What is the definition of HDR? Of course we know the acronym stand for High Dynamic Range but what do we mean by that?
To the vast majority HDR is a “Look”. That image looks like HDR. Typically that look is a little out there, a little CGI doesn’t look like a standard photograph and maybe they are not supposed to. That look is very popular amongst HDR fans and photographers or it may be abhorred by others.
But of course just because something has that Look, doesn’t mean it is actually an HDR but to many, as long as it has the look, that makes it one. But that look can be made without standard HDR methods, in fact using many HDR programs on a single standard image or using Post Processing programs such as Topaz Labs Adjust 5 or Nik Color Efex Pro 3 can yield images with that “Look”
Others believe it is all in the technique that is used, if you shoot 3 or more frames at different exposures and then combine them using sophisticated software. That makers it an HDR
But are either of these definitions true? Does either thing actually make them an HDR? Did the scene that was shot have a wide dynamic range? Did that single image we tone mapped have a wide DR?
After all, we first must acknowledge that our final product (Print or screen image) in not truly a High Dynamic Range but merely a compressed representation of what our eye sees…Ohhh wait are they even that? Do they truly represent what our eye sees?
As the eye sees
Which brings us to my definition of HDR. Now you don’t have to agree, that fine in fact I don’t even need to debate it. You should believe what you want to believe. I will simply give my viewpoint.
Now of course there is debate about what constitutes a High Dynamic Range Scene but for my purposes I like to use the contrast ratio of 1000:1 or higher as my threshold of HDR or close to that. That roughly works out to about 10 stops or a 10EV range or better.
Now you may be saying, wait. A lot of us are doing HDR images with just 3 Exposures of +- 2EV or a 4 EV range, even you recommend that. And we think those are HDRs, so how can you say 10EV or better?
Well we must remember that each image we take does not make up just 1 or 2EV. Each image has its own dynamic range. Typical DSL’s have a dynamic Range of 7 to 11 stops. So in our typical example, you have your 0 Image that has 8EV of DR and we add 4 more stops which gives us a range of 12EV.
We do have to consider that every exposure we take will not have the full dynamic range of the camera. The end exposures are limited by both the Noise Floor and the Highlight Ceiling. So some of your exposures especially if you are doing 5 or more may have smaller total DR in those shots. Also one other th9ought to remember is that DR decreases as ISO increases.
The second part of it for me is processing the image, As the Eye Sees. Now our visual memory may not be all that good but that is why I take a moment and don’t constantly shoot during a session. I take a moment not only to sit there and enjoy what may be a magnificent scene. But I take a look around me. How does the ground at my feet appear, how does the sun look right now. The sky the clouds, the tree line and I try to record that into my memory for when I am processing the image later to try my best to bring back in that image, what I saw at that time. Not always easy but I try.
So, that’s my story and I’m sticking to it. It doesn’t have to be yours. That’s why we have Artistic vision and it is different for all of us.
Hope that helps