by Bob Simpson (One Stop Photo Workshops tutor for the Sunshine Coast)
Nail the focus
Accurate focusing is fundamental to achieving sharp images….no surprises there! A common selling-point for new camera models is the promise of better and faster auto-focus, with more AF sensor points, new focus-tracking modes, and improved AF performance in low light. As clever as these advancements are, and as useful as they are in certain scenarios, for most landscape photography I’d recommend turning off the AF functions and learning how to manually focus your lenses.
The thing with landscape photography is that we often want to keep the whole image, from close foreground to distant horizon, in sharp focus. So rather than focusing on any particular object in the scene, the aim is to maximise the depth of field so that all objects in the scene appear sharp. An old rule of thumb to achieve this is to set a wide aperture, say f16, and focus one-third of the way into the scene. This usually works okay with a wide-angle lens but it can be hit-and-miss in a lot of cases, especially as you move to longer focal lengths.
A more precise way of working out where to set your focus is to use the hyperfocal distance. By focusing at the hyperfocal distance, everything in a scene from half of the hyperfocal distance to the horizon will appear acceptably sharp. The hyperfocal distance is different for every combination of focal length and aperture, but you don’t need to memorise these things or be a mathematician to work them out – hyperfocal distance charts and apps are readily available online so you can either download one and keep it in your pocket or just refer to your smartphone. I carry a small laminated chart for each of my lenses in my top pocket every time I go out.
As an example, the hyperfocal distance for a 17mm lens (on a full-frame DSLR) with the aperture set at f11 is approximately one metre. This tells you that by setting your 17mm lens to f11 and focussing at one metre, everything in the image from a distance of 0.5 metres (half the hyperfocal distance) to the far distance will appear acceptably sharp. You can check this using the depth-of-field preview, if your camera has one, or by zooming into a captured image on the LCD screen.
While this method works fine in most cases, there are techniques available to take the matter further and achieve virtually unlimited depth-of-field at any aperture or focal length. Focus-stacking is a process of taking multiple images with the focus set at a slightly different position in each, and then combining the sharpest bits of each image into a single, final result. This method is especially popular in macro photography where the depth-of-field is often so narrow that it would be impossible to get the whole subject in focus with a single image. So a series of images are captured at different focus settings and then bundled into a program like Helicon Focus, Zerene Stacker, or Photoshop for automatic blending.
Focus-stacking can also be used to expand the depth-of-field in landscape photographs. I’ve found it useful when shooting with longer focal lengths where hyperfocal focusing won’t produce the depth-of-field I want to achieve. Often in these cases, only two or three images at different focus settings are needed to ensure everything is sharp from front to back, and these can be easily blended together manually using layers and masks.
It isn’t always the case that we want our landscape images to be sharp from front to back. A wide aperture can be selected to minimise the depth-of-field so that only the portion of the image that we want to highlight is in sharp focus and the rest is blurred. In this case, precise focus on the main subject is required. Auto-focus can do a good job here, but for full control, I’d recommend using manual focus in conjunction with the liveview LCD screen – just zoom in to the part of the image where accurate focus is most critical and adjust the focus-ring as needed.
I’ve run through some of the most important factors that can affect image sharpness but the story doesn’t stop there. Below is a list of other tips to keep in mind to help maximise image quality and sharpness.
Use good quality filters
A filter placed over the front element of your lens has the potential to reduce image quality and sharpness. Higher quality (and more expensive) filters are engineered to precise standards and include coatings to minimise lens flare and other aberrations, so it’s worth buying the best filters you can afford. The risk of reduced image quality increases if you stack filters together, especially if they are not kept spotlessly clean, and when shooting directly towards a light source.
Use a lens hood
Lens flare occurs when strong light enters the lens and is reflected around by the internal lens elements before it hits the sensor. It is a common problem in landscape photography when shooting towards the sun and will often show up in images as colourful polygonal shapes or washed-out areas of reduced contrast. To avoid it, you need to keep direct sunlight off the front element of your lens and one way to do that is to attach a lens hood. Unfortunately, with wide angle lenses a lens hood can’t extend too far out from the front of the lens or it will cause vignetting so its effectiveness is limited. You can overcome this by using your hand or some other object to shade the lens while an exposure is made – just make sure to keep your hand out of frame. Of course, a lens hood (or your hand) isn’t much use when shooting directly towards the sun, but there are other ways of minimising flare in these situations – but that will have to wait for another article!
Think about distance from subject
Objects that are close to the camera will invariably appear sharper and more detailed than those that are far away. The light that reaches us from a distant object has been diffused and deflected as it passes through the atmosphere so the distant object will often appear hazy, less clear, and less sharp than a close one. This is a simple fact that is easily understood and experienced by all of us on a daily basis – we expect distant objects to appear less contrasty and well-defined. It’s worth keeping this in mind when processing an image and resisting the temptation to add too much contrast or sharpening to distant objects. A natural graduation of contrast, decreasing from the foreground to the background, adds a sense of depth to an image.
Don’t zoom to extremes
In many zoom lenses, image sharpness and quality tend to fall away at the extremes of the zoom range. You will often find the focal ‘sweet spot’ of a lens is somewhere in the middle of the zoom range, so it can pay to back off a little from the widest focal length or the longest telephoto setting.
Take multiple shots
A good insurance policy to employ when photographing in strong winds, or any other situation where there is a high risk of camera-shake, is to take multiple shots of a scene in the hope of getting at least one sharp one. The LCD screen on your camera allows you to review an image for sharpness after each shot, but small amounts of blur might not be obvious until you get home and view the image large on a computer screen. Taking a few extra shots costs nothing and could mean the difference between bringing home a keeper and having to discard your morning’s work because it’s all blurred.
Keep everything clean
And a simple common-sense rule to finish – start each session with a well-cleaned lens and filters, and make sure they stay that way throughout the session. Always carry several clean microfibre cloths, and maybe some lens cleaning fluid or a LensPen for more persistent grime. A greasy thumb-print on your ND filter will result in a blurry patch in your image that can’t be easily fixed with processing, if it can be fixed at all. Windy days at the beach are especially problematic when fine salt-mist can settle on all surfaces, including the front element of your lens. Wiping this with a cloth will just spread the salt around, so a small dose of lens cleaning fluid is sometimes needed to restore a sparkling, clean finish.Continue reading
by Bob Simpson (One Stop Photo Workshops tutor for the Sunshine Coast)
Most digital images benefit from some post-capture sharpening. Digital camera sensors and lenses always blur an image to some degree and to correct this, photo-software like Photoshop has a range of sharpening options like unsharp mask, smart sharpen and the high pass filter. These tools are great for polishing an image before it is presented to the viewing public, but the path to getting consistently sharp images begins well before we go anywhere near Photoshop. Good camera technique and a knowledge of all the factors that can work against the apparent sharpness of an image are vital if we want to take control and produce the sharpest images we can.
There’s no doubt that expensive, high quality lenses generally have the edge over cheaper models when it comes to sharpness, but the reality is that most of us can’t afford the thousands of dollars it takes to own one of these top-end lenses. But there’s no need to despair – even the relatively cheap kit lenses around today will produce excellent results if they are used to their full potential. You don’t need to break the bank to get consistently sharp, high quality images.
So here, in no particular order, are some capture tips and tricks to help you squeeze that extra bit of sharpness out of your images.
Keep it steady
It’s no secret that a steady hand and/or a stable tripod are important factors in getting sharp images. Setting a fast shutter speed can help overcome the blurring effects of camera-shake but from a creative point of view, we don’t always want to use a fast shutter speed to freeze all motion. And in low light situations, it may not be possible to achieve a good exposure with a fast shutter speed unless you set a very high ISO, which in turn will reduce the quality and apparent sharpness of the image.
There are lots of little tricks to help keep your camera stable and motionless when you’re not using a tripod. If you’re standing up, find a comfortable posture with your feet comfortably apart and elbows tucked into your sides. If possible, brace the camera against a tree, fence-post or some other structure to keep it steady, or consider sitting down or kneeling to reduce the chance of your body swaying. Hold the camera firmly but not tensely, breathe evenly, and practise operating the shutter button with a gentle squeeze or roll of the fingertip. If your lens has image stabilisation or vibration reduction, turn it on. There is an old rule-of-thumb that says the slowest shutter speed you should use when hand-holding a camera is the reciprocal of the focal length of your lens – so for a 50mm focal length, use a shutter speed of at least 1/50th second. This of course depends on a lot of factors, including how good your hand-held technique is, and it is often possible to use a much slower shutter speed if your lens has image stabilisation or vibration reduction.
As a landscape photographer I use a tripod most of the time, but there are still occasions when this alone isn’t enough to ensure a stable platform for my camera. Expensive tripods tend to be more stable than cheaper ones so it is worth buying the best you can afford, and new materials like carbon fibre help to dampen any vibrations that do occur. The risk of vibration increases in windy conditions and when the tripod is standing in moving water, like a flowing stream or at the beach. You can reduce this risk by hanging a heavy weight (like your camera bag) off your tripod, and in windy conditions, by using your body to shield the tripod from gusts. A tripod will also be more prone to vibration the higher it is set, especially if the centre column is raised, so try and keep it set lower if the conditions are less than ideal. In soft substrates like sand and mud, a tripod can slowly sink without you noticing – take some time to push the legs firmly down into the substrate before capturing your image. Image stabilisation or vibration reduction can be counter-productive when your camera is mounted on a tripod so read your camera manual to see what the manufacturers advise. Finally, invest in a cable release or wireless release so you don’t have to touch the camera to fire the shutter – an alternative is to use the self-timer, but a remote release makes it that much easier.
Choose your camera settings wisely
The three camera controls we use to set exposure – shutter speed, aperture and ISO – all play a role in image sharpness. Shutter speed is perhaps the most obvious factor here. As discussed above, a slow shutter speed is more likely to produce an unsharp image than a fast one, although a tripod will overcome this issue in most cases.
But what about the situation where we are photographing a scene that has moving elements in it, like grass swaying in the wind or water tumbling down a cascade? We can just use a fast speed, like 1/1000th second, to freeze all motion but from a creative point of view, this is not always ideal and can make an image look static and lifeless. By using a slower speed, say 1/4 second, the moving elements in a scene will be captured with some degree of blur which helps convey the sense of movement and dynamism in the scene. This approach is particularly effective when an image is composed around the stationary elements of a scene, like rocks and tree-trunks, and there is a strong contrast between the sharpness of these features and the motion-blur of moving elements. This contrast can really highlight the apparent sharpness of the static elements. Many photographers take this approach to extremes by using a strong neutral density filter to produce a very long exposure – say several minutes. In this way, even clouds will be rendered as streaks across the sky, which can create a pleasing, artistic backdrop that further enhances the apparent sharpness of any stationary elements.
The ‘best’ aperture setting (f-stop) for any given scene should be considered from several angles. One of the first things we learn as photographers is that a large, wide-open aperture, like f1.2 (or maybe f4 on some lenses) will create a shallow depth-of-field. This just means that a relatively small part of a scene will be recorded in sharp focus – closer elements and more distant elements will appear out of focus. On the other hand, a small, closed-down aperture, like f16 or f22, will produce a larger depth-of-field so that all parts of a scene, from very close elements to the distant horizon, appear sharp.
So it seems obvious from this that if we want maximum sharpness throughout an image, as is often the case in landscape photography, we just choose the smallest aperture available on our lens and use that. Unfortunately it’s not quite that simple. Most lenses, even very expensive models, don’t retain the same level of sharpness throughout their aperture range – they have an aperture ‘sweet-spot’ that will produce the sharpest possible results. The sweet-spot is usually several f-stops down from the widest aperture setting, often around f8 or f11. Choosing a smaller aperture than this may produce a larger depth-of-field, but sharpness will begin to drop off. This might not be apparent unless you make large prints of your image but it is something to keep in mind. You will find information on the sweet-spot for many lens models with an internet search, and lots of websites explain how to carry out your own tests to determine the sweet spot for your lens.
The ISO setting on digital cameras determines the relative sensitivity (or light-gathering capacity) of the camera sensor. A high setting, say ISO1600, means the sensor becomes very sensitive, and it only takes a small amount of light to properly expose an image. A lower setting, ISO100-200, means the sensor is less sensitive and more light is needed to expose the same image. As we adjust the ISO setting, we also have to vary the shutter speed and/or aperture to allow more or less light to reach the sensor as required.
The problem with choosing a high ISO setting is that it leads to increased digital noise in an image. This is unavoidable in some cases where the only way to achieve a good exposure is to bump up the ISO – a noisy image can be better than no image at all. And there is always the option of using noise reduction software to counter the problem post-capture – that is, or course, if you see it as a problem. A little noise in an image might be to your liking, in the same way that the ‘graininess’ of images captured on film was often deliberately used to create a certain look. But I think it’s fair to say that most current photographers, particularly those who focus on landscapes, would prefer to minimise noise as much as possible most of the time. That is my preference and I always use the lowest ISO setting I can.
As for the relationship between ISO and sharpness, there are some differing views. A common opinion is that a noisy image will appear less sharp than a ‘clean’ one because any fine detail in an image is made less clear and well-defined by the presence of noise. Others say there is no real relationship between ISO and sharpness, and some suggest that a little noise can actually make an image look sharper. I can see where this idea (noise = sharpness) comes from, but it is a gritty sort of sharpness that I prefer to avoid in my landscape images.
There is less argument about the effects of applying post-capture noise reduction to an image – this invariably leads to a softening of fine detail, and if it is applied too heavily will result in an unnatural ‘plastic’ look. As a general rule, I believe that the best path to achieving a high quality, sharp image is to use the lowest ISO possible and avoid the issue of noise altogether.
In the second part of this article, I will look at how focus, filters and other miscellaneous factors can affect the sharpness of our images.Continue reading