CAMERA TYPES

• There are many types of cameras
  
• Single Lens Reflex (SLR)
  
• Twin Lens Reflex (TLR)
  
• Rangefinder
  
• Point & Shoot Camera
  
• Box Camera and others
  

SLR

An SLR 35-mm camera is most useful for starters, and a necessity for professional photographers.

•  Single Lens _  The camera uses one lens for both taking and viewing. In other words you look through the same lens as the camera uses to expose the film or sensor (as opposed to twin-lens reflex cameras).
  
• Reflex _ Refers to the mirror and its movement that makes the use of a single lens possible.
  

When you press the shutter release, the first thing that happens with a modern SLR is that the lens aperture stops down from its wide open setting to the taking aperture.When you take a picture, the mirror flips upward, the shutter opens and the film/sensor is being exposed, and after the shutter closes again the mirror falls back down. TLR

The camera uses two lenses, one for viewing and for taking.
The scene is viewed through the top lens, the bottom lens (the taking lens) exposes the film/sensor.

Rangefinder Cameras
Rangefinder cameras are those that focus using some sort of coincident-viewing distance-determination mechanism.
Leica is one high end manufacturer of range finder cameras.

Point and Shoot Cameras
Point and shoot cameras mean just that, point the camera at something and trip the shutter. The camera does all the work for you.Such a small camera is only useful to have with you all the time when you are not photographing with your SLR equipment. Through following tutorials the site offers a guide to using digital SLRs, covering topics from the physical components of the camera to the principles of camera technology. You'll also find some useful tips on composition.

Aperture

When you look at the technical specifications of a digital camera, one of the specifications mentioned is its maximum aperture. The main function of a camera lens is to collect light. The aperture of a lens is the diameter of the lens opening and is normally controlled by an iris.The larger the diameter of the aperture, the more light reaches the image sensor or film.

Aperture is measured in F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture). When you read the specifications of a camera, the aperture may be expressed in a number of different ways, the following ones being the most common:

Maximum Aperture:
Max. Aperture   F1.2

 This means that the maximum aperture for the lens is F1.2.

Aperture Range:

Aperture Range  F1.2-F22

This states the max. and min. aperture.

Maximum Wide-Angle and Telephoto Apertures:

Aperture        F2.8-3.5

This gives the max. aperture for the wide-angle (F2.8) and telephoto (F3.5) focal lengths of a zoom lens. It easy to understand that a stated range deals with maximum apertures and not maximum and minimum apertures: the mimimum aperture should be quite small at F8, F11, F16 or F22. A 'fast' lens is one that has a large maximum aperture  i.e F2.4, F2.0 . The latest digital cameras have controls which changes iris opening by quarter of a stop or even lesser.
F1.8 - F16
one stop increments being ...
F1.8    F2.8    F4      F5.6    F8      F11     F16

This means that the camera has an aperture range of F1.8 to F16; the maximum aperture is F1.8, and the minimum aperture is F16. There are 5 f-stops between the max and min aperture. If your camera's lens is currently set at an aperture of F5.6, closing it by 1 f-stop would mean selecting F8; opening it up by 1 f-stop would mean selecting F4.

F1.8    F2.8    F4      F5.6    F8      F11     F16

A large maximum aperture is preferable to a smaller one since it gives the photographer more latitude with the kind of photography that can be done. The larger the aperture, the better your digital camera will perform in low-light situations, since a larger lens opening means it should be able to admit more light than a smaller lens opening. A larger max. aperture also allows you to use a faster shutter speed to capture faster movements. So, let's say the light meter in your digital camera calculates that for proper exposure , you need an aperture of F4 and a shutter speed of 1/60 sec.

F4
1/60

To use a faster shutter speed (say, 1/250 sec.) to freeze action, you have to open up the aperture to allow more light in for that shorter amount of time. For every shutter speed increment we go up, we need to open up a f-stop of aperture. From 1/60 sec. to 1/250 sec. there are 2 increments, so we open up the aperture by 2 f-stops, going from F4 to F1.8. Note that the camera would give proper exposure at 1/60 sec. at F4, 1/125 sec. at F2.8, and 1/250 sec. at F1.8, since all three aperture/shutter speed combinations allow the same amount of light into the camera. [Some digital cameras provide a 'Program Shift' function to allow that very shifting of aperture/shutter speed combinations in tandem.]

F1.8    F2.8    F4      F5.6    F8      F11     F16
1/250   1/125   1/60    1/30    1/15    1/8     1/4

In a digital camera set on Auto mode, you can select Sports scene mode, and the camera will automotically select a fast shutter speed and the appropriate aperture. Likewise, in Shutter-Priority mode, you can choose which shutter speed you want (fast or slow), and the camera will select the appropriate aperture for proper exposure.

In our example above, let's say the lens on your digital camera only opens up to a max. aperture of F2.8. If you now select 1/250 sec. (in Shutter-Priority mode), the camera will not be able to select an aperture larger than F2.8 (in our example, it  needs F1.8). It would then give you an "underexposure" warning. If you go ahead and take the picture anyway, your picture would be 1 f-stop underexposed (i.e. you really needed to open up the aperture by 1 more f-stop for correct exposure).

Similarly, if you select a shutter speed of 1/4 sec. and the lens only closes down to a min. aperture of F8 (in our example, it really needs F16), the camera would give you an "overexposure" warning. If you go ahead and take a picture anyway, your picture would be 2 f-stops overexposed (i.e. you really needed to close down the aperture by 2 more f-stops for correct exposure).
There is also a third variable -- the ISO. This is the sensitivity of the image sensor  We may cover this in a later tutorial. A small minimum aperture is preferable to a larger one since it also gives the photographer more latitude in the kind of pictures that can be taken. Suppose we want to take a picture of flowing water. As mentioned above, to depict flowing water, we usually want to use a slow shutter speed so that the water blurs. It is this blurring that makes the picture so effective in depicting water motion. So, let's say the light meter in your digital camera calculates that for proper exposure on a bright sunny day, you need an aperture of F8 and a shutter speed of 1/125 sec.
F8
1/125

Well, if you decide to use a slower shutter speed (say, 1/30 sec.), this means that you have to compensate by closing down the aperture to allow less light in. It makes sense really. Since you have increased the time the shutter remains open to allow light in, you must compensate by allowing less light in to expose the image sensor in that longer amount of time, if you still want a properly exposed picture. But, what if the lens on your digital camera closes to a minimum of F8? You're stuck at the shutter speed of 1/125 sec. If you use 1/30 sec. at F8, your picture will be overexposed, i.e. burnt out. At 1/125 sec. and F8, your picture will be properly exposed but the fast shutter speed will freeze the water motion and you won't obtain the blurring effect you desire. If your lens does not close down to F16, you could use a Neutral Density (ND) filter to reduce the amount of light coming into the lens, and thus allowing you to use a slower shutter speed.
F1.8    F2.8    F4      F5.6    F8      F11     F16
1/2,000         1/1,000         1/500   1/250   1/125   1/60    1/30

Aperture and Depth of Field (DOF)

The Depth of Field is the distance wherein objects are in focus. There are times when you desire a great depth of field, i.e. where objects both close to you and far from you are in focus. This is especially true when you are taking a landscape picture and want as much as possible to be in crisp focus. Then there are times when you want to isolate your subject, as when you are taking a portrait and want your subject to be in sharp focus but the background to be out of focus. In this case, you desire a shallow depth of field. One way to influence DOF is by selecting the appropriate aperture.

The rule of thumb is this:

   * Select a large aperture (or small f/value or small aperture value), e.g. f/2.8, to obtain a shallow DOF
   * Select a small aperture (or large f/value or large aperture value), e.g. f/8.0, to achieve great DOF


Note: Since we are on the subject of DOF, DOF also changes with focal length. Use a small focal length to increase DOF, a longer focal length obtain a shallower DOF. I.E. if you zoom, the DOF decreases.

Recap

A large maximum aperture allows more light to reach the image sensor, and so allows you to use a faster shutter speed. A faster shutter speed freezes action and negates the effect of camera shake, resulting in pictures that are not blurred. Another advantage of a large maximum aperture is to provide a shallow depth of field. This allows the background to blur nicely thus isolating your subject (especially effective when taking portraits). A small minimum aperture allows you to use a slow shutter speed on a bright sunny day. A slow shutter speed allows you to depict motion. Another advantage of a small minimum aperture is to increase the depth-of-field. An increased depth-of-field allows you to take landscape pictures where as much of the picture in the foreground and reaching all the way to the background is in sharp focus.

Frame Your Picture

The use of a frame can turn an otherwise plain picture into a pleasing one. Usually a foreground element is used to create the frame. Examples are an overhanging tree branch, a window frame, a door,a fence , arches,  rows of trees, etc. A frame serves to isolate your main subject and create an interesting composition. Oftentimes, it's the feeling of depth you're after. You may choose to keep the detail of the frame (as in a wall, fence or branch), or let the frame go completely dark (as in a window frame). When you are composing a shot, keep your eyes open to foreground (and sometimes, even middle or background) objects that can be used as a natural frame. You may need to physically back up a bit, kneel down for a more pleasant composition, or zoom in to include your subject within your chosen frame.

Caution Advised About Artificial Frames

Framing can also be done after the fact by combining two or more pictures in an image editing software. Very dramatic effects can be accomplished this way and you are only limited by your imagination. However, a word of caution is necessary here. Though there is nothing wrong with combining different images to create another one, be very careful about employing artificial frames on recognizable scenes and landscapes. So, before you take that shot next time, look around and see if there is an object that you can use as a natural frame. Take a picture without the frame, and another one with the frame, and compare.

White Balance

If you come from the world of films, you may remember using filters to correct for incandescent or fluorescent lighting. Most people don't bother and their indoors pictures invariably come out with a yellow/orange or bluish cast. In the digital world, these correction filters are no longer necessary, replaced by a feature found in most -- even the entry-level -- digital cameras called, "White Balance."

Light Color Temperature

The reason that pictures turn out with a yellow/orange cast in incandescent (tungsten) lighting and bluish in fluorescent lighting is because light has a color temperature. A low color temperature shifts light toward the red; a high color temperature shifts light toward the blue. Different light sources emit light at different color temperatures, and thus the color cast. By using an orange or blue filter, we absorb the orange and blue light to correct for the "imbalance" -- the net effect is a shift in the color temperature. In digital photography, we can simply tell the image sensor to do that color shift for us. But how do we know in which direction of the color temperature to shift, and by how much?

Manual White Balance

This is where the concept of "White Balance" comes in. If we can tell the camera which object in the room is white and supposed to come out white in the picture, the camera can calculate the difference between the current color temperature of that object and the correct color temperature of a white object. And then shift all colors by that difference. Most advanced digital cameras therefore provide the feature to manually set the white balance. By pointing the camera at a white or gray card (angled so that it is reflecting light from the room) as a neutral reference, filling the screen completely with it, then pressing the White Balance button (or set it in the menu), the camera does its WB calculation. From then on, any picture taken will have its color temperature shifted appropriately. It's quite simple, really, and you should not be afraid to try it out and see your indoors pictures improve considerably (assuming there is enough light for correct exposure).

[A "neutral" gray is 18% gray and will reflect all colors equally.]

Caution:

- Ensure the card is not in shadows, but illuminated by the artificial light in the room
- If you are bouncing light off the walls, ensure the card is reflecting the bounced light
- Beware of mixing artificial lights -- in this case, you might want to use RAW and adjust in post processing for each light
- Fluorescent lights do not contain all the spectrum of light, you may obtain unexpected results

Preset White Balance

To help us in those special situations without having to go through the trouble of manually setting the white balance everytime, cameras provide preset WB settings such as, Tungsten, Fluorescent, Cloudy, Sunny, etc. Using preset WB can improve on a picture, especially under indoors lighting.

White Balance
     

Auto WB	Preset Tungsten WB
AWB	Preset WB = Tungsten

Usually just selecting a Preset WB setting appropriate for the lighting situation is enough.

Auto White Balance

Since the days of the Kodak Brownie cameras, manufacturers have tried to automate everything for us. Hence, today's digital cameras also all sport an Auto White Balance (AWB) function. Depending on the camera brand, some AWB works better than others. On the whole, though, AWB works very well in sunny and cloudy outdoors, and fine for most indoors situations (a little orange or bluish cast does sometimes contribute to the mood of the picture anyway, e.g. the warm orangle glow of a candle). Set your digital camera to AWB and take pictures under tungsten, fluorescent, and mixed lighting (i.e. tungsten or fluorescent, plus natural light coming through the window), and see if the results are OK. If they are, you can just use AWB.

Snow

Pictures of snow scenes typically reproduce the snow not as white but with a bluish tinge. Sometimes, the blue adds to the mood of the picture, but at other times you may want to remove the blue.
If your digital camera allows custom WB, then set the White to the snow and the blue should disappear.

Snow	Using Custom WB
Auto WB	Auto WB
AWB	Custom WB

RAW File Format

A discussion in WB would not be complete without a mention of the RAW file format available in many advanced digital cameras. When you save an image in RAW file format, you are saving it the way the image sensor sees it -- without applying any adjustments (including white balance) to it. In fact, the camera ignores any WB setting you set in. Later, in an image editing software with the appropriate RAW plug-in, you can convert the RAW image to JPEG/tiff, and apply any color temperature shift.You can fine tune the changes until you obtain perfect color balance. Some professional photographers always use RAW file format. Saving in RAW file format comes at a price because it takes so much longer to save a RAW image that it might not be practical in many picture taking situations. Professional dSLRs (and some prosumer models) have internal buffers that allow RAW images to be taken one after the other in quite rapid succession without having to wait for the saving of one image to be completed before you can take the next picture. If you are taking landscapes, and it's early in the morning or late in the evening, or you are not too sure of which WB setting to use, try it in RAW. A few digital cameras even allow you to save an image in both RAW and JPEG simultaneously, though time to write to memory card is proportionally increased.

Summary

For most of us, Auto WB is fine and does a pretty good job in diverse situations, outdoors and indoors. For those occasions when you are not happy with the color cast of your picture, choose one of the preset WB settings. If this still does not give you what you want, consider manually setting the white balance by using a white card or sheet of paper. And, for ultimate control over white balance, consider shooting in RAW file format, and adjust in post-processing.

Depth of Field

Depth of field (DOF) is the distance wherein objects are in focus.

To be technically correct, DOF is the zone of acceptable sharpness, the area in front of, and behind, a focused subject that appears in focus.


What Affects DOF

What we really want to know as photographers is what affects DOF so we can control DOF in our pictures. For a long, long time, photographers have gone with the following three criteria:

   * lens aperture
   * distance from subject
   * focal length

While the first two are technically correct, the third one has raised somewhat of a storm of controversy among certain circles. Why exactly, we will make clear later. Let's look at each of the three criteria in more detail.

Lens Aperture

The aperture is simply the size of the opening that allows light to go through the lens. It is expressed in f/stops (also referred to as f/value or aperture value), and a typical aperture range is f/2.8 - f/8, giving the range from maximum (large at f/2.8) to minimum (small at f/8) aperture.

A small f/value (e.g. f/2.8) indicates a large aperture.

A large f/value (e.g. f/8) indicates a small aperture.

So, f/2.8 is a larger aperture than f/8.

Generally, a large aperture gives a shallow DOF, and a small aperture gives great DOF. If you want only the subject the lens focuses on to be sharp, and everything else to be out of focus -- such as a portrait with the background nicely blurred -- then you would "open up the aperture," i.e. use a large aperture. If you need most of your picture to be in sharp focus -- such as a landscape scene -- then you would "stop down the aperture," i.e. use a small aperture.

Shallow DOF     Great DOF

In most consumer digital cameras, you may not be able to directly control the aperture. Many, however, provide a Portrait scene mode and a Landscape scene mode that basically do what we are after, i.e. use a large and small aperture, respectively. As most of you have found out by now, it is quite difficult to obtain a shallow depth of field with most consumer digital cameras even with the aperture opened up wide. Why? See the section on focal length below.

Distance From Subject

When you focus on a subject close to the camera, the DOF is less than when you focus on the subject farther away from the camera. Putting Distance From Subject into practice. Step away from your subject to obtain greater DOF, or move in closer to decrease DOF.

Focal Length

Summary

Even though the subject you focus on is the only thing technically in focus, some objects in front and behind your focused subject also appear to our eyes to be acceptably in focus. This zone of acceptable sharpness is the DOF. We can increase the DOF (or the appearance of it) by using a small aperture, moving away from our subject, or using a wide-angle lens. We can decrease the DOF (or the appearance of it) by using a large aperture, moving closer to our subject, or using a long focal length.

Shutter Speed

 The speed at which the shutter of the camera opens and closes to allow in light. Expressed on the controls as the denominator of the fraction.It is used in combination with aperture to attain correct exposure.On automatic cameras, this is generally accessed through a menu and displayed on a screen on the back of the camera. In manual cameras, the shutter speed is generally controlled and displayed on a knob on the top of the camera. The shutter speed is measured in fractions of a second but is generally shown as the denominator only.
may be more of it later.