High Dynamic Range Images an easy option

posted on 9th of august, 2010

This adapted from an article on HDR found in the "Garden Route Photo" web site, written by Hougaard Malan”

HDR is in no way some miraculous technique to make a mediocre photo an amazing one, neither is it the gateway to becoming a great digital landscape photographer. Post processing will always play a minor role in creating a great photograph but the main effort will always be in the planning and shooting phase.

HDR is popular because a camera can’t always capture the dynamic range of light in one exposure. This results in areas of the image that have no detail due to shadows or highlights. Traditionally we would use graduated neutral density filters to balance the exposure, but they are rather expensive and limited by many situations found in landscapes everywhere, like uneven horizons, tall objects like trees, mountains etc. When digitally blending 2 or more images we are basically simulating an ND filter, but we have full control over how the graduation of the filter would have been.

HDR opens new doors in landscape photography. Moving objects within an image creates a lot of problems for HDR blending, because your images have to be identical.

The basic concept of HDR is to capture the total dynamic range of the scene ( when it is greater than the camera can capture in one exposure ) in multiple exposures and combine select parts of the various exposures using Photoshop.
The first thing we need is the multiple exposures of a scene. In most natural scenes, the sky is brighter than the land/foreground and if you expose for the sky, the foreground is too dark and if you expose for the foreground then the sky is too bright. So we take a separate exposure for each.
The easiest way is to use your camera’s AEB (auto exposure bracketing) function. It allows you to capture a sequence of 3 exposures, each a certain f-value apart. In most situations, you simply need one exposure for the sky and one for the foreground.

If this is the case, meter the sky and foreground separately, check the difference and set the bracketing so that the exposures are that f-value apart so that you get an ideal exposure for each. So if the sky is 2 stops brighter than the foreground, set the bracketing for 0;-2;+2 and expose it for either sky or FG and you will have the 2 necessary exposures in your sequence.
Sometimes however, a nasty highlight or shadow requires a 3rd exposure.
In a short sentence : You need multiple exposures of which the darkest image may have no highlights and the brightest image may have no shadows.

A final shooting tip, use a tripod and ensure you have a common apperture to ensure continuous depth of focus.

Blending a 2 exposure image in Photoshop

1. We start by just opening our 2 images that we are going to blend. RAW adjustments should already have been applied and make sure your layers window is open (F7)

2. Now, stack the exposures ( in this case 2 ) from darkest to brightest by using the move tool (v) and simply dragging the one image onto the other one. Hold shift in as you drop the image and it will align itself within the frame. You have now stacked the 2 layers and you will see the 2 thumbs in your layers window. Clicking on the eye to the left of the top thumb will hide the top layer and reveal the layer below.

3. You can now close the bright exposure as you have it in a layer on the darker one. Maximize the window simply for better viewing. You will be working on a layer mask so that any mistakes can be easily corrected. At the bottom of the layers window there’s a rectangle with a circle in, click on it to add a layer mask (make sure your top layer is selected ) to the top layer.

4. To simulate the graduated filter, we use a gradient on the layer mask. Press G to select your gradient tool. Check at the top of the window for the following (if everything is on default, it will be right )

a. The gradient type must be foreground to background ( top left )
b. Orientation of the gradient must linear ( left )
c. Mode – normal
d. Opacity – 100%

5. Press D to make sure your FG/BG color is on default.
You will now blend the two exposures. Where you click the gradient tool, the gradient will start, you then drag it to where you want the gradient to end. You can drag the line at any angle and the gradient will be in that direction. The gradient starts where you first clicked, transitions over the path you dragged and ends where you released the mouse. The black pixels will reveal what’s on the layer below them. The pure black will reveal everything with the gray pixels resulting in a smooth transition that fades the 2 exposures into each other.

6. You can now touch up the gradient by painting on the mask with a brush. Once you are happy with the blend, you should flatten the image and treat it as one exposure. Doing separate adjustments to the blended layers can sometimes make a nasty unwanted transition between the layers visible.

7.You can now do your usual processing steps to get to the final result

When starting out with this stuff, the most common errors people usually make is simply not having the correct layer or gradient tool or palette colors selected so always double check your tools when something isn’t working as it should!

Comments (9)

Posted by Mikefoto on August 12, 2010
Thanks for the comments, I will post a sequil which allows for more than 2 layers to merge and using filters and high pass filters between the varying layers.
Posted by Ebamo on August 10, 2010
Thanks for the information, very useful! I liked your photos, they are beautiful :-)
Posted by Rosedarc on August 10, 2010
Thank you for taking the time to write such a nice tutorial blog, I have to try as the result is beautiful.
Posted by Egomezta on August 09, 2010
Great blog, thanks for sharing...
Posted by Kk8737 on August 09, 2010
Posted by Cristalloid on August 09, 2010
Thanks for the tips! I'll try it at next time...
Posted by Dmccale on August 09, 2010
thanks for the tips..great photos
Posted by Yuritz on August 09, 2010
thanks for sharing,good tips and nice the way you explained it;great pictures as well :)
Posted by Joe1971 on August 09, 2010
it is very beautiful!!!

Comments (9)

This article has been read 1624 times. 7 readers have found this article useful.
Photo credits: Mike Ehrman.

About me

I used to shoot commercially. Thankfully the bug has never left, I always look for the image in any given scene, enjoying the visual and mental exercise. At present I enjoy shooting small table top set-ups of all kinds using focus and light; outdoor - nature, landscapes and seascapes; food and cooking; and people, where they work, what they do. And then I aim to just have more fun out there!

Great Brak River, ZA

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