HDR 101 – High Dynamic Range Imaging

Written by:

A friend of mine is really into HDR.  This wasn’t something that I was really aware of up until six months ago and because I’m curious by nature I did a little research about what HDR is, what photographs make for a good HDR project and how to go about doing it.  So here’s the 101 version of HDR.  If this is an area you’d like to hear more about please drop me a comment and we’ll get into 200-300 level explanations on HDR.

What is HDR (or HDRI)?  It takes a normally exposed digital image and allows you to enhance it emphasizing the differences in the light and dark areas on the photograph.  Some times HDR is used to improve the look of the photograph so it looks more naturally enhanced.  Other times it is used to create a creative effect that is less like a photograph and more like a piece of digital art.  At its essence HDR is about light – about capturing a shot at different exposure levels and then merging those different shots to get the best of each of the exposure points.  

An analogy about HDR: This is where I personally had the aha, I get it, moment.  You are putting on makeup and you have different grades of makeup you have the full coverage, the light coverage and the stuff you use when you are going out to see people you haven’t seen in ten years and you broke out the night before.  HDR is like using each of those different makeups on your face in different areas so that you are perfectly highlighted with cheek bones and no under eye circles even though you have a baby that isn’t sleeping for more then 3 hours at a time.

Where can you see examples of HDR images?  Check out this Flickr Group with features all HDR images.

How do you get an image suitable for HDR?  There are two schools of thought here.  School one says that you should shoot with the purposes of HDR in mind and you should take pictures of the same subject using a tripod to ensure you are getting the exact same shot at different exposures.   You then use the different exposures of the same shot to merge into a single image creating the HDR.  You could also use AEB (auto exposure bracketing) but that’s for a different post.  School two says you take one picture and using a photo editing tool you alter the exposure of the shot saving the shot at different exposures (lightness/darkness) and you use these photos to create your HDR.

What type of shot makes for a good candidate?  Remember that HDR is about the merger of light and dark so photos that have different areas of lightness and darkness that can be manipulated greatly by exposure are good candidates.  The larger the contrast the larger the impact you can make with your HDR shot.

How do I do it for the first time?  Using your raw photo and an editing tool that allows you to work with RAW formats (check your own program, most of them have this ability) open your photo.  I’m using this SOOC image and Aperture – full admission that I took this photo with the wrong exposure – but I love the idea of it so I wanted to try to use it for HDR to save the shot.
CassJustCurious 2009-01-18 - Version 2 (1)

I create four duplicate versions of my photo at different exposures making sure that I have at least one photo overexposed and one photo underexposed.  This is what I’ve done:
Picture 1

Now you use a tool such as Photomatix (Photoshop does have a plug in for this, as does a few other photo editing tools).  You can download a free trial for experimentation purposes. Here are the results using the tool without doing any additional tone mapping.
Picture 2

So heres the before and the after right next to each other
CassJustCurious 2009-01-18 - Version 2 (1)

Picture 2

It’s an effect that’s for sure and I’m going to be tackling the custom tone mapping function in an upcoming post…that is if you want to see it.  Let me know.

Previous Post:

Comments are closed.