Friday, July 30, 2010

Hand-held HDR photography

One of the practices for successful HDR photography is to make multiple exposures with the camera mounted on a tripod. I regularly ignore this. Not because of a crafted methodology, but out of laziness.

Except when I set out to shoot landscapes, I’m usually wandering around with my camera around my neck and tripod safely stowed in my car. But that doesn’t stop me from exploiting the advantages of HDR photography when the lighting and my visualization demand it.

I got turned on to hand-held HDR shooting after reading an article months ago by Katrin Eismann. It might have been in Photoshop User … I don’t remember. It was a short article with a few pictures to illustrate her point. What I took away from it is that HDR software is so good today, we can potentially bracket all our pictures and exploit HDR processing whenever we deem appropriate in our post-capture processing. As long as the images reasonably overlap, the software will often take care of the small details that don’t .

I was intrigued, and picked up a copy of Trey Ratcliff’s book, A World in HDR, to learn more about HDR techniques. In his copiously illustrated book, he strongly advocates for mounting the camera on a tripod (which I routinely ignore) and offers specific advice about technically executing the HDR process in the computer using Photomatix software (to which I carefully attend).

My personal workflow

This is my own personal workflow when I shoot HDR. It is idiosyncratic to my own style and personality and in no way do I represent it as a “best practices” methodology. Because I’m basically lazy but pragmatic, I’ll continue to follow it until something better is demonstrated to me.

1. Set the camera to bracket mode. I shoot Canon DSLR’s, so I have 3 frames to work with in auto bracket mode. I push the exposure to 2 stops above and below the middle frame.
2. Take a test shot of the bracketed frames. Check the histograms. Ideally, the middle frame will show a reasonably centered graph, and the two brackets will pile up against the extremes on the right and left sides of the histogram respectively. The overexposed framed will bring all the pixels out of the black left side of the histogram, with a lot of them hitting against the right side of the graph. The underexposed frame will place all (or most of) the pixels away from the blown out whites of the right side of the histogram, and much of the image will be in the darkness of the left side of the graph.
3. If necessary, readjust the exposure settings on the camera to achieve the 3 histograms described in step 2.

With my Canon cameras, when I’ve set the camera to an auto bracket mode and the drive to high speed, all I have to do is keep the shutter button depressed and the camera will take all 3 bracketed exposures in rapid succession.

Here are 3 bracketed shots of roofers at work on top of a house in Georgia in the middle of the summer. If you look carefully you will notice that they didn’t stop to pose for me while I made the 3 exposures. I hand-held the camera as steadily as possible throughout the time it took (less than 1 second) to make the 3 frames. There was some movement, especially by the roofing material caught mid-air being thrown down into a dumpster.

And here is the final HDR image I produced from those 3 shots ...

This is the sequence of steps I use to get the images from the memory card into the Photomatix HDR software.

1. Import (“ingest”) from the memory card to my computer. Copy raw images into my computer as dng files and they are automatically named and organized as instructed. I have everything preset so that images immediately show up in the Library mode of Lightroom for review and selection.
2. I do a quick review of all the images imported and give “one star” to the initial selects. Images in bracketed exposures all receive the same rating.
3. I open the Photomatix software, click on Generate HDR Image, click on the Browse button, and go to the proper folder to select the files to merge into a single HDR image. The software will work directly with dng files.
4. An Options screen will pop up. For the above images I selected Align Source Images by matching features and Attempt to Reduce Ghosting Artifacts for moving objects/people. I set the detection to high.
5. For Raw Conversion Settings I leave white balance as shot. Since my default color space is ProPhoto RGB, that’s what I select.
6. All the other boxes in the Options screen I leave untouched.
7. When I click on OK, the software takes a few seconds and then produces a totally unacceptable image in the HDR Viewer. There is a message next to the image that says the following: The HDR image is in unprocessed state. Standard monitors cannot directly display the large range of information available in an unprocessed HDR image. Processing the HDR image through Tone Mapping will reveal the image details in highlights and shadows.
8. I click on the Tone Mapping button.

The software takes over and in several seconds another screen comes up. This is where the heavy lifting happens. The two tabs on the top left allow a choice between Details Enhancer and Tone Compressor. I check the preview for each, but almost always go with Details Enhancer. In my opinion, it usually provides a better image than Tone Compressor.

Here are the various slider adjustments I made on this screen for the image above.

1. Strength … All the way to 100. I do this for all my HDR images.
2. Color Saturation … The default of 46 is fine for this picture.
3. Luminosity … I move the slider back and forth to see the possibilities. For this image I settled on a value of 6.0.
4. Microcontrast … Moving the slider to 0.4 seemed to work best.
5. Smoothing … Playing with the slider reveals the possibilities. Here a value of -7.5 worked well. 6. White Point … This is not the place to be conservative. I gave it a generous 2.656%
7. Black Point … I played with the slider until settling on 0.132%
8. I left the other sliders alone, as I usually do.
9. Clicking on the Process button creates the final HDR image.

I save the HDR image as a 16bit tif file and then import it into Photoshop CS3 for a few more adjustments. I need to repeat that these steps represent my own preferred workflow. They are idiosyncratic and don’t necessarily constitute a “best practice” but are the steps I comfortably take with almost every HDR image I process. Here they are, with the reasons why I take them.

Once the image opens in Photoshop CS3 (the latest version I own), the first thing I do is open a plug-in called Topaz DeNoise which I conveniently access through the Filter drop down tabs. HDR processing can amplify noise, and this plug-in effectively reduces that. Once I’ve reduced the noise I sharpen the image to recover some of the sharpness that has been lost in the digital process. This is called capture sharpening and I also use a plug-in for this step. My preferred plug-in for sharpening is produced by a company called Pixel Genius and is called Photo Kit Sharpener. The whole thing is automated and I love it.

After I’ve gotten the noise under control and performed capture sharpening, I go to another plug-in called Topaz Adjust to give the image a little more punch. For this shot I used the preset called Photo_Pop in Topaz Adjust.

At this point I’m reasonably happy with what I see on the screen, so I flatten the image and save it as a tif file. Then I import it back into Lightroom 3 for final last touch adjustments.

Here are the final adjustments I made in Lightroom 3 to this particular image
1. Cropping
2. Adjust blacks slider to 21
3. Move brightness slider to +12 and contrast slider to -7
4. Increase the clarity slider to +77
5. Increase luminance noise reduction to +24 (this increases the smoothing of some irregularities in the faces on the roofers)
6. Play with the post-crop vignetting until satisfied

To see more of my HDR images, go to my website and follow the link to my gallery. Or click on the link to my gallery at the top of this Blog. Check out my New Orleans pictures. Many of them were shot as hand-held HDR images.

1 comment:

Dr.Kshitij Shankhdhar said...

i read about HDR photography and am very interested in it and its results.

deciding between d3200 and d5100
major difference is

d3200 does not do auto bracketing (required for HDR), while d5100 does.

but my query is...for the HDR we will be taking 3 after these 3....all shud be static....both camera and view
this is a major problem i to keep camera static without tripod (which i will never use) or how to keep kid/scenery tree/leaves etc static.

incase tripod is dire necessity or its practically difficult to keep kid static for those 3 pics to be takes (this takes 3 seconds).......then whats point in HDR......for a casual photographer.......
its only for professionals who use tripod etc.

whats ur comment

i am involved coz incase hdr is out, my interest in d5100 will reduce.

u may email me ur reply. my email is