Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "pr_roark" <paul.roark@...> wrote:
>
> >... compensating for the limited dynamic range of the camera
> > using multiple exposures. ...
> 
> I assume that is the main point of HDR.  I suppose reducing noise in the shadows even if they are nominally within range has some value.  Are there other uses of HDR?

True HDR is 32 bit floating point, which nothing can display - let alone print. On a normal monitor it is so lacking in contrast it actually looks like mud.

Quite a while ago there were some people trying to implement a panorama viewer for HDR.
It took the 32 bit float values scaled to suit what portion you were viewing - to display it with normal contrast. 
So it would brighten the shadows and darken the highlight as the panorama spun past. Think of it like the autoexposure on a video camera and going from inside to outside or vice versa.

> 
> With film I often using a tripod and simply took 2 exposures -- one for the highlights and one for the shadows.  Since they were on roll film and scanned together, the images were rotationally aligned and easy to deal with manually.  Shots like my Grand Teton used this approach and were easy.  See http://www.paulroark.com/GrandTeton.html
> 
> I tried this approach with the Canon 5D2, but with hand holding the camera, and the approach failed.  Neither the HDR or auto-aligning of layers could be done in Photoshop CS4.  I suspect there are insufficient details that match in the 2 frames.  I take if from this that, at a minimum, more frames are needed.  I suspect with a tripod my manually merging the frames would work, but, frankly, the quality of image with strong back-lighting is not close to the film quality I'm accustomed to.  So, I suspect even with a tripod I'd want more frames.

> 
> I've noticed some third party HDR software is often recommended.  Do these (or even PS) have a way to assist the alignment by telling the software some points that do match and having it then so the rest?

You can use some of the panorama stitching software to get precise alignment on hand held stuff, try Hugin (free - open source) or Ptassembler (commercial).

You don't have to be stitching mosaics or panoramas to find them useful. Hugin includes automatic point matching software for alignment as well as enfuse which can blend different exposures.

I'm going to give Hugin a whirl again over the break to see where it's at.

> 
> Paul
> www.PaulRoark.com
>