For years, many digital photographers have been fooling themselves that low ISOs are inherently good, and high ISOs are inherently bad. But that’s all based on very outdated thinking. In fact, the advances of successive generations of cameras means that we need to rewrite the rulebook on ISO.
How many times have you read a technique article that says, “set the lowest ISO for the best image quality”? It’s true that, on the same camera, the lower the ISO setting, the freer from noise the image will be – but how free does it need to be? And what do you call noisy? At what point does interference become a problem? If you’re really obsessed with looking for noise up close you’re probably not thinking the right way about photography at all.
Noise is a natural part of digital image making – embrace it and you'll be able to get shots you didn't think possible. ISO 500 was used here.
The amount of digital noise you can see in a picture depends on many things. For instance, the exposure, how it’s been edited, how close you look at the image, and the size at which it’s displayed. For instance, take the same image and create a low-res version of it, say at 1200 pixels across – view it alongside the original and it will look a lot less noisy because the downsizing will have removed a portion of the interference.
The smaller you display an image, and the less you brighten it in post, the less noise you'll see. This was shot at ISO 6400.
Cameras today can produce very tidy images at high ISOs, like 1600, 3200 and 6400, and it’s only when comparing shots at very high magnifications you can see much difference from the lower settings. It’s a far cry from the middle of the last decade when venturing over ISO 800 could lead you down the path of horrible banding, unnatural colour shifts and detail-wrecking layers of grain.
So what does this increased ISO performance really mean for photographers? Here are 6 new ways to think about ISO. . .
A new everyday ISO
Once it was difficult to imagine, but on today’s cameras there’s no real reason to use ISO settings under 800 for general photography. Anything lower can be reserved for situations where you want to drag the shutter speed a little longer for creative effects, or to work with wide apertures in bright light. In that way, lower ISOs can these days be seen a bit like popping an ND filter on your lens when you need extra control – normally you can do without them. The benefits, of course, are that you’ll be operating with faster shutter speeds and therefore get sharper images, free of motion blur when you want them.
This image used an ISO of 800 to achieve a useable handheld shutter speed of 1/20sec. But unlike previous generations, noise is scarcely visible.
You may find you're only using the lower ISO settings for wide-aperture work and long exposures. Here, ISO 160 was used to drop the shutter speed.
Avoid subject blur
Low ISO settings are actually quite bad for many subjects. You might think you’re getting superior quality, but the risk is that your exposures at low ISOs will be too slow for a sharp shot. And not just in terms of camera shake when handholding. Sure you can compensate for slow shutter speeds with image stabilisation, and avoid camera shake that way – some systems might let you hand hold at shutter speeds of 1/4sec or even slower – but you’ll still get subject blur if they’re moving. Moving to higher ISOs will fix that.
Getting more comfortable with higher ISOs means you can freeze subjects more easily. A few years ago, shooting an image like this at ISO 800 would have been a problematic.
Use slower, smaller lenses
Do you still need that big, heavy, fast lens to work in low light? Or can you offset a few stops of aperture with a similar hike in ISO. Of course you can. The only thing you’re missing is less control over depth-of-field, and while that’s a genuine loss for some subjects, using smaller apertures, and therefore greater depth-of-field, might help you keep the subject in focus more easily. Take the difference between an f/2. 8 and an f/4 lens. That’s only one stop of ISO adjustment to get the same shutter speed. And at f/5. 6 it’s only two stops, so an equivalent of going from 200 to 800. Not much at all by modern standards. A slower lens will also cost you less, and most likely weigh less, so it’s good news all round.
Do you still need fast lenses? Maybe, but modern ISO performance means you can bump the sensitivity a few stops to use slower glass, like variable aperture zooms.
Shoot right at night
If you’re into astrophotography, or shooting landscapes at night, there used to be a big tradeoff between the high ISOs required to record faint starlight and the quality of pictures you’d get from it. Not any more. You should now be able to confidently use ISOs like 3200 without fear of the image tearing itself to bits, but make sure you get the exposure as close to ideal as possible, as you won’t want to push it much in post. Using higher ISOs also makes focusing easier in astro shots as you can use smaller apertures and keep more of the scene sharp.
There's little need to be nervous about shooting nightscapes at 1600, 3200, 6400 or above, and higher ISOs mean you an stop down a little, for greater sharpness, too.
Make more use of Auto ISO
Having greater confidence in higher ISO settings means you’re more likely to use Auto ISO, and once you start with that, there can be no looking back. Your camera’s Auto ISO setting allows it to vary the ISO depending on the amount of light metered, so it will naturally bump up the ISO when things are gloomy. For day-to-day subjects, try using an Auto ISO setting that keeps your shutter speed at a minimum level like 1/250sec and you’ll see a real improvement.
Walking around and shooting handheld you can make great use of Auto ISO - this shot used an Auto ISO of 720 giving a handy 1/160sec shutter.
Decide what’s best for you
The most important thing is being comfortable with the noise your camera is producing and that means deciding on a limit you’re happy to put up with. This doesn’t need to be set in stone, but if you take some test shots throughout the scale you should quickly be able to spot the point at which things start breaking up too much for you.
The only way you'll know what sort of noise levels you're willing to shoot at is by shooting test pics throughout the range and comparing them.
. digitalrev.com2019-4-25 03:00
