Basic Principles
This is a first post on this topic here, so i will keep to the basics. These basics are:1. How to equip your self to get enough light for a good quality photo
2. How to actually capture the light needed for a photo
3. How to actually get the right photo
4. What do mega pixels really do for you
5. Conclusions - how to choose cameras
1. The basics for a good photo- light!
Capture a photograph, you capture light. The more light you capture, the higher the quality photograph is possible. There are three ways to capture the sufficient light for a good photo-1) A bigger lens/sensor will capture more light from any given subject
2) Only take photos where there is a lot of light
3) Use a long exposure and capture the light over a longer period of time.
To take the absolute best photographs, professional photographers use large formate cameras, intense studio lighting, and have the everything keep still so they can use a long exposure. This of course is not always practical, so here is a look at all these factors and how they apply in a wider set of circumstances.
A bigger lens/sensor.
There are a whole set of sizes of photographic equipment. The sensor size partially determines the lens size, and is one area often not understood by people new to photography so i will discuss it first.| Camera Type | Sensor diagonal size | area mm2 |
| Large Format | size varies, but usually 156mm diagonal | 12,000 |
| Medium Format | anywhere between large and 43mm...but 78mm diagonal is typical | 3,000 |
| 35mm Film | 43mm (24mm x 36mm) | 864 |
| 35mm digital | 27mm to 43mm (26mm ='apsc', 43mm= full frame) | 337 to 864 |
| 4/3 four thirds | 21mm | 221 |
| typical digital camera (non DSLR) | 6mm to 12mm | 20 to 50 |
| mobile phone or webcam | usually 3mm to 5mm | 8 to 18 |
The bigger the format, in theory, the better photo is possible. But there are trade offs- notably, the bigger the format, the bigger the lens you need for the same application. No one makes long range telephoto lenses for large format or even medium format cameras to take photos of small subjects 100m away- these lenses would be just to large to be practical.
In practice, (at time of writing in 2007) fashion covers are mostly photographed with medium format cameras and 35mm DSLR cameras (43mm diagonal) are now able to be considered for this application. Professional sports photographers mostly use 35 DSLR cameras, but often with reduced 35mm diagonal sensors. These photographers cannot use a larger format because they require telephoto lenses.
As technology enables extracting more detail from the light falling on an given sensor area, better photos will be able to be taken with smaller sensors, but there is only so far you can take the laws of physics.
Given the same technology, and all else being equal, the bigger the sensor you use, the higher quality photo it is possible to take. To get the best photo, uses the largest sensor you can.
2. How to actually capture the light needed for a photo
Regardless of the size of the sensor, it is still necessary to get sufficient light (or photons) to land on each mm2 of the sensor. The three ways or increasing the light are to collect it from a larger area (known as 'aperture'), collect light for a longer time (know as 'shutter speed') or simply have more light in the first place. The more light that lands on each mm2, the more detail it is possible (with the right technology) to extract from that mm2.Every lens has a maximum 'aperture' or 'hole that light passes through'. To hole cannot be bigger than the diameter of the lens, so the larger the lens, the larger the possible aperture. So if you buy a really big diameter, expensive lens, you can take better pictures with less light. However, it is not all a matter of money- the larger the aperture, the shorter the range of distance that is in focus in your picture. Sometimes a blurred background is a desired effect but other times it just means not everything you want is in focus.
The second factor, 'shutter speed', allows capturing the light over a longer time. It is obvious that if the subject of your photo moves while you are capturing the light, you get a blurred photo. For fast action, a long shutter speed is not possible. There is also another problem! You have to hold the camera still. Now this may sound easy, and for photos of close objects, it is not such a big problem. However, when taking long range 'zoomed in' telephoto pictures, just the tiniest movement of the camera becomes magnified and will blur your picture. If the subject is not moving there are two solutions. a) use a tripod and b) image stabilisation. A tripod is great, but a pain to carry sometimes. Real image stabilization that physically steadies the camera and/or lens is called 'optical image stabilisation'. Beware of 'digital' image stabilization which generally simply doesn't actually allow a long shutter speed or capture more light. 'Digital image stabilization' generally means the camera will try to do the best it can without getting enough light and does not solve the problem.
The third way to get enough light is to take photos where everything is brightly lit. Most of us do not take photos in our own light controlled studios, the best we can do is bring a flash. Using flash also has limits. The light from you flash has a limit as to how far away it will still provide sufficient light. The flash is not appropriate in many situations and you may even be told flash photography is prohibited. The light from a flash is just not artistically substitute for natural light when capturing nature.
To have the most flexibility in capturing the right light:-
1) have a flash but only use it when no other solution is available
2) either have a tripod or good 'optical image stabilisation', particularly for telephoto pictures.
3) have the largest apertures lenses you can. these are measured by 'f' stop ratings and the lower the number, the larger the aperture. 'f1.0' is almost unobtainable, 'f2.0' is wonderful if you could get it, 'f2.8' is great and 'f6.0' is only for when enough light is just not a problem.
3. How to actually get the right photo
There are three ingredients to getting the right photo.
a) be able to take your photo quickly enough
b) either get close enough to what you are photographing or have a lens that makes your subject look close from where you are.
c) have your camera and lens with you
Outside studio photography, capturing the best photograph
3a. be able to take your photo quickly enough.
A critical difference between a good and a bad camera is the time delay from when you press the shutter button, to the picture acutally being captured. Early digital cameras, and some newer budget cameras, have such a delay that you need to literally need to anticipate the right moment, and press the shutter seconds in advance. I recall a friend trying to take a picture of a child on a 'merry go round' needing to press the shutter when the child two positions in front of his child was in the viewfinder in order to get a picture of the correct child, as the delay between pressing the shutter and the picture being captured meant the child in the frame would change.
Bad as this situation is, some problems can be even worse. He was still able to get a photo, as the child was going round and round and he could practice timing and the time delay was predictable.
Apart from the predictable 'shutter lag' which can be found in specifications, another delay occurs when the camera is slow to be able to focus on the subject. You press the shutter, and no picture is taken as the camera is still attempting to correctly focus on the subject, or the picture is taken without correct focus so there is still no useful photo.
The third timing problem is that adjustments to camera settings are required to get the photo you want, but the adjustments are hidden several levels deep in menus and simply take too long.
3b) either get close enough to what you are photographing or have a lens that makes your subject look close from where you are.
A fixed focal length camera requires 'pedestrian zoom' where you are able to walk to stand the appropriate distance from your subject. This doesn't always work as a solution. During a football match you may not be permitted to walk to ideal position to take a photo unless you also have a number on your back. Wildlife, and particularly bird life, may not allow you to get very close. At dinner you may not be get far enough away to get everyone in the frame. The solution is either interchangeable lens or zoom lens, or both. The greater zoom range you have, the greater your ability to capture that special moment.
Do not be fooled by 'digital zoom'. Imagine having a picture of a crowd of 100 people when you really wanted a picture of one person in the crowd. Digital zoom is the effectively taking the photo of the crowd, cropping away everyone buy the person you want and then magnifying that picture. There is still no more detail of the person you want than in the crowd picture. Digital zoom is merely cropping the picture and produces no better detail than cropping in 'photoshop' yourself. To quote megapixels, if you have a 5 megapixel camera, 2x digital zoom yeilds the centre 2.5 megapixels. At 10x digital zoom you have the 0.5 megapixels at the centre of the lens. The only way this helps is if you do not have enough room to keep the whole 5 megapixels until you can crop the photo yourself later.
3c) have your camera and lens with you
A big zoom or multiple interchangeable lens, the ability to capture the most light and focus it on a reasonable size sensor : all of these requirements make the camera and lens larger, heavier, and more of an inconvenience to carry with you every where you go.
4. What do mega pixels really do for you
Pixels, or megapixels, capture the detail of the photo. If comparing cameras with pixels of equal quality, the more pixels the more detailed the photos that can be taken. A DSLR with 10 megapixels will typically have each pixel collecting over 10x the amount of light as each pixel in a 10 megapixel compact digital camera. Despite the same pixel count, the capability of the cameras are worlds apart.The bigger each pixel, the more light it captures, the better photos in can take in all light but especially in low light or fast shutter speeds.
The more pixels you get in the same size sensor, the smaller and lower quality each pixel. For any given size sensor, there is a point of diminishing returns where increasing the number of pixels simply reduces the quality of the pixels, producing no improvement in the photos.
For compact digital cameras with current technology and current sensor sizes, around 5 to 6 megapixels is the point where quality no longer increases. As of late 2007 these cameras are offered in pixel counts as high as 12 megapixels, but the image quality has not improved significantly since around 5 or 6 megapixels. Now the 10 megapixel camera which is a new model that replaces an older 6 megapixel model may show some improvement due to newer technology, but never a 6 to 10 improvement.
Camera phones will normal phone size sensors have not got significantly better than 3 megapixel quality, even though 3 and 5 megapixel models are available. The following table shows how as of 2007, practical megapixel counts on smaller sensors are exceeded by many products. New technologies can increase practical limits, but the limits can only go so far.
| Camera Type | maximum available pixels | practical limit |
| Large Format | dont know | dont know |
| Medium Format | 60 | not reached |
| 35mm Full frame | 24 megapixel | not reached |
| 35mm cropped | 12 megapixel | not reached |
| 4/3 four thirds | 10 megapixel | ? |
| typical digital camera (non DSLR) | 12 megapixel | 6 megapixel |
| mobile phone or webcam | 8 megapixel | 2 megapixel |
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