Adjusting the ISO sensitivity is a setting found in all cameras. Knowing how to handle it will greatly improve your photographs, regardless of whether you are in the worst light conditions, or are using a tripod.
Steps
Step 1. Plug your headphones into an amplifier connected to your computer or MP3 player, and listen very carefully - don't worry, we'll get to the point
Turn down the volume on your computer or MP3 player, and then turn up the volume on the amplifier. You will notice that the volume of the music increases, but as the volume increases, so does the noise (generally a slight hissing sound).
This is not that different from the ISO level adjustment feature! The sensor of your digital camera has an inherent sensitivity, which corresponds to its physical sensitivity to contact with light. If a photo is too dark (which will happen with a slow shutter speed), then your digital camera can amplify the sensor signal, just as you have increased the volume of the amplifier. The downside is, as in the case of music, the amplification of the signal also increases the noise (granularity) in your photography. A compromise must therefore be found: if you want a faster shutter speed, then you will have to increase the ISO level (“turn up the volume”), but you will pay for this with an increase in noise. We will go into detail on this compromise later.
Step 2. Find the command for ISO adjustment
Generally, in compact cameras, this feature is nested within the menu, while most DSLRs have a dedicated button for this setting. Consult your camera manual to see if you can find it yourself. Check how many ISO settings are available on your camera. Normally digital SLRs allow adjustments from 100 or 200 up to 1600 or more; compact machines, on the other hand, offer a smaller range of adjustments.
Step 3. Take shots outdoors in P (rogram) mode
Take a shot with each of the available ISO levels, and examine the photographs on a computer. Depending on the camera, the results will differ; however, you will notice that the image with the higher ISO level will also have a higher noise level and / or be more attenuated (due to the noise reduction feature applied by the machine).
Compare the noise level of your photos, and decide which ISO settings you would always use for your photos, which ones you would only use in certain circumstances, and which ones you would avoid using in any case. Only you can make this decision; every camera is different, and personal tastes are even more different.
Step 4. Do a few more tests by shooting in time priority mode
What you want to find out is what is the shutter speed that always allows you to have well-defined photos. Pay attention to the focal length, which is expressed in millimeters. Photograph the same scene, but at different shutter speeds, with variations of about half a second at a time. Some people have a very steady hand and good technique, and can take good photos even at very low speeds.
Now, among the various photos taken, determine which is the one taken with the slowest shutter speed, but which is still well defined, and keep this number in mind as a factor for the particular focal length used. So, if you have used a 30mm lens and have been able to get, by shooting handheld, a well-defined photograph with a shutter speed of 1/15 of a second, then you will need to increase the ISO level if the speed becomes shorter than half the focal length used (regardless of the lens used).
Remember: a faster shutter speed not only freezes the image, but also reduces the likelihood of you moving during the shot. A photograph with a high level of noise but defined is much better than a less noisy but shaky one (due to the movement of the camera).
Step 5. Don't worry about this if you photograph using a tripod
In this case, use the lowest ISO setting available. You will only need to raise the ISO level in case you need a faster shutter speed (which would have been available in better lighting conditions). This doesn't matter if your subject is still, and if, in the case of handheld shooting, you don't have a problem with camera shake.
Step 6. Don't worry about this if you photograph outdoors on a very bright day
Unless you're using a really powerful zoom, you'll have more than enough light to select whatever shutter speed you want. Keep the ISO low and everything will be fine.
Step 7. Evaluate if you need to freeze a movement and act accordingly
In this case we mean the movement of the subject and not that of the camera. This is more relevant to those who intend to take photos of sporting events indoors, or in low light conditions. Using a shutter speed of 1/250 you will be able to freeze most of the movements, and even more by setting 1/500. However, you will only learn to select the most suitable speed for each case by trying and making mistakes.
Keep an eye on the shutter speed: if it falls below the desired value, increase the ISO level until you get a shutter speed that can freeze the movement you are interested in. Likewise, if the shutter speed increases beyond the necessary value, consider lowering the ISO level to get a photo with the highest definition possible.
Step 8. Use ISO adjustments when shooting handheld to avoid blurry photos
You've probably already done some testing to determine what is the maximum speed, for a given focal length, with which you can shoot handheld (if you haven't, do it now!). Again, a noisy photograph is better than a blurred photograph, so don't hesitate to increase the ISO level until you get the desired shutter speed.
