Monday 20 February 2012

Photography: ND Filters & Photography

Recently, I am fascinated by photos such as the following ones!
Image from Serious Amateur Photography

Stunning, aren't they? They are not fake, they are genuine photos taken with real cameras. You may ask, then how come my iPhone and compact cameras cannot take such photos? Well, in fact, they may just be able to take photos like these, but first, you will need to set them to a long shutter speed (from 0.5 seconds to 30 seconds, or even longer depends on the amount of light you need) and something which is called an ND Filter, or Neutral Density Filter.
Effect of an ND Filter on a photo in bright daylight
Image from Wikipedia

Basically, what this filter does is to limit the amount of light that can pass through the lens, so as to buy you more time to expose the sensor / film to the image, creating that smooth silky fog for the moving object.

An ND filter is to a camera lens what a pair of sunglasses is to a human. (Peter Hill, 2010.)

Since the last time Chase Jarvis used an ND filter on a Lego camera, I was already curious to find out more as to what this filter can do. Searching through the web and I found some amazing photos like the ones in this entry.
Canon EOS 5D Mark II, Canon EF 16-35mm f2.8L II Lens at 35mm with Hoya ND x400 Filter, ISO 50, 160 seconds at f8, single RAW file.
Caption and image by Peter Hill

When taking photos of moving water, it will look like milk or fine white silk.
Image from north lake photography
There are many levels or optical density of ND Filters, and each will offer different amount of lights to pass through, thus creating different effects.

Image from evolving beauty
The biggest problem is, ND Filters are really expensive!!! Each filter ranges from $200 to $2000 easily, if your camera lenses have different lens diameters, then you need to buy even more! Bankruptcy won't not far away. Then again, because Peter Hill said ND Filters are just sunglasses for cameras, can sunglasses be used instead of ND Filters? Or are there ways to DIY? Turns out that I am not the first one to think about this.
Image from Wikipedia
Many websites offer the use of a piece of welding glass (a piece of glass used to protect the eyes when welding) instead of an ND Filter, because welding glass is cheap (around US$3, and HK$4 a piece according to my students Alan) and also comes with different "darkness", it allows the users to choose how silky they want for their photos.

Photography Matters suggests glueing the glass to the lens,
Glued to a filter
Image from Photography Matters
But I prefer to use Electric Arc's method for interchangeability,
Welding glass rubber-banded on len hood
Image from Electric Arc
Adding cloth to prevent light from leaking in
Image from Electric Arc
One thing you need to pay attention to is that photos taken with a welding glass as ND Filter will most probably look green, so you will need to reset your White Balance, but once that is done, your photos should look alright.
Image from funadium
Here are some photos taken by Wild World using a welding glass.
Welding glass as ND Filter
Image from Wild World
Welding glass as ND Filter
Image from Wild World
If you can't even get hold of welding glass from local hardware stores, you can try this Magic Cloth Method introduced by Alex Wise Photography.
Magic Cloth Method
Image from Alex Wise Photography
  1. set up your camera on a tripod
  2. use long exposure time
  3. meter the image in your camera around 2 stops over exposed when using the technique to get the best possible exposure. 
  4. begin by starting the exposure and covering the lens with the object. 
  5. over time, gradually move the object up (towards the sky or the top of the frame). 

As a result, the slower you move your cloth up, the darker the covered part of the image is.
Photo taken using the Magic Cloth Method
Image from Alex Wise Photography
Alex Wise also has some extremely detailed tutorials for taking waterfalls and a guide to long exposure with step-by-step photos for you to compare, even beginners can understand. Highly recommended!

Longer shutter speeds can be achieved by using a low ISO setting, shooting at a relatively high f-stop (f.16-32) or by introducing filters such as neutral density filters or circular polarisers. 
-- Alex Wise

For the most technical details on ND Filters, do visit Peter Hill's The Ultimate Guide To Neutral Density Filters.

I'll try it and post some photos here once I have succeeded.

ND Filter / Neutral Density Filter -- (n)[C] a neutral density filter or ND filter can be a colorless (clear) or grey filter. An ideal neutral density filter reduces and/or modifies intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition.
hardware store -- (n)[C] sometimes known as DIY stores, sell household hardware including: fasteners, hand tools, power tools, keys, locks, hinges, chains, plumbing supplies, electrical supplies, cleaning products, housewares, tools, utensils, paint, and lawn and garden products directly to consumers for use at home or for business.


ND Filter @ Wikipedia

Hardware Store @ Wikipedia

Welding @ Wikipedia

Photography & Websites: Chase Javis With Lego Camera & Fujifilm X100 @ Locky's English Playground

Frankenfilter @ Photography Matters

Electric Arc @ Flickr

Wild World @ Alan Wild

The Magic Cloth Technique - DIY Graduated Neutral Density Filter @ Alex Wise Photography

How to Photograph Waterfalls - Tutorial @ Alex Wise Photography

Guide to Daytime Long Exposures @ Alex Wise Photography

The Ultimate Guide To Neutral Density Filters @ Peter Hill