high definition ranging at home

Since some folks have asked how I go about generating the wild images I post from time to time, here is the general break-down.

What You Need:

– A camera capable of capturing images in RAW image format. Think of RAW as the "negative" your digital camera takes, and the JPG you are used to as the print Wal-Mart hands you back after you take in your film – the former generally has a lot more detail, clarity, and information on it, and that holds true in the digital world too.
– Image-editing software that can handle RAW files and adjust their exposures. I use Digital Photo Professional (DPP) because it came with my Canon.
– Alternatively, you can use a tripod and a camera capable of exposure bracketing. You can do this manually, of course, but unless your subject is sitting very still, it is generally better to have a camera that can take 3-5 shots as fast as its shutter can move. The tripod is necessary to keep the images perfectly aligned, though clouds will still probably shift. Just remember whether your camera starts at the top of the exposure scale or the bottom.
Luminance, formerly known as "Qtpfsgui". There are other options out there, but this one is free, and constantly updated.

What You Need to Do:

1. Take some pictures. I am not going to help you with this part, as I have no formal training of any type, but one of the keys to making HDR really pop is finding scenes that have a high degree of contrast. Play with shadow and light, clouds, light sources, etc. But, whatever you do, make sure you either use your tripod or take the pictures in RAW.

2. Sort out the chaff. HDRing images is a time-consuming process, and you do not want to waste that time on an image that you do not like. Thankfully, Picasa can view RAW files straight, and that will give you some idea of what the end result will look like (its tonemapping is remarkably conservative, and understandably tends towards "realistic").

canondppbrightnessadjustment3. (This part is only applicable if you use RAW.) Load up your RAW image in whatever program you are using, and figure out how to push the exposure around. I have a screenshot of what it looks like in the Canon software to the right (you want the "Brightness adjustment" slider). In my experience, three images are usable, but five give a better output, so I drag that slider over to "-2", export the file (CTRL+D in DPP) to a 16-bit TIFF (a lossless image format), and save it as "filename-2.tif", then "-1", "0", "1", and "2".

luminancenewhdr4. Boot up Luminance, and start a new HDR. It asks you to open the files you will be using to generate the HDR, so feed all of the TIFs or JPGs or whatnot you are using for this image into the system, and then click through each one notating what its exposure setting is (this is why I save that number in their filename). If you used exposure bracketing, it might be worth using one of the alignment functions on the screen where you set exposures; my experience with a previous version of this software indicated the aligning did not work well, but I have not done bracketing in a while. Click "Next" and "Finish" until you get to the main window of the program (I have not messed with those settings much).

luminancemainscreen5. You are now faced with the "straight" form of your HDR – untonemapped, and while the data is technically what your eye saw when you took the picture, it probably does not look right (mostly because monitors suck at reproducing reality, but that is another post that I probably will not write). Now comes playtime. On the left of the screen, you will see a drop-down menu at the top with folks’ names being its options – those are the tonemap algorithms that you can apply to your image. Alternatively, on the right, you have mini-previews of what all of those functions will do to your image in their basic settings. However, each tonemap has anywhere between one and five slider bars that allow you to tweak the various aspects of what they do. So fool around and find out!

6. My "post-apocalyptic" imagery is generally created through the use of the Mantiuk ’06 algorithm, with contrast equalization on, contrast set to 0.1 or 0.001 (depending on how badly I want to push it), saturation at 0.75 (gives it that washed-out feeling), and detail at 1.0 to 5.0 depending on taste.

7. Render small to begin with – the processing takes time, and the smaller the file, the more options you can fool around with faster. To do a full 2592 x 3888 image takes about 30-120 seconds of background crunching on my three-year-old-but-cutting-edge-at-the-time box. However, some tonemaps do not scale up – what you see on the thumbnail may not be representative of what you get in the bigger image. No idea why.

8. Save your tonemap in your favorite low-definition range file format (probably JPG or PNG), and then save your HDR as a *.HDR (seems the most-widely accepted). Luminance uses tabs at the top of the main working window, and does not seem to overwrite itself… ever, so you do not need to worry about that. It does, however, hog RAM like a monster, and you should only do one image at a time, with reboots of the program periodically (again, it is free, and you get what you pay for).

9. Post-post-process as you see fit. I find that running the tonemapped HDRs through Picasa’s "I’m Feeling Lucky" makes the image pop even more, you might like Photoshop, or they might be fine as-is.

Addendum: Luminance’s onboard help file is actually rather comprehensive, it is just not reproduced online. Any questions I did not answer here are probably solved there.

And that is about it. I promise it is a lot easier than it looks – the only significant element is time. Well, apart from actually getting out there and finding some decent pictures to take, of course… Most of the "difficulty" just comes from figuring out what the sliders do for the tonemapping algorithms, and then finding a setting or group of settings that you like. Feel free to sound off with any questions you might have, and I will do what I can to answer them.

(Luminance screenshots borrowed from Luminance’s webpage.)

2 thoughts on “high definition ranging at home”

  1. And if your camera doesn’t do exposure bracketing (mine doesn’t… my next one will), it’s probably best to change only the shutter speed, not the aperture, when taking the various exposures. Changing the aperture would affect the depth of field. And I’d guess that manual focus or some sort of focus lock would be best, so the camera doesn’t try to refocus on every shot.

  2. True – I forgot to mention that not all cameras come with full-manual modes, and if you screw around with the exposure, other things might/will change.

    On the other hand, never buy a camera that does not have a full-manual mode, unless you want a cheapie you are not afraid of losing/damaging :).

Comments are closed.