Digital cameras demysitied - All you ever wanted to know about Digital cameras

This is a compilation of few mails i received recently and I'm thankful to the original authors for the efforts.Very informative

Dear All,

"Point and shoot" digital cameras have become an important part of
lives of anyone and everyone who wants to take pictures and have made
taking pictures as easy as point and shoot. For most people they are
good enough and at most times they are good enough. Besides others,
one down side has been that people don't need to know some very basic
stuff about photography. One of them is about the way we can control
"depth of field" in a photograph.

We need to have a short/small depth of field while taking pictures
like portraits, as we are focusing on one subject and we want
everything else to be blurred so that the viewers attention only goes
on the object of interest. We need a long or deep depth of field while
taking pictures like landscapes as we want all objects, near and far,
to be in focus.

Depth of field/focus is controlled by the aperture size of the
shutter. It is represented by a number written after the letter "f" eg
f/5.6 , f/29. The smaller the "f" value, the bigger the apertures size
and vice versa. A large aperture number (eg f/29) means a very small
aperture and that acts like a "pin hole" and that makes focusing not
that important and all objects, near or far, are in focus. A small
number (eg f /5.6) means a large aperture and precise focusing becomes
very important.

While taking pictures two very important factors which control the
light exposure are the shutter speed and the aperture size. If the
aperture is large, we need to shutter to close quickly to let a
certain amount of light to pass through. If we make the aperture
small, we need to have the shutter open for a longer time for the same
amount of light to pass through.

In the two photos attached, I have focused on the red cap of the
bottle as I took the pictures. The two pictures have however, been
taken with different aperture settings and corresponding shutter speed
changes. You can read the settings in the bottom left corners of the
photos. You can make out that in the first picture the depth of field
is pretty good and almost all seems to be in focus unlike in the
second photo.

I hope you find this information interesting.

regards

Sarbjit


that was an excellent introduction to the wonderful world of photography.
i cannot resist but to add a few things - hope you do not mind...
1. these settings mentioned can be adjusted only with an slr ( single lens reflex) pentaprism cameras. i am not too sure if any regular point and shoot digital cameras can allow such aperture and shutter speed adjustments.
2. to go to more basics - cameras were divided into rangefinders and slr s. in rangefinders the view one gets is not through the main lens, but a different path. however in pentaprism slrs the view to the view finders is directly mirrored from the main lens. when the photograph is clicked the optic pathway is momentarily changed by lifting of the mirror, so that the light reaches the film. so obviously the slrs were better cameras and more so when closeups and macro mode was used. the hot shot cameras of yore and the present day digital cameras are modified rangefinders. the digital cameras however have the ccd sensor and the lcd screen linked so that we can get a live view of the picture that is to be taken. so this feature mimics a slr. if you could have noticed, the view in the view finder of a digital camera ( ie if it has one) is slightly a different perspective from what is displayed on the lcd screen. this is most obvious when taking a closeup. the only limitation then in the digital camera is the ability to control the aperture diameter and shutter speed. most of the time this is very well programmed in the digital cameras. there are fixed programs in the camera menu for different situations and needs, which are usually satisfactory for amateur photography. however for the shutterbug, more control is needed to satisfy the imagination and artistic needs. i remember the times when we used to experiment with rolls of film to get that ideal exposure with our film slr cameras..but now times have changed - with the advent of digital slrs - called dslrs. so now with these dslrs there is no limit to the creativity of the photographers. bracket a lot of exposures and just delete the ones that are not needed. so photography is a lor less expensive as a hobby now than then.
3. as has so well been explained about the depth of field, to get a good exposure apart from shutter speed and aperture size, the other determinants are the iso setting ( vestigeal term from the time of film rolls - higher the iso or asa rating, the more sensitive the film/ccd sensor is for light, but more granularity in the picture), ambient light conditions, and camera shake or motion blur due to prolonged exposure as well as a preplanning of the picture in the mind of the photographer.
4. most slrs and now dslrs have features called aperture priority or shutter priority or both. means if we set one parameter, then the other parameter is calculated by the camera with the help of a built-in light meter. that is to say the camera automatically compensates to your setting to get the ideal amount of light to get a good photograph for a given iso/asa setting. for eg. if one wants to take a portrait - the face needs to he highlighted by accurate focussing, while the background needs to be blurred - that is to say a very narrow depth of field - then a wide aperture is needed preferably with a tele lens. once we set a particularly wide aperture, the camera measures the ambient light and sets the shutter speed automatically for the given asa/iso setting, to get a perfectly exposed picture. this is called aperture priority. aperture priority is great with hobbyists. the other way is shutter priority. however a professional photographer may require more control over the exposure and would prefer both settings to be manual to get special effects and enhanced naturality in the picture.
5. now the present range of dslrs - i personally prefer the nikon still cameras as the very best - and now their d series - have much better features which support a totally novice greenhorn to take a great picture to the hardcore professional with total control over the focussing, zoom and exposure control to satisfy his needs. the only problem with the dslrs is that they do not have liveview on the lcd monitor. but the moment the picture is taken, the picture is displayed on the lcd screen. there are a few cameras from the canon range that have a simulated liveview, but i seriously doubt if there are really of great use...
6. all said and done the regular point and shoot digital cameras are more than sufficient for ophthalmic use and regular slit lamp photography. .. as well as for one's vacation photography. and for the occasional special need, there is always the professional photographer. ..who can give a much better result than all your efforts...!! ! but still if the urge of creativity is there, then nothing like a nikon dslr d60 with twin zoom lenses.....! no financial interest, though..!


with best regards,

dr. m.s. prashanth

sukruthieyecare@ gmail.com