[HDR-photo] Re: Photomatix and noise

[Royce Howland]

Dave Feltenberger wrote:
> How many images
> do you typically have in e.g. a landscape shooting away from the sun,
> or an interior photo with a window included, etc.?  The former I can
> usually catch in just a 3 shot sequence, while the latter varies
> widely depending on very specific lighting conditions.

I do pretty much the same as what you describe. Outside shots without 
overly bright highlights, my default is 3 shots at -2, 0 and +2 EV. This 
combination covers a lot of territory.

Bright outdoor highlights, or interiors with mixed light including 
bright outside windows, usually take a fair amount more range. For the 
sake of simplicity I typically shoot two 3-shot AEB sequences (since my 
Canon 5D has a max of 3 exposure in AEB mode), with a manual adjustment 
between the pair. The results is either 5 shots covering -4, -2, 0, +2, 
+4 EV (throwing away one overlapping exposure from the second set); or 6 
shots covering something like -4, -2, 0, +2, +4, +6 EV (no overlap). 
These latter cases are more likely to include an overly dark and/or 
overly bright frame. I don't necessarily worry too much about trying to 
optimize a longer sequence in the field. If I end up with 1 or 2 
unusable frames on the ends of the exposure range, I just drop them later.

Since the way we tend to shoot our exposure sequences is probably biased 
to relatively more under-exposed pixels than over-exposed ones across 
the sequence, it makes sense to watch out for overly dark frames. They 
can't really contribute a lot of useful detail to the HDR sampling process.

Where I personally have the biggest challenge dealing with this is not 
so much on single frames shot with multiple exposures, but multi-frame 
shots such as rotating for a panoramic stitch. The brightness range from 
the left side of the pano to the right can be very high, and so on one 
side the bracketed shots are often more heavily weighted towards the 
really dark tones.

Royce Howland
http://www.vividaspect.com/