For all the newbies in photography..
One of the key concepts for getting a good pic is setting the correct exposure. Exposure is basically, the measuring and balancing of light
Too much light and the picture will be washed out. Not enough light and the picture will be too dark. A good pic depends on calculating the exposure settings that will give the film the "right" amount of light.
The photographer can control how much natural light reaches film by adjusting the camera's shutter, aperture, or film speed.
All cameras have an inbuilt light meter...
It looks similar to this...
In some cases, the numbers may be reversed, but they still have the same meaning. These numerical positions are called "stops". A 'stop' is a rough measurement of light being exposed in your picture.
If you start with a single lightbulb(assume at 0) and then add another bulb, the light intensity will increase by one stop (1)
To increase the light by another stop you would need to double the light for a total of 4 bulbs( 2) and so on..
Double the light is one stop brighter (+1 stop)
Half the light is one stop darker (-1 stop)
While you may think that at "0" the exposure its perfect, that isn't technically the case. You have to experiment with the camera and find your own "sweet spot". In my camera its usually half stop behind 0. Basically, there is no general rule for a good picture...you have to experiment. Some guys like darker photos, some prefer brighter ones... try shooting the pics yourself and figure out your style.
We will get back to stops in a little while.
Don't ask me the full form of ISO..I haven't a clue. It isn't important anyway..just meaningless trivia. Basically, ISO describes how quickly the film reacts to light.
ISO 100 has medium sensitivity to light..its usually the lowest you can go on DSLRs. At ISO 100, you get a nice contrast, and virtually no grain in the pictures. IF you shoot a pic here with the right shutter speed and aperture, you will generally get a high contrast, colorful image.
Now if you jump to ISO 400, your light settings increase by 2 stops..soo, if you shoot the same picture, making no changes to shutter speed and aperture..your picture will be overexposed..and slightly grainy. To correct the lighting, you would have to adjust the shutter speed and aperture values.
lower numbers = slower films = need more light = longer exposures
higher numbers = faster films = need less light = shorter exposures.
The higher you go, the grainier your picture gets. I can't speak for all cameras but I do know that for Nikon D80, if you go beyond ISO 800..there is just too much noise in the picture. For the Nikon D700, you can go up to ISO 3200 and manage to get a decent shot.
As a general rule I prefer always to use ISO 100, unless there is very low light, and I am not carrying a tripod. If you have a tripod then you could just keep your shutter open for a longer period of time
Shutter speeds and aperture.
The shutter blocks all light from exposing the film UNTIL you press the button. Then it quickly opens and closes, giving the film a brief flash of light.
You can control the length of time the shutter remains open by setting the SHUTTER SPEED.
Longer shutter speeds = more light
shorter shutter speeds = less light
Its common sense..
if you keep your shutter open at say..1/30th of a second, you will capture more light than at 1/125th of a second.
Sometimes when you are shooting the sun directly, you may reach speeds upto 1/3000 to 1/4000 of a second..with the appropriate aperture setting..and it could still be slightly overexposed..depending on your lens. So even though the number may look bigger, don't be deceived!
A half second exposure is ONE STOP darker than a one second exposure.
A 1/125 exposure is TWO STOPS brighter than a 1/500 exposure.
A 1/1000 exposure is THREE STOPS darker than a 1/125 exposure.
Best way to learn shutter speed :-
Set your camera at ISO 100 and aperture f/2.8...or the lowest equivalent that your lens might have...generally kit lenses have f/3.5.
Now go to your window and look through your camera viewfinder.
Adjust the shutter speed until your light meter points at '0' Take a picture.
Now adjust it so the light meter reads at "-1" and take a pic...do it again for "+1" (incidentally, that's what you do for creating HDR pics...but that's a tutorial for another day )
Hopefully that will give you a better idea on shutter speeds.
As a general rule, the 'lower' you go..that is.. at 1/60 to 1/30 to 1/15 etc.. the more blurry your picture might get, either due to movement in the background, but mostly due to your own hands shaking.
A fast shutter speed will result in “freezing” a moving object and a slow shutter speed will let you capture the motion of a moving object.
For beginners, I prefer you not go below 1/125th of a second... at least not without a tripod. Once you learn to control your hands a bit better you can reach until 1/60th of a second.
Like the pupil in a human eye, the aperture on a camera controls light.
It does so by closing up to restrict light, and opening up to let it through.
moving from f16 to f8 is: TWO STOPS brighter.
moving from f5.6 to f8 is: ONE STOP darker
moving from f4 to f2.8 is: ONE STOP brighter
Now, if the exposure is made with a wide aperture ( like f2.8 ), then objects farther away from the subject are thrown out of focus...which is why you see many macro shots with a blurry background. This effect is referred to as "depth of field"
So.. if the aperture is small (like f22) then objects in the background (and foreground ) will appear sharper. However, since less light is being taken in at f/22, you have to increase the shutter speed a lot..and it could result in blurring the image due to camera shaking.
Basically, you have balance it out using the "stops" in the light meter.
Since aperture and shutter are both measured in stops, keeping balance is easy. If you take away 2 stops from the aperture, you can give 2 stops back with the shutter and end up with the same exposure level.
Soooo, hope all you newbies learned something today.
A quick recap of everything.
Newbies can actually print the bottom part out, though I personally don't recommend it. The best way to learn all this is via direct experimentation. That's how I learned in the first place.
ISO 100 is always preferable unless you are in very low light conditions with no tripod.(unless you WANT noise in your picture)
Try not going below 1/125th of a second without tripod, else it will result in camera shake and blurry pictures.
Pictures taken at f/22 will result in the background being much more clearer than at f/2.8...though most of the times you don't really want to show too many details in the background. However, f.2.8 will give you much more vivid photos and is thus extremely preferable around 80% of the time.
There is only so much one can learn from reading.
Get off your butts and go take some photos. I advise everyone to shoot in manual mode at all times. It will help you learn your camera settings faster.
Try different timings during the day and shoot different objects... landscape, portrait, bottlecaps, wall textures..virtually anything and everything. For the next week or two..just shoot everything while tinkering around with the settings. By the end of two weeks you will have fully understood this part of your camera.
We will carry on after that..
This is Hershey Desai, over and out.