Tuesday, February 16, 2010

Photo Tutorial: HDR Photography

HDR Photography done right can be a valuable tool in any photographers arsenal. Unfortunately HDR has more of a reputation as a gimick to create an unrealistic photo that's blown out and over-saturated and pictorial. The nature photographer however can use this trick to penetrate those big blocks of black shadow and bring back a blown out sky in full detail.

A normal photograph captures a range of light starting at a middle grey and moving out to a certain point, anything darker or lighter than that point becomes a blown out white blob or impenetrable black mass. HDR Photography expands that range by taking one overexposed and one underexposed photo along with your original exposure. The result is a photo that can more accurately capture what the eye sees as you stand on a mountain summit, or in a grassy field. The process won't always add anything to a photo and care must be taken to keep the photo from becoming too pictorial.

1) The process begins in the camera by turning on automatic exposure bracketing in the cameras options and making a set of three exposures. Be sure to have the camera mounted on a tripod to keep the camera still between photos (I've improvised using trekking poles, fences, rocks, and sticks in case you don't have a tripod).

2) Once you have your three exposures load them into photoshop.

File > Automate > Merge to HDR


Select your three exposures from the automatic bracketing done in the camera earlier and hit OK.
This part is a bit of a letdown... I had expected some fancy looking product from the HDR merge. Sadly the photo should look pretty much the same as it did in the best exposure of the three. Nothing fancy going on. At this point you can play with the white point as you like but make sure to set the bit depth to 32 bit and hit OK to get to back to the standard photoshop layout.

 A 32 bit image does not have much use unfortunately, but now is a good time to save your file a a high resolution bitmap so you can pick up where you left off or start over if need be. To convert your photo from 32 bit to a more easily manipulated 8-bit, go:

Image > Mode > 8-Bit Channel

Photoshop will want to know how to convert all that extra information that was contained in the high resolution image down into the normal 8-bit format. Up comes with HDR Conversion menu. You can play around but for the purposes of this tutorial change the method to Local Adaptation to see the greatest result.

Now that looks more like the high resolution mess of colorful crap I think of when I think of HDR photography! I crank down the Radius and Threshold to prevent any glowing effects that give the photo a pictorial look. The real trick ends up being in the curves which can be accessed by dropping down the "Toning Curve and Histogram". Add a couple anchor points and try to generally get a gently undulating S Shape. The devil is in the details, and some fine tuining and knowledge of curves will be helpful.
To Finish the photo apply a few adjustments as they are needed, at this point those its just standard photo finishing rules that apply.

Image > Adjustments > Shadows & Highlights - Bring out as many of those shadows and highlights as you like. The more you use this the more artificial the end product will apear.

Image > Adjustments > Hue & Saturation - The image might look a little muddy at this point, gently raising the saturation level will help the image pop a little more. Be careful though, because this is where lots of editors loose their way and turn their images into heaps of unrealistic color.

Image > Adjustments > Levels - Fine tune your image as needed darken it up a little, or lighten it up a little bit. 

Filter > Sharpen > Unsharp Mask - Sharpen up the image as a final step to really make it pop.

Save as a .jpeg format and you are done. I'll compare my image to the original.

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