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Dynamic Range, and High Dynamic Range Photography

I know I mentioned in my last post that I'd talk about building a photo from things we can practice with, but I'm actually gonna save that for another post.  The Artist Project is right around the corner (February 19-22 at the Better Living Centre), so I'm going to switch gears to landscape photography!  

Beware!  This post is somewhat long as I've tried to include some teaching points. 

We've all taken pictures, and we've all had that moment where we look at our picture and think, "#&$*@! - that totally didn't look like what I actually saw!"  For example, the sky is the right exposure (brightness), but the foreground is so dark everything is a silhouette, or the foreground is the right exposure, but the sky is not the colourful blue it's supposed to be.  The main culprit here is your camera's dynamic range.

Huh?  Dynamic range?  It sounds complicated, but the concept is pretty simple.  I'm going to explain it in terms of your computer monitor first, then apply the same principle to a camera.  Here's a little grayscale chart that we've all seen before:

DRchart

Your monitor's dynamic range is its ability to see each box as being unique, starting with white on the left, and black on the right.  If your monitor has a limited dynamic range, some of the boxes will look the same (for example, +5 and +4 might look exactly the same, and -4 and -5 might look exactly the same), and that's due to the fact that the monitor just isn't able to display all the levels of brightness between pure white and pure black.  If you're lucky and have a monitor with a large dynamic range, you'll be able to see each box as being distinct.

Now instead of pure white and pure black, let's think of the +5 as being a really bright part of a scene, and the -5 as being a really dark area of the same scene.  Your camera's dynamic range is its ability to show detail across all ranges between the brightest and darkest parts of the scene.  If your camera has a limited dynamic range, you might be able to see the bright areas, but the darker areas will just be black, or you might be able to see the dark areas, but the brighter areas will just appear as white with no detail.  

So why does all this technical mumbo jumbo really matter?  Our eyes have a larger apparent dynamic range than our cameras, and are thus able to see more detail across a scene.  Here's a picture I took of St. Peter's Basilica at sunset:

sunsetdark.jpg

I took this picture with a Nikon D800, which has excellent dynamic range, yet, as you can tell, although the sky is the correct brightness and color, you can barely see any detail in the foreground - it's just too dark.  This definitely isn't what my eyes saw!!  You might be asking, "well, why didn't you change the settings of your camera to make sure the buildings were properly exposed?"  Well, luckily for you, I have that picture as well!  

SPBbright.jpg

Yikes!  Yes, you can now see the bridge and the buildings in the foreground, but that sky is U-G-L-Y, and St. Peter's Basilica looks terrible.

We've all taken pictures that resemble the above two shots, and while software will allow us to bring some of the detail back, it's usually not enough.  So how can we save our pictures!?  Wouldn't it be awesome if we could take the sky, Basilica, and water from the darker picture, and combine it with the buildings from the brighter one?  Indeed it would be awesome, and that's where HDR (high dynamic range) photography comes in.

With HDR, you take at least three shots - usually one that exposes for the darkest area of the scene, one that exposes for the normal parts, and one that exposes for the brightest ones.  This is best done on a tripod as this ensures each picture will perfectly align with the others in the HDR software (misalignment may cause weird artifacts to appear in your final picture).  Once you have these pictures, you can use software (ie Photoshop or HDR dedicated software) to merge them into one properly exposed photo.  Think of the software as taking each individual photo and stacking them one by one on top of another.  It then only chooses the parts from each that are the correct exposure, and then spits out what it considers a properly adjusted photo.  Now the software isn't perfect, and you'll usually need to make some manual corrections in photoshop, but what these programs can do is still incredibly amazing.  

The above photographs are part of the set I used to create the final HDR photo.  Yes, when I travel, I pretty much always carry my tripod with me, because I know I'll need to use HDR to create my photographic art.  It's definitely a bit more of a burden, but it's almost always worth it.  Here's the final HDR of the Basilica shot:

hdr.jpg

Now that's much closer to what the scene looked like in reality!  Amazing what HDR can do for a photo, eh?  That being said, HDR isn't everything - you still need to find a perspective that is appealing, you still need to compose the image well, and you still need good photographic technique.  However, if you've mastered the fundamentals and are looking for other avenues to push your photography further, HDR is definitely a step in that direction =)