The Kaleidoscope series (Low tide evenings on the pier at Port Hueneme). Part III - The technical approach - producing the base image.

The technical approach followed in the Kailedoscope series boils down to a combination of hdr, calculations, and very very careful selections. 

What I found most appealing and challenging in these series is to render detail in both the dark pier and the beach and sky due to the high dynamic range of the scene. 
This is where Photomatix comes to the rescue, providing a very rich base image with lots of detail that can be further enhanced through sometimes very tricky selections.

To illustrate the process, I will use one of my favorite shots in the series, 'Storm Approaching' to the right. The base image to work with is generated with Photomatix from three bracketed exposures at +-2/3, see base frame below.
 

The three frames are taken in RAW format and processed with Canon DPP in wide gamut, 16 bits per channel. Only mild sharpenning is applied in the conversion from RAW to TIFF format. 
The three resulting TIFF files are then combined with Photomatix to create an HDR image. 

Before I continue be warned: I have a love/hate relationship with Photomatix. I love it because it can sometimes in seconds bring detail and produce amazing blends of images that would take me hours to accomplish with my very limited technical skills. That being said, I find its user interface for both HDR generation and tone mapping very unintuitive and downright poor. 
Some of its default choices for tone mapping are just let's say interesting, such as the highlights clipping (.25%!) and they often create an initial disaster when applied to the photo.
Below is an example of the default settings applied to 'Storm Approaching'. It is awful.


I would like to offer a recipe to work successfully with Photomatix, but I have been using it for over a year now and have found none so far. My only advice is:
- Photomatix magnifies noise incredibly. In my experience, photos shot at ISO 500 or higher are unusable. This might depend on the camera you use though, but regardless, ISO should always be kept at a minumun.
- always make sure that there is not highlight clipping before you save and move on to PS, so that you have so space to manuever. 

Modifying the highlights clipping usually causes the whole default adjustments to fall apart (which is probably a good thing anyway) and it just takes time to come up with the right combination of settings to produce the right output. At this point, what I mean by 'right output' is an image with no halos and clean RGB channels.

Color channels bring me to something else that I find very poor in Photomatix - there is actually no way to check the RGB histograms once the tone mapping is done. Photomatix is not oriented towards B&W work - and what sometimes looks like an okay file in color, often has noise in some channel. 

So, how do you know when you have a good HDR to continue working with? Basically, I have found these possible outcomes when generating HDRs:
- Best case scenario: the exposures contained a perfect range of shadows and highlights and Photomatix has done its small miracle and produced a workable file.
 
- Mild disaster: Photomatix has done its small miracle but some color channels are noisy in very localized areas. 
Luckily, areas affected by the noise can be replaced by blending a pristine new RAW conversion, optimized for that specific area. 
This situation often happens with skies, such as in this other photo of the series. 

- Complete failure: Photomatix pushed one or more of the exposures too much and one or more channels are noisy. These channels are key for the B&W conversion and there is no way to replace them without loosing the work that Photomatix did bringing out detail. Here you just need to look at why the conversion didn't work (exposures too light? too dark?) and then start over, reprocessing the RAW images tweaking expose as needed to produce a new HDR image. 

The only way to know how good (or bad) the HDR process went is by opening the resulting file in PS. 
In 'Storm Approaching', the color channels are pretty good. 
There is an obvious halo around the pier, some semi ghosted birds here and there (another curse when producing hdr images - moving subjects) and then of course some dust spots around and a tilted horizon, but nothing that PS cannot take care of. 

What is important is that the histogram looks promising, all channels are clean and there are not ghosts that cannot be taken care of in PS. 
In the next (and last at least!) blog entry I will describe the final work done on PS.