Introduction to photography
What is a gray card, grey card how to use the grey card usageGray card is a benchmark for accurate detection of exposure. Rich, color-saturated photographs from the accurate exposure. If the light is too bright or too dark scene, it may lead to errors in exposure. Gray card of complex light scenes can be balanced for 18% neutrals, by light meter will record the reflected light gray card, you can obtain accurate exposure value!
Gray card suitable for hand-held light meter, TTL digital SLR cameras and light meters the rangefinder camera. Use the gray card take high quality photos of assurance, is the indispensable tool for photographers! So, how to use a gray card?
determine the exposure value
set the meter to measure the reflected light feature (removed white reflector). In order to obtain accurate measuring values, should ensure that the gray card shot of light coming from the same direction. Measured value shall ensure meter and gray card at a distance of 15 cm or less, and should avoid any bright light reflection on the gray card, or its shadow on the gray card. Measurement Studio light, Gray card should be placed the subject of positive and as close to your subject. While rotating grey grey surface, between the gray card, camera and light source form a certain angle and elevation.
angle is 30 °-45 ° isosceles triangles, Gray card should be facing the camera angle of 1/3 with the main light source. Common light is the Deputy should be closer to the optical axis of the camera.
in natural light grey card can be placed in the subject position, measured values can also be placed in the camera's location. But must ensure that the grey card on the received light intensity consistent with the objects of light intensity. If you experience cloudy day or in the context of weak light camera, you can use sky scattered light, portable location lights or reflectors as source of light to measure the exposure value.
to make exposure more accurately when the data is sometimes measured in camera Aperture or adjusted speed value.
If subject is dark in color and very dark tones, adding dark layers should turn up the 1-1/2 aperture; if objects lighter than the color or light should be reduced 1-1/2-stage aperture. Normal contrast scene without the need for adjustment. But in case of strong backlighting when shooting scenes or contrast ratio, recommends that the photographer in this case surrounded by light.
determine of main and auxiliary light
light is the main light plus under light illumination intensity and under separate lighting when lighting intensity ratio. Under normal circumstances than color photos should not be more than 3:1; ratio should not exceed 5:1 of the black and white photos. If more than this number will lead to imbalance of colors and levels of loss.
using a gray card can determine the shooting ratio. Determine the ratio can be carried out according to the following steps:
read the numerical-light grey card placed before the subject and as close as possible to the subject, all main and auxiliary lights on (does not include reverse light). Adjust the gray card toward the light the light angle, with light meters measure the gray tab of values. Light meter showed maximum readings recorded the readings.
read Vice numeric-before the gray card is placed objects, light main lights off and rotate the gray card so that alignment of the camera lens. Light meters measured values on a gray card and recorded.
made two numerical grade can be calculated the scenario of light. Is given in the following table is to use light and only used under light illumination intensity ratio.
determine the density and color balance
grey card can determine a photo's color balance. During shooting of the gray card shot into the screen as you corner or gray card shot with a piece of film. Chongkuo photos and grey card physical alignment, simply through the eyes or color Analyzer to determine the photo's color balance.
the gray card image as colored, extended reference colors. Gray card shot a transparent positive or negative, can help her work to determine the best color balance and density.
Gray card shot the film process is the process of recording scene light colour. Light colour can lead directly to filter results in a color print is different.
most colour films could not be shown absolutely gray value. So between nude and neutral colors are hard to balance. If the grey card printed in a slightly lighter than the neutral color, color balance so that we can ensure that all printed photos.
Gray card image is as best neutral references for assessment of Density, it can pass the vision and colour density gauge to judge the black and white film, color negative, color density of the print and print photos. Grey neutral grey card is the ability to determine colour balance and the best color film density.
determine the exposure close up and remake
Gray card where you want to remake an object on the same level, meter and adjusted the speed camera on the light sensitivity of film used, measured along the optical axis of the camera exposure value on a gray card. If the subject is less than the distance from the camera when the lens focal length multiplied by 8 times, should be considered for extension and reduce the effective aperture of the lens. This should increase the exposure adjustments. &Nbsp;TTL can not consider increasing the exposure of the camera.
specific conversion formulas are as follows:
determine white balance
cameras have automatic white balance function, which can handle most shooting scenarios. But in a complex light environment, the automatic white balance feature and cannot be completely avoided tonal imbalances. Gray card about 90% of the white surface reflects incident light. To get more accurate colors, using the manual white balance function to take white flour can solve this problem.
white balanced camera set up stalls in the host environment (indoor or outdoor). The cameras were trained on gray cards, white surface and press down the white balance button, the camera will record this value. With manual white balance, digital camera and film camera white balance in complex scenes can be determined as described above. Inspection camera light meters
Gray card you can test your camera light meters measure the accuracy of the readings. Following determination must ensure that the meter is accurate, and the test was carried out under the same lighting conditions. Set the meter for measure reflected light (take off the white reflector). Meter set to a speed value, such as; 1/60 seconds. Then the gray card gray-measure reading and recording.
value is set to 1/60 seconds at a speed of the camera and the gray card gray surface measured readings, if measured by the camera's Aperture and light meter aperture values are the same, the camera's metering system is proved to be accurate. Detected by the cameras numeric and meter values of tolerance cannot exceed 1/3 an aperture.
currently on the market existing products
there are two most common gray card on the market: a Kodak Gray card is imported. A standard Kodak Gray card priced at around 180 yuan, which includes 8*10-inch Gray card two, 4*5-inch Gray card, including a small plastic bag containing 4*5 Gray card. Grey card front using standard 18-grey, as opposed to pure white.
another homemade merol Gray card, includes 8*10-inch Gray-card x, 4*5-inch Gray-card one, market prices for 68 Yuan a set. It is worth mentioning that, after Beijing merol and national sectoral studies and found, in practice, 17.6 degrees grey white and 88 degrees can be better applied to a variety of complex light situations. Merol reflectivity of the gray card using this configuration.
the two Gray card is strictly adhering to the traditional idea of a, and other innovations. Kodak Gray card can be given a small plastic covers, is indeed very intimate design. Merol reduces a redundant piece of gray card, drive down costs and prices around the original loading 1/3 to market, shoot friend to focus on price/performance, is undoubtedly the best choice.
Gray card notice
card nearly as much as possible;
reflective   avoid facing the camera;
for the body of the plane (for example, when a remake), Gray card should be parallel to the body, preferably directly on top of the main body.
When solid objects was taken, Gray card for the middle of the main light and camera angles, avoid card faces the camera reflection.
along the optical axis of the camera direction is toward the gray card measuring reflected light.
If the subject is very light, according to the measured exposure readings of minus 1EV
If the subject is very dark, according to the measured exposure readings then add 1EV
If the body is very light or dark, do not use this method of metering. Using multiple measurement reading is more appropriate.
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