HDR Tutorial
14th May 2012
An HDR photograph is a photograph with a High Dynamic Range. The dynamic range of a photograph refers to the difference between the darkest and the lightest colours or shades. In an HDR photograph, there is a much larger dynamic range than in an ordinary photograph. The purpose of using techniques like the one published below by David Meredith (whose work is in our No Briton is an Island exhibition) is to overcome the limitations of the camera equipment, which can only capture a limited range of the photograph in ideal contrast. For example, if you are taking a photograph of a flower against a bright sky, either the sky will appear too bright (over exposed), and the flower in detail (correct exposure) or the flower will be very dark (under-exposed) and the sky in detail (correct exposure). The HDR technique offers a solution to this problem by taking multiple photos of the same scene, with different exposures and then merging them together. This way each part of the image can be seen in optimal exposure. Read on to find out how to create this effect. For this tutorial you will need the programmes Photomatix and Adobe Photoshop.
Taking the Photographs
Three or five shots need to be bracketed; there are various settings available on each camera, a degree of experimentation is required to find what you are happy with.
It's best to use a tripod and shutter release to avoid movement, although handheld is possible, a higher ISO has to be used to get a fast enough shutter speed, the higher ISO will cause more noise/grain.
In the case of handheld bracketing 3 shots is going to be better as there is less chance of movement.
I use RAW files only. There is no need to alter WB unless you want to experiment. I do not use flash and I try to get the lowest ISO possible bearing in mind any possible movement in front of the lens; anybody in the shots will cause 'ghosting' if they move.
Processing
1. Open Adobe
2. Go to File>Automate>Merge to HDR. A grey window will open.
3. Click Browse to find the files. Select the files & click OK.
4. The files selected will now appear in a new window.
5. Uncheck 'Attempt to Automatically Align Source Images' if you used a tripod. If handheld, make sure this IS selected. Click OK.
6. Once the program has finished running, a window will open with 3 to 5 images down the lefthand side with various EV settings and a green tick in each box. On the righthand side is a histogram and the middle has a very odd looking image, perhaps looking 'blown out' in places. The bit depth should read 32 Bit/Channel. There is no need to alter anything here just click OK.
7. a) The HDR file will reopen in a conventional window. Go to File>Save As.
b) Another window will open. Choose a file name and location as you would for any other file, BUT in the format field choose Radiance{*.HDR,*RGBE,*.XYZE} then click Save.
8. OPEN PHOTOMATIX
9. Go to File>Open then locate the Radiance file just created, Click Open.
10. A fairly dark looking image will open.
11. a) Go to Process>Tone Mapping. A new window will open.
b) On the righthand side is a box with various sliders, make sure you select the Details Enhancer Tab.
c) On the Presets drop down select Default (do this every time a new HDR project is started)
d) Now enter the following settings. I find them a good starting point.
Strength: 100
Colour Saturation: 100
Light Smoothing: Click the Middle/Medium setting
Luminosity: 10
White Point: 0.010%
Black Point: 0.632%
Gamma: 1:00
Colour: Leave as it is
Micro Contrast: 6
Micro Smoothing: 0
S/H: Leave as it is.
12. Click Process.
13. A fairly odd looking image will appear, parts of it may look grainy/noisy no need to worry that is normal.
14. Go to File> Save As and SAVE THIS AS A 16 BIT TIFF
14a. Name this file TOP
OPEN the Radiance file again in Photomatix – On Presets click Default
15. Enter the following settings:
Strength: 84
Colour Saturation: 69
Light Smoothing: Click the 2nd from right/High setting
Luminosity: 0
White Point: 0.250%
Black Point: 0.059
Gamma: 1:00
Colour: Experiment with this to get something you like but +/- 3 either way
on any setting is enough
Micro Contrast: 2
Micro Smoothing: 8
S/H: Depends on the image
16. Click Process.
17. Go to File> Save As and SAVE THIS AS A 16 BIT TIFF
17a. Name the file BOTTOM
18. Go back to Adobe
19. Go to File>Open and select the 2 TIFF files created.
20. Now what I do is place one image on top of the other, holding down the shift key while dragging and dropping, this will 'pin' align the 2 images.
21. I then change the opacity to merge the 2 shots together.
22. I then use a layer mask to remove or bring out various parts of the image.
23. Flatten the combined image and again save as a 16 Bit TIFF.
23a. One or more of the 'original' RAW files once processed and saved as a TIFF can also be layered. Any cloning, perspective changes or cropping should be done before moving to the next step.
24. Many of the colours will be very bright and the image will need other adjustment so the next step is:
25. Go to File> Open As, a window will open and select the 'combined' image. At the bottom of the window is an 'Open As' drop down, select Camera Raw and click Open, this will open a TIFF file in the RAW interface. Adjust the shot as desired here.
26. Click Open Image again as a 16 Bit TIFF, at the bottom of the window there is some underlined text click on this to change the settings.
I do the following to most images.
27. On the layers palette make a copy of the image then go to Filter>Blur>Gaussian blur and set the radius at about 60 pixels, click OK.
28. Change the layer palette blending mode to Soft Light and reduce the opacity to what suits the image. Then from the layers palette Flatten Image.
29. You may wish to do a curves or levels adjustment
30. Go to Filter>Distort>Lens Correction and add a Vignette, click OK and from the layers palette Flatten Image.
31. Go to Image>Mode and select 8 Bits/Channel
Sharpening
32. Go to Filter>Sharpen>Unsharp Mask. Apply the following settings:
Amount: 200%
Radius: 2.0 pixels
Threshold: 0
Click OK
To reduce artifacts created by over sharpening and to soften the effect:
33. Go to Edit>Fade Unsharp Mask. From the Mode drop down select Luminosity and then adjust the opacity to suit.
