WHAT YOU DON’T KNOW ABOUT ISO

WHAT YOU DON’T KNOW ABOUT ISO

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ISO speed is one of three settings that control how much light each exposure captures. The shutter speed controls how long the hole is open. Aperture controls the size of the hole. And ISO speed, as we mentioned, controls the light sensitivity of the film or sensor. By adjusting these settings to different light conditions, experienced photographers can get the clearest and sharpest shots.

The funny thing about ISO is that it is an acronym, but nobody really knows what it stands for.  It is always just called ISO even though it really stands for International Organization for Standardization.  Every once in a while, you’ll hear an older photographer pronounce it “I-so”, but almost everyone pronounces it “I.S.O.” The ISO controls the exposure by using software in the camera to make it extra sensitive to light.

When you change your ISO setting, you’re adjusting your camera’s sensitivity to light.

A high ISO such as ISO 1,600 will produce a brighter picture than a lower ISO such as ISO 100. The drawback to increasing the ISO is that it makes the picture noisier.  Digital noise is apparent when a photo looks grainy. Have you ever taken a picture at night with your cell phone or your pocket camera, and noticed that it looks really grainy?  That is because the camera tried to compensate for the dark scene by choosing a high ISO, which causes more grain.

What constitutes a “high” ISO is constantly changing.  Camera companies are constantly improving the ability of cameras to use high ISOs without as much grain.  A few years ago, only the highest-end pro DSLR cameras could achieve 2,000 ISO, and now even entry-level DSLR cameras can shoot at this level.  Since each camera is different, you would do well to do a few tests with your camera to see how high of an ISO you can shoot at without making the image overly grainy.

Right now, you will commonly find new DSLRs that advertise expandable ISO ranges.

A graphic explanation of how ISO settings work in basic photography

Finding the right ISO setting

First of all, you should know that a higher ISO typically translates to a noisy or “grainy” image, so as a general rule you want to use the lowest setting possible for your photos. Check out the picture below to see the difference it can make.

ISO difference

A lower ISO will usually produce more color-accurate, aesthetically pleasing images, but there are situations where a higher ISO is desirable. The proper ISO setting really depends on the level of lighting you’re shooting in and the visual effect you’re going for, so rather than relying on one over-arching rule, consult this list of tips:

If your subject is moving and you’re trying freeze the motion for a still, you’ll likely need a higher ISO setting to compensate for the high shutter speed and ensure your image gets enough light

If you’re going for more of a vintage aesthetic and want to add a little bit of grain to your photos, don’t be afraid to bump up the ISO a few notches

If you’re using a tripod to stabilize your camera you can usually get away with a slower shutter speed, which in turn allows you to use a lower ISO 

If you’re shooting an image that doesn’t require a large depth-of-field, you can increase the camera’s aperture (thus allowing more light into the lens) and use a lower ISO

If you’re shooting with artificial light (i.e., using a flash) you can typically get away with a lower ISO setting

You’ll probably need to experiment a bit until you hit the sweet spot, but while you tinker with settings, keep the following in mind:

  • Never trust your camera’s display. Don’t assume that your picture will turn out just because the tiny 2-inch preview looks adequate. Your shots almost always look different on your computer, and you probably won’t be able to spot noise on your camera’s small, low-resolution display. For this reason, we highly recommend that you zoom in a bit to check your images for grain. There’s nothing worse than taking a bunch of seemingly great shots only to discover they’re noisy and speckled when you upload them to your PC.

Native Versus Extended ISO

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Many digital cameras these days give you the option of selecting between the camera’s ‘native’ ISO range and a special ‘extended’ (or expanded) ISO range. If you are just starting out in photography, you may be confused about what each labeling means and whether or not there is a technical difference or if it just a bit of marketing. Today we’ll be taking a look at the differences between native ISO and extended ISO ranges.

Native vs. Extended ISO Ranges

Before explaining the differences between the two ranges, it is important to know exactly what the ISO setting on a camera changes from a technical standpoint. As most people already know, increasing the ISO number makes your camera more sensitive to light, and thus able to shoot in darker environments. Your ISO setting is one of the important factors in the almighty exposure triangle, alongside your shutter speed and aperture.

Image Sensor | Attribution: Bengt Nyman
A photo of a digital camera sensor by Bengt Nyman

When you change the ISO on your digital camera you are adjusting the signal gain. Or putting it simply, you are changing the amount of analog amplification applied to the sensor’s reading. Each sensor’s reading can be amplified in this way a certain amount before a manufacturer deems the result unusable. This range, from the lowest amount to the highest amount, is known as the ‘native’ range.

So, what is the extended ISO range? Simply put, an extended ISO range is pushing the sensor to its maximum native ISO, then further pushing stops of light via software processing. Some cameras also have the ability to pull the sensor to its minimum native ISO, and then further decrease the stops of light. In the end, shooting with an extended ISO is the same as importing your photographs into Lightroom then pushing their exposure ahead (or behind) a few stops.

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What it Means to Your Photography

As an example, let’s talk about the Fujifilm X100T; this camera is advertised as having a sensor with a ‘standard output sensitivity’ (native) ISO of 200-6400, and an ‘extended output sensitivity’ of ISO 100, 12800, 25600, and 51200. If you choose to shoot a photograph at ISO 51200, the camera is pushing the sensor to its circuitry maximum of ISO 6400 then increasing it another three stops via software.

In the end, extended ISO is almost entirely about marketing. Hearing that a camera can shoot up to ISO 51200 is quite impressive, but you aren’t purchasing a sensor that can capture light with that level of sensitivity – it is all software trickery.

Another example is Nikon’s D7200, which can shoot at an extended ISO range of 51,200 and 102,400. Both modes are merely pushing the Nikon’s sensor to its max and then pushing the rest via software. In fact, the images are so poor in quality that they are only displayed in black and white; there is that much color noise.

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So, when would the extended ISO range matter versus just pushing the photo in post? You may notice that your camera may only shoot within the extended range when working with the JPEG file type and not the RAW format; this is because a RAW photo is a digital negative with minimal digital processing (although some manufactures may adjust the negative if they choose). Shooting in the extended ISO range forces the camera to digitally process your image further, which may be useful for photographers who don’t want to deal with RAW files later. If you shoot only JPEG, then the extended ISO range may be helpful, but we wouldn’t recommend it due to the sheer decrease in quality.