Experimenting with HDR

Over the last couple of years I’ve dabbled with HDR but mainly using the default settings in Photomatix Pro 3.0.  I’m wary of the the unreal over-saturated images that find favour with some HDR enthusiasts and so I’ve tried to learn to use it in a more subtle way.  I’ve enlisted the help of David Nightingale’s ‘Practical HDR’ book to provide me with some guidance as I put together my own workflow.  The notes that follow set out my initial approach to such a workflow and doubtlessly I shall be fine tuning them later.

Exposures

I’ve already got a well established approach to generating my in-camera exposures.  I use a Canon and I’ve set the custom mode to automatically bracket the shutter speed on a 3 shot sequence of -2 stops, metered exposure and + 2 stops.  Usually I will make the exposures on a tripod.  If not, I ensure that the +2 stops exposure falls within the 1/focal length rule in order to prevent camera blur and I also use IS to help prevent this.  As this in-camera approach seems to work well for me, I don’t intend to make any changes to it at this stage.

File format

The first change to my approach.  I use Lightroom 3 and I have previously set up Photomatix 3 as an additional external editor – which means that I can select my 3 images in Lightrooom and simply choose Edit In/Photomatix Pro to generate three new TIFF files that automatically open in Photomatix.  However, my research into best HDR practice suggests that I should use RAW files as my sources.  This is slightly more inconvenient as I have to select them in Explorer but it’s worth experimenting to see if I can discern a difference in quality.  (See the comparison below).

Generate HDR options

Unless the image warrants different treatment, I’m going to use the following as my workflow defaults:

  • ‘align source images’ ON, with ‘by correcting horizontal and vertical shifts’
  • ‘attempt to reduce ghosting artifacts’ OFF
  • ‘white balance’ : ‘As Shot’
  • ‘Color primaries HDR image’ : Adobe RGB

Having generated the HDR file, I save it as a .hdr<Radiance RGBE> file so that if I want to tryout several tone mapping variants, I don’t have to repeat the whole generate HDR process.

Tone Mapping using Details Enhancer

Rather than go for the easier to use Tone Compressor I’ve elected to use the Details Enhancer which arguably gives more control although it is often used to generate hyper-real HDR images.

  1. The strength slider needs to be adjusted first.  In my example below, I’ve reduced the strength from the default of 70% down to 50%, I’m hoping to obtain a more photorealistic result.
  2. Saturation – season to taste.
  3. Luminosity/Gamma – changes to the luminosity slider which controls the tonal compression almost always require a related change to the gamma slider.  In my example image I’ve actually reduced the luminosity to -2  and increased the gamma to 1.2 to reflect the nature of the scene.
  4. Light Smoothing – set to ‘high’ in my image which reduces both the haloing and reduced contrast produced by the lower settings.
  5. Microcontrast/gamma – this seems to act like the clarity slider in Lightroom.  I’ve increased it to ‘2’ in my image and then slightly reduced the gamma to 1.15 to lighten the image.
  6. Tone controls have been ignored, white and black points will be set in post production.
  7. Color/Saturation Shadows/Highlights – minor amendments made to each of these.
  8. Micro-smoothing reduces from default of 2 to 1.
  9. Highlights Smoothing – changed from 0 to 15 to make the sky look a little more natural.
  10. I save the file as a 16 bit TIFF and then carry out post-production in Lightroom and/or Photoshop.

As you can see from the three images, (click each one to see it at full size), I’ve not quite achieved my goal of using HDR in a subtle way – well this is a learning log after all!  The Details Compressor image on the right has succeeded in that the shadow areas, particularly on the right hand side, have been opened up and have detail.  The colours within the lower half of the image are reasonably cool and not too over the top.  The sky is the area that has gone awry, much too dark and heavy and not consistent with the lighting on the corrugated fencing.  I suspect the highlights smoothing is at least part of the problem, and of course there is the opportunity to amend the sky in post-production.   I’ll post some more attempts at HDR on another day!

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