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Cosplayers Photography Tutorial - Exposure

 

Metering

In photography, the term "exposure" means the amount of light that falls onto the sensor of your digital camera. If you are using your carmera in fully automatic mode, the exposure setting is done for you automatically. In human, the iris in your eye will quickly adjust to different lighting/exposure so you can use the entire range of contrast (black to white) in real life. However, carmera is just a machine with a particular setting at one point of time to capture the image you want to take. As a result, your carmera will try its best to evaluate the exposure using a mechanism. And this mechanism is called "metering".

The default metering system is "center weighted average". As the name suggested, center wieghted average metering setting instructs the carmera to use the middle of the frame as the average reading of the whole scene during exposure. In many cases, your subject might not be in the center of the frame. What you can do is to hold your button half-way in order to set the focus, exposure reading with aperture and shutter speed, then, move the camera to compose the final picture while holding down halfway on the button.

Here are the formal definitions.

Center-weighted average metering

In this system, the meter concentrates between 60 to 80 percent of the sensitivity towards the central part of the viewfinder. The balance is then "feathered" out towards the edges. Some cameras will allow the user to adjust the weight/balance of the central portion to the peripheral one. One advantage of this method is that it is less influenced by small areas that vary greatly in brightness at the edges of the viewfinder; as many subjects are in the central part of the frame, consistent results can be obtained.

Partial metering

This mode meters a larger area than spot metering (around 10-15% of the entire frame), and is generally used when very bright or very dark areas on the edges of the frame would otherwise influence the metering unduly. Like spot metering, some cameras can use variable points to take readings from, (in general autofocus points), or have a fixed point in the centre of the viewfinder. Partial metering is found mostly on Canon cameras.

Evaluative metering

Here the camera measures the light intensity in several points in the scene, and then combines the results to find the settings for the best exposure. How they are combined/calculated deviates from camera to camera. The actual number of zones used varies wildly, from several to over a thousand. However performance should not be concluded on the number of zones alone, or the layout.

 

Methods to control the amount of Light

In general, there are four different ways to control the amount of light falling on the sensor of your digital camera.

1. The Environment Light: The amount of light reflected from the scene to the subject. You can still control natural light in some degrees. If you are indoor, you can close the blinds / windows / turn off lights. If you are outdoor you can try to place a filter blocking some of the light to the subject.

2. The ISO setting: Back in the days, my dad used to tell that that you can buy "faster" film with higher ISO number to catch quicker actions. The fact is that ISO sensitivity expresses the speed of photographic negative materials. Since digital cameras use image sensors instead of film, the ISO equivalent is given. Another way to look at ISO number is that the higher the number, the more sensitive the sensor is. In other words, the more surronding light will be captured in the picture with higher ISO number.

If you are using a fully automatic DSLR or normal digital camera, there is a "ISO Auto"' mode where the camera will set the ISO for you. However (and hopefully), if you are using manual mode or other semi-manual mode, you can set the ISO yourself to create different effects. You will use higher ISO to shoot pictures in darker environment. But higher ISO will usually result in higher noise in the picture. Noise causes your picture to have altered details. It is apparent by the presence of color speckles where there should not be.

Here is how ISO will change your picture.

ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600

3. The f-stop number: Here is a new term if you have not see it before. There is a mechanism in the lens that will open and close to allow light to fall onto the sensor. The camera can control the amount of light input by controlling how big the hole is opened and how long the hole is opened. The f-stop number indicates how big the hole is opened. The technical term for the "hole" is called "aperture". The aperture is implemented as a hole in an adjustable diaphragm set between the lens and the shutter.

(Image from google / sympatico)

The f-stop number and the hole's width is in an inverse relationship. In other words, the larger the f-stop number, the smaller the aperture and the less light that enters the camera. Each f-stop setting lets in half as much light as the next smaller f-stop number. Thus, the setting f/2.8 (with the same speed of opening) allows the camera gets twice as much light as the setting in f/4.

The following illustrates how f-stop affects the picture.

f/2.8
f/3.5
f/5
f/9
f/20

4. The shutter speed: Shutter speed is the term to indicate how fast the aperture ("hole") is opened for to allow light to fall onto the sensor. It is measured in fractions of a second.

Adjusting the shutter speed and aperture settings have other quite different effects on the photograph. As just for exposure to make the picture darker or lighter, shutter speed and aperture are interchangeable. Make the hole twice as big and open the shutter for half the time and you will expose the sensor the same amount of light.

With ISO set at 100, F-stop at f/2.8, Focal length at 45mm. Here is how shutter speed will affect the picture.

1/4000 sec
1/2000 sec
1/800 sec
1/200 sec
1/30 sec

 

White Balance

White balance (WB) is the process of removing unrealistic color casts in your picture. The goal is to make the subjects that appear white in person are rendered white in your photo. Proper camera white balance uses color temperature of a light source, which refers to the relative warmth or coolness of white light. Modern DSLR provides various WB settings that will affect your photos. Here is some examples:

Average
Daylight
(5200k)
Shade
(2000k)
Cloudy
(6000k)
Tungsten light
(3200k)
White Fluorescent
Light (4000k)
Flash
(WB only)

 

 

 

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Equipments Exposure Cosplay Modeling Photographer

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