Quick Tip: ISO and its Effects on our Images
by Alan Winslow – May 18th, 2018
Camera ISO is an often overlooked setting in the world of photography. More often than not, photographers set their cameras to Auto ISO and forget about the feature. Today we’re going to explore this setting so you can make the most informed exposure decisions.
What is Photo ISO
Photo ISO is one of the three pillars that make up a perfect exposure. The other two being Shutter Speed and Aperture. In its simplest definition, ISO is your camera sensor’s sensitivity to light. The lower the number, the less sensitive it is to light, the higher the number, the more sensitive it is to light. Increasing the sensitivity is particularly helpful in low-light situations when you don’t want to use a flash or tripod.
If you’ve ever photographed with film, the process is similar. A 100-speed film is typically used for outdoor shooting in bright light, where a 3200-speed film is used for dark situations like inside restaurants and bars. One of the beautiful things about digital photography is that now our camera’s are packed with all the options. If we walk into a dark restaurant after photographing outside, we can simply make the change on the fly rather than changing rolls of film. ISO options inside the camera are one of the many reasons why digital cameras changed the whole practice of photography.
How Photo ISO is Measured
ISO is measured in Stops. A stop is a unit of exposure measurement that is either doubling or halving the amount of light reaching the sensor. Typically, our camera’s ISO settings are 100, 200, 400, 800, 1600, 3200, 6400, etc. So ISO 400 will be twice as sensitive as ISO 200 and ISO 100 will be half as sensitive as ISO 200.
How Photo ISO Affects Images
There are side effects of increasing your ISO. The higher your setting, the more noise you introduce. Noise is a visual distortion in the image, meaning that the pixels are not displaying the correct exposure or color. Two common types of noise you might see in your images are luminance and chrominance. Luminance noise only affects the brightness of the pixels, where chrominance noise shows up as colored pixels, typically they’re red, green or blue.
The total amount of luminance or chrominance noise in a particular image depends on the make and model of the camera. As technology continues to evolve, camera companies can minimize noise at higher and higher ISO settings. Below we pointed out the location of noise within a couple of images.
How Much Noise is Acceptable
Especially relevant the amount of acceptable noise in a final image is photographer dependent. You can run a simple test to judge what you think is acceptable or not. Every camera comes with a native or base ISO which is the lowest setting typically 100. Ideally, you would photograph in this ISO at all times, but that’s not always possible. To do this test, you’re going to need a tripod (or something stable to put your camera on) and a couple of different lighting scenarios. I like to test my cameras in a dimly lit room, outside at dusk, a bright day, and at night.
Perform the Test
-Place your camera on a tripod and frame up your shot.
-Lock your aperture to f5.6 or f8.
-Take an image an every ISO setting. You’ll have to adjust your ISO and shutter speed to remain exposed correctly.
-At the completion of the test import your images into your computer and zoom into at least 200%.
-As your scroll around the pictures, you’ll see where noise has formed.
-For each scenario note the ISO ranges that are acceptable to you.
-Keep these ISO numbers in the back of your mind when you’re out shooting in the future.
Remember that it’s best practice to try and make the cleanest exposure in camera, but in certain situations you’ll have to photograph in high ISO ranges, knowing that you’ll get noisy images. Commonly used image editing software like, Lightroom and Photoshop have tools to reduce image noise, but remember it’s almost impossible to remove it completely. You’ll notice that the more you apply these corrections the more the final result will lead to unnatural looking images. To me, when too much of the noise correction filter is applied an image looks like it’s wrapped in plastic.
Example – Still life
You can see in both the original and magnified views that a significant amount of noise has developed in the ISO 2000 and 4000 images. This test informs us that for this particular camera the ISO should be kept under 2000 to achieve clean images. Consequently, this is all camera dependent. If you’re using a newer model, then you will be able to reach higher ISO’s with minimal noise.
The Difference Between Noise and Grain
In the days of film, photographers would often photograph in high ISO(ASA) speed films to get the effect of grain. Depending on the subject matter grain can add to the aesthetic of the picture. Digital noise is much different visually and technically than grain and should never be used as an aesthetic feature. Film grain is developed by chemical crystals suspended in the film stock and is various sizes and shapes. Digital noise is generated from increasing the voltage to the digital camera’s sensor and will be in the form of the pixel. Due to the process in which digital noise is produced you’re degrading both the color and tonal range of the file as you increase the ISO. If you are looking for a classic film grain aesthetic, make the cleanest possible image in camera and apply a filter or preset later in post production.
What Does ISO actually stand for
Popular belief is that ISO is an acronym for International Standards Organization, but that is incorrect. The term ISO comes from the International Organization for Standardization. So why isn’t the acronym IOS? We will let them explain. “Because ‘International Organization for Standardization’ would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek isos, meaning equal. Whatever the country, whatever the language, we are always ISO.” – www.iso.org
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