Do optical WB filters improve RAW color latititude?

Started Aug 26, 2012 | Discussions thread
alanr0 Senior Member • Posts: 2,153
Re: Do optical WB filters improve RAW color latititude?

Vitruvius wrote:

Yes, yes, and yes. I understand all this... Filters reduce incoming light in specific color channels. Makes total sense, since that is the point of a color filter.

But the point is that you are also reducing the amount of light recorded in specific channels and/or boosting the amount of light in other channels post exposure in Photoshop to achieve the SAME result. Once the exposure is taken there is a limit to the DR of each color channel. The further off your white balance was during exposure the more you will need to Push or Subdue the (limited) amount of light in each channel.

So wouldn't it be better to optically correct for WB during exposure and increase the general exposure time a bit. That way the WB is closer to what you want PP.

Everyone knows that you need to get your general exposure as close as possible during exposure because you can't get 'blood from a rock' later. This question really is about getting the exposure as close as possible PER COLOR CHANNEL during exposure.

Although Mako2011's contributions are too didactic for my taste, the contributions are not completely contradictory.

You have folk (John Sheehy, myself, etc.) who broadly support your statements quoted above. Maximising the signal in each channel (at low ISO) will improve the signal to noise ratio. Provided you can increase the exposure time, a colour balancing filter can increase the dynamic range available for subsequent post processing.

You have folk like Barry Davies and Olaf Ulrich adding their practical experience, with careful explanation of the conditions under which their observations are valid.

You have Mako2011 quoting Luminous Landscapes and stating that optical filters are practically never worth using.

In terms of your original question, I believe that balancing filters can increase the dynamic range available. I also agree with Mako2011 that sensor performance has improved considerably since Josef Wisniewski's 2008 post. With a state of the art camera, there may be fewer occasions where you will see a substantial improvement using optical filters.

The latest digital filter products may be wonderful, but I am sure they are equally wonderful working on a lower noise image from a colour balanced exposure.

However, bear in mind Jirka-'s point about reflections and flare introduced by filters with poor quality anti-reflection coatings. The benefits of colour balancing are most apparent in high contrast scenes, and these are particularly susceptible to degradation by flare.

How about trying some test shots with an incandescent light or candle in the frame to create a high contrast scene, and see how well this pans out in practice?

Hope this helps
Alan Robinson

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