HDR - High Dynamic Range explained

HDR – High Dynamic Range

Don’t be scared of the title! I know it looks extremely difficult and technical, it’s really not that hard. As with everything in photography though, it does require a lot of practice! So don’t be disappointed if your first HDRs don’t come out as good as the images of the pro’s out there, you’ll get there, just don’t give up too easily!

HDR stands for High Dynamic Range. You are probably wondering what dynamic range is. Dynamic range is the range of light you, your camera, or monitor is able to see (or display).

Have you ever taken a picture of a sunset, and found that when you reviewed the pic on your (cameras’) monitor, the sky had beautiful color, but everything else (the landscape) was totally blacked out? That’s because normal digital camera’s have much lower dynamic range than our eye. So with a normal photograph you will be able to either: get a correctly exposed sky, or a correctly exposed landscape. This is because there is a lot of contrast between the sky and the landscape.

This is where HDR comes into play. HDR is a technique where you’re able to get more dynamic range with your digital camera. When you look at some of the HDR pictures being made, you’ll notice how everything is correctly exposed; no underexposed shadows, no blown out highlights. Because of this, it will look like there is a lot of detail in the picture. It sometimes is even too perfect, and will look rather surreal, making it look like it was a scene in a computer game.

I’ll use the example of the sunset to explain how it works: Like I said before, on a sunset with a lot of contrast, you’ll get either get: correctly exposed sky, or a correctly exposed landscape. How do we fix this problem? We combine the two pictures!

That is the only thing HDR actually does – it combines pictures of different exposures and merges them into one HDR image, which will result in a picture with a correctly exposed sky and a correctly exposed landscape. Of course, this technique can be applied on more than just landscape photography.

Enough of the blabla, let’s get down to the real fun: get out and make some HDR pictures! Hooo, before you go, let me explain exactly how you get it to work. First some things you need before you start:

  • A camera that lets you change either: shutter speed or exposure compensation (EV). Preferably it should have a mode which locks the Aperture (diafragma), so that your depth of field doesn’t change.
  • Something to stabilize your camera with (preferably a Tripod, but you could use anything else, or even try shooting handheld – this will result into blurry pictures though).
  • dynamic photo HDR or Photomatix – to combine the pictures (free trial on: http://www.hdrsoft.com/download.html)

1. Taking the pictures

So this is what we’ll do: take three pictures with three different exposures. One underexposed for the sky, one normal exposed for everything, one overexposed for the landscape. Make sure your camera is stable during this proces!

If you have a dSLR:

1. Look for a function called “Bracketing�? (Nikon) or “AEB�? (Canon). This will make three pictures after another – one underexposed, one normally exposed, one overexposed. You’re able to set how much it should change per step. I mostly use steps of 1 stop (so, -1 EV, 0 EV, +1 EV).2. Set your camera in Aperture Priority mode (“A�? on Nikon, “Av�? on Canon), so your depth of field won’t change.3. Set your shooting mode to burst (so it’ll continuously take pictures).4. Hold down your shutter button till it has taken three pictures.5. Look if the pictures are correctly exposed (landscape is light enough in one pic, sky is dark enough in another). If not: set your camera to overexpose a little (EV, +/- button, make it like +1, or just try some different values)6. Go to the part where we combine the three pictures.

If you don’t have a dSLR, you might not have this bracketing function. If you don’t, you’ll need to change the exposure manually. You can do this either by:

  • Changing the exposure compensation (EV, +/- button). (easiest)
  • Changing the shutter speed. (bust have a mode that will let you lock the aperture (F number, ie. f8)

Exposure compensation:

1. Take a picture, look if it’s “okay�? exposed (sky is looking quite good, but a little too light, and background is too dark, but not black)2. Set your exposure compensation to -1 EV, take a picture. (underexposed, for the sky)3. Set your exposure compensation to 0 EV, take a picture. (normal exposure)4. Set your exposure compensation to +1 EV, take a picture. (overexposed, for the landscape)5. Look if the pictures are correctly exposed (landscape is light enough in one pic, sky is dark enough in the other). If not: set your camera to overexpose a little (EV, +/- button, make it like +1, or just try some different values)6. Go to the part where we combine the three pictures.

Shutter speed:

1. Look for a mode that will let you lock the aperture (F-number, ie. f8) and will let you change the shutter speed manually.2. Take a picture, look if it’s “okay�? exposed (sky is looking good, but a little too light, and background is too dark, but not black). Let’s say we set our aperture to f8, and our shutter speed is 1/125 seconds.3. Set your shutter speed to 1/250 seconds, take a picture. (underexposed, for the sky)4. Set your shutter speed to 1/125 seconds, take a picture. (normal exposure)5. Set your shutter speed to 1/60 seconds, take a picture (overexposed, for the landscape)6. Look if the pictures are correctly exposed (landscape is light enough in one pic, sky is dark enough in the other). If not: set your camera to overexpose a little (EV, +/- button, make it like +1, or just try some different values) or take longer shutter speeds (in this example, start with 1/60 as your normal exposure, 1/125 under, 1/30 over)7. 7. Go to the part where we combine the three pictures.

2. Combining pictures:

1. Open dynamic photo HDR or Photomatix2. Go to File => Open, and open your three images3. Go to HDRI => Generate HDR4. Check “Use opened images�?, click OK5. Check “Use standard response curve�?, check “Align LDR images before..�?, click OK.

Photomatix will now generate an HDR image. Don’t be scared by the first result, I know it looks terrible!

6. Go to HDRI => Tone Mapping

This is starting to be more like it! From this point on it’s just playing with the different settings. I’ll explain a couple of them:

Strength: controls how much of the HDR effect is applied. Be careful not putting this too high though! A lot of beginners will raise this all the way to 100%, because it looks very extreme, but it will also make the sky look rather grey in comparison to the landscape. I often use a strength of 50-70%, and use Photoshop to give the whole more contrast.

Luminosity: makes the shadows (and the overal pic) brighter. Make this higher if your pic is too dark, lower if it is too light.

Color saturation: Makes the colors come out more (or less).

Smoothing: Controls how much the light between the different parts of the images is smoothed, set this to medium or high. Try playing with this together with luminosity

Microcontrast: Just set this to high.

When you’re happy with the results, click ok, save your image (if you chose 48-bit, you cannot save as JPEG). I almost always edit my picture in Photoshop afterwards to give it more contrast, but that’s up to you!

HDR – High Dynamic Range

3. Some tips:

  • Make sure you turn bracketing OFF when you’re finished shooting HDR pictures.
  • If you have bracketing on, and accidentally have taken a picture, take 2 more and start over.
  • Photomatix preview and result may not be identical, if you’re unhappy with the result, go to HDRI=>Undo Tone Mapping, and tone map again.
  • If your picture looks flat after tone mapping, open it in Photoshop (or another image editing program) and enhance contrast. Save your image as a TIFF file if you’re going to edit afterwards, with JPEG you’ll lose information!
  • If your pictures look blurry, make sure your camera is steady next time!
  • You’re able to get a HDR effect using a single raw image with different exposures too. If you want to know how, let me know.
  • All other rules of photography still apply here, so take care of your composition!
  • Don’t let my post limit your creativity – feel free to expirement!

This was all for now. I am not a pro on HDR yet, but I’m enjoying it a lot and learning along the way! If you have some tips, feel free to leave a comment! Have fun!

taken from here http://www.cre-aid.nl/2006/06/13/hdr-high-dynam...

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