[HDR-photo] (no subject)

[Royce Howland]

Don Kuespert wrote:
> I want to streamline the HDR process by using  RAW, produce three 
> exposures separated by a speed factor of 4 to 8, all at the same 
> aperture to control depth of field.

Don, I'm not sure what you mean by "speed factor". If you mean the 
factor for dividing/multiplying shutter speed, this equates to 2 - 4 
f-stops (or EV). Merging multiple exposures into a single HDR file is a 
sampling process. The wider the gap between samples the more potential 
there is for reduced quality in the results. I think most folks on this 
list are using exposures 1 - 2 EV apart; personally I don't recommend 
stepping exposures farther apart than 2 stops.

Partly this is determined by the exposure bracketing function of your 
camera. Again, I reckon most are using AEB rather than manually 
adjusting exposure for each successive frame. AEB means you touch the 
camera less, leading to less potential for image registration problems 
during the merge. And AEB also means shooting through the frame sequence 
faster which may reduce the amount of mismatch potential from objects 
that move within the frame.

You are correct to maintain the same aperture to hold DOF constant.

As others have stated, how many shots you need separated by any given EV 
spacing depends in large part on how much dynamic range exists within 
the scene, and how much of it you need to capture for your purposes. A 
good tutorial on how to bracket your shot sequence can be found here:
http://beforethecoffee.wordpress.com/bracketing-number-of-images/

I also discussed the matter, though less thoroughly :), in my older HDR 
tutorial at NatureScapes.Net:
http://www.naturescapes.net/072006/rh0706_4.htm#exposure

> Will this produce high quality HDR?

I'll leave this question for now since the issue of quality is 
subjective and depends on many factors. :)

Royce Howland
Calgary, Alberta