Diffusion Filter Buying Guide

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Diffusion Filter Buying Guide

A camera filter is a round piece of glass or plastic that facilitates photographic effects at the image source, rather than in post-production. Although many of the effects available have been integrated into DSLR settings menus, full control over any imagery is always preferable.
The number of filter options available can be bewildering, but ultimately, having a full understanding of the function parameters of a filter – as well as the technical knowledge to implement them appropriately – is important to controlling the outcome of any shot.

Filter Effects

The use of lens filters can produce a wide range of effects, so figuring out what result is required will dictate the choice of filter purchased:

Ultraviolet (UV) Filters

UV filters cut through any atmospheric haze – not visible to the naked eye - by reducing the amount of UV that get through to the lens. A strong UV filter will also cut out some of the visible light in the violet part of the spectrum, and has a pale yellow colour. Such filters can also reduce purple fringing in digital cameras.


Polarizing Filters

A polarizing filter has two applications: it reduces reflections from some surfaces, and it can darken the sky. Typically used for photographing water or glass, a polarizing filter increases saturation in colour photographs, leading to richer tones, and protects the lens from damage.


Neutral Density (ND) Filters

A filter that reduces or modifies light intensity equally, causing no change in colour rendition, neutral density filters are generally used to show motion when slow shutter speeds would overexpose the image. These filters are particularly useful when photographing rushing liquids and to allow slow shutter speeds in bright daylight.


Graduated Neutral Density (GND) Filters

Graduated neutral density filters are most useful when the subject image requires two different exposure methods – such as photographing the earth and sky in one image. Used when a single aperture and ISO setting will either over or underexpose each part of the shot, graduated neutral density filters are partially dark and partially clear, allowing the photographer to control exactly which part of the lens receives what amount of light, all with a single exposure setting.


Warming Filters

Helpful at counteracting the bluish cast of snowy scenes and fluorescent lighting, warming filters reduce blue tones by bringing out red and orange shades and help to clarify imagery when shooting in the shade or in overcast conditions.


Cooling Filters

Frequently used to offset the yellow glow of photos taken under incandescent light, cooling filters can help to equalise very bright outdoor shots by reducing the red and orange tones and emphasising blue shades.


How to Choose a Filter

Dark filters can force an operator to move one or two stops down to compensate for the filter's light absorption and, as a rule of thumb, filters should always be inspected for scratches and debris to ensure a clean, clear image.

Choose an attachment style

Available in both screw-on and front styles, filters are either screwed onto the front of the camera lens whereas a front style filter is held up to the camera lens while taking the shot. Be aware that screw-on filters will only fit onto certain lenses, so it is best to check before purchase that the lens chosen will be suitable.


Choose a size

Sized in terms of diameter, screw-on filters are listed in millimetres. Front style filters, however, are available in one size only.


Choose a thread pitch

Screw-on filters are available with different thread pitches that will be specific to a camera. It is vital that the thread pitch is appropriate to the camera lens in question as cross threading will not only damage the thread permanently, but will also cause the filter to become jammed.


Diffusion Filter Effects

As well as the ultraviolet, polarized, neutral density, graduated neutral density, warming, and cooling filters, there are also diffusion filters available, which can create a series of softening effects on an image:

Blemish Removal

Diffusion filters soften not only the lighting, but also reduce any notable blemishes of portrait subjects. That is to say, wrinkles, freckles, scars, and other flaws will be reduced. I will also create a smoothing effect for skin on flexible areas such as hands, feet, elbows, and knees.


Dreamlike Haze

A diffusion filter will create a dream like haze in an image, and a sliding filter will increase not decrease the level of diffusion and therefore the effect. A strong filter will create a fog-like condition, whereas a mild to medium strength filter will make landscapes look ethereal.


Age Reduction

As well as reducing blemishes, a diffusion lens will also reduce apparent age of human subjects - skin is lighter, wrinkles are reduced, age lines are smoothed and subjects generally look more youthful.


Coloured Diffusion

A coloured diffusion filter will change the overall tone of skin. For example, a gold diffusion filter will give it a warm glow, bare skin standing out more prominently, and black filters will reduce the ostensible visibility of non-reflective services.


How to Fit a Filter

It is important to be aware that using more than one filter simultaneously may cause vignetting, which is when the edges of the filter overlap the lens and create dark corners on the final image. This side effect can be reduced by either buying more expensive, extra-thin filters or by using only one filter at a time.

Wash and dry hands

Damp or dirty hands may cause slippage – and potentially a dropped and damaged filter – so ensure that hands are clean and dry before removing or fitting a filter.


Attach the filter

Quite simply, either screw the filter onto the lens or hold the filter in front of the lens and take a picture.


How to Remove a Filter

Always clean a filter when the session has been completed or the filter is removed. Never use glass cleaner as the chemicals may dissolve the coating, but instead use a specialist lens-cleaning brush and a blast of canned air to clear off debris.

Apply pressure

By spreading fingers around the edge of the filter, pressure will be evenly distributed and make it easier to turn the attachment. If removing a circular polarized filter, grip only the back part of the filter since the front part rotates freely.


Do not squeeze

Do not squeeze the filter while unscrewing it as it may cause damage, and unscrew by turning the filter counter clockwise until it is completely free.


How to Remove a Stuck Filter

If a filter is stuck, make sure not to squeeze too hard as the opposing, focused, dual pressure of fingers will damage the thread and filter. Instead, grip the filter edge with a rubber jar opener or put a rubber band around the edge of it to aid grip and then – again – evenly spread fingers around the edge before turning.


A camera filter is a round piece of glass or plastic that creates different photographic effects, but knowledge of function parameters as well as the technical knowledge to implement them is vital.
Filters each have different functions and effects, so deciding on a desired outcome is important to the decision making process.
As well as the ultraviolet, polarized, neutral density, graduated neutral density, warning and cooling filters, there are also diffusion filters available which can aid blemish removal, dreamlike haze, and age reduction.

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