speed at f/4? The ISO speed you would choose to obtain that:_.ĩ. You need to gain faster ISO speed, at least three stops. You know this is too slow a shutter speed for sharp pictures ot a volleyball game. You know this means the widest the aperture can open is f/4. You have a variable focal length (zoom) lens marked 1:4. You wish to change your shutter speed to 500. You wish to change your shutter speed to 250. You wish to change your shutter speed to 60. Your shutter speed will be_?Ģ, Indicated f/stop: 5.6. To obtain a shutter speed of 1000, you must set your ISO number at_? Answer: 800, equivalent of one stop more light (more sensitive).ġ. To achieve this, you must change your ISO number. (Two stops less light, to compensate for two stops more light based on change in f/stop.)īut you also want a still faster shutter speed than 500.
To compensate, your shutter speed will be_? Answer: 500. You want a more shallow depth of field, so change your f/stop to 5.6. Assuming you wish to maintain the same amount of light striking the film for proper exposure, calculate the comparable numbers for each alternative. Your light meter shows you a combination of f/stop and shutter speed as indicated. Many digital cameras can set half shutter speeds. So if you want to change f/stops, shutter speeds or ISO numbers while maintaining the same exposure, you need to also adjust the other variables. ISO numbers too are measured in comparably: 100 is half as sensitive to light as 200 400 is twice as sensitive as 200, etc. That is, changing your f/stop from, say, 4 to 5.6 (one stop) is the same as changing your shutter speed from 125 to 250.
Keep in mind that f/stops, shutter speeds and film/digital sensor speeds are nearly always related by precisely half or double.
COMM 242, Advanced News Photography (Photojournalism)
0 kommentar(er)
