HDR Soft Photomatix Pro - 2.2 User Manual

Photomatix Pro 2.2 Help

I - Introduction..................................................................................................................... 2

Why would I need to shoot the same scene with different exposures? .......................................... 2

What is the added-value of Photomatix?..................................................................................... 2

II - Getting started .............................................................................................................. 3

Taking differently exposed images ................................................................................................. 3

III - Using Photomatix....................................................................................................... 4

Exposure Blending.................................................................................................................... 4

HDR Tone Mapping .................................................................................................................. 4

Using the Batch Processing....................................................................................................... 4

IV - Exposure Blending..................................................................................................... 5

V - Generating an HDR image ....................................................................................... 6

VI - Processing HDR images ........................................................................................... 7

Introduction .............................................................................................................................. 7

Tone Mapping settings .............................................................................................................. 7

VII - Batch Processing....................................................................................................... 9

VIII - Image information tools ..................................................................................... 11

Image histograms ................................................................................................................... 11

Histogram Comparison............................................................................................................ 11

Image Properties..................................................................................................................... 11

HDR Viewer............................................................................................................................ 12

IX - Working in 16-bit mode ......................................................................................... 13

X - Advanced image alignment .................................................................................... 14

Photomatix Pro 2.2 Help 1

I - Introduction

Photomatix enables you to get the best possible results out of images of the same scene taken with different exposures. The software works with images taken with digital cameras and images scanned from films.

There are basically two ways to obtain an image with increased dynamic range out of a sequence of differently exposed images:

1. Exposure blending

Differently exposed images of the scene are combined into an image with details in both highlights and shadows.

2. HDR Tone Mapping

A High Dynamic Range Image (HDRI) is created from differently exposed shots. The HDR image is then tone mapped in order to reveal the image details in highlights and shadows. The tone mapping process results in an image with 8 or 16 bits per color channel that can be properly displayed on standard monitors and handled by printers.

Why would I need to shoot the same scene with different exposures?

A general problem in photography is the rendering of scenes presenting very bright highlights and deep shadows. The problem exists with traditional silver halide photography and is more pronounced with slide films. In digital photography, the problem is made even worse as the linear response of the sensors imposes an abrupt limit to the dynamic range captured once the sensor capacity is reached.

This is why you can not get what the human eye is seeing when viewing an HDR scene on common devices. If you capture details in the shadows thanks to long exposure times, you then get blown-out highlights. Conversely, you can capture details in the highlights with short exposure times, but you then loose contrast in the shadows.

Creating an HDR image from differently exposed shots is a way to solve this problem. However, HDR images present a major inconvenience for photography: they can not be displayed correctly on standard computer screens and can even less be reproduced on paper.

What we call Dynamic Range Increase is the process of correctly reproducing the highlights and shadows of a high contrast scene on common monitors and printers. That is, producing a standard 24bit image that represents the original high dynamic range scene as the human eye has seen it.

What is the added-value of Photomatix?

The process most commonly used for Exposure Blending consists in manipulating the images in image editing softwares such as Photoshop, using multiple-steps masking techniques.

This process is complex, time-consuming and may lead to disappointing results. Moreover, Exposure Blending alone may not be sufficient when the dynamic range of the scene is particularly high. This is why we have designed Photomatix, a software that blends exposures hassle-free and processes High Dynamic Range images with a tone mapping technique that preserves local contrast.

Photomatix Pro 2.2 Help 2

II - Getting started

Photomatix works with photographs of the same scene taken under different exposure settings. Such images are often called "bracketed" images in reference to the auto-bracketing exposure functions available on many camera models.

If you don't have such images available yet, you can start using Photomatix with the sample bracketed images provided with the application under the Samples folder. To try Photomatix with your own images, follow the instructions in the section “Taking differently exposed images below”.

You do not necessarily need several exposures to use Photomatix though. The Tone Mapping tool also works with a single 16 bits/channel file converted from RAW. The same applies to the 48-bit Compression tool.

Another trick is to use different exposures derived from the same RAW file. This can work quite well with the Exposure Blending methods of Photomatix available under the Combine menu, especially Highlight & Shadows - Auto. However, the dynamic range you can retrieve from a RAW file is limited, so it will not work for challenging scenes such as the interior of a room with a bright window. Also, please note that such process in not suited to the creation of HDR images.

Taking differently exposed images

Below are general recommendations for taking a High Dynamic Range scene under different exposure settings. The calculation for the number of exposures is based on a stop spacing of two EV (Exposure Value). You will need to adapt if you are using a different stop spacing.

We recommend a stop spacing of 1.5 to 2 EV. A lower stop spacing will require more images to cover the same dynamic range without adding much benefits. A higher stop spacing may result in loss of precision in the tonal range between successive exposures. If the maximum auto exposure bracketing spacing of your camera is lower than 1.5 EV, then you will probably have to take two –or even threeseries in auto exposure backeting mode, changing the exposures manually between both, in order to properly capture the dynamic range of the scene.

A stop spacing of two EV means that the exposure for one photo will be four times higher or four times lower than the other photo.

Mount your camera on a tripod (though Photomatix includes a feature to align hand-held

images, using a tripod is still highly recommended)

Set your camera in manual exposure mode. Select an appropriate aperture for your scene, e.g.

f/8 or less (i.e. higher f number) if you need more depth of field. Select the lowest ISO setting, unless your scene includes moving objects.

Measure the light in the brightest part of your scene (spot metering or in Av mode to point only

the highlights) and note the exposure time. Do the same for the shadows of your scene where you want to see details in.

Determine the number and value of exposures necessary. For this, take as a basis the

exposure time measured for the highlights. If you are using a stop spacing of two EV, multiply this number by 4 to find the next exposure time. Multiply by 4 successively for the next exposures till you pass the exposure time measured for the shadows. (Note: For most scenes, 3-4 images should be sufficient to cover the dynamic range).

You can make use of auto-exposure bracketing if your camera supports it and if it allows a stop

spacing of at least 1.5. Otherwise, just vary the exposure times manually.

Photomatix Pro 2.2 Help 3

III - Using Photomatix

Photomatix offers two types of processes to produce an image with increased dynamic range from two or more differently exposed shots. One process is called Exposure Blending and is available from the Combine menu. The other process is called HDR Tone Mapping and is available from the HDRI menu.

The Exposure Blending process is the easiest to understand. This process combines your differently exposed photos, merging them into one image that shows details in both highlights and shadows.

The HDR Tone Mapping process involves two steps: The first step creates an HDR image from your differently exposed photos. The second step tone maps the HDR image created. This second step is necessary to reveal the details in both highlights and shadows in the HDR image.

Both processes are designed to produce an image with increased dynamic range, but their results are different. We recommend to try both and then choose the result that works best with your images. This is easy to do with the Batch Processing available under the Automate menu.

Exposure Blending

Open images of the same scene taken under different exposures.

Click on Highlights & Shadows - Auto from the Combine menu.

Try another combination method (for instance Highlights & Shadows - Adjust) with the same

images. Photomatix will only combine the source images you have opened, i.e. excluding resulting images.

HDR Tone Mapping

Click on Generate HDR from the HDRI menu to create an HDR image from photos of the same

scene taken under different exposures.

Click on Tone Mapping from the HDRI menu to reveal details in highlights and shadows in your

HDR image.

The first time you are using Photomatix, it makes sense to run it from the interface, as described above, so that you get familiar with the functions of the software. For subsequent uses, we recommend processing your images in batch mode, and then only use the interface to view and compare the results. This will save you a lot of time and make it easier to process large files.

Using the Batch Processing

Click on Batch Processing from the Automate menu.

Check the process(es) you want to run on the PROCESS frame.

Select the number of differently exposed images on the combo box at the bottom of the

PROCESS frame.

Select the location of your source images and where you want to save the results on the

LOCATION frame.

Click on Run.

More details are available under the section “Batch Processing”.

Photomatix Pro 2.2 Help 4

IV - Exposure Blending

Introduction

Photomatix lets you combine images with different exposures using the Average method or one of the Highlights & Shadows methods. Those latter methods perform a process known as Exposure Blending

The Highlights & Shadows methods make use of advanced algorithms to select and blend together the details available in the different exposures.

The Average method combines the images using the same average formula everywhere, regardless of whether the computed pixels are in a dark or bright area. This is why averaging can not produce the dynamic range extension that you can get with one of the Highlights & Shadows Exposure Blending methods. However, averaging has the effect of reducing noise and is often used for a process called Image Stacking.

To use the Exposure Blending functions of Photomatix Pro

Open the images taken under different exposures.

On the Combine menu, click one of the Highlights & Shadows item. For help on choosing an

item, see the section “Which one of the Highlights & Shadows combination methods should I use?” under the FAQ document.

The window lists the source images (see note below) that will be combined into one image with

details in highlights and shadows. If the images are not aligned (e.g. shot without the aid of a tripod), check the option Align images.

Save the result.

To blend exposures automatically and/or process large files, please refer to the section “Batch Processing”.

Notes:

Source images

All image files that you have opened, excepted images in Radiance RGBE format, are considered

source images. source images should be images of the same scene taken under different exposure settings. Once you have combined source images or applied tone mapping to an HDR image, the resulting images are not considered source images. This way, you can easily compare the results of different combination methods by running them successively on the same source images without having to close the window showing the previous result.

If the source images do not have the same size, the resulting image is computed based on the

size of the smallest source image.

To function properly, the combination requires that the source images are perfectly aligned. Even

though Photomatix provides automatic and semi-manual/advanced alignment tools, it is recommended to use a tripod when shooting the different exposures. A tripod is less necessary if your digital camera has an automatic bracketing function and you make sure that the camera does not move during shooting.

Photomatix Pro 2.2 Help 5

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