Three Essential Filters for your DSLR camera

     Because the effects of many on DSLR camera filters can now be emulated in software. It’s no longer necessary to buy a stack of them. Warm-up filter, which add a sunny amber glow to make a picture more attractive, were always a necessary purchase for film users, and colored grad filters were hugely popular for adding a hint of blue (or any other color) to a bland sky.

     The latest versions of Photoshop and Elements include a Photo Filter (found in the Image Adjustments menu) and this allows you to add and control just about any filter effect you’d want to apply. There are three filters, though, which can’t really be created in Photoshop, and these are the ones worth buying if you’re serious about your landscape shots

ND filter

     With landscape shooting, there are times when you want to reap the creative rewards of a long exposure. To obtain this, set the lowest ISO value, then switch to Aperture Priority mode and set your f/number to the highest possible. This is usually f/22 or f/32 on DSLR camera, and f/8 or f/11 on compacts. Your shutter speed will drop to slowest it can go.

     Trouble is, on bright days this still may not give you a very long exposure, so you have to make the scene darker. A Neutral Density (ND) filter places a neutrally-colored “pair of shades” over the lens to allow less light in. ND filters come in various strengths, and the best bet is to get a three-stop mode (a 0.9 or 8xND). This allows only one-eighth of the light to get through, and consequently gives you shutter speeds 8 times longer.

     With this, you’ll be able to make water “flow”, or if the shutter speed is slow enough, make moving people disappear from the scene. You’ll need to use a tripod to hold the DSLR camera still.

Polarising filter

     A polariser suppresses reflections in glass and water, darkens blue skies, and intensifies colors in a scene. Polarising filters come in two types; linear and circular. This doesn’t refer to the shape of the filter, but in the way the pattern is etched onto its surface. Linear polarisers tend to be cheaper than their circular brethren, but they can confuse the AF and metering system in DSLR camera, so avoid them. After you’ve fitted a polarizer to your lens, you apply the effect by rotating the bezel on the filter. Maximum polarisation occurs when you shoot at 90 degrees to the sun’s position, so you’ll see the effect deepen and then back off when you rotate the filter. At the maximum point, a polarizer will steal around three stops of light from your DSLR camera, so unless conditions are really bright, that means you’ll need a tripod to avoid DSLR camera shake.

Neutral Density graduated filter

     An “ND grad” filter is a sheet of glass or optical resin with a dark half like an ND filter and a clear half. The idea is to position the filter over the lens so the gradual divide runs roughly along the horizon. This results in a darkening of the sky, which helps balance exposure between sky and land. Depending on conditions, skies tend to be 2-3 times brighter than land, and although our eyes don’t see this, a DSLR camera sensor does. If you expose correctly for the sky, you’ll get an underexposed foreground, and if you expose for the land, you’ll be burn out the sky.

     An ND grad filter will balance the two, and they come in different strengths for different conditions. They have numbers of 0.3 (1x), 0.6 (or 4x), and 0.9 (or 8x) corresponding to the amount of light held back in the dark half. Most useful are the 0.6 or 0.9, which hold back 2 or 3 stops or light.

     They’re really easy to use – just position the filter and shoot as normal, then check your LCD to see if any highlights are burning out to white. If the burn-out is too prominent, dial in some negative exposure compensation (the +/- button), and shoot again, and continue until there are only a few small areas of peak white in the display. ND grads filter should be bigger than the front element of your largest lens.

Get creative with Aperture

     Now you understand what aperture is, and how its affects the depth-of-field in a picture, let’s put it all into practice. It’s hugely important to develop a good understanding of this area because, after composition and accurate focus, the control of depth-of-field is what distinguishes real photographers from casual snappers. Creative photography is all about making choices based on the options available to you, and trust us – you really need to nail the aperture thing! Here’s quick exercise to help you master the whole thing…….

1.       Start set the right mode.

Find (or set up) a subject and make sure there’s a reasonable distance of a couple of meters between it and the background. With your DSLR camera on a tripod, compose your shot and set Aperture Priority mode (A or Av) on your DSLR camera main “MASP” mode dial.

2.       Use maximum aperture.

Dial in the maximum aperture value (the smallest f/number) by rotating the appropriate control on the DSLR camera body and, after switching to Manual Focus mode, focus on the subject in the foreground (MF will stop your AF wandering about). Take a shot, and your subject will be sharp but the background will be defocused – just like it appears in the viewfinder.

3.       Use minimum aperture.

Now adjust your aperture control until it displays the smallest aperture (the highest f/number). If your DSLR camera has one, depress the depth-of-field preview button to check how the background has changed, and then take another shot. Your shutter speed will be much longer (hence the need for a tripod) and this time, the subject will still be sharp, and the background will be much more in focus.

4.       Final step Experiment!

Because you have a whole range of apertures in between the extremes you’ve just used, your job as a photographer is to decide which one gives the best overall effect for your subject. Leave your DSLR camera set to Aperture Priority mode, experiment with different aperture settings, and get used to thinking about depth-of-field every time you take a picture. Enjoy!

Hyperfocal distancing

     On DSLR lenses with distance markings (mainly prime lenses, nowadays) you can set your focus manually to generate the maximum possible depth-of-field. This technique is called hyperfocal distancing, and is really simple to do. In Aperture Priority mode, first set your aperture (say to f/22), and then compose your shot. With Manual Focus mode selected, turn the focus ring to align the infinity symbol with the furthest f/22 marker. Now you can read off the closest distance that’ll be in focus with the nearest f/22 marker. That’s it!

Understanding depth-of-field

     Although you only focus your DSLR camera on one point of a scene, you’ll have noticed that some pictures appear to be sharp all the way through from front to back, while others are only sharply focused at one point. The depth of this zone of sharp focus is caused by the size of the hole in the lens, so the aperture setting isn’t just for ensuring correct exposures – it’s also used for controlling which areas of a picture are sharp, and which are defocused.

     Though small apertures (large f-numbers) require longer shutter speeds to get enough light onto the sensor, they also give the greatest depth-of-field, so if you want a picture that’s sharp from front to back, you’ll need f/16 or f/22 to make it happen. Unless it’s extremely bright, you’ll probably also need a tripod to keep the DSLR camera steady because the shutter speed will be much longer than at f/2.8.

     There are many times when photographers want to isolate a particular part of a scene and throw the rest out of focus, though, and for these occasions you need a large aperture, like f/2.8 or f/4. This will ensure that only a narrow zone around the point you focus on will remain sharp. This means that focus has to be  as accurate as possible.

     Many DSLR cameras are equipped with a depth-of-field previews button, which helps take the guesswork out of what will be soft and what will be sharp in your picture. Depress this button when you’re framed-up, and it’ll reveal how the shot will be in the viewfinder.

     The only downside of depth-of-field previews is they make the scene very dark with small apertures (because less light is entering the lens) and this can make it tricky to see what’s happening – especially in low-light conditions. If you’re struggling to see what’s going on, just take the shot and check the screen image to see what’s sharp and what’s not.

Depth-of-field & digital compacts

     Although creative compact cameras have an Aperture Priority mode which generally allows all apertures from around f/2 to around f/8, they cannot offer the same depth-of-field control as DSLR cameras because of the smaller sensor size and very short focal lengths on the lens units.

     For shots like landscapes where you’ll often want a large depth-of-field, this is not a problem as huge depth-of-field comes built-in, but when you want a narrower plane of sharp focus, it’s a real issue. Even at large apertures of f/2 or f/2.8, compacts can’t produce the same kind of defocused backgrounds as DSLR cameras, so you’ll need to resort to Photoshop’s Gaussian Blur or Lens Blur filters to generate these kind of effects.

Understanding Aperture

What is aperture?

     In the simplest of terms, aperture is the “hole” in the lens that light passes through on its way to the sensor of DSLR camera. It’s adjustable, so you can let more or less light through by opening up or closing down respectively. How much you can open up aperture of your DSLR camera is determined by the maximum aperture that’s stated on the lens.

     If there’s just one setting written on the barrel, such as 1:2.8, it’s either a fixed focal length lens or it’s a professional zoom lens that allows the same amount of light to pass through regardless of the zoom setting. When there are two numbers like 1:4-5.6 (seen on most enthusiast zoom lenses) it means the lens has a maximum aperture of f/4 at the wide setting, dropping to f/5.6 at the long end of the zoom. In this case, the maximum aperture has been reduced because the extension of the lens has forced its light-gathering ability to fall.

What are f/numbers?

     Aperture is described in f/numbers (like f/2.8, f/4, f/5.6, f/8, etc) and these refer to the ratio between the diameter of the hole and the focal length of the lens. F/2 on a 28mm lens, therefore, would be a hole with a 14mm diameter (28/2), and f/2 on a 100mm lens would be a hole with a 50mm diameter. This makes it inappropriate and confusing to talk about aperture sizes in mm, since they vary with focal length, so we talk in terms of ratio.

     The good news is that the ratio remains constant over all lenses on offer, so if an aperture of f/8 is required with a shutter speed of 1/125sec to get a correct exposure, that will be true for all lenses, regardless of their focal length, and the type of DSLR camera they’re on. This keeps things simple, which, if you’re anything like us, you’ll recognize as a good thing.

     Each full f-stop represents a doubling in the area of the hole in the lens, and hence a doubling in the amount of light that can get through. The other way to achieve this is to expose the sensor for twice as long via the shutter speed control, so it starts to become clear that aperture and shutter speed are used together to establish the correct exposure.

……. and depth-of-field?

     So now we know that aperture is used to control the amount of light passing through the lens, and getting it right will give a good exposure. This may be enough for the casual snapper, but for creative photographers there’s a lot more to it, because aperture also controls what’s known as the “depth-of-field” in a picture, or the zone of sharp focus – and that’s where true photographic creativity comes in.

How to control the aperture setting

     On all but a few very specialist DSLR cameras, aperture is set by rotating a dial on the DSLR camera body and choosing the f/number you want in the viewfinder. A few lenses still offer aperture rings with the f/numbers inscribed, but these are generally for use with older film cameras. They’re still compatible with DSLR cameras, but if they’re on the wrong setting, they’ll give an error warning when fitted. Turning it to the right setting will solve this.

Types of ND Filters for DSLR cameras

When should you use neutral density filters, and with so many on the market, which one do you need? We explain the differences between them, give you some hints and tips and show you how to use your ND filters to get perfect results, every time.

SOLID NDS

These filters carry even density across the whole filter to reduce the light wavelengths. As they are designed to be neutral, this should not affect the coloring of the image, just the strength of light. The most common use for this type of filter is to create a blurred effect in bright conditions, and is often used to create a cotton wool effect with water. This is not its only use, however, night scenes can become more dramatic with increased light trails, or crowded scenes can appear to empty out simply by using an ND filter. For very bright conditions an ND filter may simply be used to allow the lens to use a wider aperture for creative effect, without going beyond the camera's shutter capability, or while keeping a slower speed for creative purposes. The orientation of the filter in front of the lens doesn't affect its job.

GRADUATED FILTERS

These are the bread and butter of any landscape photographer's kit. They provide filtration over roughly half of the square filter, with a gradual lightening towards the center. Their aim is to equalise the intensity of light in the image, usually between sky and land, to allow the DSLR camera to retain all of the image information within its parameters. The aim is not to equal the two levels completely as this would appear false in the photo, but merely to restrain the levels enough to show detail in each. There are two main types of ND grad filter and the distinction comes in how severely they are graduated. The soft grad has a gentle fall-off of density which suits busy horizons or more awkward extremes, while hard grads have a more sudden fall-off which leaves a definite line across the filter. This hard grad can be suited to very straight horizons or where there is a solid distinction between the bright and darker areas. They can also be easier to line up. There's no right or wrong choice, some photographers swear by soft grads or hard grads, while others may use a mix of the two, depending on the shot.

ND grads filter generally come in square formats that sit in a holder in front of your lens. They need to be accurately adjusted for each shot, and taken off again before putting back in your bag. Make sure they go back in their sleves or pouch every time though, as one scratch could ruin them.

ND Filters for DSLR camera

ND Filters

Shooting your DSLR camera  with Neutral Density Filters (ND Filters)

     If you aspire to take great-looking landscape images, you need filters. They are as essential a part of your DSLR camera kit as your tripod, or even your memory card. Back in the day, film users would rely on a catalogue of filters to provide a range of effects, from tobacco tones to soft focus. While these kinds of effects can be digitally recreated, one critical one can't, and that's neutral density. Photographers recognised that the sensitivity of film could not capture the same wide range as our eyes can see. We typically see a range of around 24 stops, while your average 35mm film could cope with between four and seven stops. This meant that in a darkened room with a bright window, where we could see detail in both window and the room, the DSLR camera would end up with either the room in complete darkness or the window completely overexposed. Similarly, on a bright day, an apparently beautiful view appears on the DSLR camera with either a white sky or dark and shadowy foreground. By using a graduated neutral density filter, photographers were able to even out the difference in brightness to levels the film could cope with and produce an image in keeping with how our eyes see it. Your typical JPEG image captured on a digital sensor offers around the same dynamic range, if not less, than 35mm film closer to the four stops of transparency film. Therefore it is even more important in digital photography to even out the brightness. Raw files do allow an increased dynamic range that can stretch to as much as 14 stops but this still pales into insignificance in comparison to human eyes.

     A solid neutral density filter provides a slightly different, but equally as important, role. By reducing the amount of light to the whole image it allows the photographer to use longer shutter speeds in brighter conditions. This may be when a shallow depth of field, and therefore a large aperture, is needed, or when motion is wanted to be blurred severely for creative effect.