Ophrys Photography

Wildlife photography by John Devries, Kent UK. Inspirational images from nature.
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Tips and tutorials
Photographing wild birds Part 6

In my earlier tutorials on photographing wild birds I have covered points 1 to 4 in my list of common errors:
1) Subject too distant.
2) Subject not in focus
3) Blur due to subject movement - motion blur
4) Blur due to camera movement
5) Incorrect exposure
6) Little consideration given to lighting or composition

Let's now carry on moving down the list and finding counters to these issues.

5) Incorrect exposure

I should probably start by saying that there is probably no such thing as incorrect exposure, as it depends on what the photographer is trying to portray. In the first image below I exposed for the background at the expense of the subject and in the right hand image I exposed for the subject at the expense of the background. There is no right or wrong here - it is your choice, this is where your skill and artistic interpretation come into play. As it happens in this instance I prefer the left image.

   

Despite what I have just said, what we are trying to achieve in this tutorial is to learn how to get the classic well-exposed shot of a subject without blowing out highlight or shadow detail.

Thanks to the accuracy of current metering systems and the ability of digital cameras to preview a histogram of exposure immediately after taking the shot on the screen on the back of the camera, getting the correct exposure has never been easier than it is today. If my subject allows me the time to do it, I always get the camera set up in advance and take a few test shots to get the exposure right before taking pictures in anger. This is equivalent to a studio photographer in the days of film taking a polaroid test shot before commencing a shoot.

Checking the exposure with the camera histogram

If you don't already use the camera's histogram you should start immediately as it is the key to perfect exposure. It looks a bit daunting at first, but trust me, it is easy really and it will soon become your best friend when it comes to getting your exposure right.

I have already discussed levels and histograms in another tutorial so I won't try and re-invent the wheel by explaining the theory here again. However, in a nutshell, the image is made up of pixels ranging from the darkest tones (to the left of the histogram) through the midtones (in the middle) to the highlights (on the right side). The distribution of the pixels (the shape of the peaks) is entirely dependant on the tonal values of each scene but what you are trying to avoid with your exposure is taking the pixels off the graph at either end of the scale as you will have "clipped" those values and you will have lost them for good. If you set your camera to shoot RAW images you will have far more chance of recovering an image with blown highlights than if you shoot Jpeg.

Under exposed
Well exposed
Over exposed

If your test image is under exposed you will need to dial in some positive exposure compensation and if your highlights are clipped (over exposed) as they are in the image on the right below you need to dial in some negative exposure compensation.

Correct exposure with feather detail retained
Over exposed image with clipped highlights

To avoid digital noise (grain) creeping into your images, it is best to apply sufficient exposure compensation to push the histogram as far to the right of the graph without clipping the peaks. This technique is termed "exposing to the right" and I explain it more fully here.

Metering modes

You have a choice of camera metering modes to use when photographing birds and all are equally valid. There are partial, centre weighted, evaluative (matrix on Nikon) and spot metering to choose from. Your camera handbook will explain all the modes in detail and when to use each type. I don't know why, but I always wanted a camera with spot metering - I think it was because it sounded more professional, but now I have got it I can't recall the last time I actually used it !

Despite all the metering mode choices, I would advise that you try them but adopt just one of the modes and stick to it and learn its strengths and weaknesses. The metering in all of the modes relies on light reflected from the subject rather than the incident light actually falling on it. Therefore they are all fooled under certain subject or background lighting conditions such as when a large area of a tone which is significantly darker or lighter than a midtone is present - think of black crows or white swans as subjects against white snow or very dark trees as backgrounds. These are the extremes and the kind of occasions when you will have to take control and override your camera.You can arrange some still life setups using black and white cloths and subjects of various tones and see how your camera copes under each circumstance

Different photographers have personal preferences but I use evaluative metering most of the time as I find it the most intelligent and it is often the simplest to use in the heat of the moment. Exposure measurement in this mode is based on complex algorithms evaluating the entire scene but is also linked and biased towards the focusing point in use. It tends to get the exposure right most of the time in bright conditions, but you have to understand what it will do in shady situations and adjust accordingly. I will come back to this later in the section on exposure compensation.

Aperture or shutter priority ?

Like many wildlife shooters, I shoot almost exclusively in aperture priority AV mode. That means I choose the aperture and the camera automatically sets the shutterspeed to compensate. I never use programme modes as the camera is taking control of the image away from me and I might as well have bought a point-and-shoot snapshot camera rather than an SLR which is intended to produce art.

I don't tend to use shutter priority TV mode either, not because shutterspeed is unimportant - of course it is, but I know that if I choose to set my lens to its widest aperture I will get the fastest shutterspeed available to me anyway before resorting to changing ISO. Unless I am purposely trying to create motion blur in an image, I look upon shutterspeed as a necessary evil - something that you have to have to stop camera shake and subject motion blur. My creative thoughts are usually aperture-related. e.g. Do I want to blur the background more with a wider aperture, or do I want to get more of the subject in focus by stopping the lens down to a smaller aperture ? I have to still be vigilant to the resultant shutterspeed that my choice of aperture will give me, but I know that if the shutterspeed seems too low at my chosen aperture I am going to have to increase the ISO setting. Some Nikon and a few of the recent Canon cameras have an auto ISO facility which sounds very useful - you set the aperture and shutterspeed and the camera sets the lowest ISO accordingly to achieve the correct exposure. If it can't balance the exposure at the lowest ISO it will try again at the next ISO setting and so on until it can.This has really only become of interest in recent times as the high-ISO noise performance of the latest cameras has become so good.

In shutter priority TV mode where you select the shutterspeed, I find that if the light level drops - such as the sun going behind a cloud, the camera quite frequently is forced to open up the aperture to its fullest in an attempt to balance the exposure and if that is still not wide enough to let in enough light, then it has nowhere else to go and under exposure results. I really don't want this happening when concentrating on photographing birds in flight (BIF) for example.
I have recently read about a solution to the problem when shooting in TV mode on the Canon 1D mk III which could be worth trying for BIF. If the cameras is set to CFn I.8.2 (Safety shift ISO enable) and you input any ISO setting other than the slowest one, then the camera will open up the aperture to balance the shutterspeed as usual, but this time, if it runs out of aperture it will select a lower ISO instead of underexposing the shot. This is pretty clever.

It is similarly theoretically possible to get an overexposed image when a very wide aperture is set in Av mode if the subject is so bright that the camera can't apply a fast enough shutterspeed to balance the exposure. However, with cameras now shooting at up to 1/8000 sec I have never actually come across this problem in the real world.

Manual exposure for birds in flight

I like to use manual exposure (where you set both the aperture and shutterspeed yourself) for situations such as birds in flight (BIF) when the light is fairly constant but the brightness of the background is changing as the bird flies across it. When I was photographing red kites at a feeding station in Wales I found that I was repeatedly getting incorrect exposure as the birds swooped around against the wildly differing background - sky,dark conifers and grass.

As the light was fairly constant and there is only one correct exposure for the bird itself , I knew that if I dialled the correct exposure into the camera manually it would be fixed at that and I could then shoot away regardless of the background and forget about the exposure unless the sun went behind a cloud for example.

But how do we know what exposure setting to manually put into the camera ? The most accurate way would be to carry an incident light meter and take a reading in the same light as your subject. However, assuming you don't have such a thing in your camera bag, what you need to do is look for a midtone area in your scene, take a meter reading from it and set this into your camera. This does depend on accurately judging midtones by eye but you get better with practice. Sunlit grass is approximately a mid-tone, as is a brick wall, a deep blue sky and a grey rock. At the first opportunity check the histogram and apply exposure compensation if necessary.

Exposure compensation required for evaluative metering using a Canon camera

I have to thank the American bird photographer Art Morris for my knowledge on exposure compensation when working in evaluative metering. The table that follows is a summary of information I gleaned from his bulletin 190 published in December 2005 with some tiny tweaks of my own. I have used this ever since and I find it to be pretty much spot-on. Remember this won't work for other exposure modes. I have not tried this method with a Nikon set to Matrix metering so I have no idea if it would work.

You should be working in Av mode and will need to adjust the exposure using the big exposure compensation dial on the back of the camera. The situations described in the chart are when the entire scene in the viewfinder averages out to the tones described. To get a feel of the average tones you can defocus the lens and look at the overall tone of the scene much easier. You will have to use your own judgment as to what a midtone looks like. An 18% grey card is a mid tone and can be purchased cheaply from a photographic supplier. The following block is approximately 18% grey :



Situation
Sunny
Cloud/shade
Mid tone
0
+1/3
Darker than midtone
- 1/3
0
Lighter than midtone
+1/3
+2/3
Much lighter than midtone
0
+1
White
0
+11/3
White-out conditions
0
+2
Bright highlights against midtone
-1/3
0 or +1/3
Bright highlights against darker than midtone
-2/3
0

To simplify the chart even further, you can see that the camera gets the exposure pretty well right all the time in sunny conditions when used in evaluative metering mode. You just have to watch blowing bright highlights a little when shooting a scene with a dark background. If you are shooting in RAW there is sufficient latitude to correct all of these slight exposure errors in the RAW converter. So in sunny conditions you can virtually trust the meter - this is why I like evaluative metering.

In dull or cloudy conditions evaluative metering needs a helping hand when the scene is lighter than a mid tone. Basically, the lighter the scene is, the more light you need to add. In fresh snow, your camera's meter will try to turn it into a nasty midtone grey, so remember to overexpose the camera's reading with the exposure compensation dial. The amount you over-expose will depend on how much snow there is in your image compared to subject.

It may help to remember this with the expression "Add light to white".

Willow tit in snow - 1/400 sec f5.6 +11/3 exposure compensation on a dull day

If a subject suddenly appeared unexpectedly in front of me against snow on a dull day I would quickly dial in + 11/3 of over-exposure in the evaluative (matrix) metering mode. The correct exposure should be pretty close to this and as I shoot RAW, I can fine-tune the exposure in the RAW converter and still get good results.With a little more time, I would take a test image and then look at the camera's histogram. Don't give up in low light levels or if it starts to snow. You can get some very atmospheric shots in falling snow.

Don't forget that a lot of bright highlights on water or very pale sand can reflect nearly as much light as snow and you will need to expose in a similar fashion.

In summary

  1. Shoot in AV mode, shoot in RAW, and use evaluative metering
  2. Trust the meter in sunny conditions but watch out for blown highlights with subjects against dark backgrounds
  3. Add positive exposure compensation in dull conditions if the scene averages to be brighter than a midtone.
  4. Take a test shot if time permits
  5. Check the histogram and make any adjustments
  6. Consider switching to manual exposure with birds in flight and take your exposure from a midtone in the same light as your subject. Check the histogram again and make any adjustments.