aperture and shutter speed are the two most vital parameters which determines the qulity of the picture by controlling the exposure.
Aperture is the opening of the diaphragm of a photographic lens. Technically it is expressed as the ratio of focal length to the diameter of the circular opening of the diaphragm and denoted by “F” numbers. Confused, right ?
Let’s talk in simple terms. Every photographic lens is accompanied with a diaphragm, which regulates the amount of light going onto the sensor. Bigger opening means more light and smaller opening means lesser light.
Aperture is expressed as the ratio of focal length to the opening size i.e. the diameter of the circular opening of the diaphragm. So, focal length being constant in most cases, as the opening size increases, the ratio decreases.
→ Smaller aperture number → bigger diaphragm opening → more light intake.
→ Higher aperture number → smaller diaphragm opening → less light intake.
Few examples are F2.8, F3.5, F6.3 etc. the same may be denoted as, f/2.8, f/3.5, and f/6.3. Here, once the values are denoted by capital letters and once, with small letter “f” and that too as a reciprocal form. Don’t get confused. Both are exactly same.
Aperture value is said as f-stops. It doesn’t have anything to do with the technicality. It is just a fancy name to the measure of aperture.
Just like aperture, there’s another parameter which can regulate the amount of light intake, although not manipulating the diaphragm opening size, but, the speed of opening and closing of the diaphragm.
This parameter is known as shutter speed and is measured as the time taken to open and close the diaphragm. It may range from (32 seconds)32”, (16 seconds)16”, 8”, … etc to 1/8(1/8th of a second), 1/250(1/250th part of a second), 1/1250 etc.
Higher speed → less time to open and close → less light.
Lower speed → more time to open and close → more light.
Hence 8” or 16” of shutter speed will let more light to pass onto the image sensor than a shutter speed of 1/10th of a second.
Now you can easily imagine how these two parameters can be used to arrive at the best possible exposure for any subject.
Although, it seems that both the two parameters serve the same purpose, yet one cannot be replaced by the other. Both the two parameters have their unique usage in terms of photographic maneuverability.
We would discuss the usages of aperture and ISO setting in a separate post.