Monday, May 20, 2013

Aperture, Part 1 of understanding the Exposure triangle.

      Ever wonder how your camera picks the right setting when you take a photo? If you are in "Auto" mode, it picks an aperture, shutter speed and a ISO to come up with an exposure that your camera uses. If you are in an area where light is an issue, the camera will use that little POS pop up flash to help it take this photo. So what is an Aperture? what is Shutter speed? and what the hell is ISO? well that is what we are going to talk about and break it down for you.

      A lot of people talk about F-stop or something like "I took this at 2.8." I know that when I started into photography, I had no clue what this meant and how it effected a photo. How aperture effects the light coming into the camera, how it effects the depth of field, and the bokeh effect. Inside of a lens has a number of aperture blades that open and close depending on the F-stop. The larger the opening, the lower the "F stop". It could be like F3.5 on a kit lens or 2.8 or even 1.8 on a high end or a fix prime lens.  So lets go over aperture and the stops of light.

 0   /   1   /  2  /   3   /  4  /  5 /   6   /   7   /  8 
F2 /F2.8 /F4 /F5.6 /F8 /F11 /F16 /F22 /F32

So if we use F2 as a base, if we go to F4, that is 2 stops of light that you lose. so the picture is going to be underexposed (dark) by 2 stops of light, and it will have a greater depth of field (more things in focus) and their will be less bokeh effect (the round points of light). lets say you are doing a portrait shoot and you want to get that blur in the back ground so you cant see what is be hide the person, then you are looking to get a low F-stop. if you go from F4 to F2.8 without changing any thing else, now you are 1 stop of light over exposed. now the photo is bright.
From left to right and top to bottom. its the F stop changing in Aperture mode. only thing changed was Shutter speed.

Shot in manual mode. shutter speed and ISO stayed the same. only changing the Aperture

Now you are doing a landscape. You want to have everything in focus, then you might want to pick a higher F-stop number. I would start with F8-F10. This will give you a high amount of the photo in focus. However, with you being at F8, you now needing to have longer shutter speed or higher ISO to take a photo with correct exposure. if you want to keep the ISO down, now you are talking about a tripod and that is different cup of tea that we will cover later.

Shot with a Aperture of F-9 to have the rail in focus and have the mountain peak in the back in focus also.

If you go to the farther side of the Aperture number like F16, what is happening is that the aperture blades are creating a small opening. so small that only a little bit of light come into the camera and then you will start to get even longer shutter times. Now you will get that star burst effect on lights.

Shot with a Aperture of F22. you can see the star burst on the street lights and head lights

So a F-stop is a number that relates to aperture. The higher the number the less light that gets into the camera that requires a longer shutter speed or higher ISO (noise) to get a correct exposure but you get a larger amount of greater depth of field.  if you go to a lower F-stop like F2.8 you will get a shallow depth of field, the amazing bokeh effect in the back ground, and faster shutter speeds and low ISO.  The aperture is something that you change depending on what you are needing. You want to get a group shot of 6 people? then you are better off going with a mid range F-stop like F5.6 to get every one in focus. You are doing a landscape? simple, dial in F9 and work with that. You are doing a portrait of a person with ugly stuff in the back ground? Lowest F stop your camera/lens will do!

Hope you have learned something from this and stay tuned for Part 2 of this. SHUTTER SPEED!