The Basics of HDR Photography

Hello…yes, I’m finally back with a new post after my biggest break so far – had a great time in Dalat, Vietnam…got plenty of photos to process and share, look out for that soon…but in this post, I’m gonna talk about a technique that has gained a lot of popularity recently, and one that I used a fair amount on my recent vacation: HDR

Ok, so…what is HDR? HDR stands for High Dynamic Range. It is mainly used for scenes with high contrast in highlights and shadows…lights and darks i.e. scenes with large areas of brightness, and large area of shadow as wel. Unlike the human eye, which can look at such a scene, and manage to gather detail from both the bright and the dark parts of that scene, a camera’s sensor (or film) does not have this ability, it does not have this range, this dynamic range…i.e. its dynamic range is limited. When you take a landscape picture, for example…the sky is bright, the land is dark. If you shoot a normal single photo, you can either expose the land properly, or the sky. If you choose the sky, you will get a nicely exposed sky but the land area will almost definitely be underexposed (too dark)…and likewise, if you expose the land, the sky will be overexposed (too bright) – sure, you can try to get something in between, but then you’d probably end up with neither sky nor land looking too good

Source: Wikipedia

Some people use a graduated neutral density (GND) filter in these situations – a sort of sunglass for the lens (look at the picture on the right?) which effectively cuts out light from a part of the image, (in this case the top) so you expose the land correctly, and the filter cuts out some of the excess light from the sky, allowing both parts of the picture to be exposed correctly. This is a bit of an overly simple explanation of the GND filter, you could do a quick Google for more on that

The other technique to get a correctly exposed image is to use HDR. Ok firstly, HDR is a form of processing…it is not a really a shooting technique…although you need to prepare for the processing while you’re shooting (you’ll see as you read more). Some cameras have HDR modes built in, which do this process for you automatically, in camera…some mobile apps do this too (hence the gaining popularity in HDR photograph) but it’s still a processing technique. How does it work?

Like I said, HDR extends the dynamic range of your digital camera’s sensor…allowing it to grab much more detail from both the highlights and the shadows than normally possible. This allows the image to see a picture much more like the human eye would see it…and as we’re not often used to seeing a picture with the dynamic range close to that of the eye, the results always look pretty cool! In that landscape picture I was talking about, again…if the sky is cloudy, and you expose the land correctly…your overexposed sky would be a flat, boring, dull white…really making a boring image…but if you get both land AND sky exposed right using HDR, your clouds would be given a dark, gloomy look, making your shot much more interesting and dramatic…AND the land is properly exposed too, allowing you to see all the detail in all the scene without compromise

Ok, wait…I was trying to explain how HDR works. I get carried away. HDR works by blending pictures of different exposure values (of the same scene)…fusing them together…into one single image. This means you need to take more than one shot (usually 3 or more) of the same scene…at different exposure settings – one shot at ‘normal exposure’ where (in the landscape example) both the sky and land do not look so great…then another shot which is overexposed, so that the land is nicely exposed with lots of detail…and then another underexposed shot, where the sky is beautifully exposed, with lots of detail too. Use Photoshop or an app I use called Photomatix (which specializes in HDR processing) to fuse these exposures together…and it’ll take the detail from the sky from one shot, the detail from the land from the other shot, merge them with the original shot, and give a very cool output image where everything is nicely exposed, with good detail from all parts. Sounds easy? Yes, it is

Ok, so HDR is a processing technique, BUT…you need to plan for it while you’re shooting. Why? Coz to make an HDR shot, like I said, you need more than one shot of the same scene…you need multiple exposures of the scene, each one shot at different exposure values (different exposure settings). The shooting technique used before you can use the HDR processing technique, the technique to get your multiple exposures is known as exposure bracketing. Most DSLRs (and most other digital cameras these days) have this feature built in. If not, you can do it manually too

When you turn on exposure bracketing, what this does is it takes multiple (usually 3) shots, at different exposures settings, of the same scene. Usually, your camera meters the light in the scene, and takes one shot at what it considers normal exposure…then you shoot again and it takes one more shot which is overexposed by one stop (+1EV)…shoot again and it takes one more shot which is underexposed by one stop (-1EV). This is just an example, of course…you can set it to under/overexpose by half a stop, two stops…it’s up to you…but I’ve found that one stop (+/- 1EV) works fine in most situations. Read your manual and you’ll figure out how to use exposure bracketing (find it under AEB in your camera menu). If your camera does not have this feature, no problem. Just take the first shot…then manually underexpose your shot by one stop or whatever you want (most cameras have this exposure compensation feature)…take the shot…then manually overexpose and repeat

However, be very mindful that your composition has to remain exactly the same for all 3 shots i.e. do NOT move your camera at all until all the exposures are completed. It is highly recommended that you use a tripod when bracketing exposures…if you have the AEB feature, you should be able to fire 3 shots quickly without moving the camera…but if you have to manually under/overexpose while holding your camera, this will definitely change your composition in each of the shots, and will ruin your HDR. Another tip I should tell you about when exposure bracketing is: first autofocus on the subject you want…once you got it focused, switch your lens to manual focus…what this does is, it locks the focus at that point, so when you shoot the second and third shot, your camera does not have to focus again…so all three images will be focused exactly the same, and you will also be able to shoot faster (without focusing between shots)

So once you have your shots (it can be 3 shots, it can be 5, it can be 10…more on that later), what do you do? That’s it from the camera. Upload em to your computer, it’s all processing from here

Like I mentioned above, I use Photomatix Pro to process my HDR photographs. I believe Photoshop works too, but I’m not sure how to use that…I always use Lightroom for my basic editing, and never learned Photoshop CS4/5/6 etc. Lightroom does not have any feature you could use for HDR…although there’s a GND feature which can be very useful if you forgot to bracket exposures for HDR. If you use Photoshop, it can definitely be used for HDR. Google is your friend on this one!

But yeah, once I get my exposures on my computer, I import them to Photomatix. From here, it’s all automatic. Photomatix lines all the images, so that they fuse into one seamlessly (your composition accuracy will really show here), and then combine the exposures. It takes a minute or so to process…and once it’s done, you get a preview. You can adjust how strong the effect is, in this preview…you don’t want to get an overly dramatic effect which can look fake…usually it does a pretty good job at giving a natural-looking image…tweak it a bit, click Process…and save. Done

I earlier mentioned using GND filters for similar effects – however, firstly…they are rather costly, for a good one. Secondly, they only work in some situations…such as landscape, where there’s a flat line between the contrasting tones…i.e. the horizon. In other cases, this filter wouldn’t do such a good job. HDR works in most cases

Ok, before I end, here’s a quick example of a shot (or three) that I took recently – the scene looked perfect for HDR. If blue skies were present behind the building, I would’ve just taken a single shot (in RAW) and tried to increase the detail in the blue when editing in Lightroom…but if these clouds were overexposed, they would’ve been very bland, and been hard to recover when editing…so yeah, definitely HDR. I handheld this shot…a bit tricky from a low angle, not a very steady pose…so I think I was kinda lucky to have got it steady…set my exposure bracket to 0EV, +1EV, -1EV…and fired off the three shots…and here’s what I got, RAW:

This was the ‘normal’ shot – 0EV. If I didn’t shoot HDR, this is what I would’ve ended up with…not bad, but not great, right?

here’s the second one – underexposed by one stop (-1EV) – that really brought out the clouds, but as you can see, very little detail in the building/grounds

and the final shot, overexposed by a stop (+1EV) – this one lit up the building and the grounds…but completely blew out the sky…I gotta admit this one looks the best out of the three as a standalone shot! But no…wait for the next one!

Ok, are you ready for it? After fusing these three RAW files, which looked just like that…using Photomatix Pro…and a bit of tweaking…here’s the result:

here it is: the combined picture, the HDR processed image…dark, dramatic sky, clear and well exposed buildilng/grounds…nothing too overexposed…and hopefully not overdone…there is still quite a bit of shadow in there, which helped keep the image looking natural…if I shot say 8 different shots at different exposure values, the result would’ve had absolutely no shadow, and looked… bad

It’s really easy to get right, really. The ONLY place you could go wrong is if you didn’t shoot all three (or more) exposures composed exactly the same, composition-wise. If you move your camera even a little bit for one of the exposures, when it is blended with the other 3, the features of the images won’t line up, and the result image will have a blurry look with ‘ghosting’ on the edges of objects…not the sharp look you’d be going for. So use a tripod, especially if you’re manually bracketing exposures…or be very, very steady. My example above, and all the HDRs I took on this vacation were handheld…and just one got screwed up! Just didn’t have room to lug my tripod around. But the point to taken from that: one got screwed up. Such a waste. Oh well

Another tip – try to avoid combining too many exposures into one. I find that 3 work just fine. If you’d like, and the scene calls for it, you could try 5 exposures. But more than that, and you’d get a rather fake-looking result, where every single part of the image is perfectly exposed, with too much detail and color…even your own eye would probably not gather all that detail from the scene. So if you’re going for a dramatic but natural look, try to keep it natural…3-5 shots should do it, don’t get carried away

Like I said earlier, many digital cameras these days, especially compacts, have built-in HDR ‘modes’. Mobile apps too (HDR+ Camera for Android is pretty good if you’re interested) These do a fair job…but if you’re really interested in doing good HDR work, I urge you to try this method…doing it manually…fusing it yourself…tweaking it, and getting exactly the output you want. It gives you complete control over the process, and obviously once you get involved in the process itself, your result is much more…well, it’ll be much better…for you, anyway

Alright, that’s about it for this post. I’ll be posting many pictures from my vacation to Dalat soon…including a couple of HDRs that turned out well…I’ll probably update my gallery as well. Thanks for reading! Any comments/questions…you know what to do. Until next time

Technorati Tags: photography, photoshop, lightroom, exposure, hdr, high-dynamic-range, hdr-photography, shutter-speed, iso, aperture, image, pixels

All images used on this post are my own or licensed for sharing

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