Tuesday, September 27, 2011

Taking good HDR Pictures

Tips on good HDR pictures

I am copying it to have a good reference

Source : http://www.lightstalking.com/hdr-primer

  1. Always use aperture priority mode.
  2. Always utilize the lowest ISO possible to reduce noise.
  3. Any errors introduced into the work-chain will always run the entire path from the point of introduction.
  4. Reduce or eliminate errors by recognizing common or frequent ones and become cognisant during the workflow.
  5. Perform as much of the “heavy lifting” as possible in the HDR merge/tone-mapping application.  We use Photomatix Pro.

Aperture Priority Mode
Most modern DSLR cameras give the photographer the ability to select several different “priority” modes.  In the holy trinity of camera settings, being ISO, shutter speed and aperture setting (f/stop), if you select aperture priority mode it allows you to specify the f/stop and ISO, and the built in light meter will automatically select the correct shutter speed for you.  If you are in shutter priority mode, you would select ISO and shutter speed, and the built in meter would automatically set the f/stop for you.
I always use aperture priority.  The reason for this is it will create the most crisp and detailed merge possible as each frame, referred to as brackets, will be the identical focus and depth of focus.  If you were to go with shutter priority, each bracket would have a different f/stop and thus a different depth of focus.  This makes for much less clarity in the final merged result.
From here for me, the tricky part is selecting the right f/stop and ISO setting to achieve the result I am going for.  I find that sometimes I have to increase the ISO to get faster shutter speeds to avoid motion blur.  For the style of photography that we do, moving objects like birds and foliage are our biggest nemesis.  I tend to shake my fist at the wind.
Lowest ISO
I always try to use the lowest ISO I possibly can to reduce noise and produce better quality results.  The more noise that is evident in the source files, the more noise you’ll have in your output.  But, as mentioned before, motion is the hardest thing to compensate for with our style of imagery, and therefore we sometimes have to forgo using 100 ISO to offset external lighting and movement issues.
Errors In The Chain
Any time an error is introduced into the work-chain, that error follows forward to the end of the chain; your final result.  This really drives us to be as accurate and careful through each step of the process to avoid or at least vastly reduce these errors.
For example, if I didn’t properly tune my settings during the image capture process and wind caused massive blur in the trees in my picture due to a slow shutter speed, I cannot correct that.  This error will follow through to the bitter end.  These images never make it “live” and end up archived on my long term storage never to be seen again.
Taking this concept further, if during the merge and tone-mapping step I blow out my whites on the histogram, those details are lost forever and cannot be corrected.  What this all comes down to is by the time I am finalizing my image in Photomatix to bring into my final post-processing software, it contains no major errors and has all the dynamic range I want… it just needs some tweaking to really bring it to life.
Reduce or Eliminate Common Mistakes
As I was going through (and continue to) my learning process, I started to notice common mistakes I was making that resulted in sub-standard image quality.  At this point I became aware of these issues and started to look for them before they were introduced into the work-chain.  I can honestly say that our percentage of internet ready images shot up when I started to do this.  You may believe this to be common sense, and I can`t really disagree, but it`s so important I felt it merited discussion.
Heavy Lifting in the Merge
I try to do as much heavy lifting as possible in the merge process.  When the image is loaded into my final post-processing software, no whites or blacks can be blown out, no ghosts can remain, no color banding can exist; these are things that cannot be remedied.
There are many settings, in Photomatix Pro these are represented as sliders, that the photographer can adjust in the tone-mapping phase.  This is a critical phase of image creation.  I have several sliders that almost always remain the same, and several that need to be manually adjusted for each image processed.  I cannot use batch processing, I must merge and tone-map each picture individually.  This is where the personal style comes into play.  Once I identified what I was trying to do with my HDR work, it became a matter of finding those settings that produced these results.
From this point, the final merged and tone-mapped image is saved as a TIFF file and brought into my final phase post-production software.  I only typically perform the following actions in this software, in this order:
  1. Remove any blemishes in the sky, usually perfect, tiny little circles that are darker than their surroundings.
  2. Adjust brightness and contrast, color saturation, and sharpness.
  3. Apply a minor filter that tends to shift the tone scale ever so slightly to a darker tone; I find this accentuates the light and shadow regions in our photos providing a better looking end result.
  4. Apply a high pass sharpen filter to accentuate the details, using a very low threshold setting to avoid over-sharpening.
That`s it.  We have our final image.