What is HDR

HDR stands for High Dynamic Range and is a way to combine multiple shots with different exposure times, using the bracketing mode of your camera. For best results, you should shoot one photo as normal, and the others, two stops either side, underexposed and overexposed. (EV0, EV -2, EV +2) HDR photography consists of taking bracketed exposures of the same scene, and then combining them to create an image which will have gorgeous details and clarity in both the highlights and shadows.  

The dynamic range in photography is the number of stops between the darkest part of an image where you can still resolve detail, and the lightest part. The problem is, when you’re shooting heavy shadows and bright lights, you are forced into losing detail in one range or the other. With HDR photography, both the foreground and bright background, will be properly exposed resulting in an amazing picture. 

How to shoot and what do you need

Camera - Any camera (preferably a DSLR) with manual mode or AEB (Automatic Exposure Bracketing) will do. If you want to take HDR’s handheld, AEB is a must.
Tripod - A tripod is a must when you want the exact same image multiple times. Movement between shots will mess this up and register exactly the same scene. Also, a tripod can help for a better composition. You can think more about the photo and have more time to setup the shot.
Cable release - Not really necessary, but can help. 
Software - Such as Photomatix Pro to create the HDR from your separate shots.

Shoot in RAW.
This is really important. They contain so much more light information than a jpeg image which allows you to make incredible adjustments to the shadows and highlights. Even if you have overexposed areas, you still can recover them.You don’t have to worry about white balance, you can change it at anytime. 

How many shots do you need.
Use the bracketing function of your camera and shoot in 2 EV steps. Most of the time you are fine with three shots, at -2, 0 and +2 EV. But when you need more brackets, you can go as low as -4EV and sometimes it is still not enough. You can simply check your photos directly on your camera. The brightest photo should have no complete black areas (histogram does not touch the left side) and the darkest should have no overexposed areas (histogram does not touch the right side). 

The scene itself should be as static as possible. Any moving parts (like leaves fluttering in the wind, waves crashing on the beach, or cars or people passing by) won't be the same in each image, causing scene shake in the processed HDR file. Although Photomatix has an option to reduce these ghosting artefacts, it is still best if movements are minimal. 

Taking the shots from a tripod.
After you set up your composition, you need to set up the camera. Turn on AEB and set it so you take shots at -2,0 and +2 EV (or -2,-1,0,+1,+2 if you have a Nikon camera). Switch your camera to AP mode (aperture priority) You do not want to have images with different depths of field. The aperture should be f8 or f11, if you want to have the whole image sharp and in focus. The ISO on your camera should be as low as possible (100-200) if you want to avoid noise in your final HDR. Use the self timer function on the camera or a cable release and take the shots.  
Check your camera manual to find out how to turn on AEB and how to under/over-expose a photo on your camera.

Taking handheld shots.
 If you want to get the same result as taking from a tripod, you have to have the exposure times as short as possible. Turn on AEB and select the self timer function on the camera,  Use a higher ISO. Based on you camera ISO 400-800 is still acceptable. Use a bigger aperture (f5.6) and try to hold the camera as still as possible. Don’t forget, that you can correct noise, but not an out of focus blurry photo. A good practice is to lean on something, or to place your camera on an even surface, hold it down and take the photos using a self timer. Also try to have your slowest exposure time faster than 1/the focal length you are using. So if you use a 50mm lens, the slowest exposure should be not more than 1/50s. This is that your shots should be max 1/50s, 1/200s and 1/800s if you take your photos at +2, 0 and -2.

Once you have your three differently exposed photos, it is time to process them in Photomatix pro.

Photomatix Pro

Open Photomatix Pro and select 'Load Bracketed Photos'. Browse for them and choose OK. The pre-processing window allows you to the following options before processing the image:

Align source images
Choose 'correcting shifts' when you used a tripod and 'matching features' when you shoot handheld. Don’t select that you want to crop. Even when you used a tripod, sometimes you have to select to align by matching features. This can be for instance when there was a lot of wind.

Remove ghosts
If there is something moving in the image, such as a person, water or a tree e this option will tell Photomatix to try and reduce the ‘ghosting’ effect. Always use the first option. It gives you the option to select the areas you want to deghost.

Reduce noise
Select 'underexposed' image only and strength about 100%.

Reduce chromatic aberrations
Turn this on.

In the RAW conversion settings select 'as shot' for the white balance and choose the color profile. 

Select OK. The HDR processing begins..

If you have choose 'remove ghosts' in the pre-processing window, the deghosting popup will open. Follow the 2 steps and select OK.  

Tone mapping in Photomatix pro.

Now you have all your options to tone map your HDR photo. In the left upper corner choose 'Tone Mapping' as process, and 'Details Enhancer' as the method. When your photos are combined, you get your HDR with the default settings. For first time users its good to start from the default settings. When you get more used to Photomatix, you don’t need to reset anymore.

You have the following settings:

Strength – This is the overall effect of the HDR process. The higher the number, the more HDR look. If you compare the photo at strength 0 and strength 100 you see that a lot of detail is added as you go higher. For a more realistic and cleaner look use a setting between 70 and 80. 100 gives it a more unnatural look.

Color saturation – This is the amount of color in the image. The greater the saturation, the more intense the color. For best results stay somewhere between 50 and 70.

Luminosity – Makes the dark parts of your photo lighter. Great for more details. For a more realistic photo, use a smaller number, between 1 and 4. A high setting can make your photo more like a drawing than a photo.

Detail contrast – Using higher values will add more contrast in the details of your photo and also makes the photo darker. Stay between 0 and 8 here.

Lighting adjustments –This affects the overall look. Move the slider to the right to make the image look more natural and to the left to make it look more painterly or surreal. 

More options:

Smooth highlights – Reduces contrast in the highlights. It smoothes out the lighter areas in your photo, making them lighter, less noisy, but can also remove detail. Sometimes helpful for reducing halos around objects placed against bright backgrounds.

White point – Sets the value of the maximum of the tone mapped image. If you have a lot of overexposed areas in you photo, use a lower number, if your photo is to dark use a higher one. Check your histogram when changing this, so you don’t loose any detail because of a high white point.

Black point – Sets the value of the minimum of the tone mapped image. This adds nice contrast to your photo, so it shouldn’t be left at 0. Check the histogram.

Gamma – the overall brightness of the photo. The default value is 1

Temperature – makes your photo cooler or warmer. Moving it to the right will give a more warmer look(red) and moving it to the left a more colder look(blue)

Advanced options:

Micro smoothing – gives the photo a cleaner look and can help a lot to reduce noise, but can also remove details. Keep it around 2 to 6.

Saturation highlights – adjust the color saturation of the highlights.

Saturation shadows – adjust the color saturation of the shadows.

Shadows smoothness – reduces contrast in the shadows.

Shadows clipping – cut out noise in dark areas.

Most of the time, these options can stay at default values.

The biggest effect on a photo are the strength, color saturation and lighting adjustment. If you are satisfied with the settings for your image, select 'process'.

When you are done, save the HDR photo as a full quality 8 or 16-bit TIFF or JPEG.
If there are any problems which need to be fixed in Photoshop or Lightroom, such as sharpening, noise reduction, white balance, save as TIFF.

There is a certain aversion against HDR photos and it depends on the photographer how the final photo looks. Artistic or more realistic. Starting with HDR is easy, creating a good looking HDR photo is quite hard.