Ian Barber Photography
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Quick Guide To Long Exposure Photography 
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Welcome To My Quick Guide To
 Long Exposure Photography. 
 When we refer to long exposure photography we are usually dealing with shutter speeds of 1 second and longer. In this short guide, I will be talking about shutter speeds which are in the region of about 2 minutes and upwards, sometimes as high as 5 minutes during the middle of the day. So why on earth would we want to have an exposure of around 2 - 5 minutes during the day and more so, how would one go about achieving that in such bright daylight? Having an exposure that lasts around 4 - 5 minutes is required if you are wanting to have moving clouds render as streaks across the sky and also the still calm milky look of moving water. Obtaining such long shutter speeds during the day can be a challenge and in order to achieve this, we need to use a Neutral Density Filter otherwise known as an ND filter. ND filters have the same effect as placing sun glasses over your eyes, they block light. How much they block light by depends on how strong or how dense they are. Usually we choose a specific strength of an ND filter based on how many F Stops of light we want to reduce. The common strengths of filters that photographers use are:
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Density
F Stop Reduction
0.6
2 stops
0.9
3 stops
1.8
6 stops
3.0
10 stops
4.8
16 stops
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F Stop Reduction & Density Chart ! The chart below shows a full range of filter densities and the corresponding FStop reductions in whole stops. Example: Using a 0.9 density filter would reduce the light by 3 full stops. F-Stop Reduction
Filter Density
1
0.3
1.3
0.4
1.6
0.5
2
0.6
3
0.9
4
1.2
5
1.5
6
1.8
7
2.1
8
2.4
9
2.7
10
3
11
3.3
12
3.6
13
3.9
14
4.2
15
4.5
16
4.8
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ND Filter Shapes & Sizes ND Filters are available in different shapes and sizes, some are round and screw directly onto the end of the lens and others maybe square or rectangle which are designed to slot into a holder.
Whether you decide on buying a screw on or slot in type is really a personal choice. I personally prefer to use the slot in ones simply because I find them more convenient.
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ND Filter Manufacturers ! There are various manufacturers on the market today producing ND filters, Hoya, B+W, Hitech, Lee, Singh-Ray, Cokin to name just a few. Over the years, I have tried various designs by a variety of manufacturers and each one have there own strengths and weaknesses. One of the main issues with High Density filters is colour casting. Some produce a brownish cast whilst others seems to produce more of a blue cast. At the time of writing this document, Hitech have just launched a new brand of ND Filter which they have called Firecrest. I have recently purchased one of these filters and I have to say, they produce in my opinion an absolute neutral image right out of the camera thanks to a new technology which they are using.
4 minutes @ f11 (16 stop Hitech Firecrest)
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Calculating Exposure ! One of the most difficult aspects of using an ND filter which is high in density like a 10 or 16 stop is working out what the correct exposure should be. These filters are so dark that when attached to the camera it is virtually impossible to see through them and even those cameras that can see through them with Live View mode enabled will have a difficult time calculating the correct exposure by using the cameras in-built light meter. I find the easiest way to determine the correct exposure is to figure out the exposure with no filter attached and then use an exposure chart like the one you receive FREE when you buy this document or the one which is available directly from my website. You can also use a smart phone / iPad app.
The purchased version of this document includes a pro exposure chart which includes exposure times calculated for 1/3 stop increments. 
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Typical Workflow 1.
Compose the shot to suit your aesthetic liking and put your camera or lens into Manual focus.
2.
Take a meter reading of the scene to establish a good exposure. Use the Histogram in the camera to expose to the right otherwise known as ETTR.
3.
Attach the ND filter and use a chart or app to determine the correct exposure based on your initial exposure without the filter in place and the density of your filter.
4.
If the calculated exposure is beyond 30 seconds you will need to set the camera to BULB mode which allows the shutter to remain open for the length of time you have your finger on the shutter button.
5.
Cover any areas of the camera which run the risk of letting light through such as the eye piece, lens barrel etc.
6.
Open the shutter for the correct length of time. To prevent any camera shake, it is strongly advisable to use a remote shutter cable and a sturdy tripod.
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White Balance If you are using an ND filter that produces a colour cast, try setting a custom white balance inside the camera to about 9000k. Remember that if you are shooting RAW you will be able to correct the colour cast in post production and what ever you see on the rear of the camera is only the JPEG preview of the RAW file. Another alternative to setting a custom white balance is to place an 18% grey card in to the scene and use that as a reference point for setting the white balance in your post processing software.
18% Grey Card
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Long Exposure Examples !  
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Ian Barber Photography
 
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Ian Barber Photography
 
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Ian Barber Photography
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How To Find Me. ! Black and White Learning Website http://www.digitalblackandwhite.co.uk
! My Personal Website: http://www.ianbarberphotography.co.uk
! My Facebook Page: https://www.facebook.com/IanBarberPhotography
! Buy This Document & Receive Free Exposure Charts including 1/3 stop calculations. http://www.digitalblackandwhite.co.uk/ebooks/
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