Here are two powerful methods to do exposure bracketing: the quick and dirty method and the sniper method.
1. The quick and dirty method
First, set your camera in aperture priority mode and average metering mode, then choose the lowest ISO value possible and display your histogram onscreen. Set your exposure compensation dial value so that half of the values at the left hand of the histogram move towards the centre of the histogram. Now, this is a case-by-case scenario and good judgement. If, by doing that, the whole picture turns completely white, you have gone too far. The main point here is too get details in the dark zones of the picture. Do the same with the opposite end of the histogram. This time around, you don't want the whites to clip, which means that the histogram doesn't touch the right side (the whites are not clipped)... unless there is an intense light source like a light bulb or the sun, for instance. In most cases, two-bracket pictures should do the job but more often than not, I prefer to take a third shot with a balanced histogram. These are only guidelines and, of course, it doesn't apply to all situations.
2. The sniper method -- Extremely useful when shooting HDR panoramas!!
Shooting a panorama means taking several pictures, either vertically or horizontally, of a scene and stitch them together. However, it is very important that you shoot your panorama as if it was a single picture, meaning each picture should be shot with the same shutter speeds as with the other pictures of the panorama so you can have the best results and make the stitching as seamless as possible. But in order to do so, you need to know the exact shutter speeds you need to cover the whole dynamic range of the panorama.
Now, let me say something about the auto exposure bracketing mode in every camera. You can find million of videos on Auto Exposure Bracketing. Every DSLR has the capacity to automatically shoot at different exposures like -3, 0, +3 EV, -1, 0, +1 EV, etc. or more values depending of your camera. All that is well except that I don't recommend using that function because neither you nor your camera know the correct exposure values for your scene. because each scene requires different exposures! It's like spray and pray! I can promise you that you will certainly end up with too few or too many pictures and will lose your time choosing which picture you should use for HDR processing. A professional photographer is a sniper, not a grenade launcher who throws a bunch of grenades in the hope of hitting his target. If you want to be a professional, you have to know exactly what your target is and calculate accordingly. If you want to be a sniper, you have to use the spot metering mode. Therefore, you should take the right amount of pictures, with the maximum of dynamic range, to make your life much easier in post-processing.
Most DSLR cameras have three or four metering modes called differently by many manufacturers (evaluative, average, matrix, partial, center-weighted and spot), but anyway, here is the idea. Depending on the metering mode selected, your camera will evaluate the exposure based on a specific area of the sensor, and that area is determined by the metering mode. Either it covers the full sensor, 50 % of it or 5 % of it, which is the spot metering mode. This is the most precise metering mode because it covers a really tiny area of the sensor which enables to get the right exposure of a small area of the subject. If you are into HDR photography, getting the optimal dynamic range is the first step for best results. The principle is to use the spot metering mode and aim the meter at the brightest and the darkest parts of the picture and make a reading of the shutter speed, but before doing that, make sure to...
1. Set your camera to the lowest ISO value possible (not AUTO).
2. Set the shutter speed to AUTO.
3. Set the exposure compensation to 0.
4. Make sure you select the Spot metering mode.
5. Choose your preferred lens aperture.
6. Never use a polarizer to shoot panoramas!
You are now ready to make the reading of the brightest and darkest parts of your picture. For that step, I will always do it handheld because I can aim easily anywhere I want. Aim the camera at the brightest part and check the shutter speed that your camera gives you. Caveat! If you have a very bright source of light in your scene, it is usually not a good idea to aim the meter right into that source of light because we almost never exposure for the sun or other extreme bright light source. What I do is aim the meter a little bit off the light source so I can catch about 50 % of its intensity. Let's say our speed is 1/250th. Do the same with the darkest part of the whole panorama or a dark part where you really want to have details. Remember that value (let's say 2 seconds). You now have your dynamic range for the whole panorama. Depending on the size of the dynamic range, you may have to take more than two shots for each picture of the panorama. For example, you cannot hope getting a realistic well-blended picture if your dynamic range (in shutter speed values) is 1/4000th and 10 seconds. If you want to end up with a realistic HDR picture, try to within the limit of 8 stops as a dynamic range.
Down below, you'll find a table of all the shutter speeds values and shutter speed stops in bold. If the gap between the slowest and the fastest shutter speed is less than 3 stops, there is no need to do HDR. If the difference is 4 or 5 stops, there is no need to take more than 2 pictures. If the range is 6 or 7 stops, I usually take a third shot at the average speed or sometimes I switch to the average metering mode and take a picture. It's always good to have a third shot which is more balanced than the extremes. If the range is 8 or 9 stops, I usually take two extra shots spread out evenly within the limits of the dynamic range. If the difference is
If your range is 9 stops, I recommend ignoring the speed to exposure for the shadows and start a stop higher. Why? Because the light flood will be too high. 9 stops of difference in dynamic range is starting to be quite high and your final image will look at bit unrealistic since your HDR software will have a hard time dealing with the blown out zones of your picture.
If your range is 10 stops, remove the two last shutter speeds. The light flood will definitely be too high. You have to keep things balanced if you want to end up with a realistic HDR picture. In your HDR software, you can stretch the elastic by playing with all the sliders (highlights, shadows, etc.) but you don’t want to stretch the elastic too much because you’ll introduce either noise or other unwanted artifacts. The whole idea is to try to get the most in camera without relying too much on the digital side of things.
When you have all your pictures, it's time to head to your HDR software. There are a bunch to choose from but this is another entire topic.