Pro Photography Learning: HDR- High Dynamic Range

Friday, December 16, 2011

HDR

(High Dynamic Range)

You've undoubtedly heard of HDR or High Dynamic Range. What the term means is that in a photo you may have a big difference between the brightest areas (called highlights) and the darkest areas (called shadows). This is most true on a bright sunny day or in a winter scene of a dark brown car on white snow. With film the film simply could not record or capture all of the spread or "range". So some areas of the photos had to be "sacrificed" or lost. If you exposed for the dark brown car, your snow would overexpose and you'd lose any texture to it. If you exposed for the snow, you'r brown car, would turn into a bump, and most likely would not have much detail to recognize it as a car. Flash fill would help a bit in this situation.

Now in the DE (Digital Era), someone came up with an idea. Why not take a minimum of varied or bracketed exposures ranging from at least -1, 1 or +1 (underexposed 1 f-stop, normal exposure, overexposed 1 f-stop), and then "blend them" in an image-editing software (e.g. Photoshop). Well the idea became reality, and now you have this capability.

Of course, there are limitations or restrictions to this marvelous function:

1. You need a tripod

2. The same f-stop is kept, but the exposure changes are done with the shutter speed

3. The scene has to be still, so you need a cable release to avoid any camera shake.

4. Action of any kind won't work as the images will not fit exactly over one another when the HDR process is applied to the exposures.

YThge above are a series of underexposed to normal to overexposed images, with most being underexposed.

The 5 images all Together

Where to Apply the HDR Process in Photoshop

Photoshop asks you which files you want to merge to HDR

Here are the files

Here is the result.

To the right are a set of adjustment sliders

The problem with the above image is that one of my images was out of focus due to camera shake.

As a result, not all of the images fit perfectly over one another.

I removed it, and started over (below) with 4 images.

You need a minimum of 3 images for HDR to work.

Here's the 5-image HDR enlarged.

Notice the blur from the camera shake.

Here are the 4 in-focus images.

Notice the variation in exposures. They're expressed as

"Exposure Values", denoting a change in 1 - shutter speed changes. The EV 1.32 is slightly more than 1 f-stop difference from EV 0.00 which is "NIormal".

This is the blended HDR result.

This is the final image after some minor adjustments.

The image above was "easy" as there wasn't much contrast of subject matter (except for the light fabric and dark red car). Also the lighting was "controlled to present the toy on E-Bay.

Remember, what is the main goal is when we use HDR or when I use 2 lights (main and fill) or 1 light with reflectors ?

It's to be able to get very good detail both in the highlight and shadows, and of course the mid-tones.

Of course, if you want "drama" just shoot an exposure and let the shadows be extreme, or the highlights be too bright.

In the BDE (Before Digital Era) seeing a scene and then taking it would get you more what you wanted if you knew a bit about photography. Nowadays, there are too many adjustments and programs to make your photo show all!

So here below is a more difficult scenario:

1. The subject matter ranges from almost white to almost black.

2. The lighting is harsher than in the previous single red car image.