easyHDR BASIC is an image processing software that produces and tonemapps High Dynamic Range images from photo sequences taken with a normal digital camera. EasyHDR can also tone map already created HDR images saved in Radiance RGBE (*.hdr) format or 48-bit and even 96-bit TIFF. You can also process RAW images from your camera by loading them directly into the program. Another great feature is single Low Dynamic Range (LDR) photo enhancement.

What is a HDR image?
High Dynamic Range image covers much wider dynamic range (light to dark ratio) than a normal digital camera can record (due to noise and overexposure). A HDR image is created by blending an image sequence of photos taken at different exposure values (various exposure times or ISO sensitivity). Each photo in the sequence shall cover a part of the dynamic range of the photographed scene. The resulting HDRi will therefore contain the full information from all of the photos.

EasyHDR BASIC is much less featured than easyHDR PRO. There are implemented only the simplest and most basic HDR genearation and tone mapping functions. However this version is free.

How to take an image sequence?
If you try to photograph a scene and get some unwanted over- or underexposured areas you may consider taking a bracketed sequence that could be later blended to HDR and processed. The easiest way to do so is to turn on autobracketing (AEB) in your digital camera, set the number of photos in the sequence and the EV (Exposure Value) spacing. The 0EV photo will be taken at the exposure time, ISO and the f-number measured by the camera as the best for the particular scene. The other photos will be deliberately underexposed (negative EV) or overexposed (positive EV) so they will contain details that are lost in the 0EV photo due to noise and overexposure. The photographed scene should be static - there should be no movement or light change during the photo sequence acquisition, otherwise ghosting effect will be visible in the assembled HDRi. Therefore you should use a tripod to take the photo sequence. EasyHDR, however, has a built-in auto-alignment feature that compensates for shift and rotation between photos, so taking a photo free-hand won't necessarily mean a bad result. If the autobracketing isn't sufficient you may want to manually vary the exposure time, with the constant ISO and f-number. When you i.e. take 3 photos at 1/200 (A), 1/100 (B) and 1/25 sec (C), this will mean that the photo (A) is underexposed by 1 EV relatively to the photo (B) and the photo (C) is overexposed relatively to (B) by 2EV - so you have a photo sequence: -1EV, 0EV and +2EV.

What is tone mapping?
The pixel value to real scene radiance ratio is linear in case of the assembled HDR images. The CCD and CMOS sensors both have linear sensitivity too, but the photo taken with a digital camera undergoes processing before it is stored as JPEG on the memory card. That processing include contrast (or dynamic range) compression, so the photo looks natural when is displayed on a computer screen. We could do the same with the HDR images (tone mapping with a global operator), but this will prevent us from preserving the proper local contrasts in the output photos. That's why special, local operators, are used to tonemap HDR images. Tone mapping simply allows the HDR images to be displayed on a screen or printed.

What are the benefits of LDR enhancement with easyHDR?
In many cases the photographed scenes do not characterize with very wide dynamic range, so taking an image sequence in order to assemeble and tonemap a HDR may be too much effort. Also, by taking a RAW photo, instead of JPEG you can achieve a slightly higher dynamic range, so a single photo may be sufficient.

The license of this software is Free Trial Software, the price is $39.00, you can free download and get a free trial.