ISO: A Photography Tutorial
Good morning my fellow photographers and scrappers! It seems like forever since I last wrote to you all about the basics of f-stops and exposure settings as well as focal length. We are talking this week about ISO and how that affects our photos and we will finish up our beginner photography tutorials next month with a lesson on metering...which will help tie all of these lessons together!!
ISO, or International Standards Organization, refers to how sensitive the camera's sensor is to light. Most, if not all, digital cameras allow you to adjust the sensitivity. A low (or slow) ISO speed requires a longer exposure while a high(or fast) ISO speed requires less time to give the same exposure. The lower the ISO number (50 or 100), the more light is needed to get proper exposure when taking a photo. You would use a low ISO in the bright, outdoor sun. The lower the ISO, the better the image quality. However, as it gets darker, in order to have the proper aperture and shutter speeds you would need to get the photo you that you want, you would need to raise the ISO in order to let in more light. The result would be a photo with more 'noise'. The higher the ISO, the noisier the photo. This is because at higher ISO's you are taking an image with just a smaller amount of light, so the signal to noise ratio drops. The following photos were taken with different ISO settings. Take a look:
I shot all the photos above with an f stop of 3.2. My shutter speed changed according to the ISO setting in order to meter it correctly. You can see that with each change of the ISO, it added a little bit more light onto my subject until you were finally able to see the details of the flower in the last photo.
In the photo below, notice that with each stop of the ISO a little more noise was introduced so that by the time the ISO of 1600 is reached, it is very grainy or 'noisy'. In saying that, noise is less obvious in print than it is on screen, so you can get away with a little higher ISO than what you might think. It is a good rule of thumb, however, to shoot with the LOWEST ISO possible and still be able to get the depth of field and the shutter speed that you need.
Are you wondering how in the world you are EVER going to get all these things to work together? Well, the first answer is.... it takes practice and a lot of trial and error, but, it is also good to remember that if you need more depth of field(that is your f-stop) and you don't want to reduce your shutter speed (i.e. 1/250s), then increase the ISO and reduce the aperture. However, if you need a faster shutter speed and you don't want to lose the depth of field, increase your ISO and your shutter speed. For the most part, I decide what two of the three settings are THE most important to me. If I want to make sure that I am shooting with an f-stop of 3.5 and and ISO of 200, then I will change my shutter speed. However, if it is important to me to freeze my subject, then I will set my shutter speed to around 1/1000s (if outdoors) my f-stop to around f4.5m, and then I will set my ISO to the setting that gives me the proper light.
Finally, more often than not, I find that I am OK with a little noise rather than a blurry photo especially if I am taking sports photos. I would much rather see my kiddos great shots instead of just a blur of motion....a little noise can always be fixed in Photoshop. There are a lot of great plug-in programs available for Photoshop. I use Noiseware but I also have heard good things about a program called Noise Ninja. These programs can be run on your photos to help reduce the noise and make your noisy photo even better!
In the close up photo on the left, I ran the Noiseware plug-in to show the difference in the original photo and the treated photo. Can you see the difference in the treated and untreated parts of the photo? The noise is very evident on the lower half of the photo.
Sometimes, no matter how hard you try, you are going to have noise......especially if you are shooting basketball pictures in a very dark gym.... so these programs can be a lifesaver! Of course, it is ALWAYS better to try and get your shot correct in camera (and really more satisfying too) but there are ways to save those photos...just in case!
This week, I want you to practice changing your ISO. Shoot in all different lighting situations and get yourself familiar with which ISO works best in any given lighting situation. What ISO do you use in outdoor, bright light? Shade? indoors and low light situations? Try NOT to use your flash in low light areas. I want you to adjust your ISO settings and see what happens when you change your f-stop and shutter speed settings as well....these three settings all work together to create the perfectly exposed photo..so practice, practice, practice!
Until next month, have a great week and happy shooting!