[ Originally posted on Facebook 18 August 2015 ]
So I’ve started dabbling a bit in High Dynamic Range (HDR) photography.
You’ve probably already seen plenty of HDR photos without realising it—they’re the ones that seem super-realistic or even outright surreal. For instance, any water photo where the water looks airbrushed is almost certainly an HDR shot, for reasons that we’ll come to presently. The human eye, it seems, views the world in HDR, so the technique can produce shots that resemble more closely what we actually see.
It’s not a particularly new thing, but I only just came across it (via John Dvorak of ‘PC Magazine,’ to whom undying thanks).
Now I’m no photographer, but long ago did on an impulse buy an entry-level Canon DSLR. And have underused it consistently ever since, eschewing the arcana of ISO, shutter speed, f-stops, white balance etc. in favour of the camera’s (admittedly very good) point-and-shoot automatics.
Which till now has worked fine. But having discovered HDR, I find myself eager to learn all about these many variables, mostly because now I have to.
See, HDR uses multiple images which are then merged to create the final photo. I’m sure that good photographers have been doing this for decades, but now digital has made it much, much easier.
What you do is take several shots of the same scene in quick succession with different exposures. This is known as exposure bracketing, and bless ’em, most DSLRs have a feature that will do it for you automatically—called (natch) Automatic Exposure Bracketing, or AEB. (And just in case it sounds like I know what I’m talking about, I’m still very much learning about all this myself. But, aside: it is interesting how quickly you can learn even abstruse technical stuff when there’s a reason to—I remember way back giving my sister Caro a quick intro to processor speeds, RAM size, hard-disk capacity/spin-speeds, other like stuff when she was looking to buy her first computer, and before I knew it she was in the shop authoritatively talking price/performance with the salesman like a seasoned pro . . . )
Anyway, in the simplest HDR you take three exposures—one normal, one under-exposed and one over-exposed. These you then put through software (I’m using Photomatix) that merges the three shots and offers you various preset/manual options of what bits to take from which. If you want to get fancier you can merge five, seven or even nine different exposures (if your camera can take ’em), giving you more options and more potential richness—as well as exponentially greater complexity and more opportunity to screw up the end result.
The attentive will already have spotted one limitation: because the different exposures are taken SEQUENTIALLY, HDR works better with subjects that aren’t moving too much (time-difference between frames = moving stuff moves). Also, unless you’re rock solid you’ll screw up the merge doing it handheld. Which tends to mean using a tripod for stability, at the risk of losing spontaneity.
So for all you inventors out there, first one to figure out how to take multiple exposures CONCURRENTLY wins the big prize . . .
And going back to airbrushed water, any technique that involves taking multiple, sequential shots of fast-moving water will produce a composite that doesn’t freeze the water’s motion at one particular time (I’d always wondered . . . ), although this issue (called ‘ghosting’) is already in part being addressed, and I’m betting will eventually be resolved as computers get quicker and the software cleverer.
The photo above shows what HDR can do, in this case using a 7-frame composite (not mine, I hasten to add): the one on the left is the original shot (it’s also the middle one in the frameset underneath). Not bad in itself, but see how merging in elements from the 6 other frames creates the stunningly detailed image on the right. (Bit garish for my own taste, but you get the, er, picture . . . )
The HDR photos below were all taken from the balcony of my Copenhagen apartment. They are a little crude I admit, but do give an idea of how HDR can add depth, and enhance the display of extremes of darkness and light.
