In the previous post of this series I explained what happens in a digital camera – how a batch of photons is converted into a digital file. This post will cover how to use that file to create an image which can be displayed electronically or printed. This activity is called post-processing, because the initial processing of the image is done by software within the camera.
For wildlife photography, I believe the aim of post-processing is to produce a final image that replicates what you saw as closely as possible. And by “what you saw” I mean what you saw with your eyes through your binoculars, and not what the camera thinks you saw. Modern cameras are extremely capable, but their abilities are vastly inferior to those of the eye, especially the eye aided by precision optics. Occasionally the camera will manage to capture an image exactly the way you wanted it, but most of the time, especially in wildlife photography, the raw material produced by the camera will need some help.
The above images show the out-of-the-box version (Dusky Antbird 1) and the final version after post-processing (Dusky Antbird 2). Which would you prefer?
This article was also published in The Blue Bill, the Quarterly Journal of the Kingston Field Naturalists, Volume 67, No 2, June 2020.
I started this article intending to talk about post- processing – the business of editing your wildlife images. But I rapidly realized that it is too big a subject to deal with at once, so I’m going to break it into manageable chunks.
How the Camera Creates an Image
The first stage of the journey requires us to look at what happens when you snap the shutter. In the days of film cameras it was relatively straightforward – light passed through the lens and onto a film of celluloid or plastic. Light-sensitive chemicals on the film reacted to the exposure, producing a negative or a slide.
Digital cameras use a different process to capture an image. As photographers we need to have a basic understanding of how this works so we can understand how the different image file formats work.
In very simple terms, in a digital camera the light is focused on a sensor, which is a grid made up of very small photosites. Each photosite contains a diode that converts light into digital information. In simplistic terms the diode counts the number of photons that fall onto it while the shutter is open, and the circuitry in the photosite coverts that information into a numerical value.
In order to provide a digital image that matches the level of detail and colour that the eye can see, a camera sensor needs to contain millions of these photosites. This density of information allows a digital image to be at least as good as an image from a film camera. But it also explains why digital image files tend to be very large. Each of those millions of photosites generates a numerical value expressed as a byte of between 12 and 24 bits. To give you an idea of how that adds up, with my current camera set to the highest resolution the information stored by those photosites totals 62 million bytes of data for a single image.
The camera’s onboard processors convert those digital values into an image file. There are two main formats for an image file – JPEG and Raw. These formats take very different approaches to the challenge of storing all this data. In simple terms, JPEG transforms data within the camera to produce a finished image, while Raw stores all the information and the user then processes the information at a workstation. Each approach has its the pros and cons. I want to briefly illustrate the difference so you can make an informed choice about which format to use.
JPEG (Joint Photographic Experts Group) has emerged as the standard format for most photography tasks. For virtually all digital cameras JPEG is the default format, so if you have not been experimenting with the settings menu you are almost certainly shooting JPEG.
The JPEG format was developed to allow onboard compression of digital images. If you recall that figure of 62 million bytes you will see why for many applications there is a need to compress digital images.
Large files are problematic for several reasons:
They demand large storage capacity on your camera’s memory card
They take more time to write to the memory card, which can limit the number of images you can take in quick succession
They take up a lot of room on the storage drives of your PC, laptop, or mobile device
They require a lot of bandwidth to transmit, so websites will be slow to load and sharing is tedious
To avoid these problems the JPEG format compresses the raw information gathered by your camera sensor and then transforms it into a finished image. This image is stored on your camera’s memory card.
For many uses JPEG format is ideal:
JPEG images are small enough to be easily viewable and shareable.*
Virtually all devices and software are compatible with JPEG files.
The simple image editing software available on your cell phone, tablet or computer is designed to use JPEG images.
JPEG is supported by HTML, the language used in creating web pages.
*Note: JPEG files can be created using different compression levels. Lower compression levels lead to better quality but also larger file size. JPEG Fine files are the least compressed (4:1) but therefore the largest. At about 10MB each in the Large size they are not easily shareable.
However, there are limitations to JPEG that you should consider. Most of these limitations result from the way the JPEG algorithm compresses the image file size.
The process by which JPEG compresses a file is highly technical bordering on incomprehensible, but in the simplest possible terms it reduces the size of the file by calculating average values for 8×8 blocks of photosites (thus each block replaces 64 sets of information with one). It then reduces the level of information about colour. Based on the understanding that humans have difficulty discerning small variations of colour, JPEG looks for areas that have similar hues and replaces these small variations with a single average colour.
This process can result in a much smaller image file, but the key thing to remember about the JPEG conversion process is that once the image is created any information that the conversion algorithm considered unnecessary is lost and unrecoverable.
This is why JPEG is classified as a “lossy” format. As noted, a certain amount of information is discarded when the image is originally created. Moreover, each time you recompress the image, by making a change and then re-saving it, some additional information is irrecoverably lost. And if you crop an image – for example to provide a close-up view – the parts of the image that you cropped out are lost forever.
A further implication of JPEG is that, because it produces a final image, the camera settings in use when the image was taken are “baked in”. If you realize afterwards that you had the wrong white balance or picture control settings for example it may not be possible to correct the image.
Raw is a generic term for a file that saves all of the information from an image, with only minimal processing. This information needs to be converted and edited at a workstation before an image is produced.
Raw format is not available on all cameras. All modern digital single lens reflex cameras (DSLRs) and mirrorless cameras can shoot Raw, but only a minority of bridge cameras have the capability and point-and-shoot cameras generally do not.
There are several disadvantages to shooting in Raw:
Raw files are big. With the camera set-up I currently use, each image file is about 29MB. So a 64GB card will hold about 1,300 Raw files instead of 13,000 JPEGs.
You need to process your Raw files at home in order to generate finished images. This is time-consuming compared to the instant image generated by JPEG.
To process the files you need specialized image editing software (though note that you can download free editing software from your camera manufacturer – all the major camera brands provide this).
Each camera manufacturer has its own a proprietary standard, so a for example a CRW file from a Canon camera is not compatible with a NEF file a Nikon generates.
For Raw files to be printed, shared on a mobile device or posted on the internet you need to create and export a JPEG image.
So why do most professional wildlife photographers shoot in Raw?
Lossless. Raw files are lossless. All the information your camera gathered is available to you. Nothing is averaged out or approximated. As an example, an 8-bit JPEG image is limited to about 16.8 million colours, whereas a 12-bit Raw image can show up to 68.7 billion. What this means in the real world is that you will get more even transition between colours, without the possibility of the pixilation that sometime happens with JPEG (remember that JPEG averages out colours into larger blocks).
Non-destructive. The adjustments you make in post-processing do not change the original file. All changes are saved in a separate hidden file called a sidecar. So regardless of how much you crop and adjust an image, you always have the original file available. With JPEG every significant change degrades the image, and things that are cropped out cannot be recovered.
Settings are not baked in. With Raw you have complete ability to adjust most of the camera settings during post-processing, including exposure, white balance, sharpening, colour gamut, picture control, and contrast.
Greater dynamic range. Raw files are typically created in 12 or 14-bit format, compared to 8-bit for JPEG. This may not seem like a big numerical difference, but remember we are looking at a file made up of millions of bytes. The math is somewhat beyond my ken, but the impact is that in each stop of a camera’s dynamic range there is far more information space available in a Raw file. At the bottom end of the dynamic range – areas of deep shadow in a photograph – there are 65 times as many gradations in a Raw file as in a JPEG.
This has important implications for wildlife photographers. We often find ourselves trying to capture images in areas where there is both bright light and deep shadow. Using JPEG, those shadows will tend to be featureless dark blobs, whereas with Raw we will be able to see the same details that our eyes would see.
Moreover, the greater ability of Raw to capture detail in shadow allows us to apply shadow reduction – a very useful capability that I will talk about in future articles on post-processing.
But perhaps the most striking advantage comes when we shoot images at incorrect exposures. The perfect photographer would never do this, but for the rest of us there will be numerous situations were we have the camera set up for bright daylight only to have a momentary glimpse of a bird – and typically it’s a good one – peeping out of a dark corner.
The higher dynamic range of the Raw format means we can correct a badly underexposed shot in post-processing and end up with a good image.
Consider this example. I deliberately underexposed this shot of an American Goldfinch in my garden. I did this as an experiment, so please ignore the uninteresting composition. The camera took two simultaneous images – one in Raw and one in JPEG Fine.
The images were very dark – I had to increase exposure by about four stops. But the results are clear. The quality of the Raw image is pretty good: there is full feather detail and the colours look right . The JPEG image on the other hand is dreadful. The colour is over-saturated, green blobs have appeared in the breast and belly plumage, and the whole bird looks flat and dull.
If you have read this far, you have probably realized that I am a fan of the Raw format. I believe that in wildlife photography the aim is should be to produce an image that replicates as closely as possible how the creature (bird/animal/plant/butterfly/reptile) looked in the wild. I have found that using Raw format and carefully post-processing the image gives me the best chance of doing that. And there is an element of craftsmanship involved that I find appealing – I prefer to make my own choices rather than having the camera make decisions on my behalf. I am also not worried about file size given that hard drive storage capacity has become increasingly inexpensive.
So is there an argument for using JPEG? The fact remains that some very good images have been created using JPEG. You may well decide that you prefer the simplicity and efficiency of JPEG. If so, I would recommend that you use the lowest compression setting: JPEG Fine. This setting creates a 4:1 compression, so the files are still fairly large, but at 4:1 you will not see any of the artifacts or errors that can creep in at higher compression ratios.
This article was also published in The Blue Bill, the Quarterly Journal of the Kingston Field Naturalists, Volume 67, No 1, March 2020.
If I had to pick a single technique that made a dramatic improvement to my capability as a wildlife photographer, I would choose Back-button Focus. It’s a technique used by professional wildlife and sports photographers, and can help you take your photography to a higher level.
It starts with the recognition that crisp focus is perhaps
the single most important quality of a good photograph.
Because focus is so central to photography, camera manufacturers have developed ways to make it easier to get an in-focus image. Any camera produced in the last 20 years has the ability to focus automatically – indeed autofocus is the default option, and may have to be turned off if you wish to focus manually.
Autofocus is engaged when you press down on the shutter release. This happens so quickly some beginning photographers don’t even realize it is happening, but with practise most people learn that if they depress the shutter release halfway they can focus the camera without taking a picture.
For most types of photography having the autofocus engage when you press the shutter release makes life easier – a single action both focuses the image and releases the shutter. Wildlife photography, though, has its own requirements and many wildlife photographers find that the simple shutter release/autofocus approach actually creates problems.
Instead they use back-button focus, where the autofocus function is disconnected from the shutter release and assigned to a different button.
I am not going to explain how to do this. Each camera system has its own way of assigning buttons, and you will need to consult your manual to learn how to make the change on your camera. Instead, I am going to explain why you might want to make this change.
Targets obscured by foliage
If you have spent any time trying to photograph birds in the wild I am sure you will have had this experience. You are trying to capture an image of a bird roosting in a tree within a tangle of branches, twigs and leaves. You can see the bird clearly, but frustration creeps in because each time you take a shot the camera focuses on a different one of the surrounding twigs and only occasionally on the bird.
For all the capabilities of modern autofocus systems, remember that they are not actually intelligent – they try to guess what you want to focus on but they are frequently wrong.
Using back-button focus can solve this problem. You centre your camera on the bird and engage the focus. You may have to do this a number of times until the focus point is actually on the bird. In cases where there is a lot of background clutter you may even have to use manual focus. But the key point is this: once you are focused on the right point you can shoot as many images as you want without the camera trying to refocus each time. As long as you stay at approximately the same distance from the bird it will remain in focus. The camera will not be able to “help” by randomly changing the focus point.
And even if you have to move slightly to get a better angle, if you engage autofocus again it will most likely zero in on the bird because it will be the closest object to the focus point.
I think you will find that once you try this technique you will be reluctant to go back to shutter release focus. Time that you might have wasted in focusing and refocusing can be spent on adjusting ISO and shutter speed and choosing the right moment to shoot.
Focus and reframe
Wildlife photographers often find that they want the focus point of an image to be off-centre. There are two main situations where this occurs:
Large or close-in target
Say you have a chance to see a Moose at fairly close range. You want to capture the whole beast in an image, without cutting off its tail or legs. But you also want your focus point to be on the eye, as tends to create the most compelling image. And not surprisingly, the Moose’s eye is at one side of the image.
You have a bird in your sights but you want to frame the
image so that the bird is off-centre. You might want to better show its within
its habitat, or to give it some open space in front of it, or just because
people are more attracted to images where the main points of interest are
In these situations back-button focus is your friend. It
allows you to focus on the desired point, and then without changing focus
reframe the image by moving the camera until you get the result you want.
Note that landscape and portrait photographers deal with this need by manually adjusting the camera’s focus point. In principle this would also work for wildlife photographers, but in my experience the focus and reframe method is much more intuitive and much faster to use. For subjects that tend to move suddenly and unpredictably I think it provides better results. Moreover it allows you to set your camera adjusted to centre point focus, which is the most accurate autofocus mode.
For moving targets, such as a bird in flight, holding down the back button allows you to keep it continuously in focus while you wait the right moment to shoot – such as when it banks to show its upper wings. You can also hold focus on a stationary target, and you will be in focus when it pounces, takes off, or otherwise moves suddenly. Without holding focus the camera will need to refocus at the critical moment, with unpredictable results.
In principle you could also accomplish this by holding the
shutter release halfway down, but in the real world of wildlife photography,
where you will often be wearing gloves and your hands may be stiff from the
cold, using a separate button removes the need for such fine motor control.
Of course you could just “spray and pray”, firing off twenty
images at high speed and hoping one of them works. As long as you don’t mind
everyone nearby assuming that you are clueless. 😊
Back-button focus – further advantages
While the above points are the key reasons for adopting
back-button focus, there are a few minor advantages as well:
If you are using manual focus, you won’t then risk spoiling your
own efforts when it’s time to press the shutter release.
Use of back-button focus reduces battery drain somewhat. Unlike
shutter release focus it doesn’t automatically engage the lens’s image
stabilization/vibration reduction motors.
Back-button focus is possible on most DSLRs and mirrorless
cameras, but it may not be possible if you are using a bridge or superzoom
camera. Check your manual to see if you can use this function.
And if you ask someone to take a picture using your camera, don’t expect great results. You can explain carefully the need to press the focus button and then press the shutter release, but I find that most people don’t “get” this and the images tend to be out of focus.
Originally published in The Blue Bill, the journal of the Kingston Field Naturalists, Volume 66, No. 4, December 2019
Freezing the Action – Shutter Speed and Shutter Priority Mode
One of the major challenges of wildlife photography (and sports photography for that matter) is the need to choose a sufficiently fast shutter speed. Like all photographers we need to balance available light, depth of field, metering modes and focus points. But unlike, say, landscape or portrait photographers our subject matter tends to move quickly in unpredictable ways.
If our camera’s shutter speed is fast enough we will be able to “freeze” the action of fast-moving subjects and get a crisp image. So in principle the solution is to always use a fast shutter speed. And there are some circumstances where this approach will work. But much more often we will be engaged in a balancing act, adjusting variables such as shutter speed, aperture, and film speed (ISO) to get a correct exposure.
The Basics of Exposure
In very simple terms the image your camera produces is governed by the amount of light that falls on the sensor. A correctly exposed wildlife image will show the creature or plant in natural light with no areas that are too dark (underexposed) or too bright (overexposed), and will be crisp with no motion-induced blurring. Photo 1 shows an American Pipit, and to my eye the exposure is good – all detail is visible and the bird’s foot is frozen in mid-stride.
Exposure is controlled by three settings: aperture (the amount of light that the lens allows to reach the sensor); shutter speed (the length of time that the sensor is exposed to the light); and film speed or ISO (the sensitivity of the sensor).
Each of these variables has implications that the photographer needs to understand:
As noted above, the primary way to get a crisp exposure of a moving animal (or a plant blowing in the wind) is to use a fast shutter speed. The downside of fast shutter speeds is that less light reaches your camera’s sensor. Shutter speed is expressed in fractions of a second. Each step up in shutter speed (e.g. from 1/250 to 1/500) halves the amount of light available. So except in very bright, sunny conditions faster shutter speeds can lead to underexposed images. To an extent you may be able to fix underexposure in post-processing, but artificially adjusting the exposure by more than a small amount adversely affects the quality of the image.
For stationary subjects you can use a slower than normal shutter speed and hope for the best, but typically the creature will move just as you snap the shutter. Photo 2 is a Coatimundi seen just after dawn. I had to use a slow shutter speed and a high film speed to get the shot. If you look closely you will see that the face is slightly blurry as it moves its head to the side.
So if shutter speed isn’t the whole solution, what else can you do to increase your chances of getting a crisp image?
Wide apertures allow more light in, so in the low-light conditions we are often dealing with a wide aperture seems like a good choice. The more light that passes through the lens, the faster your shutter speed can be. But as you might guess there are no easy solutions here. First, telephoto lenses capable of wide apertures are ruinously expensive. For example the Nikon NIKKOR 300MM ƒ2.8G ED lens, a favourite of professional wildlife photographers, will set you back a cool $6899.99 plus HST. So most of us will be using lenses with narrower apertures, and thus will have less light to play with.
Moreover, the wider the aperture, the shallower the depth of field. For the wildlife photographer, this creates a problem: the image may be correctly exposed but parts of the creature are not in focus. Photo 3, a Pearl Crescent, is correctly exposed. But even at ƒ7.1, a middle of the range aperture, the depth of field is shallow enough that the wing closest to the viewer is not in focus. The tails of birds can also fall prey to depth of field issues. In photo 4 the tail of the Canada Jay is a bit soft-edged, as it was beyond the optimal depth of field.
Film Speed (ISO)
Before the advent of digital cameras, photographers adjusted for low-light or fast-moving subjects by using faster film. So instead of ISO 64 or 100 film they might switch in a roll of ISO 200. This involved a big trade-off in image quality, as faster films producing grainer images. ISO 400 was about the maximum usable speed.
Now we have digital cameras capable of ISO equivalents of up to 51,000 so is the problem solved? Yes and no. Good quality digital cameras can produce very good images at higher ISO ratings, but only to a point. Just as fast film was prone to graininess, digital camera sensors can generate “noise” at higher speeds.
With my camera I can get excellent images at ISO 800, and very good ones up to ISO 1000. Speeds faster than that can work reasonably well depending on what you want the image for. Photo 2, for example, was shot at ISO 2000. The image is reasonably crisp and good enough for a record shot, but if you look above and to the right of the creature’s haunches you will see that the image becomes fuzzy (“noisy”) with some random colour blobs.
So what does it all mean? Simply that there is no single recipe for achieving crisp, properly exposed images of wildlife. While we are in the field we have to make continuous judgments about shutter speed, aperture and film speed to enable us to get the images we want.
Shutter Priority Mode
If you spend too much time thinking about these variables you may end up missing some of the action you went out to photograph. So most wildlife photographers use their camera’s mode system to automate part of this work.
All DSLRs and most bridge cameras have four basic operating modes: Manual, Shutter Priority, Aperture Priority and Program. I want to explain Shutter Priority mode here because I think it is the most useful option for wildlife photographers.
Your camera will have an easily accessible way of selecting this mode – most often by a rotating dial on the upper right side (Photo 5). For most DSLRs rotating the dial to S puts you in shutter priority mode. Eccentrically, Canon and Pentax call it “Tv” for time value, but the effect is the same.
When you are operating in this mode, you can select the film speed and shutter speed you desire and the camera will automatically adjust the aperture within its limits to ensure a correct exposure. If there is not enough light to get a correct exposure at maximum aperture the camera will warn you somehow, often by inactivating the shutter release. Check your manual to see how your own camera works and what adjustments you can make.
You can actually go a step further and automate your choice of film speed as well. Somewhere in the menu system of your camera there will be an option to select “auto ISO”. This is a tempting option for wildlife photography, as it minimizes the chance of a missed shot. However beware of the fact that cameras left to their own devices tend to bump up the film speed to fairly high levels, so if you use this function check your manual to see if you can set an upper limit on auto ISO.
Recommended Shutter Speeds
So the final piece of the shutter speed puzzle is: how fast is fast enough?
In principle, unless forced to by low light I would recommend a minimum shutter speed of 1/500 for wildlife. Birds and mammals, even if they appear stationary, are often flicking their ears or looking around, so it’s best to err on the safe side. I did a quick check of the wildlife photos I am most proud of and almost all were shot at 1/500 or 1/640. There are exceptions, such as the Chestnut-naped Antpitta at photo 6 (1/00 at ƒ5.6) but I was fortunate that the bird held still for a moment.
For frogs, turtles, and perched butterflies and odonates you can often get by with a slower speed, as they can sit still for lengthy periods. But the Snapping Turtle at photo 7 was being aggressive so I needed 1/500 to freeze her.
Birds in Flight
There is a simple rule of thumb here: the fastest shutter speed you can manage is the one to choose. But you can cheat to some extent based on the type of bird and its activity. The Trumpeter Swan has fairly slow wingbeats, so in photo 8 even 1/250 was enough to get a crisp image. The gliding Red-tailed Hawk in photo 9 was shot in bright daylight so I was able to go to 1/3200 and ensure that the image was crisp.
The Greater Prairie Chickens at a lek in photo 10 were tricky. We were shooting at dawn so there was very little light available, and the birds were actively jousting. I found through trial and error that a shutter speed of 1/2000 was enough to freeze the action. To make that work I had to bump the ISO up to 8000. The resulting image is reasonably good.
By the way, don’t even think about trying to photograph butterflies in flight. That way lies madness.
Hummingbird wingbeats are so fast that it is difficult to get a crisp image even in optimal light. Shutter speeds of at least 1/3200 will be needed. And because their wings move in strange ways to allow them to hover, even if you do get a crisp image it will often look rather odd. So unless you can find a perched bird, I find the best approach is to intentionally allow a bit of blur in the wings, which gives the impression of movement. The Western Emerald in photo 11 was shot at 1/320 while hovering. This is about right for the wings, but as you can see the tail is a bit blurred, so a slightly faster speed would have resulted in a better image.
So that’s the bluffers’ guide to shutter speed. if you have mastered the basic operation of your camera and want to dip your toe into more advanced options why not try experimenting with shutter priority?