Tip of the week: ISO Explained
Here in Lancaster it seems like it’s been winter forever and with winter you have shorter days and more low light than bright sunny days to take photos. How would you like to take photos at night and in lower light with only available light? That’s right, no flash at all and no tripod. You may not realize this, but other than the shutter speed on the camera and your aperture on the lens/camera, you have a third way to control how bright your photo will be. You can do this by changing the ISO on your digital camera.
ISO, originally, was the measure of how sensitive film was to light. It has now been adapted to the digital realm and can be changed on a whim versus needing to change film out of your camera, which is very time consuming. While thinking about ISO in the digital realm, it is now considered how sensitive the camera’s sensor is to light. Basically, the lower your ISO number the more light you need, or the slower it will expose the sensor to the scene, a higher ISO number will expose faster and allow you to photograph in a lower light. A good ISO for daytime would be 100 ISO, but in the shade or in the early morning or dusk hours you may need a faster ISO to compensate for the lack of available light. You can also add more light by opening up your aperture and slowing down your shutter speed. But, you can only slow down your shutter speed so much before you can’t hold the camera in your hands and take the picture because you’ll get what’s called camera shake. Which means the exposure is too long and you start to see ghosting and areas blurred in your image. So, if you raise your ISO it means that you should be able to keep your shutter speed up in an area where you should be able to hand hold your camera without getting any camera shake.
This is great to know especially when you have a DSLR and can change your ISO quickly. However you can change your ISO on a point most point and shoot cameras as well. The problem is that most P&S’s don’t handle the higher ISO range very well. What do I mean by this? Well, below are two examples of how ISO affects the quality of an image. The more you raise your ISO level, the more noise you get in your photo and the lower the sharpness and detail becomes in your photos.
I’d like to thank Imaging-Resource for the images below and for taking the time to review every digital camera out there and showing samples from each camera on their website. Go check them out, they have the best info on every digital camera. The first example is from a Canon 50D and show the difference from a range of 100 ISO (f/8 at 1/15 of a second) on the left and 6400 ISO (f/8 at 1/1000 of a second) on the right. You can see that the detail of the text on the bottle is clear and crisp, where the text on the circle on the right is soft and degraded by the noise. You can really notice the noise on the gray flat background where the noise has simply taken over the background all together. This happens a lot with ISO noise in large flat areas and something to keep in mind when photographing skies and such with higher ISO’s.
The next sample is from a Casio EX-G1 point and shoot. The range on these images are from 80 ISO (f/5.4, no shutter speed recorded) and 3200 ISO (f/5.4 and again no shutter speed) on the right. You can see that the quality on the left isn’t great to begin with. This has to do with a smaller and less accurate sensor in the Casio. But on the right, the image is totally unusable. If it’s all you had, no flash and no tripod, OK you would get a picture. But you can see how terrible the quality is and that you almost can’t even read the text on the bottle in the middle. The noise has taken over the whole photo and compromised the sharpness and quality of the image.
I just want to leave you with the thought that ISO can be great to allow you to take photos in lower light situations, however you need to keep in mind that the quality of your image may be compromised and the image may be unusable for your final output. But, don’t be afraid to use ISO and take some time to test your camera’s ISO by taking a series of photos and checking out the difference in each one so you know the limits of your camera.