Camera Exposure Bracketing
So what is exposure bracketing and why do we need to do this? Well we saw in the last tutorial about dynamic range that your camera cannot record the extreme variations in light and dark that your eyes can see. You can click here to read that post.
Where the scene’s brightness is a mixture of extremes – a range from very dark to very bright – then unfortunately this can prove to be too much for your camera to record in one photograph.
Often you will find that the camera has only correctly recorded either the bright or dark parts in the image accurately.
So what can you do about this?
This is where exposure bracketing can be invaluable.
Exposure bracketing is simply where you take a number of shots of a scene (usually three) and record various levels of exposure. Please click here to read my earlier tutorial about exposure compensation (if needed).
one stop under-exposed:
one stop over-exposed:
This will enable you to record sufficient information from the scene to del with the extremes in light and dark and be able to use this information later to create a well balance image. I will explain this process shortly.
How do you record bracketed exposures?
Well you have two options – to do this manually or set the camera to do it automatically.
Firstly you take the normal of the scene you want to record.
Then using the exposure compensation control change this setting to a negative, take a shot. This is so that you are able to record parts of the scene without over-exposing any brighter areas.
Then simply change the exposure compensation to a positive setting and take a final image so that you are revealing image data from the darker areas.
It is important to note that this method will inevitably result in camera movement when you change the settings and this will affect the framing of your image. I strongly recommend to have your camera on a tripod to minimise any movement between shots if you use this method .
Automatic Method (AEB):
Most cameras now have the option of setting automatic exposure bracketing (AEB). You just have to dial in the levels of exposure that you wish (i.e. how much over and under exposure you want in each shot – se below) and then using burst mode on your camera, you take the shots in immediate succession. Your camera will automatically change the exposure compensation settings for you as it records these images as a bracketed sequence.
This is the method that I recommend that you use. Not only is it less fiddly, it will result in much less movement as your camera records these images very quickly. As all cameras are different, I recommend checking the manual or online how to do this for your specific model.
What Exposure settings should I use?
Whilst your camera may allow you to take brackets of 3, 5 or 7 shots, I usually find that if recording in RAW, 3 is usually enough for the dynamic range for most scenes.
The actual amount of under and over-exposure required (number of negative or positive stops of light) will inevitably depend on your particular scene and the levels of light and dark that you are trying to record.
A good starting point is usually 1 stop under and 1 stop over exposure so that your exposure compensation control will look like this:
one stop underexposed:
one stop over exposed:
Then review the images and histograms (click here to see my earlier tutorial on histograms) and decide whether that was too much or too little and adjust accordingly.
The next steps – What to do with your bracketed images?
So now you have three (or more) differing exposures of your scene recorded. What do you do with these? How can you merge them into one well balanced and correctly-exposed image.
Well there are a number of options available to do this, the most commonly used is utilising HDR (High Dynamic Range) software to process them for you. However, personally I don’t like this software or processing as I don’t feel that it provides you with enough control and can often be pretty dramatic in the final images.
I actually prefer to use layer mask techniques in Photoshop to combine just the specific sections of the exposures that I want to specific areas of my image. This provides me with complete accurate control of exactly what parts of each exposure will be revealed.
Layer masking sounds daunting but actually is extremely simple and straightforward. I have created a simple guide in the form of a short ebook. You can obtain my ‘Guide to layer masking in Photoshop’ for free by just signing up to my newsletter on my website here.
In the meantime, I will write a follow-up article about HDR and simple processing and software options in my next tutorial.
I hope you found this article useful and please feel free to pass this onto anyone you think will benefit from it. Please also contact me if you have any questions about this or anyting on my website and I will be happy to answer these.
Many thanks and until next time.