High Dynamic Range (HDR)

Thursday, October 8, 2012

High Dynamic Range

(HDR)

     I'm going to explain this term simply because I find that many writers overcomplicate things. In the future, I'll get more in depth.

     High Dynamic Range simply means that the brightest to darkest area of a photo are too much for the camera to record.  A low dynamic range  would mean that there isn;t a large difference between the brightest to darkest areas or shades or colours. In this case, the camera can easily record the scene.

   A high dynamic range can result from extremes of sunny areas and shadow areas, extremes of light to dark tones (colours) or a combination of the 2. AS a result, the camera can only do so much in "capturing" all of the details. In photographic terms, he brightest areas of a photo are called highlights, while the dark areas are called shadows. Both of these area need to gave detail that can be seen! Highlights without detail are said to be either "washed out" or "blown out". Shadows without detail simple are said to have no detail or shadow detail.

The Film Era 

 I'll briefly talk about the photo below that I will be using for today's instalment.  In the BDE 

(Before Digital Era - my term), a photographer would either:

1. Have to wait until the sun was lower in the sky and less bright. 

    This would allow the sun to be less bright in proportion to the indoor light intensity. The "range" would thus be less, thus allowing the film to capture all of the detail. By the way, the word  "range" simply means the variations from high to low. If we had 100 people weighing from 100 to 300 pounds, then the range would be 100-300 pounds.

1. Add additional lights (flash) inside 
   
    This would allow the inside light intensity  to be much brighter. As a result the "range" between the brightest and darkest areas would be lower. With regard to the range of a photograph, we talk about f-stops. A photographer would take careful measurement readings of exposure with a light meter, and then add additional lights (flash) into the darker areas to reduce the range of bright to dark areas. Polaroid film would be used to test the final exposure, before "real film" was used.

The Digital Era

Today, with digital cameras and image-editing software such as GIMP (Free) or Photoshop, the photographer can combine several different images of different exposures. The computer and the software will then "compute" the best exposures for detail in all areas, and then process the image.

There are some careful requirements that are needed in order for HDR to work:

1. A tripod is needed to maintain the absolute same camera angle, distance, and focus.

2. A bean bag (counterweight) is needed to keep the tripod solid and avoid any movement from the wind.

3. A self-timer is needed to avoid camera shake.

 4. The same f-stop is needed all of the time in order to main the exact same focus in all of the photos. Different exposures are set by the shutter speeds. 

     The above images are from one of the fine Hawaiian hotels that allowed me to photograph for my portfolio. I should have taken between 6-8 different exposures, but I only took 3! As a result, I lost detail in the highlights. I should have taken a few more underexposed images that would have recorded detail in the highlights.

     What you do see though in all 3 images , is the fact that detail is missing in either the shadows or the highlights, depending on how you took the exposure.

Where to Find HDR in Photoshop 

 I always open the files that I'm Going to use for HDR.

However, you can select the files wherever you have them.

 Here are my 3 Opened FIles in Photoshop

There is an extensive menu to the right of the large photograph in the centre.

The term "EV" stands for "Exposure Value".

An EV of + 1.00 is an overexposure of 1 f-stop.

An EV of - 1.00 is an underexposure of 1 f-stop.

An EV of 0.00 is the "correct exposure"*

* of course the correct exposure is dependent on where the camera meter pointed, and the # of spots that you used to gather the exposure.

I left the settings on the right-handed menu at the "default" settings.

Later, I will show you a screen capture of a personally-adjusted menu.

Press the "OK" button in the lower right-hand corner when you are ready to proceed.

The HDR result with the default settings.

My "customized" and adjusted menu for HDR.

The result.

Much, much better, but there are still things to be done!

Conclusion

    There are many software companies that make HDR software, and you should try them out. Photoshop is excellent, but it's not the only player in town. Since most software programs can be downloaded for a trial basis,why not try them out. 

   The HDR in Photoshop and other programs will help you to dramatically and successfully improve your photography. However, they cannot solve all of the problems in a photograph. 

   In my next post, I'm going to show you how I could improve upon the final HDR image that you see above.

If you have any questions, suggestions, or correction, then by all means please e-mail me.

My address is toysearcher@gmail.com.

Thanks for visiting and

as always, have a fgreat part of the day,

wherever you may be.

Stacey