Thursday, September 22, 2011

Shutter, Aperture, ISO, Depth of field

In my opinion, composing a picture requires two things, you have to have an eye for it, and you have to know how to capture it. If you have a beautiful picture in your mind but can’t capture it, its worthless. If you know exactly how to capture an image, but do not have an eye for it, your pictures will not look good. Today I will explain how to capture an image just like you picture it.

A camera is nothing more than something that captures light. Film cameras used film to capture light, now we use digital image sensors (much easier, cheaper, and convenient). There are three main variables used while capturing this light. Shutter speed, aperture, and ISO. All three of those effect how bright or dark your picture is. If you have your camera set on “auto”, then the camera decides what all of those should be set at. If you have ever taken a picture before, you have probably realized that the camera does not know what looks good, the camera simply wants the amount of white and black to equal a predetermined amount, or more specifically, about 75% of your picture to be neutral or grey. If you want your picture to come out how you picture it in your mind, you must understand shutter speed, aperture, and ISO.

Shutter speed. This is how long your shutter stays open. The longer your shutter stays open, the longer light hits your image sensor, and ultimately, the brighter your picture will be. Shutter speed is measured in fractions of a second. So a shutter speed of 1/200 will be a lot brighter than a shutter speed of 1/4000. Remember, if your shutter speed is too slow (stays open too long) you will have a blurry picture because your image sensor will capture your wobbly hand. I try not to go any slower than 1/60 when holding my camera. To “stop” a fast moving person/bird/object, you need a fast shutter speed. If you have ever noticed a fast moving object being blurry in your picture, it is because your shutter speed was not fast enough. Image stabilization (canon) and vibration reduction (Nikon) lenses help with camera shake at slow shutter speeds.

Aperture. This is just like the pupil in your eye. This regulates how much light is let in. The bigger your aperture, the brighter your picture will be. Easy. Your pupil gets bigger in the dark because it needs more light, it’s the same with your camera. Aperture is measured with “F/” The SMALLER the number the BIGGER your aperture. An aperture of F/3.5 is actually BIGGER than F/5.6. Most standard kit lenses can get as big as F/3.5 and as small as F/22. So if you want your picture to be brighter, open your aperture (smaller number!!) Need it darker, close it up (bigger number). If you have ever wondered why a lens is so expensive, it is usually because it can shoot with a high aperture such as F/1.4 or F/2.8. In the lens world, you pay a lot of money to be able to shoot in low light. Cheap lenses usually open up to just F/3.5.
-The aperture also effects your depth of field , to learn more about this, see bottom.

ISO. ISO is how sensitive your image sensor is. Entry level DSLRs usually have the ability to go from ISO 100 to around 4000. If your ISO is set at 100 it is not as sensitive as an ISO at 800. If you want a brighter picture, change your ISO to a higher number. If I am shooting inside (less light) I usually set my ISO to around 1000, that way it takes less light to make an image because the sensor is more sensitive to light. You also have to keep in mind that the higher your ISO, the more “noisy” your picture will be. Noise is pretty much grain, small dots, or sometimes a slight “blur” on your image. Higher end (more expensive) DSLR’s handle higher ISO’s better, meaning they have less noise. An entry level DSLR might not do so well with an ISO above 1000.

Over all, there are three ways to change your images exposure. To make a picture brighter, you can leave the shutter open longer, You can open your aperture to allow more light , or you can change your ISO.
When shooting in manual, you have to be aware of all three of those things at all times, but it gives you the greatest control of your images. When shooting in auto, the camera does it all for you.

Depth of field- I am not going to get into why but I will tell you that the bigger your aperture, the shallower your depth of field. Depth of field is how blurry your background and foreground is compared to your subject (what is actually in focus). The best way to explain this is to show you.

Notice how just the closepin is in focus with an aperture of F/2 but when you make your aperture smaller, more of the background comes into focus. The piano is an even better example, the first picture has a shallow depth of field, notice how only a few of the keys are in focus.
Just to make things more complicated, your focal length (how far you are zoomed in) also effects your depth of field. The more zoomed in you are (the greater your focal length) the shallower your depth of field. So if you want to blur the background of your subject, back up and zoom in.

Notes-Also, just to make sure you are not confused; the pictures shot with different apertures are also shot with different shutter speeds. If you were to shoot the picture of a closepin with an aperture of F/2 and then all you did was change the aperture to F/16 WITHOUT changing your shutter speed, the image would be way too dark. When the photographer made the aperture smaller, they also had to make the shutter speed slower in order to get a proper exposure. The shutter speed and aperture work together to get a properly exposed image. The same is true for the pin wheel picture. If you leave your shutter open for a long time in order to get a blurry pinwheel, your aperture has to be small (bigger number) to let mess light in. So if you want to “stop” or freeze the pinwheel in place, you speed up the shutter speed, which means you have to make the aperture bigger in order to get enough light.

Brighter picture

Darker picture


Slow shutter speed ex. 1/60

Fast shutter speed ex. 1/2000

Faster shutter “stops” moving objects

Big aperture ex. F/2

Small aperture ex. F/11

Bigger aperture=shallow depth of field

Higher ISO ex. 2000

Low ISO ex. 100

Higher ISO=more noise/grain

Disclaimer- None of the above pictures are mine… stole them all.
For questions, e-mail me at

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