Digital Camera World » ISO sensitivity

Reduce Noise: a quick, proven method for bagging clean images

jmeyer — Tue, 23 Oct 2012 15:30:21 +0000

Are you disappointed by grainy images every time you shoot? It doesn’t have to be this way! Our quick tutorial below shows you a quick and easy way to set up your DSLR to reduce noise and start cleaning things ups.

Follow these three simple steps and you’ll reduce noise sufficiently, building confidence in your ability to shoot just about anywhere.

How to set up your camera to reduce noise

01 Use a low ISO
Select the lowest ISO your camera will allow. This will ensure there’s no ‘gain’ applied, which  will result in digital noise. Most SLRs’ default ISOs are 100 or 200, so don’t be tempted to use an extended lower ISO because this will also introduce noise.

02 Shoot in raw
Always shoot in raw mode because the captured image won’t be processed in-camera, which would introduce noise and other compression artifacts. There’ll be much more room to tweak exposure and smooth any noise present in the raw file.

03 Remove noise
If you do end up with noisy images, which is something that often occurs in low-light situations, use a raw editing program to initially reduce noise before reducing it even further in Photoshop (or a specialist noise-reduction program).

Low-light photography tips: set up your camera to shoot without a tripod

jmeyer — Tue, 11 Sep 2012 10:30:07 +0000

If you’re drawn to the heavy saturated colours of night photography but hate lugging a tripod – or perhaps you physically cannot carry a tripod – you’re in for a treat. Here we show you three quick and effective low-light photography tips on how to set up your camera to shoot hands-free night photography.

See more great night photography tips!

The latest digital cameras offer excellent high ISO performance. Increasing your sensor’s sensitivity enables you to achieve fast enough shutter speeds to shoot handheld in very low light conditions – and even at night!

Better still, even at these high ISO settings, you can capture detailed, colourful images with very little noise pollution.

By following our low-light photography tips below you will learn how you can really push your camera’s ISO capabilities and shoot sharper pictures handheld!

Set your ISO high
First you need to set your camera’s sensitivity. Press the ISO button on top of the camera and choose the maximum setting, such as ISO3200 or ISO6400. You can expand the ISO further – eg to H1 (12800) on the 7D, or H1 (51200) or H2 (102400) on the Canon EOS 5D Mark III used here – but we’d suggest you stick to the maximum unexpanded ISO setting for the optimum combination of sensitivity and quality.

Noise reduction
Your camera will be working hard to try and keep the noise levels down, but when you’re shooting at your highest ISO settings you’ll need to give it a helping hand. In the Menu, set the High ISO Speed NR (Noise Reduction) option to High. Take some shots with and without this setting enabled, then zoom into the images at 100% to compare noise in the shadow areas.

Exposure settings
If you’re shooting a night scene with a wide-angle lens, you only need an aperture of around f/5.6 to capture enough depth of field for the scene to be sharp enough from front to back. And your shutter speed (with a little help from the Image Stabilisation) only needs to be fast enough for your focal length: 1/50 sec at 55mm for instance, will be fine for night shots without a tripod.

6 tips to improve your Mars landscape photos

jmeyer — Thu, 09 Aug 2012 12:24:25 +0000

All Photos: NASA/JPL-Caltech

The landing of NASA’s newest rover, Curiosity, on the Mars landscape marks another small step for the American space agency, but it represents one giant leap for photographers everywhere.

Landscape photographers, in particular, have reason to cheer, for certainly Mars’ landscape offers a new set of challenges from the now rather repetitive roster of slow-motion seascapes and fields of autumn mist that populate online photo galleries.

Mars has long the final frontier for the tapped-out landscape photographer. Anyone who has visited some of Earth’s best photo locations fantasized about the day when technology (and ISO ranges) would let us photograph the deserts of our deserted neighbour in the Milky Way.

So it was with great anticipation we followed the journey of Curiosity. And surely we at Digital Camera World can’t be alone in raising a concerned eyebrow at the quality of what we’ve seen?

Let’s face it: landscape photography isn’t rocket science. Which is all the more shocking when viewing some Mars landscape photos beamed back from Curiosity.

How quickly the euphoria of this great triumph of engineering wore off when seeing such consistently poor composition, exposures and use of white balance!

Were no landscape photographers consulted when calibrating Curiosity’s camera to shoot photos of the Martian landscape?

We’ll check our Junk Mail folder here at Digital Camera World, but we don’t think we had an email from NASA. If we had been asked, we’ve compiled 6 easy tips you can use for making sure all your Mars landscape photos are keepers.

Click here to get started

Obliterate image noise in Photoshop: 6 easy steps

jmeyer — Sun, 22 Jul 2012 12:00:11 +0000

SLR technology is always improving, and one key area is the image quality of photos shot at high ISO settings. Not that long ago, shooting at anything over ISO 800 on most SLRs would result in images too noisy and degraded to be considered usable. But these days on the latest cameras, it’s possible to shoot above ISO 1600 – and even ISO 3200 – and not have to worry too much about image noise (learn when to increase ISO).

But what if you don’t have the newest SLR or have raw images with potential that are suffering from image noise? Help is at hand! By utilising the power of Adobe Camera Raw (ACR) software, it’s possible to rescue noisy raw images in a flash.

Under the Detail tab are sliders to reduce both luminance (greyscale) noise, which makes an image look grainy, and colour (chroma) noise, which is visible as coloured artefacts.

We’re using Photoshop CS5 and ACR version 6.2, which has more options under the Detail tab than previous versions, and produces better results when reducing noise in images suffering with pixels starting to ‘break up’, but the basics also apply to earlier versions of CS.

We’ll also show you how to correct the colour temperature of images that have been shot indoors under artificial lights, and how to do all your sharpening without leaving the comfort of the ACR interface.

WHAT YOU’LL NEED Photoshop CS5 or Photoshop CS6
IT ONLY TAKES 15 minutes

How to remove image noise in Photoshop

1 White balance correction
Download the noise_start.CR2 raw file in your version of Photoshop CS5 or CS6. As this track cycling photo was shot indoors under artificial lights, the white balance is a little bit off. To correct the colours here, adjust the Temperature slider to around 3750, and then drag the Tint slider down to -50 to get rid of the purple tint.

2 Raw basics
The two cycle wheels in the top-right corner are distracting, so grab the Crop tool, set mode to Normal from the drop-down menu and crop them off. To reduce the clipped highlights, set Recovery to 30. To brighten the riders and the dark Lycra, set Fill Light to 10 and set Blacks down to 0. To further lighten the cyclists, set Brightness to +60, keeping Contrast on +25.

3 Turn down the noise
First, you need to reduce the luminance noise of this image shot at ISO800. Click the Detail tab and zoom in  to 100% (Ctrl+Alt+0) so you can see the enhancements. Luminance noise is less tonally distinct than colour noise, so watch you don’t overdo noise reduction and end up blurring detail. We used the following settings: Luminance at 40, Luminance Detail at 50, leaving Luminance Contrast to 0.

4 Colour noise
Colour noise is generally more noticeable, so the ACR default colour noise reduction setting is 25, not 0. A good rule is to match the Colour noise slider with your Luminance setting, so for this image, set Colour noise to 40 and Colour Detail to 50. Experiment with your own photos as the amount of noise can change depending on the SLR, lens and exposure.

5 Clarity and vibrance
Click back on the Basics tab. Before you sharpen, adjust the Clarity slider – which adjusts midtone contrast. Set it to +20. While you’re there, set the Vibrance to +10 to boost the colours of the bicycles and clothing. The Vibrance slider minimises clipping as colours approach full saturation, by altering the saturation of lower-saturated colours without affecting the higher ones.

6 Sharpen up
Always do your sharpening last, or further editing (including resizing) can introduce ugly artefacts. On the Detail tab are several Sharpening sliders that adjust edge definition. Now the clever bit: hold down Alt as you move each slider to see which parts of the image are affected. We set Amount to 40, Radius to 1.5, Detail and Masking to 30. Don’t overdo it, as it’ll add noise. Click Save Image in the bottom-left and you’re done.

Making the case for Auto ISO

jmeyer — Wed, 18 Jul 2012 10:09:21 +0000

Readers often tell us that one of their most common photography problems is forgetting to adjust the ISO settings on their camera when switching between indoor and outdoor shooting. Many often ask if their camera has a reminder they can set.

Well, kind of. The sound of very slow shutter speeds is often a good reminder that you’ve forgotten to increase your ISO setting when shooting indoors or in low light!

Going outside, though, is more of a challenge.  If you’re sightseeing, shooting a wedding, or in other situations where you’re switching between indoor and outdoor settings, it’s worth considering your digital camera’s Auto ISO function.

Now, suggesting an auto setting to a serious photographer will often draw a look of scorn, but bear with us. Your Auto ISO function will keep the sensitivity as low as possible without giving shutter speeds that are so slow that camera-shake results.

As lighting gets dimmer, Auto ISO will raise the sensitivity by only the amount that’s really necessary, so you should always get a good trade-off between sufficiently fast shutter speeds and the best available image quality.

That’s because pictures taken at very high ISOs are likely to have increased noise and a drop in fine detail. With many SLRs, you can customise the way Auto ISO operates, choosing the slowest shutter speed you want to use as well as defining the maximum ISO permissible.

There are times to avoid Auto ISO. For example, if you want to use a slow shutter speed to create motion blur, you’ll need to apply a low sensitivity setting manually (find out step-by-step how to set your Auto ISO function).

Auto ISO works very well in most cases, but when you want a slow shutter speed to blur movement, like in this watery foreground above, you’ll need to set the sensitivity manually (learn from some of the common mistakes at every shutter speed – and the best settings to use).

Here we’ve set the ISO manually to get more motion blur in the water and a stronger reflection.

Similarly, if you want to freeze action, you’re likely to need a faster shutter speed than Auto ISO will deliver, especially in dull lighting conditions.

What is ISO? When to increase sensitivity, types of noise and more

jmeyer — Wed, 20 Jun 2012 03:00:15 +0000

If you’re new to photography you may have asked yourself, ‘What is ISO?’

Back in the days before digital, film came in a variety of different speeds. The ‘faster’ the film, the more sensitive it was to light – allowing you to use faster shutter speeds than with ‘slower’ film.

Using these higher-sensitivity film emulsions was useful for moving subjects – and particularly so in low light. This film speed was measured using a number of different scales – with two of the best known, the American ASA and German DIN scales, eventually being brought together to give us the standardized ISO system.

ISO 1000 - 1/15sec at f/5.6

Digital cameras, of course, do not use film – but the same ISO scale is now used to measure the camera’s sensitivity to light. Although the camera’s imaging chip cannot be changed to suit the subject (unlike film), its sensitivity can effectively be boosted by the camera’s circuitry.

This is done with the ISO control. Think of ISO as being like the volume control on your radio. If the signal is weak, you crank it up to compensate.

The signal from the sensor is simply amplified – and this helps you get the fast enough shutter speed you want in low light.

The crops inset are shown in actual pixels.

Digital advantage
The advantage of digital over film is that the ISO can be altered for each individual shot. This makes ISO a powerful tool for the photographer, helping you to get sharp shots in a variety of lighting conditions.

ISO is the name of the International Organization of Standardization: a body that creates thousands of agreed standards for a huge range of products, procedures and practices.

For the photographer, ISO is simply a set of numbers. The base sensitivity of all current Canon EOS SLRs is ISO 100.

But this can be increased by pressing the appropriate button, then rotating the main dial (on some older cameras ISO is changed through the Menu button).

The scale is such that doubling the ISO number doubles the sensitivity of the sensor. So increasing the ISO setting from 100 to 200 means that, to get the same overall exposure, you can use a shutter speed that is half as long (or twice as fast).

Each doubling of the ISO also increases the sensitivity by a full exposure ‘stop’ – with the typical full-stop ISO scale progressing 100, 200, 400, 800, 1600, and so on. The top ISO setting varies depending on the age and cost of your digital camera – from ISO 3200 to a staggering ISO 102,400 on some models.

Bizarrely, the top ISO settings on many models are ‘hidden’, and must be enabled using a custom option called ‘ISO Expansion’. The reason for this is that each time you increase the ISO setting, you also get a small decrease in image quality.

Boosting the picture signal also amplifies impurities in the signal known as ‘noise’. This noise shows up as grain and colour mottling in the image – and this gets progressively more noticeable the higher the ISO is set.

How ISO works: cheat sheet

It’s one thing to read about how ISO works. It’s another thing to see it. In the infographic below we’ve illustrated what happens in terms of sensor output as you adjust your ISO for low light. Click on the infographic to see the larger version, or drag and drop this photography cheat sheet directly on to your desktop to save if you’d like to keep it as a handy reference.

When to increase ISO
Some photographers try to resist increasing the ISO at all costs in search of getting the best, grain-free images. However, pumping up the ISO often actually increases image quality overall, as this simple change lets you use a faster shutter speed – thereby eliminating camera shake.

A grainy picture is always better than a blurry one! A higher ISO can also enable you use a narrower aperture – increasing depth of field, and thus increasing the resolution of a lens – to give you sharper-looking pictures.

Although higher ISO settings are invaluable in low light, they are not essential for all low-light situations, in fact, if you can keep the camera steady, they are often best avoided (find out how to reduce noise at high ISO settings).

If you are using a solid tripod, the slowest ISO setting (ISO 100) is usually the best option – as you can then use a longer shutter speed to make up for the lack of light.

Similarly, if you are using flash, high-ISO settings are not needed (although increasing the ISO will increase the effective range of your flash).

Types of noise
There are two different types of noise found in digital images. Luminance noise shows up as a speckled pattern, like specks of black sand, and is similar to the grain that was found when using high-ISO black-and-white films.

Chromatic noise is coloured and looks like the rainbow-like sheen when looking at a patch of oil (and is similar in appearance to the blotchy dye patterns that you saw when enlarging high-ISO colour films).

The crops inset are shown in actual pixels.

It’s important to look at these two types of noise separately – as each can be reduced using different tools during the editing stage. These are often provided as separate noise-reduction sliders by a RAW converter (such as in Adobe Photoshop’s Camera Raw utility).

Specialist software (such as Noise Ninja and Dfine) is particularly useful for reducing noise without sacrificing detail.

Auto ISO: the friend you never knew you had

jmeyer — Tue, 12 Jun 2012 15:08:20 +0000

Image copyright Mark Hamblin

With film cameras, exposure is controlled by aperture and shutter speed settings at a fixed ISO setting (which is dictated by your film). Digital cameras allow you to change the ISO setting with just the push of a button, but on most models this can be performed automatically with your ‘Auto ISO’ function.

This is very useful when the lighting conditions are changing quickly – when you’re moving from outdoors to indoors, or from bright sunlight into shadows.

With the Auto ISO function set to On, your camera will select the lowest ISO for the lighting conditions to maintain maximum image quality.

If light levels fall, the camera will increase the ISO up to a maximum setting you’ve chosen, maintaining a good exposure at your chosen aperture and shutter speed settings. On some camera models, you can also set the minimum shutter speed at which Auto ISO kicks in.

For example, if this is set to 1/60 sec, the camera will continue to shoot at the lowest possible ISO until the shutter speed required to make an accurate exposure drops below 1/60 sec, at which point Auto ISO increases the ISO to maintain this shutter speed. This is a handy way to avoid blur caused by camera shake, and it enables you to concentrate on the subject.

The downside? Auto ISO may lead to over-exposure in very bright conditions, depending on your aperture setting. It doesn’t work when using flash, either.

Follow our quick, three-step tutorial below to find out how to set your Auto ISO function.

How to set your Auto ISO

Find the Menu
Press the Menu button, then go to Shooting Menu and scroll down to ISO Sensitivity Settings. Press OK. This brings up the ISO Sensitivity Settings menu screen. Set the ISO Sensitivity to the lowest setting available – typically ISO 100 or 200.

Switch to Auto
Use the multi-controller to scroll and highlight ISO Sensitivity Auto Control. Select On then OK. ISO-AUTO will be displayed on the rear control panel and in the viewfinder. At the default setting (Off) ISO sensitivity will remain at the value selected manually.

Take some control
To set an upper limit for ISO, highlight Maximum Sensitivity and select a value. At high ISO values image noise will be apparent. Set the Minimum Shutter Speed value to determine the setting at which Auto ISO is activated. Press OK to confirm.

How to reduce noise at high ISO settings

jmeyer — Tue, 08 May 2012 15:00:44 +0000

Image copyright Ben Birchall

Shooting indoor sports action using a fast shutter speed, old, gloomy churches without flash or bright landscapes where you want to slow down the shutter speed to capture movement are just some of the many situations where you will need an extreme ISO to get better results.

ISO denotes how sensitive an image sensor is. Any change from the manufacturer’s native ISO (the lowest default, which produces the optimum image quality) will have some form of electrical signal modification that results in noise.

Most DSLRs have a native ISO of around 100 or 200; beyond that, at the extreme low end of the range, quality isn’t improved. However, some manufacturers offer lower ISO values in the menu, such as ISO 50. Others use a decimalised f-stop value to indicate when it falls below the native ISO.

Both are great for using wide apertures (for more on apertures, download our free f-stop chart for understanding aperture) or long shutter speeds in bright lighting conditions.

When using extreme ISO values above the highest setting, most cameras share the prefix letter H followed by an f-stop value to indicate when the ISO is being ‘pushed’ to the limit. Such images can be very noisy, but will allow you to carry on shooting in very dark conditions (shooting in the dark? see the 12 common errors of night photography – and how to fix them).

Step 1: Go manual
Turn off any ISO sensitivity control modes that automatically select a suitable ISO depending on the shutter speed and aperture. You should also switch off any Scene modes and select either Manual or  a semi-automatic exposure mode.

Step 2: Select the ISO
Most recent cameras will have a dedicated ISO button that’s located on the camera body. Locate the button on your camera and have a scroll through the ISO values from one end to the other to see if you have the L or H prefix.

Step 3: Reduce the noise
Any amplification or reduction of the electrical signal that’s been produced by light falling on the sensor’s CCD will suffer from noise. Dig into your DSLR’s menu and turn on any in-camera noise reduction for the very best results.

Explore your SLR

crutter — Thu, 08 Dec 2011 11:15:01 +0000

With your camera’s basic settings taken care of, you’re ready to start snapping away, but you’ll soon want to know how to take advantage of all the other features your SLR has. Read on to find out how to take your camera craft up a notch.

Exposure modes

Choosing an exposure mode gives you the freedom to stop worrying about settings and start concentrating on taking great shots. Your camera will offer a number of automatic settings, including modes that help you to shoot action, close-ups and portraits, but these modes can be restricting and should generally be ignored. Get to grips with your camera’s semi-auto and manual settings (below), and you’ll soon see an improvement in the results.

Auto

This is the basic beginner mode, with minimal manual control. The SLR effectively becomes a point-and-shoot compact, with all the exposure settings taken care of.

Program (P)

Here, aperture and shutter speed are set automatically for you. However, you can control ISO, exposure compensation and other settings, enabling you to override the suggested settings if you wish.

Shutter priority (S/Tv)

This mode is similar to aperture priority, but you select the shutter speed and the camera sets the aperture. This mode is perfect for freezing high-speed action or for creating motion blur.

Aperture priority (A/Av)

This semi-automatic mode enables you to choose an aperture value that gives you your desired effect (blurred backgrounds, for example), and the camera then selects the shutter speed that’s needed for a correct exposure.

Manual (M)

In manual mode, you set both the aperture and shutter speed for any given scene, which places you in total creative control. It gives you access to all of the available aperture values and shutter speeds, and an exposure level indicator in the viewfinder (or on the LCD screen) tells you whether your shot is correctly, under- or over-exposed. The Bulb mode enables you to shoot exposures for as long as the shutter button is held down, making it ideal for night photography, when exposures of 30 secs or more are required.

File format

As mentioned here, there are two main options here – JPEG or raw. The JPEG format was created for digital photography, and is now a universal standard that’s viewable on any suitable device. In contrast, raw files are specific to individual makes and models, and specialist photo-editing programs are required to open or edit them. The big advantage of shooting in raw is that the image contains more information, which can be used to get the highest quality images. JPEGs compress the image slightly, losing quality.

ISO sensitivity

Your SLR’s sensitivity to light is determined by the ISO setting. To produce noise-free images, it’s best to use your camera’s lowest ISO, but this isn’t always possible. In low light, for example, a slow shutter speed is often needed to expose the image correctly, and this can result in motion blur caused by camera shake. If you’re already using your lens’s widest aperture, the only way to get a faster shutter speed – and therefore avoid camera shake – is to increase the ISO. And the higher the ISO, the more noisy the image.

White balance

You can rely on the auto white balance (AWB) setting in most shooting situations, but there are some occasions where it can’t be relied upon. If you’re shooting in mixed light or in dark shade, for example, your camera’s auto white balance setting may produce images with a so-called ‘colour cast’. To eliminate this cast, switch to the preset closest to the type of light you’re shooting in. When it’s important to get the white balance exactly right, shoot in raw, because the white balance in a raw file can be fine-tuned later.

Custom functions

Scroll through your custom function menu for the first time and you’ll be amazed at the volume and complexity of the changes you can make to the way your SLR operates. Don’t be daunted, though – configuring some of these to suit your preferences will enable you to work much faster than sticking with the defaults. Some cameras enable you to save the most commonly used functions in a quick-access menu, or to assign custom function settings to different shooting situations. See your SLR’s manual for your options.

Back to: Set up your camera

Forward to: Get better exposures