I went round and round about where to begin. The main three questions I get about photography have to do with f/stop, shutter speed, and ISO. But, which one is most important? Which one is easiest to explain and understand?
This week I'm going to give you a basic overview of how light enters your camera and over the next month or two we will tease out the specifics.
There are three main ways to control the light that enters your camera. Aperture, Shutter Speed and ISO.
Your camera's aperture, also called f/stop, is the opening where light passes through the lens and onto the sensor. A "wide open" aperture allows a lot of light in while "stopping down" your aperture allows less light in. The funky thing about f/stop numbers is that the larger the number, the smaller the opening. So, an aperture of 11 lets in much less light than an f/stop of 2. If you think of it as a fraction it is more obvious that 1/2 is larger than 1/11. Just remember - high number=less light, low number=more light.
2. Shutter Speed
The amount of time your shutter stays open is called the shutter speed and is numbered in fractions of a second. 1/60 of a second is much slower than 1/250 of a second or 1/2000 of a second. On a very bright day you will need faster shutter speeds in order not to overexpose your image. In low lighting, or indoors, you will need slower shutter speeds in order to allow as much light as possible into your camera.
3. ISO
ISO refers to the sensitivity of your camera's sensor. A low number - 100 - is less sensitive than a higher number - 800, or 1600. For outdoor photography, where you have a lot of light, an ISO of 100 is perfect. When you move indoors where there is less light you need your camera to be more sensitive and a higher ISO is necessary. Image quality suffers as the ISO gets higher so shooting at the lowest possible ISO is ideal.
These are just the basic definitions of Aperture, Shutter Speed and ISO. In future posts we will explore each one in much more detail.
It is interesting to note the effect each of these settings has on the other.
In my mind I picture a perfect image exposure as a balanced scale.
If I change my aperture to allow less light in I need to increase another light factor to compensate, either by decreasing the ISO (making it less sensitive) or making shutter speed slower (allowing less more to come in).
If I make the shutter speed slower allowing more light to get in the camera but don't make a change in one of the other two factors my scale will not be balanced and the image will be overexposed. Working with the same idea, if I make the shutter speed faster, allowing less light in, I need to either close the aperture down or adjust the ISO.
This week we will be thinking about the light that enters our camera. Take an image in automatic and then switch your camera to manual. Try to get a similar exposure by changing the ISO, f/stop or shutter speed. If you have a a point and shoot try switching between the different modes of your camera (night, day, sports...) and see how it affects the image.
The goal this week is to become familiar with how these three settings affect your image. This will happen only when you practice, practice, practice!
If you mastered the Rule of Thirds last week you may shoot anything you want. If you had problems with Rule of Thirds or would like another go at it, try to shoot another ROT picture.
I will post the Assignment Due Mr. Linkey next Friday, February 12 and keep it open until Sunday, February 14th. That gives you one week day and two weekend days to get your images up.
Please let me know if you have any questions. This is just the basics on this topic, there is so much to learn!
UPDATED: I fixed the scale images to make them more in line with the laws of physics, thanks Jen!
My camera didn't come with a manual, so I don't really know what all the things do or how they relate to what you are talking about. But, I am gonna experiment and see what I can figure out. Also, speaking of doing more ROT, I put up a couple more on my xanga after the first one.
ReplyDeleteHope you are enjoying your snow. We got a foot or so, but it is still a pain in the butt. :-)
~Leslie
Thanks for the explanation. Once I took the time to read it, I realized you explained it in very simple terms that actually make sense. I just have to commit it to memory now.
ReplyDelete