Winter drought in wheat
The most effective measure to defend the winter drought of wheat is to pour in frozen water at the time of “freezing and smashing†and promptly suppress it to make up for cracks in the field. For the wheat fields that have already experienced winter drought, watering should be cautious, because nowadays it is “several daysâ€, the minimum temperature at night can reach below −10° C., the soil layer is frozen, and water can't be in time to form ice after watering. Layers, wheat seedlings easily suffocate under ice.
For wheat fields with severe drought, it is best to use sprinkler irrigation, and to select a small amount of supplements before and after noon during the day when the average daily temperature reaches 0°C or more. Without sprinkling irrigation conditions, as far as possible, measures such as covering manure and sealing joints will be used to protect the cold. After the dry wheat fields turn green, they can pour small water early.
We may have heard of the Dome Fixed Focus Camera/ Fixed Focus Dome Camera/ Fixed Focus Dome cameras/ Fixed Focus Digital Dome Camera/ Fixed Focus Dome Camera Amazon/ Fixed Focus Dome Camera CCTV, so what is the Dome Fixed Focus Camera? We know that the dome refers to the camera shape, so what about the Fixed Focus? Actually, the Fixed Focus refers to a type of the camera lens. Today let me introduce the camera lens for you.
Last time, I have introduced the camera lens and one classification for you. Today please let me introduce the 2nd classification for you---the classification according to the occasions.
1. The standard lens
The lens with the angle of view at about 50°(which is also the angle that a person can see without turning his head and eyes), is called the standard lens. The focal length of the 5mm camera's standard lens is mostly 40mm, 50mm or 55mm. The focal length of the 120 camera's standard lens is mostly 80mm or 75mm. The larger the CCD chip is, the longer the focal length of the standard lens will be.
2. The wide-angle lens
The wide-angle lens has the angle of view at above 90 degrees, which is suitable for shooting close and large-scale scenery, and can deliberately exaggerate the foreground to show a sense of perspective. The typical wide-angle lens of the 35mm camera has a focal length at 28mm and an angle of view at 72°. The 50mm, 40mm lens of the 120 camera is equivalent to the 35mm, 28mm lens of the 35mm camera.
3. The long focal length lens
The long focal length lens is suitable for shooting distant subjects. The small depth of field can easily make the background blurred and the subject stand out, but it is bulky and the difficult to focus on the dynamic subjects. The long focal length lenses of the 35mm camera are usually divided into three levels, 135mm or less is called the medium focal length, 135-500mm is called the long focal length, and above 500mm is called the super long focal length. The 150mm lens of the 120 camera is equivalent to the 105mm lens of the 35mm camera. The long focal length lens has the telephoto lens design because it is too bulky, that is, a negative lens is added to the lens behind , and the main plane of the lens is moved forward, then a shorter lens body can be used to obtain the long focal length effect.
4. The reflective telescope lens
The reflective telescope lens is another design of the super telescope lens, which uses a reflecting mirror to form an image. However, due to the design, the aperture can't be installed, and the exposure can be adjusted only through the shutter.
5. The Macro lens
The Macro lens can not only do the close-up macro photography, but also do the telephoto.
In conclusion, we can choose rake the angle of the view into consideration according to our needs, when we choose a Dome Fixed Focus Camera.
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