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Photography News | Issue 68 | photographynews.co.uk
Technique
Protectionfilters
The graduate
If you look at a landscape, your brain tells you there is detail in the (usually) darker foreground and the (usually) brighter sky. But a camera sensor is not quite so able – and that’s where the graduate filter plays a vital role to help you balance the contrast in your shots. Graduate filters are half clear and half coloured. Different colours are available, but easily the most useful are neutral grey grads. These come in different densities, typically from 1EV to 3EV, although fractional densities in various transitions (how the filter changes from clear to toned) are available. Soft (gradual tonal change) and hard (much more pronounced tonal change) filters are common. Faced by a scene, the first thing you need to know is which density filter will suit. Start with a meter reading from the foreground. You can use an autoexposure mode provided you keep track of your settings and use compensation to get the right exposure, but it makes more sense to usemanual. Let’s say the reading from the foreground is 1/125sec at f/8. Now take another reading from the sky. Should the sun be in the frame, aim the lens to one side of the sun. If that reading is 1/125sec at f/22, that is 3EV brighter, so you need a 0.9 ND to produce a better balance. ND filters are overall grey filters used to cut down the amount of light reachingthesensororfilm,whichare available inawide rangeof strengths. Weak NDs are 2, 4 and 8, which absorb 1EV, 2EV and 3EV of light respectively. Mid-range NDs are 16, 32 and 64, which absorb 4EV, 5EV and6EV. Thenwehave extremeNDs, which are 500, 1000 and 32,000 that absorb 9EV, 10EV and 15EV of light. Even stronger ones designed for solar eclipses are also available. Before we drown in numbers, the accompanying table should help (right). ND filter strengths are expressed in filter factor and also in optical density and light loss. Here we’ve quoted light loss and optical density. On the left of the table we start with the unfiltered shutter speeds of 1/125sec and 1sec and on the right the newshutter speedswith the relevant filter or filters in place. NDs give you the chance to use the aperture or, mostly, the shutter speed you want to achieve the pre- visualised effect. For intentional cameramovementshots,forexample, or for scenics where the 6EV, 10EV and 15EV NDs are popular because they allow the use of very long exposures to blur movement within the scene. Creamy water, streaky clouds and blurry windblown trees, for example.
It’s simple: do you prefer to ruin your expensive lens or a much, much cheaper protection filter? Just protect your investment with a screw- in protection, skylight or ultra- violet (UV) filter to keep off dust and water. It’ll also take the brunt of any knocks so offers physical protection, too. Prices vary depending on coating and frame quality, but to take a couple of popular examples the Marumi Slim MC Lens Protect filter costs £19 for a 77mm fit or £47 for the same sizeHoya Pro1 Digital UV filter. Putting a piece of glass (regardless of quality) in front of your lens might create issues with flare, so if it does, just take it off for that shot and replace afterwards. If you intend onusing a filter system or any of the filters we have suggested in this feature, the same advice applies. Not only will using as few filters as possible keep quality loss and flare risk down to an absolute minimum, it will also avoid any risks of vignetting with wide-angle lenses. However, with the odd exception, protection filters are worth their weight in gold, so ignore them at your peril.
With graduate
No graduate
Above Using a FujifilmGFX 50R and 23mmf/4 lens, the camera inmanual exposuremodewas angled down and that gave a 1/60sec at f/13, ISO 100meter reading. A readingwith the camera aimed up but away fromthe sun gave 1/500sec at f/13 – a difference of 3EV. AMarumi magnetic frame 0.9 soft NDgradwas used to hold sky detail with the settings for the foreground used. Both shots here are unedited so there’smore potential in post
Then you have to decide which transition to use – this assumes you have the choice, of course. Generally, a hard grad is best when you have a clean obvious horizon – the sea, for example – but if the horizon is broken up by trees or buildings, the soft-type grad is the better option. Now all you have to do is position the grad in the best place by sliding the filter up and down in the holder or rotating the filter holder. Do this while using the viewfinder or live view.
Make your exposure using the settings you determined for the foreground. If you are using autoexposure, sliding a grad filter in place can fool the camera into thinking the light levels have gone down and thus give more exposure, which negates the point of using a grad. Just use exposure compensation to give a correct foreground exposure. Another type of grad is the reverse grad, specifically for sunrise/sunset where the brightest area is a little above the horizon.
These filters are half clear and half toned, too, but the graduated area is stronger just above the halfway point where the toned area starts and gets weaker as you progress towards the top of the filter. Which type of grad to buy depends on what you shoot, but it makes sense to have a selection. A pair of 0.6 grads (one soft, one hard) can be used in combination. If you shoot mostly scenics in bright light, you could add a 0.9 hard, while if sunrises/sunsets appeal, then add a reverse ND.
Neutral density (ND) filters
Newshutter speeds (Rounded to standard camera shutter speed when applicable)
Original shutter speeds
ND filter stops/ optical density
1/125sec 1s
0 0
1/125sec 1s
1/125sec 1s
1 0.3
1/60sec 2s
1/125sec 1s
2 0.6
1/30sec 4s
1/125sec 1s
3 0.9
1/15sec 8s
1/125sec 1s
4 1.2
1/8sec 15s
1/125sec 1s
5 1.5
1/4sec 30s
1/125sec 1s
6 1.8
1/2sec 1min
1/125sec 1s
7 2.1
1sec 2min
1/125sec 1s
8 2.4
2secs 4min
1/125sec 1s
9 2.7
4secs 8min
1/125sec 1s
10 3.0
8secs 16min
Above Neutral density filters give you options with your shutter speeds that wouldn’t otherwise be possible. Here the metered exposure was 1/8sec at f/11 and ISO 50. Fitting a Marumi 64x ND (6EV) meant an exposure of 8secs at f/11 was possible
1/125sec 1s
11 3.3
15secs 30min
1/125sec 1s
12 3.6
30secs 1hr
1/125sec 1s
13 3.9
1min 2hr
1/125sec 1s
14 4.2
2min 4hr
1/125sec 1s
15 4.5
4 min 8hr
But NDs also have a use for people shots too. In bright light with a fast lens aperture you might run out of shutter speeds so an ND filter can help you out. Or if you’re mixing flash with daylight an ND filter means you can set the correct flash sync speed or use awider aperture to throwbackgrounds out of focus. Most NDs are truly neutral but that can change when you move into the stronger filters and there could
be a colour shift with shots coming out cooler or warmer than youmight expect. Buy a newND and it is worth trying it inAWB, using preset white- balances or various manual Kelvin settings to check out its effect and neutrality. Shoot Raw and correcting any colour shift can be done in editing but if you shoot JPEGs or prefer amore neutral look in-camera use a manual Kelvin or do a custom WBwith the filter attached.
1/125sec 1s
16 4.8
8min 16hr
1/125sec 1s
17 5.1
16min 32hr
1/125sec 1s
18 5.4
30min 64hr
1/125sec 1s
19 5.7
1hr 128hr
1/125sec 1s
20 6.0
2hr 256hr
1/125sec 1s
21 6.3
4hr 512hr
1/125sec 1s
22 6.6
8hr 1024hr
1/125sec 1s
23 6.9
16hr 2048hr
1/125sec 1s
24 7.2
32hr 4096hr
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