If like me you leave your camera set to aperture priority nearly all the time letting the camera figure out what shutter speed it needs, having to think instead of what shutter speed is best for my previsualised image feels like a topsy-turvy universe. So Paul’s presentation opened up a new world of interesting ideas for me to explore. He is a member of Aperture Woolwich Photographic Society and is based in NW Kent and SE London.
He said that understanding the technical aspects of exposure is vital to capturing the results you want and he began by reminding us of how the ‘Exposure Triangle’ works. When you half depress the shutter button on your camera, the TTL meter takes a light reading and calculates a correct exposure based on the ISO and the aperture or the shutter speed you have set. He also talked about the Exposure Value (EV) and how this value relates to the Exposure Triangle.
My guess is that many of you will have heard of Exposure Values but thought – blimey not another parameter to worry about on top of the other three! Paul described EV as a blend of aperture, shutter speed and ISO. In fact, camera manufacturers have already decided that you don’t need to worry about EV so modern cameras don’t give you a readout of it.
This is a bit of a digression, but as you are likely to come across the term in camera magazines etc, I thought it might be helpful to explain what an EV is. An EV is simply a reading of the brightness of the scene. It’s what your camera measures when you half depress the shutter button. EV values are on a simple numerical scale. For example, on a bright sunny day the EV will be about 12. In a dimly lit interior, it might be 5.
EV values are on a doubling scale, just like apertures, shutter speeds and ISO values. Thus a scene with an EV of 13 is exactly twice as bright as one of EV 12. Your camera’s processor uses this value to offer you combinations of aperture, shutter speed and ISO that give the correct exposure. So, the camera doesn’t need to tell you what the EV actually is.
If you need to tweak the exposure for a particular picture by, say, adding an extra stop of compensation, what you are doing is telling the camera to add 1 EV to the value it uses. Hope that makes sense!
Paul began his talk by summarising how lengthening the exposure can be used to add an extra dimension to an image – to show the passage of time. It can be used to effect in a range of genres such as landscapes, seascapes, waterfalls, architecture, people and traffic.
Then he went on to describe some of the gear that is useful for this technique. Long shutter speeds can be achieved be using a low ISO setting and a very small aperture, but there will be times when this is not enough to give you the shutter speed you want. Longer shutter speeds require the use of neutral density filters and Paul described the different types of filters and filter holder systems available. He said that if he was starting from scratch, he would go for circular screw-on filters. Buy just three: a 3, a 6 and a 10-stop filter, and make sure they are stackable so that they can be combined for even longer exposures.
If you are thinking of buying filters, Paul gave us discount codes for Formatt-Hitech filters. He has very kindly supplied us with a PDF copy of his presentation where these details can be found. For the benefit of members, this will be appended to the next Photocraft Newsletter.
The next hurdle is calculating the exposure time to get the effect you want. Take a look at the scene first, and watch what movements are taking place, whether it is clouds, people, vehicles etc. Compose your picture and try to previsualise how you would like the movement to impact on the overall composition. Having decided on the shutter speed, take a light reading without a filter. The easiest way to calculate the camera settings including the effect of ND filters is to use an App such as NDTimer. This includes a timer if you need a time longer than those available in your camera. Remember, it is not an exact science so give yourself plenty of time to experiment.
Keeping your camera still and stable during the exposure is important so use a good tripod to avoid Unintentional Camera Movement. A light and useful alternative is a Platypod, visit ALL PRODUCTS – platypod.com. (Why am I thinking Platyperipateticus….?)
When taking the shot:
- Turn off image stabilisation
- Focus on subject and take meter reading without a filter
- Switch to manual focus
- Leave aperture value unchanged
- Put filter in place
- Adjust shutter speed
- If using a DSLR, cover the eyepiece to stop stray light entering camera during exposure
- Release shutter using a cable release or the camera’s self-timer
Paul suggested a number of learning sources and a summary of these will be attached to the next issue of the Newsletter.
His next topic was Intentional Camera Movement, a technique dear to our hearts – well, some of us anyway. He made a point I hadn’t thought of: loss of sharpness due to diffraction at small apertures is not a problem because the pictures are never sharp anyway. He said it was helpful when deciding how to move the camera to think in terms of how aircraft movements are described – Roll, Pitch and Yaw, plus Zooming the lens.
He then showed us some examples of his long exposure images, a few of which he has kindly let me reproduce below. He rounded off the evening by showing us his successful ARPS panel, including his Statement of Intent. A brilliant evening Paul, thank you, and thank you for generously providing so much additional information for us to share with our members.