HDR – What is it we actually do?


I read with interest a post on Google+ the other day. A gentleman stated. “I’ve started to do more of my work in Lightroom”. Another poster asked, “You mean Tone-Mapping?” The first person replied, “No, I’m extending the Dynamic Range of a single image in Lightroom using the controls” 

So it made me think; Does anyone really understand what it is we do as HDR practitioners? I think not. 

Let’s make one thing clear up front: We are not creating High Dynamic Range images…wait let me say that again…WE ARE NOT CREATING HIGH DYNAMIC RANGE IMAGES. And in case you missed it, we… are…not…creating…high dynamic range… images. We simply aren’t. 

So what is it we are doing? We, hope to capture a scene with a high dynamic range in multiple exposures. We then take those images and compress them to fit in a Standard Dynamic Range medium – that may be Print or Screen Display. 

Our final images are Standard Dynamic Range images (or in many cases that I have seen, actually Low Dynamic Range images). The image only hopes to simulate a High Dynamic Range scene that our eyes saw but our cameras unable to capture in a single image.. 

Our Standard Dynamic Range end products may have as low a dynamic range as 100:1 in the case of prints or as high as 1000:1 in the case of a good quality monitor. The Images we captured may have a range of >1,000 all the way to 100,000:1 or more but we never see that range in our final product it is only simulated.

What we are doing is taking something1,000 inches long, compressing it and fitting it in a 100 inch box. We hope that it is not noticeable the parts we took out to make it fit. 

So really what the person in my first article was doing WAS tone-mapping- Moving a tone from one place to another- He did not extend the dynamic range of his image because you can’t beyond what is possible for that medium. 

We think Tone-Mapping is only part of HDR, but it’s done many times in our images. When a camera takes the signal from the sensor that may be 12 or 14 bit and makes a Jpeg (8-bit), it is tone mapping. 

I think it is important we know what it is we are doing; I think this needed to be said.

One Comment

  1. Martin January 8, 2013 at 7:02 pm #

    Or as I call it when I teach HDR: putting 10 pounds of potatoes into a 5 pound sack.