TRY TIME EXPOSURES FOR ETHEREAL EFFECTS

When we think about taking long exposures with a camera, night time images usually come to mind. Only dark conditions generally call for slow shutter speeds, right?

True-but there is a way to take time exposures in broad daylight...with surprising results.

So the first question that comes to mind is: how do you take a long exposure in bright light? Won’t the camera try to set a fast shutter speed to ensure that the exposure is correct, regardless of how small the aperture is set?

Then there’s the other question: why would you want to take long exposures in daytime, anyway?

OK - a long time exposure (keeping the camera’s shutter open for a long time – from seconds to minutes) will occur when:

• Light level is very low
• A very small aperture is chosen, and
• ISO is set to the lowest value that the camera will allow.

So, to answer the first question, you need to simulate low light conditions by giving your camera dark sunglasses. The device that will do this is an inexpensive thread-on piece of glass called a neutral density (ND) filter. These filters come in a wide variety of grades and are either specified in ‘stops’ or ‘times’.  They are also available as variable grade versions, often referred to as Fader NDs. Be sure to buy one that has the same filter thread diameter as your lens.

A one-stop (or two times) ND filter, with aperture and ISO remaining the same, will require that you force the shutter to stay open twice as long to get the same exposure as you would without the filter. Similarly, a two-stop filter will require slowing the shutter by four times, since a stop means a factor of two in exposure. For the kind of images I’m proposing we take, you will need a ten-stop filter in order to get exposures that are minutes long. This is equivalent to increasing exposure by a factor of 1024 times, but is usually referred to as a 1000 times filter.

Why minutes? Well, in answer to the second question above, anything moving (water, clouds) will take on a foggy (in the case of waves) or streaky (in the case of clouds) look. As long as you have stationary elements in the scene, such as rocks, ground and a tree trunk in the sample shots shown in this post, the viewer is confronted with a paradox that doesn’t appear ‘natural’. This makes for a more interesting image than if you had captured the same scene with a shutter speed of, say, 1/250^th of a second. While these images were shot in colour, I converted them to black and white, since they tend to look more dramatic that way.

And now for the practical considerations. You will need:

• A stable tripod
• A remote shutter release that plugs into your camera, since you can’t hold down the shutter button on your camera for minutes without jarring it. You can also get an intervalometer, which allows you to set a specific time interval without having to manually time the shutter.
• A camera with a Manual mode that will allow you to set the shutter to ‘Bulb’, or one that has a dedicated Bulb mode.
• A day with calm winds, so that your tripod doesn’t get buffeted during the exposure.

Look for a scene that has a combination of moving and stationary components. Getting the right exposure is definitely going to take some experimentation. As a starting point, set your camera’s ISO to the lowest value it provides. This is typically 100. Do NOT use Auto ISO. In Manual / Bulb mode, set the aperture to a value anywhere in the range of f/16 to f/22. This will depend on whether it’s an overcast or sunny day. You should get exposures in the range of 2 to 4 minutes. Use the histogram to confirm good exposure and tweak the time (or aperture) as needed to get perfect exposure or desired motion effect.

With digital SLRs, a practical consideration is the heating of the sensor during long exposures. While it won’t damage the camera, this heating tends to amplify what are often referred to as ‘stuck pixels’. Every camera has them, and they appear as unexpected bright spots on the final image.

To combat this, DSLRs generally have a long exposure noise reduction setting which can mitigate this annoyance. Unfortunately, it requires that the camera will make you wait twice as long to see your image, since it takes as long again as the exposure time to process out the stuck pixels. This could result in an 8 minute wait until you take the next shot. While this technique is effective, I prefer to take my chances and fix the spots after in either Lightroom or Photoshop.

By way of a summary, here are the steps I take:

1. Set up the camera on the tripod and compose the scene with the chosen lens.
2. Ensure ISO is at its lowest setting, and choose a small aperture to help force a long exposure and to give me the depth of field I want.
3. Plug in the remote shutter release or intervalometer (and set it to the exposure time I want).
4. Thread on the ten-stop ND filter, being careful not to disturb focal length or focus settings.
5. Cover up the eyepiece if the sun is behind me, to prevent light leak onto the image (it has happened to me!)
6. Check my image and histogram, rinse and repeat until I get the right exposure and effect.

It’s a slow process that requires patience. At the end of it though, you will get images that will be set apart from the ordinary.

INFRARED ON THE CHEAP

We've all seen the articles stating that you can get otherworldly infrared effects by having a little irreversible surgery done to your DSLR sensor. Without a special filter that's mounted in front of the camera's CMOS sensor, infrared light would normally spoil your images. So, in order to invite infrared light in, the filter needs to be removed. Not willing to dedicate a DSLR to infrared-only, I looked for other ways to easily get on the infrared bandwagon.

As I still occasionally shoot with medium format black and white film, the obvious thing for me was to get some infrared-sensitive film and a recommended filter. This filter is a deep red filter that favours light with wavelengths of 720 nanometers or longer. If this is sounding too techie and out of your league - hang in there - I have a simple digital solution.

By taking that same filter and holding it in front of my CCD sensor-based point and shoot camera, I was astounded at how well the infrared effect came through. Now, in colour, the image does look ethereal, but predominantly red. My preference is to either switch the camera to monochrome before taking the shot, or convert to black and white after in software. After shooting the same scenes using this technique and then using the film camera with the same filter, the results are surprisingly similar.

The reason that the CCD sensor works is that it doesn't have the infrared-removing filter that's built onto CMOS sensors. So, by using a deep red filter in front of a CCD camera lens, you are filtering out much of the visible light and letting mainly infrared light hit the sensor. Using the filter in front of my CMOS-based DSLR camera, however, I verified that the infrared effect is not really achievable.

What about using smartphone cameras with this method? Unfortunately, the newer phones seem to be equipped with CMOS sensors, so they're generally not a good candidate.

You may be wondering by now what this "infrared effect" is that I've been blathering on about. Simply, if you take picture through a deep red filter onto either infrared film or a CCD sensor on a sunny day, the vegetation (leaves, grass) will appear white or pale. It gives the impression that frost or snow has settled on the trees and lawn. At the same time, the sky appears dark, giving a dramatic contrasty scene.

Have a look at the two images in this post, both shot in summer with my point and shoot camera and the deep red filter. Have a tripod handy, though. The filter gives 5-6 stops of attenuation, meaning exposures are going to be very long.

New Digital SLR Photography Book for 2014

"Digital SLR Photography Demystified" is my new venture in the world of photography instruction.

Originally conceived as a reference for students taking my Digital Photography for Beginners course, it also serves as a standalone guide for those who prefer self-instruction. Written in the same way as my easy-to-understand teaching style, it includes ten practice exercises to reinforce the concepts presented.

The content goes beyond the "Beginners" course by covering panoramic, high dynamic range (HDR) and night photography. Also included is a comprehensive Glossary of Terms and a Quick Solution Guide.

While no one book can explain the functions of all camera makes, a generic model is used to help the reader locate a button or menu item on their own camera, using industry-standard icons where applicable.

Currently, the book is available as a 96 page paperback from Lulu.com for $14.95 CDN + shipping (slightly less in $US). In the coming weeks, it will also become available on Amazon and Barnes & Noble websites under the ISBN 978-1-312-03258-3.

Use the QR code below to review the book on Lulu.com.

Fill Flash: Balancing Ambient Background and Subject

I've often ranted in my courses about how horrible mid-day light is for photography. Apart from the colour temperature concerns - an overly bluish, cold tinge to the light - harsh shadows cast from overhead are unflattering, particularly on human subjects.

The flash, either the built-in pop-up variety or the accessory hot shoe type, can assist if you are forced to shoot in the daytime outdoors. Weddings fit this scenario. Turning on your flash to shoot outdoors may seem absurd, but pros use it all the time as 'fill flash'. The word fill refers to the fact that the flash illuminates the face to fill in shadows in the eye sockets and under the nose and chin. Photographic Botox®, as it were.

The modern digital SLR does its best to balance the ambient outdoor light and the fill flash through ETTL (evaluative through-the-lens) metering. ETTL uses a number of different points on the image to determine what the correct exposure setting (ie. aperture and shutter speed) should be, and controls the output from the flash to properly illuminate the subject.

As brilliant as the microcomputer in the camera is at doing this, results can sometimes be other than expected. Let's say the background looks properly exposed but the subject looks a little dark. If you have a strong backlight, this may mean re-positioning your subject. If that's not possible, you can adjust the flash output, independently from the camera's exposure setting, by using flash exposure compensation.

Accessory Flash Exposure Compensation

There are two ways you can change flash output. The accessory hot shoe flash will allow you to adjust output using either the buttons on the flash itself OR through the flash exposure compensation setting in the camera. Depending on the camera, either the camera's flash exposure compensation will be used or the setting dialled into the accessory flash will be used: they cannot be used in combination. For the built-in pop-up flash, you can (obviously) only use the camera's flash exposure compensation setting. So, for the underexposed subject, set the compensation for, say, +2/3 stop and try again. The subject should brighten and balance with the background. 

Exposure Compensation button on camera

For the opposite scenario - the subject is properly lit by the flash but the background is too dark, you can use exposure compensation to control the background exposure. This is different from flash exposure compensation in that it controls the choice of aperture and/or shutter speed but not flash output. For a dark background, dial in a positive number, and for an overly bright background, dial in a negative number. You may have to tweak the flash exposure combination again to get the best result.



Negative Exposure Compensation plus
positive Flash Exposure Compensation

So, by setting flash exposure compensation and exposure compensation independently, you can achieve a balanced image.

Let's leave the mid-day scenario and think about doing a portrait just after sunset ('magic hour'). Using aperture priority or shutter priority modes, the camera's metering system will try to expose the twilight sky properly before lighting your subject with the flash. If the subject looks overly bright and unnatural against the sky, you can balance them by using negative flash exposure compensation or a bit of positive exposure compensation, or both.

The results from doing so will amaze you. After all, the pros adjust their light sources to balance them against the ambient light.

Size matters – in sensors, that is.

When digital SLRs started to come into the market, they essentially replaced the 35mm film camera. In most cases, the lenses that fit your 35mm camera could now be used on the new digitals (from the same manufacturer, of course) without the need for any adapters. Sweet.

Those who made this transition noticed something right away. The 50mm focal length lens that gave a ‘normal’ angle of view on their film camera now acted like an 80mm lens, or slight telephoto, when attached to the digital SLR. In other words, the image was now magnified compared to using the same lens on the 35mm camera.

In some ways this was a benefit, because it meant that the telephoto lens you bought for your 35mm camera now reached a bit further on the digital SLR– about 1.6 times further. The downside was that the wide angle lens that used to work beautifully for landscapes on your 35mm wasn’t so wide anymore on the digital.

This difference is attributable to the size of the sensor in the digital camera. Most consumer SLRs use an APS-C size sensor, which is 22mm x 15mm. Compare that to 35mm film at 36mm x 24mm. Given the same lens projecting the same ‘image circle’ on the digital sensor  and the 35mm negative, the digital sensor only captures part of what the negative captures. Essentially, the digital image is magnified (by 1.6 times) since it’s like zooming in on a small part of the image circle.

For years now, professionals who could afford it have been using full frame digital SLRs (example – the Canon 5D) which use a 36mm x 24mm sensor, just like the 35mm negative size. While the manufacturers could have stuffed more pixels into this bigger sensor (and did so to an extent), the big benefit is that they can now make the pixels bigger.

Why? The bigger the pixel, the more light it can gather, meaning the camera will yield less ‘noise’ in the image in low light situations. Overall, the image is cleaner and yes, at a somewhat higher resolution. In fact, Nikon recently introduced the full frame D800 with an astonishing 36 megapixel sensor. Compare that to the Canon 5D’s 22 megapixel resolution or 18 megapixels on most consumer SLRs. Of course, file sizes bloom with higher resolution.

All of this is significant because the prices of full frame camera bodies are starting to slide below the $2000 price point. While APS-C and other similar size sensors kick-started the digital photography revolution, affordable full frames will eventually bring it full circle. The smaller sensors won’t disappear for a while yet, but those of us who came up through the film world will once again be able to shoot the way we used to – only with the immediacy of digital and a moderate size hole in our pocket.

Getting Exposure Right

For those of you who attended one of my beginner digital photography courses, you may recall me harping on about the camera's metering always trying to achieve 18% grey average exposure.

So what does that mean, really? Well, if you were to examine the histogram (that funny looking graph on your camera's LCD screen) for a picture you just took, 18% grey falls smack dab in the middle. When your camera evaluates the light in the scene before you take the shot, it measures the light over several points in the scene and makes a decision about the settings required to make the average value of the exposure fall at the middle of the histogram. This is called evaluative (Canon) or matrix (Nikon) metering.

The reason for this is to try to ensure that the shadow and highlight areas of the scene remain within the left and right ends of the histogram to prevent loss of detail. Remember, the left end of the histogram represents the darkest shadow detail that the camera can capture, while the right end represents the brightest highlight it can handle. If the histogram is not centred, and the graph is rammed against one end or the other, then chances are you've lost some detail. In short, the best histogram is one whose graph trails off smoothly at both ends, barely touching the sides.

There are times when this brainwork by the camera can do a disservice, however. If you're shooting a scene that's 90% snow or white sand, for example, the camera will try to average the exposure to 18% grey. That means your snow or sand comes out a dull grey because it dominates the exposure, and the camera wants to expose it to mid-grey. Not only that, but if there is some deep shadow detail in that remaining 10% of the scene, it may be pushed against the left end of the histogram and be lost.

Knowing this, camera manufacturers provide an exposure compensation button, pictured below. Typically, you push and hold this button while you turn the command wheel and read the exposure compensation on the LCD screen. In the snow scene example, you may need to overexpose (+) by 1 to 2 stops. Now you're ready to take the shot and check the resultant histogram to see if the white end of the graph ends up close to, but not touching, the right end of the histogram. If not, adjust the exposure compensation and try again.

Remember, most cameras do not reset exposure compensation to zero after you turn off the camera. Reset it manually to ensure you don't wreck the next day's shoot.

You can also use the camera's other metering modes, such as partial or spot, to meter the light only in the very centre of the scene. A typical use for these is where you are taking a picture of someone who has a strong backlight directly behind them. Evaluative or matrix metering would read the backlight and most likely make the face very dark. You could use exposure compensation in this scenario, but partial or spot metering will do the same thing by measuring the light reflected from the face (assuming you centre it in the viewfinder) and make it mid-grey. Again, in these metering modes, the camera takes what it measures and tries to average the exposure to 18% (mid) grey.

As with exposure compensation, don't forget to reset the metering to evaluative or matrix when you're finished with partial or spot metering.