How do I know if the scene is a good candidate for HDR?
This is a great question and one that is probably rarely asked. Not every scene in front of us is a good candidate and really if the Dynamic Range of the scene before us is not wider than the dynamic range of a standard image out of our cameras, we really shouldn’t use HDR. Not that you can’t but it really has no purpose and will in the end not look better.
So what is an easy way to determine if there is an excess of dynamic range that we need to switch over to using the HDR process?
It’s generally accepted ( and argued) that the Human Eye is capable of seeing a Dynamic range of about 24 f Stops (1 stop is the halving or doubling of light) But that is with the iris adjusting to the light. In one view, the eye is capable of about 10- 14 stops. In theory a high quality camera shot in RAW has a Dynamic range of about 11 stops, but in practice it is really closer to 6-8 stops. A print from that camera is capable of about 5 stops.
But the truth is, I’m not very good at science or math and I don’t want to be pulling out My Texas Instrument calculator or my slide rule and figuring this all out when I am shooting. In fact I really hate even having to think when I shoot. So what is an easy way to determine if the scene before you has enough dynamic range to make it worth the time to set-up and shoot an HDR Image?
We’ll use our meter
Take your camera and set it to manual exposure. Now set the metering mode to either spot or partial. These are the most precise modes for measuring a small area of your viewfinder. Point your focus point (which also is your meter point) on the brightest area of the scene and adjust your exposure so that it registers +2 on your meter. Now move that meter point over the darkest area of the scene. If the meter hits or pegs past the -2 point, there is enough dynamic range to do an HDR. If your meter reads anywhere in between. There is no need to do an HDR.
Now let me give you one important note on here because I don’t want anyone looking into or pointing their camera directly at the sun and damaging either their eyes or their camera or BOTH!! . IF THE SUN IS IN THE FRAME OF THE IMAGE IMAGE, there is more then enough Dynamic Range to shoot, Done, Game over, don’t even need to check.
Here are two examples so you can see what I mean from my backyard.
In this image, the light of the scene was very flat and really not much dynamic range. When I measured as above I only got about 1.5 f stops of change from the brightest area to the darkest
So this would not be a good candidate to shoot HDR.
But I still made one to show you, It doesn’t look better in fact it look flatter than the standard image above
Now the next morning, I had this scene in front of me as the sun rose.
As you can see the Dynamic Range is about 6 Stops ( It’s actually closer to 10 total but we won’t go there for now) and it really doesn’t make a good Standard Image at all. The sky is blown out and shadow areas are too dark and into the noise floor of the image.
Here is a 5 shot HDR of the same scene, as you can see, this one was definitely a candidate for HDR and gave us more of what our eyes would see at that time of morning.
Hope that helps!