How To Make HDR Images In Photoshop

We recently featured a gallery of photos which included a selection of the best HDR images. High Dynamic Range Imaging or HDR is a technique which allows for a far greater dynamic range of exposures than normal digital imaging techniques. This can be achieved by modifying a set of photos with Photoshop using the Merge HDR function.

This technique may seem a little advanced for novice users but with a little patience, even a beginner has hope of creating a master piece HDR image.

So first off, you will need to take your pictures. The idea is to take a photo of the same scene several times with different exposures.

If you’re new to world of manual exposure then don’t worry, follow the main steps and you should still end up with a nice looking image. People with knowledge of manual exposure settings will be able to better produce the specific image tone that they require.

If possible set your camera so that it shoots your photos in RAW format. This will capture more dynamic range data than a JPEG file and it also gives a great deal of temperature latitude.

You should make sure you camera is stabilized on a tripod so that it doesn’t move.

Now set your camera to manual exposure setting. Meter your scene and select the aperture you would like. If your camera has an ISO setting, choose a low setting to reduce noise.

If you are not sure about the metering and aperture settings; it is possible to use the automatic metering and aperture modes to estimate your values, you can then input these values into the relevant manual exposure settings.

The HDR technique requires at least three (but can be done with more) photos of the same scene to be taken at different shutter speeds.

In this example there are three pictures taken at -2EV, metered EV and +2EV. To achieve these different exposures you change the shutter speed accordingly.

A slower shutter speed allows more light to pass though the lens. If a quicker shutter speed is used, less light will pass through.

Professional photographers are able to trade off shutter speed and aperture by using units of stops. A stop up and down on each will halve or double the amount of light regulated by each.

If you’re planning to make a HDR image, it’s important that you change the shutter speed, NOT the aperture; the reason being that since you will be combining several images to make one, you don’t want your DOF to change between shots.

If all this tech talk is going straight over the head, you may just have to estimate your shutter speeds until you get the desired results.

Note that, like long-exposure photography, HDR works best when your subject isn’t moving.

Now you have your photos you need to load them up in Adobe Photoshop CS2.

Locate the pictures, highlight them and drag them into Photoshop.

Next you need to make sure that;
A: all three photos are the same color temperature and tint
B: that you turn off ALL the automatic checkboxes

You can pick any color temperature you think looks like what you saw; the important thing is that they’re all the same.

Click “Done”. Photoshop will now remember these settings so they can be automatically opened.

Now to make the HDR you must go to File menu> Automate submenu>”Merge to HDR”

In the dialog box that pops up, select the files you want to use to make the HDR.

Do not check the “Align automatically” box unless you moved the camera between shots. The automatic alignment feature can be difficult to use so treat it as a last resort.

Photoshop will then show you a preview of your HDR image.

Click okay. You don’t need to adjust the histogram, this affects the baseline for the curves in the next step but for our purposes it really doesn’t matter.

After rendering (which may take some time depending on your system specs) you will be shown your new HDR image.

At the moment it won’t look like anything special unless you are viewing on a HDR monitor. So now we want it to look good on our monitor right?

Save the file, it’s a 32 but image file that contains all the exposure data from your shots.

Next, go to the Image menu, the mode submenu, and select “16 bits per channel”.

You will be shown a new menu. Toggle the Histogram arrow at the bottom to show the histogram. Go into the little menu at to and select “Local Adaptation”:

This is just the preview window, though, showing you what it will probably look like when Photoshop is done converting it. The first thing you need to do is bring the left hand side of the histogram to the beginning of the shadows information, as shown below:

Now you can create and edit the curve until you get an image you are a happy with.

Click Okay and Photoshop will render again.

Finally you will get a nice 16 bit image, which can be toned to your tastes using a range of toning tools or plug-ins (perhaps another topic to cover in a Photoshop tutorial?)

If you would like to save the image as a JPEG you will need to down convert it to 8-bit. To do this, simply go to the Image menu, the mode submenu, and select “8 bits per channel”.

Finally you’ll get your finished image in a file you can send to anyone.