Are you stopping? ND filter strengths in photography.

In a post a few days ago, I mentioned the idea of Stops in the context of the Aperture triangle. When you use neutral density (ND) filters, the idea of Stops becomes a central issue. You use filters to reduce light entering the sensor in situations when using the shutter speed setting alone doesn’t fit the bill. ND filters are available in a range of strengths – these can be called by different names, but the easiest one to remember is the number of Stops of light which the filter offers. You have to choose, by looking at the situation, how strong a filter you want to use. If you are photographing a waterfall in bright light, perhaps 3 stops will do. If you are photographing waves then probably 10 stops would be your minimum – and you may want to stack a 10 stop plus a 5 stop. You are the judge. What you then have to do is to take the shutter speed that your camera recommends without a filter, and look it up in a table – such as that below, or by using a phone app – to find out what shutter speed you will need when you have a filter installed.

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So, if you’ve taken a test shot without a filter and the preview tells you that your exposure is OK, have a look at the shutter speed that you used, say 1/125 seconds. Now, let’s say you want to use a 6 stop filter, the table tells you that, with the filter installed, your shutter speed will need to be 1/2 seconds. At this point, you need to lock your focus, remember your settings and switch to Manual mode. Enter those settings – ISO, Aperture – and your new shutter speed (the 1/2 seconds one in this case), pop in your filter and you’re almost ready to go (I’ll say more about that tomorrow.

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I said above that filters are known by different names by different manufacturers – for example as a 6 stop filter, a 1.8 optical depth filter or as an ND 64 filter. The table above provides the equivalent types of naming for each strength. The table also shows the equivalent fraction of light that is admitted. So, a 6 stop filter admits only 1/64 of the light that would have been admitted without a filter. Think back to the first table. Without a filter you would have opened the shutter for 1/125 of a second. With the 6 stop, ND64 filter you will open the shutter for 1/2 second – ie 60/125 or roughly 64 times longer.

The table examples above are just to illustrate the principle. There are excellent phone apps, such as ND expert, where you just enter the base shutter time and the filter type and which also provide a timer.

Today’s featured image is of the lighthouse at Penmon Point, Anglesey, North Wales with Puffin Island to the right of the image.

This photograph was taken only slightly later with a 10 stop filter plus a 2 stop polariser. The light had also changed. The base shutter speed was 1/200 seconds, the filtered time was 10 seconds ie 2000/200 equalling a factor of 1000 (roughly 1024)

Tomorrow, I’ll provide a detailed checklist of everything you need to do to prepare for your long exposure outing.

Long exposure photography

Most cameras have a default maximum shutter speed of 30 seconds, so I guess the range of shutter speeds from about 1/8000 secs to 30 secs must be classed as the normal exposure range. By that reckoning any shutter speed longer than 30 seconds would count as a long exposure, but, for the purpose of this blog, I’m going to count anything longer than 1 second.

Why, though, would anyone ever need to open the shutter for longer than 1 second? One answer would be to take photographs in low light conditions where. Alternatively, say that you want to use a wide aperture in bright sunlight eg to blur the background behind a shrub that you’re photographing in your garden. In order to avoid the photo being over exposed you could use a neutral density filter (ND filter) to reduce the light entering the camera. Another would be to take photographs to smooth out movement – for example waterfalls, waves or clouds.

Compare this shot at Cleveleys beach, Lancashire with today’s featured photo in which wave motion has been smoothed to focus attention on the rocks. I took the photo on the left at 1/200 of a second but the featured photo at 8 seconds using a 9 stop filter and an aperture half a stop smaller.

I took this shot, mid morning on a bright day with a 10 stop ND filter. My shutter speed was 30 seconds at an aperture of f/8 and ISO 100.

This image was taken within minutes of the one above but the shutter speed was 1/60 secs at the same aperture and ISO. Notice how the movement of the water in the stream was blurred by using a filter.

I won’t be able to explain even the basics in a single blog post, so I’ll spread it out over a few days. Today, I’ll just show a couple of examples of long exposure. Tomorrow, I’ll say something about the various types of filter that photographers use. Then I’ll post a blog about calculating shutter speed for using different strengths of filter. Finally, probably, I’ll go into how to use filters.

Having said all that about filters, in low light conditions you won’t need them normally, your main equipment other than your camera will be a tripod to enable you to take a stable, steady shot.

For this photo of Liverpool by night I used a tripod but I didn’t need a filter. My settings were shutter speed 6 seconds, aperture f/8, ISO 100 and focal length 23 mm. Because I used a tripod I set the image stabilisation to off. Other than that, the effort was simply waiting until all the drivers were using their lights and that there were enough of them moving quickly between two sets of traffic lights.

I hope that these examples may inspire you to look at this blog tomorrow to learn more about the various types of filter.

Enjoy your day.

Look on the brighter side of life – ISO photography

ISO is a setting to increase the brightness of a photograph.

Sometimes you have a dilemma when, in low light conditions, you wish to avoid an underexposed image. Let’s say that, even though you have opened your aperture as far as your camera allows in order to retain sharpness, the image is still under-exposed. So then you have set your shutter speed as slow as you can yet still avoid avoid blur, but the image is still under-exposed. If you don’t mind blur – or if you want special effects such as light trails – you could mount your camera on a tripod and take a long exposure. (If you are taking an exposure longer than about 1/50 seconds without a tripod you risk camera shake and undesirable blur.)

In other circumstances, however, in order to increase brightness your only option other than flash is to raise the ISO setting. Unfortunately, if you raise the ISO significantly, you will begin to notice ‘noise’ or ‘graininess’ in your image. You then have to trade off motion blur against graininess – or miss the shot.

I’ve provided here a series of images of the same scene, on the same day, as darkness appears. I took this first one at 20:37 using ISO 100 at f/11 and 1/25 seconds. The focal length was 20 mm for all this series. The image is reasonably sharp and without noise.

This photo was taken 3 minutes later and yet is brighter. I increased the ISO to 200, increased the shutter speed to 1/100 seconds, but retained the aperture of f/11. At ISO 200, there is no noticeable increase in graininess.

By 22:03, I was using ISO 250, a shutter speed of 4 seconds and an aperture on f/3.5 – that’s an increase of 8 aperture stops alone. There is some noise but not much.

By 23:28 I was using ISO 3200, a shutter speed of 25 seconds, and an aperture of f/3.5 – as wide as possible with the lens I was using. There is considerable noise. In the following two images I have cropped section of this image to illustrate the noise or grain.

This is a crop from the middle- left of the picture.

This is a crop from the bottom right.

The shutter speed of 25 seconds was as slow as I could use, with the lens I was using, without causing spot stars to trail as a result of the earth’s rotation relative to the stars.

So, in summary, The ISO setting on a camera can be used to brighten a photo, but start by setting an aperture suitable for your subject. Then set your ISO to its base value – usually 100. Take a test shot and if the preview image indicates motion blur, try a faster shutter speed until you get a sharp test shot. If you still experience blur, increase the ISO but use a faster shutter speed. If after increasing ISO a few times you start getting noise in the image, try opening your aperture.

My featured photo of light trails today illustrates some of the types of trade-off issues. It’s a low light shot for which I wanted sharpness overall ie good front-to-back depth of field for the light trails, and — preferably – a starburst effect from the street lights on the roundabout. My start point was, therefore, a small aperture of f/18. However, I wanted the exposure to be long enough to capture the light trails, so I used a tripod to avoid camera shake and a fairly low ISO of 125. My focal length of 30 mm was wide enough to take in the scene I’d chosen. As the scene became darker I eventually got the shot I wanted with a 30 seconds shutter speed.

I’ve provided a link below to an excellent website that explains ISO in crystal clear terms.,aperture%20and%20shutter%20speed%20settings.

Photography and shutter speed…. and with only seconds to spare……

You may have heard of the Aperture Triangle – I’ll be dealing with that in a day or so. The three sides are Aperture (which we’ve looked at), Shutter Speed (today’s topic) and ISO (tomorrow’s item – probably). ISO and shutter speed are wonderful tools.

Shutter speed refers to how long you leave the aperture open – to let the light from the scene reach the sensor. You’ll have picked up something of that aspect yesterday, I hope. I’ve provided, below, some examples of different types of scene that you may wish to photograph – not to say that you MUST use the speeds shown – but to give you a ball park idea of the order of magnitude that may be involved.

This is a powerboat racing scene, at Carr Mill Dam, St Helens, Merseyside. The boats are moving very quickly. I used a fairly fast speed and ‘panned’, that is, before the boat arrived, I’d already focused on the place on the lake surface where I knew it had to be. I stood still but, with my camera set to continuous focus, I turned my shoulders to allow the camera to track the boat as it passed, firing off a burst of shots at 1/1600 seconds, f/5.6, 260 mm and ISO 400. If I’d used a slower speed, the image of the boat would have been blurred.

I took this photo at a horse race at Haydock Park racecourse, St Helens. Horses don’t move as quickly as racing powerboats, so I was able to use a slightly slower shutter speed and still kept the horses and the background properly focused. I still used the panning technique, focused ahead and used continuous autofocus (AF.C). As the first horse started to move into my frame, I followed it with my camera and fired off a burst at 1/1000 seconds, f/5.6, 85 mm and ISO 400

This shot was my practice session the first time I ever used panning technique. The car is on the M62 motorway in Northern England. I was stood at the edge of woodland. I wanted to create a feeling of speed by letting the background blur. A faster shutter speed would have kept both the car and background in focus – as in the above examples. My ISO of 100 and aperture of f/8 allowed me to use a slower shutter speed to create the effect. 1/30 seconds, f/8, 55 mm and ISO 100.

This is a view of the city of London at daybreak. Nothing is moving apart from the River. I wouldn’t have been able to take this photo with such low light, if I’d used my camera’s minimum ISO of 100 with an aperture as small as f/16. To get the image I used a tripod and let the camera use a quite long shutter speed. 8 seconds, f/16, 28 mm, ISO 100

I shot this view of London from the South Bank of the Thames at night. I still used a narrow aperture for sharpness and a low ISO, but I needed a much longer exposure of 30 seconds to collect enough light at f/18, 30 mm, ISO 100.

Sometimes you need to use a faster shutter speed to compensate for camera shake because you’re not using a tripod. Even with built in image stabilisation it can help. The heavier your camera and lens the more difficult it can be to eliminate camera shake. A frequently quoted suggestion is to set your shutter speed to be no slower than the reciprocal of your focal length. If you are using a 50 mm lens, set your shutter speed to be faster than 1/50th seconds. With a 135 mm lens, shoot faster than 1/135th seconds.

The featured photo today is one that I took just before lockdown, at Trefor Stacks (Ynys Mawr) on the Lyn Peninsula, North Wales. You may have expected that, with the settings below, the whole image would have been vastly over-exposed. Because the the midday sunlight was so bright, I used a 10 stop neutral density filter. I’ll say more about filters in a few days. My settings were 20 seconds f/11, 20 mm and ISO 100. This means that, because my shutter speed, in a test shot, without a filter had been roughly 1/64 seconds at that aperture and ISO, I used a filter dark enough to cut out 10 stops of light. That meant that I could use a shutter speed of 20 seconds to provide an equivalent exposure value.

What do I mean by a stop? A shutter speed of 1/32 seconds is one stop slower than a speed of 1/64 seconds. Two stops would be 1/16 seconds. Keep on doubling the speed ten times from the start and you reach 20. (i.e. 1/64, 1/32, 1/16, 1/8, 1/4, 1/2, 1.25, 2.5, 5, 10, 20) Okay, I did a bit of creative doubling to get from a half to one and a quarter, but I did say roughly 1/64 originally. You can’t be precise with very dark filters because daylight can change from sunny to cloudy in seconds. As I said earlier, I’ll deal with filters again, in more detail soon, when I write about long exposure photography

One last point, on the subject of shutter speed and blur, notice how that 20 seconds exposure has calmed the waves, focusing attention on the detail in the stacks.. You can get some great effects using long exposure. The golden lichen, by the way, really was that bright – no software trickery. I was tempted to make it duller but, what the hell, it was beautiful in my eyes, and it’s my photo, so I left it as it was.

Tomorrow I intend to deal with the third side of the Aperture Triangle – ISO or brightness.

Photography – Aperture Words, words, words I’m so sick of words

Any newcomer to photography, picking up a modern digital camera is immediately confronted with a mystery. On the lens he or she might see something like SMC Pentax DA 1:1.8 50 mm. Turning to the camera – on a dial on the top they might see some of the following – B, M, AV, TV, SV P, AUTO. On the sides and rear of the camera there are acronyms such as AF/MF, RAW Fx1, AF/AE-L, ISO, WB, LV. If they were to ask what these initials mean, they’ll hear words like Aperture, Focal Length, Shutter speed, ISO. Pressed further, their mentor might mutter terms such as Depth of Field or Exposure triangle. As Eliza Dolittle sang to Freddy in the musical ‘My Fair Lady’, ‘Oh, words, words, words, I’m so sick of words…is all that you blighters can do?’

In the next few blog posts, I’ll try to explain just a few of these terms to the best of my ability. But you can find more detail by ‘googling’ any of the terms. Anyway, I’ll start with aperture. Essentially the word ‘aperture’ in photography refers to the hole in the lens through which light reaches the sensor – the bit that actually records your image. The hole in the lens is at the centre of the shutter which opens when you press the button to take a photo and closes when the shot has been taken. The shutter is made of ‘leaves’ that move both to do the opening and closing, but can also be set to change the size of the hole to create different effects.

This is a photo that I took in my garden this morning of a heather plant. I set the opening to create a wide hole – as wide as this lens would allow. Notice how only part of the plant is in focus and everything behind the plant is blurred.

The aperture – or size of hole – that I set for the the photo was f/1.8. Let me simplify that. 1.8 is almost 2 so when you see that f/ it refers to a ratio of 1/2 or half. So if the aperture size were f/16 the ratio would be 1/16. You know from simple arithmetic that 1/16 is much smaller than 1/2 – a sixteenth is smaller than a half. Why did I choose such a big aperture? I wanted only the plant to be in focus – I wanted the background to be blurred. That’s an effect known as a shallow depth of field where sharpness is confined to a very narrow band of depth.

I shot this photo at f/8 – an eighth, so I only allowed in a quarter as much light as in the first image in one way, but the camera compensated by opening the aperture for a shorter time, 1/5 seconds, to provide the same level of exposure.

The image looks different. In a way I’ve let in about the same amount of light, but I’ve changed the recipe for doing so. I used a smaller aperture but the shutter was open for 1/5 seconds whereas in the first photo it was open for 1/100 seconds. Look at the difference between them. In the second photo, the whole of the plant is in focus and the back ground is less blurred. In other words there is a greater depth of field. The field of sharpness extends further forwards and further backwards as well.

In my final photo, the settings are an aperture of f/22 and a shutter speed of 8/5 or one and three fifths seconds. Now look at the depth of field – how sharply the back of the garden has come into focus.

I don’t want to stray much further into depth of field, diffraction, ISO, angle of view and so on. Today’s blog is just to provide a simple introduction to the idea of aperture and the kind of role it plays in photography. I’ll just provide two examples below of deliberately choosing one size of aperture over another to change the depth of field.

I don’t do portraits of people, but that’s a definite area for wide apertures. This is just a handheld photo of my daughter’s dog, Ted. It was taken indoors in low light conditions, so I had to boost the brightness of the photo in camera using the ISO setting – I don’t have flash either. I took the shot at f/3.5 – quite wide with a shutter speed of 1/320. If you were to enlarge this image you’d be able to see that only the dog’s left eye (the one on the right of the photo) is in focus. You can almost see my reflection in the eyeball.

This final example is of a lone tree at Lake Wanaka in the South island of New Zealand. I shot this at f/14 (quite narrow) and 1/80 of a second. See how the image, though handheld, is fairly sharp from the beach to the mountains.

Tomorrow I intend to post about exposure, or more specifically about what sort of shutter speeds you might use for different types of photograph.

Photography: Decent Exposure

Today will be all about something known as Dynamic Range. This term refers to the difference between the darkest and lightest tones in a scene. Having a high dynamic range isn’t necessarily bad – and the types of image that it’s Ok in don’t need rescuing.

Sometimes, however, you are faced with a scene where you know that you may need the wizardry of your digital camera settings to capture the scene as you’d like it to appear. Why might you need wizardry? Well, the problem is that your human eye can cope with a much wider range of contrast than your camera can. A bright sky that looks OK to your eyes might appear almost white in a photo. Certainly, any cloud detail in the sky could be ‘blown out’. Similarly, your camera might not be capture the details in the shadows if the contrast is too great.

What I am showing is some examples of what I mean and how I’ve used a technique called exposure bracketing to create an image that reveals the best of both worlds. All that means is that I use a tripod and take, say three photos of the scene – one normal exposure, one under-exposed and one over-exposed. With most digital cameras you can let the camera do it. With some cameras you can do this and the camera will produce a merged image for you. Other cameras simply store the three images for you to merge in your post-processing software.

This over-exposed photograph of the South Stack Lighthouse on Holy Island, Anglesey in Wales is one of three that I took using my camera settings for exposure bracketing.

On the other hand, this is the under-exposed version of the same scene.

This is the Normal photo. I should have checked my preview before I started but the bracketing process sorted that error anyway.

This is the version produced by exposure bracketing. The sky detail has been preserved and the detail in the shadows has been rescued. I still wasn’t happy so I cropped out the clifftop distractions.

The final shot – bracketed and cropped.

This is the Normally exposed shot from a bracketed group of photos shot at daybreak. The scene is the lone tree at Lake Buttermere in the English Lake District.

This is the bracketed version after merging.

To close, this is an under-exposed photo from a group of five photos of the disused Twr Mawr Lighthouse on Ynys Llanddwyn, Anglesey. I’ve used the merged version as my featured photo today. You may notice that I’ve also cropped out the photographer and his tripod and removed a sensor spot in the sea part of the image.

I’ve not decided what my next subject is going to be, but I’d like to move on from generalities to specifics of technique to use for different types of photography that I’ve tried. I haven’t tried every technique but I’ll tell all about those that I have had a go at.

Fiat Lux – Let there be light. Photography and Light

Following on from my disclaimer yesterday, nothing that I write below has anything to do with expensive equipment, or travel to exotic locations. Every photographer, whether cash-strapped or a lottery winner needs to know how to use light. The very word ‘photography’ means drawing with light: no light = no photo.

Light: directly from the Sun and sky and indirectly bounced back from the sculpture, the sea and the sand

The light we use can be direct – as from the sun or a flashlight, ambient – such as through a window, or reflected – as from the moon or bounced off something – such as a mirror.

To use light in a photograph, it has to be allowed into the camera through a shutter, focused by a lens and stored on a film or electronic sensor. For the light to be useful it has to be controlled. Once the lens has been adjusted to focus the light precisely, the shutter mechanism has to be set to limit the size of its opening (its aperture) and the amount of time that it will be held open (its shutter speed).

Different lenses for different used of light and focal length

If too much light is allowed in, the photo will be over-exposed, if there isn’t enough light, it will be under-exposed. There is one final element within the control of the photographer for a particular image and that is the sensitivity of the sensor. This is the ISO setting. In low light conditions. By increasing the ISO you can continue to take photos even when it’s quite dark, but this comes at the cost of increased graininess (or noise).

Too much light caused by solar flare

We haven’t finished with light yet.  You, as a photographer, have a role to play and this is what separates photography from snapshots. A photograph is to a snapshot as carpentry is to flat pack furniture assembly. There are exceptions. A photographer may need to take a snapshot in order to capture a fleeting opportunity. At such moments the prime objective is to get the shot. There may not be time to erect a tripod, to attach filters or even to check settings. It can be now or never, but the photographer has had to recognise the opportunity.

I arrived just at this moment, saw the light rays, dropped my bag and tripod on the beach, grabbed my camera, pointed and clicked the shutter. Two minutes later would have been too late. I hadn’t checked my settings or whether the lens was clean. Luckily they were okay. Opportunity is sometimes everything.

Normally though, with a snapshot, the camera does the photography – not the person who merely points and clicks. Photography requires judgement of the objective. More on that in another post. The photographer recognises the constraints set by light including the time of year, the time of day, the movement of the Sun, Moon and tides, the range of the tones of light given in the scene, the ‘temperature’ of the light available, and the use of shadows and reflections.

This an example of the wrong colour temperature. The previous evening I’d been taking photographs indoors under tungsten lighting.

The following morning, at Pwllheli, I forgot to check my white balance setting to change the setting from tungsten to daylight. Ooops!

I’ll try to shine more light on all of these are topics, and illustrate them by some of my own photos, in the blogs to come.

Tomorrow, I’ll be talking about Time.

My featured image today is, of course, the London Eye, from the Embankment, with lots of light, colours and reflections. To take the shot I used my Pentax K-1 36 MP full frame camera, using a 24-70 mm f/2.8 lens at 29 mm and f/8. The ISO was 100 and the shutter time 30 seconds. The shot was tripod mounted without filters.