Lesson 2 – understanding camera and basics of exposure

video tutorial

below you can see a full transcript of our video tutorial above

Second step in our series of free photography tutorials and beginners basics would be a good understanding on your camera and the relation ship with its parts, and also the translation of each part with its role in the exposure process. We have covered in the first lesson the light as the raw material for the photography, and now we are going to explore the tool. The painter needs to know his brush to be able to spread the paint on the canvas, the sculptor needs to have a good chisel to carve the stone.

Camera is a tool which helps the photographer to capture the image

Remember this, your camera is your tool, and focusing on the camera and not the subject will prevent you to see the big picture. It is very easy to get lost in the technicalities of cameras, brands, accessories, prices sizes, but at the end, the camera is just a tool, and not a purpose in itself.

Just like the human eye the camera has few important elements:

- camera body which is basically an empty dark box with a sensor at the back, and a curtain which opens to allow the light to get in. The light is projected on the sensor which captures the light, sees the image, and records it. Very simple but very important to know and understand

- the lens, or the eye of the camera is the the other important part of the camera.The lens will hep the image to be projected on the sensor for a short period of time during the exposure. The lens is very important as it projects a wider or more narrow image, a closer or a further subject, will allow more or less light into the camera

These 2 elements are the most important features of the camera as one does not work without the other and their quality will reflect in the quality of the final photograph. A camera works and is just like a human eye, the crystalline transparent muscle will allow the light to get in the eye, will sort out the distance, the focus and the intensity of light (your iris will become smaller in strong light and will become bigger in low light.

How camera works:

let’s discuss exactly how camera works, how an image is captured through one exposure. The sensor is a light sensitive recording device and it is a small surface of millions of little light sensors. I am not sure how the camera manufacturers are designing and building this but if you think about it, it’s pretty amazing. The sensor is placed in a dark room and it is exposed to light for a period of time when the curtain opens and closes. The curtain can be anything from 2 sliding doors opening and closing, or a vertical mirror or whatever , the important thing is that they close this cycle called exposure. So just to make it very clear we just came up with the definition of Exposure. During this “exposure” the lens allows the photons from outside to get in the camera projecting the image. ( we are assuming you have already went through the first tutorial – understanding light). The lens will allow arrange the flow of photons to be projected on the sensor which captures each photon in a small little bucket called pixel, cluster or whatever. Each bucket receive a number of photons coming from outside reflected by objects in nature as shown in lesson 1. Just to give you one example so you can visualise, enlarging an image on the computer, we’ll see each image is a sum of little coloured squares of an image. This is how each pixel is recorded by the sensor.

So just to say this in simple words, during one exposure, you press the button on your camera, opening a whole inside (with doors curtain or whatever), light is coming through the lens, is projected on the sensor who captures all the photons in tiny little buckets, and each bucket has an amount of light particles trapped, in a smaller or larger quantity with an overall specific colour.

Now it is very important to understand this concept. Each bucket can be empty,  no photons, that means, black point or dark, or it can be filled in various amount s until is completely filled, and overflows. If it overflows, there is a flood of light on the sensor and everything is becoming overexposed, we cannot see the individual buckets any more , it is all covered and we have an overexposed image tending the become complete white with no information on it. We have just explained OVEREXPOSURE. If there are not enough particles captured in buckets, the clusters will be under filled, so underexposed.  A good picture is defined when there is just enough particles in these buckets to reflect the reality.

Moving on, we can compare this directed flow of particles in the camera with rain falling onto a football field with buckets. Photons will always have the same speed (not sure why, you need to ask Einstein but apparently this is the rule), but they can come in larger or smaller amounts, and that is given by the intensity of the light. More particles, heavier rain, the buckets fill in faster. This is very important to understand, the more light outside, the faster the light sensor records  enough photons. This is the relationship between the shutter speed and the level of light, or between TIME AND EXPOSURE. More light need faster shutter speed, which means shorter time between the opening and closing the curtains. this is the justification and explanation of TIME as one of the 3 elements that influence the EXPOSURE.

Coming back to the sensor or the football field. If we have heavy rain, large number of particles, the buckets fill in a certain amount of time. If we have less particles falling, we need more time to fill those buckets. I hope it all makes sense. Lower light required more time.

Camera lens

I hope we understand now what happens inside the camera, but let’s talk about what happens with the light before it enters the camera. The lens has an opening, or a whole which is called aperture and that control the light intensity, or how many photons are getting inside. Larger the aperture, or the whole, the more photons get in….that means the shorter the time for the sensor to capture them. The smaller the whole, the smaller the aperture, less photons get in, the sensor needs more time. And this is the relation ship between the APERTURE and TIME  or the APERTURE and SHUTTER SPEED. I hope this makes sense as this is the most important concept in photography.

Moving on to the lens, on top of the aperture control, the lens is responsible for the focus, that means you get a sharper image or not but this is less important now and we will cover this when we will be talking about camera focus.

Basics of exposure – triangle of time-aperture-ISO

Let’s go back to the sensor and define one more and final concept which closes the basics of exposure. Each camera sensor has a specific sensitivity which is basically represented by the depth of the buckets. A deeper bucket needs, more photons to be filled, a shallow bucket needs less photons. That impact the relation ship between the Aperture (or the whole, or the amount of light) with the Time, or the shutter speed. For each bucket depth- sensitivity (ISO) there is a different amount of photons and time required to get a fill.  For deeper buckets – (that translates into less sensitive sensor) we need more photons to get in, to make a decent fill, that means we need more light, more time, bigger whole in the lens, so bigger aperture. More sensitive sensor = shallow buckets, means the fill faster with less light.

We have just defined the relationship between the TIME – APERTURE – SENSITIVITY or ISO and understanding this concept is the most important concept in photography. Once you get a hang of this concept, the rest is easy.

Understanding your camera

We has defined and explained the relationship above but how that work in practice? We need also to understand that a camera has the ability to see how much light is in front of it and make a selection of the shutter speed, aperture and ISO for a good picture. We are not going into how it does it right now, but we just need to understand that the camera can do it. Any DLSR camera today will have the facility of half press of the button to read what is in front of it, and decide in an instant which settings to use. That is called automatic camera and it can work pretty well for a large number of instances. That does not influence the sensor ability to record, and the camera can make a choice that you do not want assuming you know what you want. The sensor will capture whatever light is given to it without question. The problem is that camera has a limited number of choices as it is not intelligent to understand what you want and measuring what is in front of it can be tricky. That is why you need to take full control and tell the camera when to open, for how long, and how fast to record an image. once you can do that you are a photographer who is controlling the camera and not the other way, and you will get what you want and not what camera will give you.

 
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