{"id":6140,"date":"2013-07-07T17:00:36","date_gmt":"2013-07-07T07:00:36","guid":{"rendered":"http:\/\/www.alexwisephotography.net\/blog\/?p=6140"},"modified":"2017-01-04T20:38:25","modified_gmt":"2017-01-04T09:38:25","slug":"create-yourself-a-neutral-density-filter-for-under-10","status":"publish","type":"post","link":"https:\/\/www.alexwisephotography.net\/blog\/2013\/07\/07\/create-yourself-a-neutral-density-filter-for-under-10\/","title":{"rendered":"Create Yourself a Neutral Density Filter for Under $10"},"content":{"rendered":"

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\"Example<\/a>
The effect of what a strong neutral density filter like welding glass can achieve. Note the streaky clouds and blurred water<\/figcaption><\/figure>\n

[box type=”info” size=”large”]Neutral density filters are a great way to completely transform a scene. Using welding glass you can achieve the same effect for under $10[\/box]<\/p>\n

Creating your own neutral density filter using welding glass<\/h1>\n

Ever since getting in to daytime long exposure photography<\/a><\/strong> I’ve read about people experimenting with making their own dark neutral density filters similar to that of the B+W 110<\/a><\/strong> or Hoya ND400<\/a><\/strong>. These filters are great for day time long exposure as the filter is incredibly dark due to blocking out 10 stops of light. Rather than cough up $100 or so for one of these filters, there’s been quite a bit of experimentation with using welding glass to provide a similar effect of blocking out light so you can shoot day time long exposures for under $10. As someone who owns the B+W 110 filter<\/a> I’d never had much need to experiment with using welding glass as an ND filter but recently I decided to pick up a 4\u00bc x 3\u00bc 10 shade piece of welding glass to see for myself how making your own neutral density filter really compares to the proper thing.  Would there be a colour cast? How would I mount the thing to the camera lens? Would there be a reflection from mounting it to the camera lens? These were the many questions I had and I’ll use this post to highlight the good and bad aspects of going the DIY route for strong neutral density filters.<\/p>\n

\"Welding<\/a>
4\u00bc x 3\u00bc 10 shade piece of welding glass. Did I mention how reflective the welding glass is?<\/figcaption><\/figure>\n

<\/p>\n

A day out with the welding glass and how it compared to a proper neutral density filter<\/h2>\n

Welding glass is readily available and I picked mine up from an eBay store called Bargain-Fixings<\/a>. If you’re having trouble finding some try searching for ‘4\u00bc x 3\u00bc welding glass shade’ which will bring up welding glass of various shades. Later in the post I discuss the shade number and how many f-stops of light this blocks but to give you some understanding, a shade 10 is about the same as the B+W 110<\/a><\/strong> in terms of darkness and the amount of f-stops blocked. So how did it all go? My first outing using welding glass as a neutral density filter was at Gunnamatta Beach, Victoria on a windy afternoon. Unfortunately the filter was too big to fit in to my Cokin Z-Pro holder<\/a><\/strong> which has filters of a similar shape and size but the welding glass was too thick to fit. Some people have successfully used a Cokin filter holder but it first required them to cut down the filter. I didn’t have anything appropriate to cut the filter down so it wasn’t an option. Instead I went the ghetto option and used a rubber band (see below) to hold the filter. This method is discussed in detail over on photography-on-the-net<\/a> and DIY Photography <\/a>who deserve all credit for this idea. By using a rubber band and practically fixing the filter to the lens, it minimises reflection between the filter and lens. Using a Cokin filter holder could have potentially introduced some reflection due to the filter sitting 1-2cm in front of the lens.<\/p>\n

\"DIY<\/a>
DIY neutral density filter using a rubber band to hold the welding glass in place<\/figcaption><\/figure>\n

How to calculate the exposure time<\/h3>\n

Before you can shoot though you need to understand how dark your welding glass is and how many stops of light it’s blocking out. Welding glass comes in different levels of  shade where the high the number, the more stops of light that are blocked out. For this example I’m using welding glass with a shade rating of 10. If we take a look below that works out to be around 12.8 f-stops, 2.8~ stops more than the B+W 110<\/a><\/strong> neutral density filter which I normally use. Understanding how many f-stops your welding glass blocks is especially useful for calculating how long of an exposure time you will need to use. \n\n\n\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t
Shade Number<\/td>F-Stop Reduction<\/td>\n<\/tr>\n
1<\/td>0.0<\/td>\n<\/tr>\n
2<\/td>1.4<\/td>\n<\/tr>\n
3<\/td>2.8<\/td>\n<\/tr>\n
4<\/td>4.3<\/td>\n<\/tr>\n
5<\/td>5.7<\/td>\n<\/tr>\n
6<\/td>7.1<\/td>\n<\/tr>\n
7<\/td>8.5<\/td>\n<\/tr>\n
8<\/td>10.0<\/td>\n<\/tr>\n
9<\/td>11.4<\/td>\n<\/tr>\n
10<\/td>12.8<\/td>\n<\/tr>\n
11<\/td>14.2<\/td>\n<\/tr>\n
12<\/td>15.6<\/td>\n<\/tr>\n
13<\/td>17.1<\/td>\n<\/tr>\n
14<\/td>18.5<\/td>\n<\/tr>\n
15<\/td>19.9<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Back in 2009 (how time flies!) I put together an article on calculating exposure time for different ND filters entitled ‘Neutral density reference chart<\/a>‘. It might be old but is especially relevant to what we’re trying to achieve here. If you take a look at the article it will guide you on what exposure time to use based on the bare camera reading you receive without the welding glass attached. For example, if my camera gives me a 1\/15 reading without the filter attached according to the table in the article this will result in a 4 minute exposure time being required. Give it a look as there’s also a printable copy available if you get stuck when out shooting.
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