Why we still need optical filters

Tiffen ND filterArticle about optical filters I wrote for TechRadar:

The idea of filtering light before it enters the camera has been around for almost as long as photography itself. In the beginning there was no need for diffusers or soft-focus filters, as the lenses of the day were quite soft enough thank you. Things changed when black and white emulsions were developed that were sensitive to blue and green light, instead of just blue, and suddenly there were creative benefits to interrupting the light path with a sheet of coloured glass to control the recorded effect.

As we developed colour films and emulsions the desire to filter really took off, and as colour film reached the general population, and photography as a hobby came to the masses, filters became a major part of the required kit. However, they multiplied in number at a rampant pace, like bacteria in a warm, moist petri dish, and we saw the production of both quite useful and quite useless filters.

Read the rest of this article here on the TechRadar website

 

What’s a polarising filter – beach at Uvero Alto

Uvero Alto with a polarising filter

Uvero Alto with a polarising filter

A polarising filter is used in photography to reduce the effects of reflections and glare. When these distracting forms of light are removed from a photograph it allows colours to really shine through and appear much stronger. Polarisers are a particular favourite of landscape and architectural photographers for the dramatic effect they can have on a sky – transforming it from pale blue to a dense and impressive navy. Here you can see a ‘before and after’ demonstration of what a polarising filter can do. On this occasion I used the filter to darken the sky, firstly producing a stronger blue and secondly making the cloud formations stand out more clearly. The filter has also cut reflections from the surface of the sea, which again intensifies its colour, and the same impact can be seen on the sand as it’s colour becomes more saturated. While the non-filtered image is nice, the second is much more dramatic and eye-catching.

Uvero Alto without polarising filter

Uvero Alto without polarising filter

Rotate for control

The power of the filtration effect can be controlled at the shooting stage by rotating the filter in front of the lens. For these images I have shown the extremes of the effect, but it is easy to tone things down because the filter allows the degree of impact to be controlled at the shooting stage.

Two types of reflected light

In very basic terms there are two kinds of light illuminating this scene – light that comes directly from the sun and reflects off the trees, clouds, beach and sea into the lens. And then there’s light that’s been reflected from something aready, that goes on to bounce off those same objects, but from different angles. If you take the sand, for example, you can see there is light that’s coming directly from the sun and then there is light that has been reflected from the sky that gives the surface a slight haze. The same is true of the sea; in the non-filtered shot most of the colour we see is the reflection of the colour of the sky. Light that has already been reflected before it strikes the subject can be cancelled by a polarising filter, and thus help improve contrast and colour. The resultant reduced light levels will mean longer exposures are needed so, except in very bright conditions (such as in the case here), a tripod is the natural partner of a polarising filter. The filter I was using, made by Hoya, has particularly good light transmission, and so long exposures are less often required.

The angle of the sun

Polarising filters have most pronounced effect when the photographer has the sun on his or her back. The effect is still visible at 90° to the sun, but as soon as the lens moves to begin facing the sun a polariser becomes less useful.

Samsung GX20, with 16-45mm f/4 ED lens. Exposure without filter f/11 @ 1/250sec, with filter f/11 @ 1/125sec. Both ISO 100, and at the 16mm end of the lens.

See more of Damien Demolder’s recent photographic posts here

To see more of my pictures visit my galleries at www.damiendemolder.com

To see more of my pictures visit my photo galleries site at www.damiendemolder.com


Uvero Alto with a polarising filter

Uvero Alto with a polarising filter

Uvero Alto without polarising filter

Uvero Alto without polarising filter

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