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SLR cameras are much appreciated by military photographers because of their exposure resolution, sensitivity and versatility in the field, the availability of a wide range of lenses and because they allow an accurate image preview section of the closure of the moment. Many photographers prefer for digital SLR sensors larger than most compact digital cameras, now with image sensors of the same size as conventional film formats. These sensors enable such largeField of-view film formats as well as their sensitivity values comparable.
Over 80% of digital SLR cameras sold today are Nikon and Canon models. As a result of their dominant position, have a plethora of lenses and accessories for these two camera bodies, what an excellent choice and great prices. These include: lenses, which are fast, light, optical image stabilization, autofocus and a night vision camera modules and otherAccessories that enhance the overall performance of the camera. Note that there are other camera manufacturers offer good products worthy of consideration for some applications, only Nikon and Canon cameras mentioned in this article.
Pixel: How many? How big?
The most obvious change in the evolution of digital SLR cameras have pixels, the steady increase in the number of make-up, the image sensor. Commercial cameras have seen the number of pixelsthe camera sensor to grow twenty times as many years, 1MP (1 million pixels) in 1990 to about 20MP in 2010.
There are cameras with larger sensor array better? Not necessarily. Depends on demand. There is more to understand the effects of array dimensions as large as only the number of pixels. There are two other important issues in this case: the physical size of the array of sensor and the physical size of the pixels.
Impact of the physical size of the array
L 'DSLR first time, the image sensors) were significantly smaller than the traditional 35 mm film formats (36mmx24mm. As shown in Figure 2, digital imaging sensors are now available in several different sizes. The image sensors smaller are about 2 / 3 the size of 35mm. They are both Canon and Nikon (known as the DX format) (referred to in APS-C) are available. Canon also offers cameras with a slightly larger sensor, APS-H , which is about 28×19mm it is. TheMost sensors (known as "full-frame") are now available from both Canon and Nikon and have the same size as the original film SLR sensor, 36mmx24mm.
For cameras with an image sensor that is smaller than full-frame, a digital crop factor was defined (also known as focal length or magnification) to (43.3 mm can be calculated) the relationship between the size of 35mm on the diagonal of thecamera image sensor size. How should the focal length of term, multiply the focal length of the crop factor is, of course, the effective focal length of a lens that would produce the same field of view when used with a full frame camera. For the military photographer, the concept is seen with a crop factor of> 1 is usually an advantage. For viewing at a distance, a closer look is welcome and the crop factor gives photographers a boost infocal length, so that they frame more easily when the subject is far from filled. For example, the focal length multiplier for a Nikon DX format 1.5. With a 200mm lens on a Nikon DX format the same field ofview provide a 300mm on a full frame camera. But while there are benefits to viewing distance, the narrowing of the field of view is sometimes a disadvantage for photographers, when a wide field of view is desired. For example, a 24mm lens on a Nikon DX formatThe camera is in the same field of view as a 36 mm lens may be too narrow for the application required the use of expensive ultra wide-angle objectives, to deliver the desired field of view (16mm in this example). Of course, the cameras' image sensors, full-frame, the same size as 35 mm in size, not crop factor (crop factor is 1).
Effects of physical pixel size
To better understand the effects of pixel size, compare the performance of two cameras, which havethe same physical size but different numbers of array of pixels (pixels and sizes accordingly). For this example we want to compare the Nikon D3X (image sensor with 24MP full-screen) and Nikon D3S (full-frame image sensor with 12 megapixels). The D3X is the physical size of the pixels of about 6 microns and the pixels D3S, which are about 8.5 microns, about 40% larger. In this example, if the photographer military monitors at a distance, are the identification of objectsrelated to the number of pixels of destination. Thus, if the goal is the same one used on the two cameras are compared, the distance for the model with high resolution over the lower resolution camera. otherwise explained, to provide for the lower resolution camera on the same resolution, higher resolution camera with a 300mm lens, would be the lower resolution camera or a lens is 420 mm or the photographer would have to approach the target byabout 25% of the route.
As far as the resolution goes, smaller pixels are better and the advantage goes to the high-resolution camera, the lenses that are lightweight, easy to hold and, in essence, "faster" to use. Sorry, there are even smaller pixels is not always the best thing for a surveillance camera! All things being equal, because the pixels are smaller in size, but are also much less effective in the detection of light, resulting in less sensitivity of the camera. Pixelssensitivity associated with the area of the pixel is to be so in our comparison of pixels that are the provision of 40% larger, probably twice the sensitivity (1.4×1.4 ~ 2). This means that the sensitivity of the light itself requires further liberalization or shutter speed will double. Alternatively, have the camera's processor, the signal gain. (More details in the next section). Nikon apparently no one knows that for some photographers, more resolution is not always better. The addition of pixels means that theysmaller and smaller the pixels the lower the sensitivity to light. Fortunately, the techniques of noise reduction has improved considerably in recent years, which increases the resolution, while the sensitivity approximately constant. So what if the current strategies used to reduce noise to an existing sensor without adding more pixels? This is certainly not what the design of the Nikon D3S determined, the 12.1MP resolution allowed them to increase the sensitivityCustomers who need them. For photographers who really need higher resolution, 24.5MP, Nikon D3X.
Low Light Photography
For the military photographer, some of the most difficult situations occur at night, when some 'ambient light, or scenes from a distance. Today's digital SLR cameras have unique features and accessories available to help photographers make the most of the night-imaging.
Aperture and shutter speed
L 'primary factors that affect the images in low light conditions is still essential for photography – aperture and shutter speed. For photography at night, because the depth is usually an important factor, it makes sense, an objective which has a maximum aperture range. The choice of a target for a particular application can be as important as the choice of DSLR camera. It is possible that the Nikon or Canon body due to specific objectivesThat are available. Similarly, the exposure time for night shots should be as long as possible, but still to avoid blurring the observation set of moving objects or camera shake.
Enhanced ISO – More gain with handicaps
Aperture and shutter speed directly influence the amount of light falling on each pixel of the image sensor and touching the sensor output electrical signal. In addition, digital SLR cameras allow the photographer to adjust the gain (ie gain)the sensor output electrical signal. (This is very different from the ISO definition for film cameras, which has been adapted for film speed to be adjusted). For DSLR cameras, the profit is increasingly better signal. Like all electrical circuits are image sensors are not perfect, and the image signal, but also produce some noise in the form of unwanted random errors in the signal chain. The noise in digital images appears as patches of grain or wrong color. To avoid tooyou put a lot of noise, the photographer-night, the camera's ISO to a value high enough to illuminate the image and maintaining acceptable levels of noise. Today, the maximum is usually 1600, but some cameras produce images perfectly usable at ISO 3200, 6400 or 12800.
In addition to the standard ISO settings, digital cameras are now leading noise suppression on digital images. As a result some additional revenue is up to the camera enabled, sometimes a step(H1), and in fact, twice the maximum ISO setting, but also a short walk (H2, 4 times) and three (H3, 8 times). The ISO setting is now extended on most digital SLR cameras. For example, to allow both the Canon EOS-1D Mark IV and Nikon D3S three levels of the extended ISO, the ISO setting to an equivalent of 102,400 results! It 'important to note that the images are set as this is generally a high level of noise and significant deterioration of the resolutionbecause of noise reduction techniques. Of course, as with all electronic circuits with high gain noise significantly degrade image quality.
Night Vision Modules
Today's digital SLR cameras allow the photographer control over aperture and shutter speed ISO settings allow the collection of excellent images for use in low light conditions, the otherwise possible. But in many situations, such as photographing scenes at night with little ambient light, ortelephoto lens at night at a distance, digital SLR cameras simply do not have enough sensitivity for shooting enough. In these situations, night vision equipment modules, the ideal complement.
Night vision accessory module fits between the lens and SLR camera body. Just remove the lens, attach the night vision module for the camera and put the 'target. AstroScope night vision modules are designed tocombinations are perfectly integrated with the camera and lens, maintaining all electronic functions of the camera lens (with image stabilization) on the camera sled. The night vision module is powered directly from the camera with power and off easily by opening the shutter.
The night vision module has an automatic control of gain, that its performance is ensured relatively constant. As the camera settings, are relatively easy toConfigure as follows:
• Exposure time 1 / 30 sec (no need to make it shorter, because the amplifier has its own GAL)
• Manual iris (lens, so that the F-stop setting stays put)
• F-stop at maximum aperture (warning light)
• ISO setting to a noise level of the camera is not shown, adapted
• Auto Focus Off (image intensifier scintillation autofocus sensors can be confused)
• Image stabilization on (to maintain stable images duringThe camera is in motion)
Summary
The development of digital SLR (DSLR) continues with features that impressive speed, with a uniform. For the photographer or the military police, the new models of digital SLR cameras and new features can be very useful for portable monitoring and field to collect information, both at night and during the day. Some advantages are:
• Image sensor array to continue to grow in physical size, now withFull-frame format is the traditional film SLR cameras.
• Pixel thick, even more, the resolution and the ability of digital SLR cameras to recognize a total of more than recognize and identify objects at a distance.
• Improved sensitivity of the cameras, cameras with ISO settings up to 12,800 natives.
• night vision modules are available for the light intensity of 8-10 f-stop, while they continue to improve with the electronic controls lenscontinue to work, even the image stabilization.
DSLR continue modules are highly valued by military photographers view other styles because of their large camera sensors, resolution, sensitivity and versatility in the field, the availability of a wide range of lenses and night.
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