I read from the Photomatix site and said 2 EV is enough for good results. Can anyone tell me why 1 EV steps are better?
In the past, this question has generated vigorous debate on this site. The Photomatix manual and many published authors recommend 2EV spacing. Many members of this forum prefer 1EV spacing.
I think there are two issues that often get confused. The first concerns whether you capture the entire dynamic range of the subject. The only way you can know this is by looking at the histograms of each of your shots. If the shots on either end of the spectrum are equally under and over exposed with the tail well-contained within the end of the histogram, then you know you've captured the dynamic range of the subject. It may take 3 shots; it may take 5 shots; it may take 7 shots. It depends on the subject. However, so long as you've captured the dynamic range, then a 2EV spacing within the series will be fine.
The other issue, which gets confused with the first, is whether the final HDR will be of higher quality if you use 1EV spacing rather than 2EV spacing. I've tested this myself, and I've never seen a difference so long as the dynamic range has been adequately covered.
As a practical matter, if you shoot 1EV spacing over a broad range, then you'll be more likely to be able to pick out the best shots from the series to process. However, this takes a tripod and patience. If you have little of either, then using AEB with 2EV steps and fast shutter speeds will generally capture what you want. The major exceptions will be those in low light and any scenes that contain the image of a light source (sun, streetlamp, etc). These scenes always require a broader ranges of shots.
