PTGui Pro is panoramic stitching software for Windows and Mac OSX. Originally developed as a Graphical User Interface for Panorama Tools (hence the name), PTGui now is a full featured photo stitching application. It supports the creation of HDR (High Dynamic Range) panoramas. This tutorial explains the concept and helps you get started.

PTGui comes in two versions: PTGui and PTGui Pro. The main difference between the two versions is support for HDR stitching, viewpoint correction and vignetting, exposure and white balance correction in PTGui Pro

Features:
* Automatic stitching: create panoramas with just a few mouse clicks
* Manual mode: full control over the final result
* Live preview: instantly see the effect of different settings, without the need to stitch first
* Multi row panoramas: images can be stacked both horizontally and vertically
* Many panoramic projections
* Stitch rotated and tilted images
* Create HUGE panoramas: stitch hundreds of images into multi gigapixel panoramas
* Support for jpeg, tiff and png source images
* Support for many camera RAW source images (through dcraw)
* Create panoramas in jpeg, tiff or Photoshop format
* Photoshop large document (.psb) support (output only)
* Layered Photoshop output, ideal for retouching
* Full support for 16 bit images, for the best image quality
* Panorama editor: interactive adjustment of the panorama perspective
* QTVR ouput: directly create interactive QuickTime VR panoramas, or convert an existing panorama into QTVR format
* Support for multiple processors / multiple core computers
* Create templates with frequently used settings
* Batch stitcher: prepare your projects and send them to the batch stitcher for stitching when you are away from your computer
* Batch Stitcher can generate control points and set up a panorama
* Batch Builder: scan folders for panoramic source images and automatically create projects based on a template
* Support for Batch Lists (save and load a list of jobs for the Batch Stitcher)
* Stitch and blend HDR source images into an HDR panorama
* Stitch and blend bracketed LDR source images into an HDR panorama
* Calculate camera response curve from bracketed LDR source images
* Built in tone mapper
* Support for OpenEXR (.exr) and HDR Radiance (.hdr) source images
* Blend Priority parameter (useful for blending the nadir image in a spherical panorama)
* Viewpoint correction
* Vignetting, exposure and white balance correction
* Global adjustment of exposure and white balance
* Exposure Fusion
* Configurable Project Settings: control the behaviour of templates, custom default file names and more

Limitations:
* Stitched panoramas will have a visible watermark
* Saves only the first 2 images of panorama
* The Panorama Tools stitcher and optimizer are not supported (only the built-in PTGui stitcher and optimizer)
* The trial version expires. Updates will be downloadable from this website

High Dynamic Range (HDR) photography attempts to overcome this limitation, by combining multiple differently exposed photographs of the same scene (so called 'bracketed' exposures) into a single image. Such a combined image has a higher dynamic range, and is typically stored in a 32 bit per channel image file (regular jpeg files have only 8 bits). Since the contrast of a computer monitor and paper ink is limited as well, HDR images are tone mapped before display. Tone mapping makes local brightness adjustments to the image, to reduce the dynamic range such that it becomes suitable for display or print. For more information about HDR and tone mapping.

PTGui Pro provides extensive support for HDR imaging:
1. Stitching bracketed exposures into an HDR panorama
2. Stitching HDR source images into an HDR panorama
3. Built in tone mapper, to create displayable images from an HDR panorama
4. Exposure fusion of bracketed exposures straight into a tone mapped panorama
5. Supports the following HDR file formats: 32 bit floating point TIFF, 32 bit PSD and PSB (for output only), OpenEXR (.exr) and Radiance (.hdr)

One of the more advanced features in PTGui Pro is viewpoint correction. Viewpoint correction allows one to use different camera viewpoints in the same panorama, provided that the relevant part of the images is approximately flat. It is particularly useful when including a handheld nadir image in a panorama taken from a tripod.

Viewpoint correction is included in PTGui Pro only; the regular version of PTGui does not include this feature.

When photographing panoramas it's important to minimize any color and brightness differences between the source images. Although PTGui attempts to egalize exposure differences by gradually blending the images, the differences still remain visible in the form of a gradual change in color or brightness. This is particularly noticable in plain colored parts of the panorama, such as blue sky. Also, color and brightness differences make it more difficult to retouch a panorama since the overlapping layers don't have matching colors.

Most color and brightness variations can be prevented by setting the camera to manual exposure mode and by selecting a fixed white balance preset. But this does not prevent one cause of exposure differences, namely vignetting.

A new feature (available only in the Pro version of PTGui) is automatic color and exposure adjustment, which corrects vignetting and is also able to correct flare, exposure differences and white balance differences. The correction is fully automatic; by analyzing the contents of overlapping images, PTGui Pro can determine the vignetting characteristics of the lens and compensate for it. We will show it with an example:

The license of this software is Free Trial Software, you can free download and get a free trial.