[moracca]

When dealing with HDR images, exposure is handled a bit differently than in some other situations. I didnt get a change to read the tutorials posted above, but one quick thing I'll mention is that by changing the aperature size (f/stop), a smaller number (2.8 for example) means a larger aperature, and therefor more exposure, whereas a larger number means a smaller aperature and less exposure. Similarly, changing the shutter speed will also change the exposure. Faster shutter speed means less exposure (less time for light to hit the sensor). Normally you can compensate one by the other, ie, if you have want a faster shutter speed, you can user a larger aperature size (a smaller number) to make up for the amount of light you lose by speeding up shutter time. For HDR tho, you want to vary your exposure by changing the shutter speed only, not the aperature size. This is because in adition to changing the exposure amount, changing the aperature size will also affect your depth of field, in other words how much of the picture is in focus. This means that you wouldn't want to use it to get the different exposures on an HDR image, because you want all of your images to be as identical as possible (except for the varied exposure). For HDR it is recommended to change the shutter speed to get the different exposures. This is usually done in 2 step intervals. A "step" is defined as a halving or doubling of the previous setting, so one step up from 1/2 a second would be 1 second, and one step down from 1/2 a second would be 1/4 a second. Say your ideal exposure was at 1/15 second. If you were going to use 3 exposures for an HDR image, you would want one at 1/4 (1/8 = almost half of 1/15, 1/4 = half of 1/8), one at 1/15 sec, and one at 1/60 sec.

Someone please correct me if I'm wrong. Hope this helps!