A Basic Guide to Camera Lens Filters.

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In this day and age, nearly everyone owns a smartphone and taking random photos or videos
seems to be the norm – the insatiable urge to satisfy their social media presence.
Even tourists aren’t spared…when was the last time you see tourists in large
groups ‘heavily armed’ with cameras around their neck?

This created a paradigm shift in the way how one perceives photography these days. The last I checked, there are at least a dozen filter Apps for both iOS and Android. An average user can replicate these images without the use of physical filters. But this is where the similarity ends… This basic guide is meant for anyone who is considering venturing into digital photography or an aspiring photographer. I would assume you have at least some basic knowledge and experience in handling a DSLR or Mirrorless cameras. I would also refrain from using too many technical jargon for now as the objective of this guide is tailored for beginners.

Why and how are they used in Photography?

In a nutshell, filters are designed to deal with various lighting conditions, often
tricky. We use filters to manage the amount of light entering the lens from the
various section of the image scene. With the right setup, one can better manage
the overall exposure, ensuring the best possible shot of the subject.

Entry level filters also provide some protection for your lenses. There is no one size fits
all but specific ones for each lighting condition. Apart from reducing lights going
into the lens, it also minimizes glares and reflections, and enhances colours too.

  • Protection – standard UV lens filters protects the lens from dirt, dust and scratches. It also provides some UV protection and minimizes the bluish tint on images.
  • Accurate Exposure – outdoor daylight shooting creates challenging lighting conditions. Filters can achieve this by ‘blocking’ some of the lights that enters the lens, and this reduces overexposures.
  • Enhancing colours – some filters are designed to work and correct different colour temperatures. Better contrasts and colours resulting in vibrant images.

What are the types of filters available?

  • UV – reduces UV rays by improving contrasts. Protects the front element of your lens.
  • Circular Polarizers (CPL) – reduces glare and reflections off water or other surfaces. Improves saturation and make skies more appear ‘bluish’. Commonly used for landscape photography.
  • Cool & Warm – alters the White Balance (WB) of lighting reaching the camera sensors. Useful for night shooting where common streetlamps are sodium vapour and mercury based.   
  • Neutral Density (ND) – its primary function is to uniformly reduce amount of light reaching the camera sensors. Effective when shooting under the following conditions:
    • Oceans, streams or waterfalls with ‘smooth’ water movement.
    • Under bright lights with a shallower Depth-of-Field (DoF).
    • Requires moving objects to be less apparent or not visible. Blurring effect for instance.
    • Enabling larger aperture with reduced diffractions or sharpness.
  • Graduated Neutral Density (GND) – good for landscape scenes with simple lighting geometries from light to dark, such as sunset by the ocean. This is typical of a Soft-Edge GND. These filters are also available in several varieties.
    • Center 
    • Hard
    • Reverse
    • Soft

How are filters attached on the camera lens?

Generally, there are two variants. i) Screw-on & ii) Front attachment filter holder.

Screw-on filters are determined by the diameter ⌀ expressed in millimeter(mm) and correspond to the ⌀ on the camera lens. A typical range is between 37mm to 82mm for digital SLR. Choosing the right height of the filters is important. Only ultra-thin filters prevent vignetting when used on wide angle lens. So, test it out, or refer to the product specifications before getting one.

Front-filters are more flexible and versatile as they are compatible with most lens diameter. Filter holder kits (150mm x 150mm magnetic frames) are available to allow multiple-stacking and some special holders have ‘drop-in’ option which allows larger diameter (e.g. ⌀ 95mm) of circular filters be used.

This concludes the Basic Guide and but do stay tuned as I will be putting up more in-depth articles on the various filter types.

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