Tag Archives: hdr processing

HDR

Blending Time – HDR Photography Part 3

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HDR Photography

  1. Shooting a HDR
  2. Getting it off the Camera
  3. Blending Time
  4. Final Processing
  5. Some Inspiration

Time to Mix Exposures

If you have been following this series, at this point you will have taken some bracketed shots, grouped them together somehow, and then opened Photomatix, and set some options to have your images stacked together. Now we will cover the process of Tone Mapping your image down to 8 bits of information per pixel.

Checking Your Shot

The first thing you need to do is click the Tone Mapping button on the left in Photomatix. This will open the Tone Mapping dialog, with a preview pane to let you see the effect of the changes you are making. Once you have the preview pane available, you should check over it.
The things you need to check for are:

  • Alignment issues (even if you didn’t use the “Align source images” option, still have a quick check)
  • Ghosting issues (black or white “holes” in the image where moving objects appeared)

If you do find some issues, you can either leave them be, and fix them later in the GIMP or Photoshop (whatever your image editing app of choice is) or you can try the blending process again, with some different settings to try and reduce the effect.

Details Enhancer

Now all you need to do is Tone Map your photo, and you are pretty much done. However this is probably the hardest part of the process. There are just sooo many options, which change the results so much. When I first started I had a basic favourite few settings, and I would jiggle the sliders a little on 2-3 options, and that as about it.
After some time of this, and a bunch of rather boring HDR images, I went googling for some inspiration, and came across this set of “presets” from Stuart (whoever Stuart is!) – Stuart’s Photomatix Presets. Now there are quite a lot of presets here, and it has taken me some time to get to grips with them all, but the process I used when I first downloaded them, was to go through, and select each one, and see the result for myself in the preview window. I would then choose the one I thought looked best, and make minor adjustments (usually lower the Colour Saturation, and maybe make it a bit brighter or darker with the White/Black level sliders) and go with that.

Now that I have been using that method for a while, I know what sort of results I can expect from different Presets, so if I know a certain look will work with the image I’m working with, I can go straight to that preset, make some minor adjustments and I am done. I have also created some more Presets of my own. Most of mine are minor adjustments of the downloaded Presets, but they work for me in saving time and effort exploring all those sliders every time.

Tone Compressor

The Tone Compressor method of Tone Mapping is not one I have used very much to be honest… I find I am unable to get a good contrasty image out of it, every time I try I end up with an image with flat colours. It does tend to avoid that nasty halo-ing you get with the more “extreme” Details Enhancer methods though. I used the Tone Compressor method on this Project 52 photo – Project 52 – #1 – It Begins, but as I look back on it now, I do find the colours a little flat. Definately have a play around with this one though, it is far simpler to understand, and if you keep an eye on the Histogram as you make changes you will get a good idea of what each slider does.

HDR

Getting It Off The Camera – HDR Photography Part 2

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HDR Photography

  1. Shooting a HDR
  2. Getting it off the Camera
  3. Blending Time
  4. Final Processing
  5. Some Inspiration

Off The Card

Now that you have been out and shooting bracketed shots, or bracketed panorama shots, you have at least 3 times as many images on your memory card to deal with. These are the steps I go through when I am getting my shots off the camera and doing the initial viewing in Lightroom.

Import

I import from my card reader using Lightroom’s import function. This automatically imports images into my photos folder, under a YYYYYYYY-MM-DD (ie 20102010-01-12) format. You can also ask Lightroom to backup the photos to a 2nd location when importing, very important, and simple to do.

Review

The first thing I do after import, is a quick review of imported images in the Lightroom Library module. I work my way through, viewing every image (only briefly). If I believe a HDR set of 3 (or more) bracketed images is worth processing further, I will select all the images, then I will export each set to its own subfolder, such as “HDR-1″ or “HDR-4″ as a 16-bit TIFF file (you must not use the compression option for your TIFF files, photomatix does not support it). I then stack the selected images (stacking is a lightroom feature) using the Ctrl+G shortcut. This leaves me with a number of subfolders in my working folder, which need to be processed further. (When doing HDR Panoramas I export all the images into a single folder, ie. “HDR-Pano-1″)

Windows Explorer

I will then open up Photomatix on my main monitor (I have a dual monitor setup, with a decent 24″ Dell and an old 17″ LCD) and Windows Explorer on my 2nd smaller monitor. At this point I will navigate to my first HDR subfolder, select the images I wish to blend in Photomatix, and simply drag and drop them from my Explorer window onto Photomatix.

Photomatix

After dropping some files onto Photomatix, a small dialog asking what you want to do with the images will be displayed. If you wish to just blend them together (as opposed to HDR) then select that, otherwise you will want to choose “Generate an HDR image”. You then need to confirm the selected images. Photomatix will then ask you to select some settings to use to generate your HDR.

Generate HDR Settings

  • Align source images – If you were not using a tripod, you should check this box. I usually use the “By matching features” method, but if that does not work, then you should also try the “By correcting horizontal and vertical shifts” method.
  • Reduce chromatic abberations – I always leave this checked, as the HDR process enhances any CA in the shot
  • Reduce noise – I always leave this one checked too, again because the HDR process enhances any noise in the shot.
  • Attempt to reduce ghosting artifacts – If you have some people/cars/boats in your image which move between the seperate shots, you can try using this option to have Photomatix attempt to remove them, however it doesnt always work. If you find it results in black or white sections of the image (obvious blending errors where the moving objects were), you should start again and not select this option, you can always fix it in the final image. For this one I usually try the “Moving objects/people” option, because thats what I’m trying to remove. If you have a tree which blows about in the wind between shots, use the “Background movements” option.

Now you are ready to click OK. Photomatix will take a few moments, then display you a rather strange looking version of your image, ready to be Tone Mapped. If you notice anything wrong with the image at this point, such as the black/white sections from ghosting or misalignment of the images, you should close, and start the process again here.

I will leave it there for today, in the next post I will cover the Tone Mapping process.

HDR

How to Take a HDR Photo – HDR Photography Part 1

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I have had a few people asking me what my process or method for processing HDR images is over the last few days, so here is a detailed run down of how I shoot, process, blend and publish my HDR images. I will split this up into a number of shorter posts, but I will try to get through all the steps as quickly as I can over the next few days.

HDR Photography

  1. Shooting a HDR
  2. Getting it off the Camera
  3. Blending Time
  4. Final Processing
  5. Some Inspiration

Shooting a HDR Image

HDR stands for High Dynamic Range, and a HDR image is an image where the range of brightness displayed in that single image is more than you would normally get from a single photo. In a HDR image you are compressing really bright stuff, and really dark stuff into a more evenly lit image. By doing so you can make out the detail in the darker areas, and the detail in the bright areas, where normally, you would just see black, or white sections.

There are 2 main ways of shooting a HDR image. The first is to shoot a single frame, and have it saved as a RAW file (RAW files contain a wider range of brightness information for each pixel than a JPEG file). You can then compress the wide range of brightness in that file down into a HDR image. I rarely use this method, as I always shoot RAW anyway, and only use HDR when there is need to capture a wider range of information than a single RAW can capture.

The 2nd method is to shoot multiple frames of the same scene at different exposures, which is called “Bracketing”. Most new digital cameras give you the ability to shoot in a bracketing mode. When shooting in this mode, the camera will take 3 (or more) images at varying exposures. By doing so, you are able to capture the detail in the image over a much wider range of brightness. When you blend these 3 (or more) exposures together, you end up with a HDR image. This is the method I use for shooting my HDR images.

Bracketing Shots

If your camera gives you the option to shoot in Bracketing mode, it will often allow you to select the spacing between the exposures of each image. With my Pentax K200D camera, I am able to adjust the exposure brackets from 0.3 EV spacing, up to 2.0 EV spacing, in 1/3 EV steps (0.3, 0.7, 1.0 etc). Most people seem to recommend shooting your brackets at +/- 2.0 EV. This gives a good range of exposure, without going too far apart in your images. When shooting your brackets, it is very helpful to use a tripod. This will prevent any problems in blending the final image due to misalignment of the images, but it also helps to prevent camera shake causing blurry shots, especially for the +2.0 EV shot, as the shutter speed for this shot will be quite slow.

Other Settings

Most of my HDR shots are of buildings/landscapes and other things which do not move and require a large Depth of Field. So when shooting this type of scene I recommend shooting in Aperture Priority mode on your camera, with the aperture set to around f13 or even f16 (where possible, see 2 paragraphs down for why it might not be). Shooting in Av (aperture priority) will give the best control over your depth of field, using aperture priority mode when bracketing means that the camera will only adjust the shutter speed for your brackets. By locking the aperture down, it means the depth of field remains constant throughout the bracketed images.

It is also possible to use Shutter Priority mode for shooting your HDR, however this means the camera will adjust the aperture +/- 2.0 EV stops for each bracket, giving you varying depth of field, which may result in some parts of the scene being out of focus for the +2.0 EV image (where the aperture will be the widest).

A lot of my HDR’s are in poor light, so I almost always use ISO 100 with longer exposures to ensure the least possible amount of noise. Something to watch out for though is the 30″ (second) maximum shutter time limit on most DSLRs. If you’re 0.0 EV image requires a shutter speed of anything greater than 2 stops less than 30 seconds (7.5″ is 2 stops less than 30″) it means that your +2.0 EV shot will not be a full 2 stops brighter. For this reason I try to adjust the ISO and aperture until I am able to get the 0.0 EV shot down to at least a 10″ shutter speed. By ensuring I have at least 1.7 stops of headroom in shutter speed I am able to use the longer shutter speed shot to get the details out of the darkest areas in the image.

Extra Dynamic Range
n some cases (not very often though) a +/- 2.0 EV bracket does not give enough range in light, and you still have blown out highlights, or blacked out shadows. Some cameras allow you to specify a wider range for bracketing, but my camera does not. So a little trick I have learnt is to use the exposure compensation (or exposure bias) to help fill those ranges. What I do is set the exposure compensation to -2.0 EV, and then shoot a 3 image bracket at +/- 2.0 EV. This results in shots at -4.0 EV, -2.0 EV and 0.0 EV. Then I quickly reset the exposure compensation to +2.0 EV and shoot another 3 image bracket. So in total I have a -4.0 EV, -2.0 EV, 2x 0.0 EV, +2.0 EV and +4.0 EV images. When processing, I simply discard 1 of the 0.0 EV images and blend away.

I hope this helps you get your HDR shot. In the next post I will cover my workflow for processing HDR’s up to the tone mapping stage.

Landscapes, Pentax DA 18-55 AL II, Pentax K200D

Australia Day Sunrise

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Happy Australia Day to all the Australians :)

This shot is from a few moments before sunrise yesterday morning (Australia Day, 26th Jan 2010) from the Mt Cootha Lookout in Brisbane. The Brisbane CBD and surrounding suburbs are visible in the shot.

The shot was taken using my Pentax K200D, Pentax DA 18-55 AL II, Slik 500DX Pro tripod and Kenko CPL filter. It is a HDR shot blended from 5 images, taken at -4, -2, 0, +2, +4 EV steps using Photomatix 3.1 and Tone Mapped using the Details Enhancer. I outline how I did this below.

Shots used were all at 18mm, ISO 100 and f13. Shutter speeds were 1/20sec, 1/80sec, 1/5sec, 0.8sec, 3.0sec

Shooting and Processing as follows:

  1. Shot in Pentax RAW (PEF)
  2. Set Exposure Compensation to -2.0 EV
  3. Shot 3 bracketed shots at +/- 2.0 EV (giving -4, -2 and 0 EV shots)
  4. Set Exposure Compensation to +2.0 EV
  5. Shot 3 bracketed shots at +/- 2.0 EV (giving +4, +2 and 0 EV shots)
  6. Imported into Lightroom 2.5
  7. Applied the settings shown below to all 6 images (the first image)
  8. Exported all 6 images to full quality JPG
  9. Deleted the worst of the 2 0 EV shots (this is only 5 images remember!)
  10. Blended the remaining 5 images in Photomatix
  11. Tone Mapped in Details Enhancer using the settings show below
  12. Saved as JPG
  13. Imported HDR JPG into Lightroom 2.5
  14. Applied the settings shown below in Lightroom (last image)
  15. Exported to JPG for Web