Getting more into HDR

I have been experimenting with sets of five bracketed photos as input into the HDRi process. Both Dynamic Photo and Picturenaut  accept several photo imports, but Picturenaut kept stopping unexpectedly on me once I use 5 input files. Well until I downloaded the latest version! The artist was working in the shade, at the MGA Masterpiece in a Day event, and it was the middle of a sunny day. A recipe for bleached out highlights and muddy shadows. My steps of ±0.5 Ev are not large, but I have found that it is enough to get the detail in the shadows and reasonable lighting in the sunlit path. The best part is it can be done without that stretched out post-pocessing posterized over saturated look, so common in HDR work these days, Even when I used the Dynamic Photo's Eye Catching tone mapping. Could I have achieved this with 3 exposures and bigger EV steps? I doubt it.

Returning to HDRi

The very lightest and darkest parts of an image can often be difficult for a digital camera to capture. Especially if the scene has strong contrast in the lighting, or perhaps looking directly at the sun. The technical reason is that most digital cameras only have a limited dynamic range (the way in which it captures the lightest value to the darkest). When the scene has a wider range of lighting the camera light meter is forced to select the range that it will best try to expose. If it choose to expose for the shadow (as you have pointed the camera there) the lightest parts get over exposed. Point at the darkest areas will leave the shadows dark and without detail.

 

	This series was taken using Bracketing with 0.5 steps in EV

The first way to overcome the dynamic range limitation of your camera is to take a series or bracketted exposure setting (ie with different EV values) Like the set above and hope that at least one of them will turn out Ok! Trouble is the image with the best sky has the land mass in detail-less shadow and the one showing detail of the beach has the sky bleached out.

The technique know as HDRi (which I have mentioned before) lets you combine each of these separate exposures and make up a new image that contains the detail from the extended tonal range. In this case I have used Dynamic Photo and tone mapping to match the range of the human eye. And now I have a photo that looks like the scene I was trying to take.

and (almost gone again)

Last night there was a big storm front that swept in at dusk bringing lightening and thunder, and something that wasn’t immediately apparent till morning, a massive dust storm. Everything as and orange red. I went to echo point to see how the view was affected! What view? Although the three sisters where visible, the dust made it hard to distinguish and my camera light meter just gave me a very flat grey mistiness. Using 0.5 EV bracketing, and five steps, did give bit of detail in the overexposure exposures but nothing exciting.

So I tried post processing with Dynamic Photo, to combine these bracketed images and extend the dynamic range. The Human eye tone mapping gave be a decent result very similar to what I saw, restricted visibility but an orange glow.

This is yet another example when in doubt about exposure to bracket and take a series
PS: As I was walking back from taking this series the gusts of wind were so ferocious that I saw a small Japanese tourist sweep off her feet and blown across the Echo Point forecourt like a tumble weed. Lots of laughter suggested no damage done, except maybe to her pride.

HDR revisited, and a newbie

I was testing out my new lens (the replacement for a favorite that had an unfortunate accident) in the local rainforest. I was using it at a decent wide angle (32mm, that’s about 48mm equivalent in old-school 35mm jargon) and decided to take a EV bracketed set for some HDR post processing, even though I didn’t have a tripod.

I was happy with the original image, and below are the ±1.5 EV photo also taken at the same time. The exposures weren’t so long but with the mirror movement between shots it was long enough to guarantee that I might move and my photos would be out of registration. To complicate things there was a reasonable breeze moving the ferns.

Since my chief bug-bear with currently available HDRi software is image registration, this is the prefect set to test out the new Picturenaut program, which is self promoted  as a new breed of HDR tools. It is free to download, small and compact, fast and easy to use. Just running with all the default settings I got the expected poorly registered result.
Then I tried the the Automatic image alignment check box, and the results where not bad, still some poor registration as you move away from the center but still a much better result that most other software will do with the same image set. I think I keep Picturenaut around for some more testing! Which is a big deal for me at the moment because I am becoming more and more in favor of doing less post processing or other fiddling about on my images. By the way it has one limitation that may discouraged the die-hard digital photographers, is it does not currently have support for raw image formats.

My favored HDRi tool is still dynamic photo. Whilst I did have to do a lot of manual adjustment and pin adding rather that rely on auto registration, (and it did not do as good a job as Picturenaut on this example) I think the result with thw extra manual work is crisper and does give a more even rendering of the tone mappings, closer to what I believe I saw.

HDR Jakarta Sunset

HDRi Jakarta Sunset, originally uploaded by imageo.

The bracketted set of photos, used to create this HDRi image, were taken without a tripod and with long exposures. So without dynamic photo's pinwarping this would have just been a triple exposure blur-out.

HDR sunset

HDR sunset, originally uploaded by imageo.

This is all about colour & composition, the patterns of the silhouetted branches and intense colour on the clouds behind. HDRi image created with Dynamic Photo, using smooth compressor tone mapping.

Understanding HDR (High Dynamic Range)

You may have notice I have been playing a lot with the HDR (High Dynamic Range) technique later. I offer no excuse, I am playing, I just need to figure out how it works and how I might be able to use it. So here is my simple explanation of the general process. Note I am using FDRTools in this example because it is easier to show what is going on (I already prefer dynamic photo, see my previous post why)

1. Step 1, Take a set of bracketed photos, (three is a good number but you can take more) at different EV exposures.
2. Step 2, Load those photos into software that can analyse the exposure range of each photo, it is normally necessary to align the individual photos, if you use a tripod this will not be necessary. I actually rested the camera on a wall to keep it steady so i have jumped over this step.
3. Step 3 now create a virtual photo space with a wider range of exposure range, using a composite of all intensity recorded (ie the darks from the darkest photos, tone range from the normal exposure and detail in the light from the lightest photo). the display in FDRtool shows this nicely, you can see histograms of the exposure intensity beside each photo. At the top of tjos display you can also see the expanded range of tones in the "virtual" composite space is usually called the HDR image
4. Step4, you finally need to tone map the virtual exposure space into the dynamic range that your output device can handle. Yes computer display and even printers have a limited range that they can display compared with what the human eye is capable of seeing. i FDRTools the main control is the silders under the histogram, moving the left hand slider sets that tone to the darkest setting (in simple terms the blackest part of the photo)  and moving the right hand slider sets the lighten tone (in simple terms whitest part). there are also sliders for gamma (which i ;like to think of as colour contrast) and saturation (intesity of colour).

Providing you don't go overboard with the gamma and saturation sliders (if you do, you might get pretty radical over coloured images) to should end up with an photo to looks much closer to what you saw when you took the photo, compared with any of the actual exposures (compare the image above with any or all of the three original photos at the top of this post).

Enjoying the warmth of the sunset

It is really clear to me that the HDR techniques (performed here with Dynamic Photo) are ideal for taking "better" (in that they will look more closely like the lighting at the time) in low light, especially at sunrise and sunset, and the half light of artificially lights. In this example I took just three photos using the bracketing feature on my camera at 0.5 EV intervals (shown above).

I also used tone adjustment (via Windows Live Photo Gallery) to "stretch" inner section of the exposure captured in the center image above(the no EV adjusted image) as a comparison. The image is still a striking sunset, but harsh, it has as very strong contrast and the colours slightly shifted, not as warm or natural.