[Leica] About to take M8 plunge - but worried about blownhighlights...

[henningw at archiphoto.com (Henning Wulff)]

At 12:46 PM +1000 9/3/08, Geoff Hopkinson wrote:
>Hi Simon, there is very sound advice in the thread, as you would have
>already seen.
>Some additional comments from me on technique for the situation you
>describe.
>Firstly the chromatic aberration you mention is very likely from the lenses
>used. Another great reason to have superb Leica glass!


Actually, the 'chromatic' issues around highlights are not a function 
of the lens, but of the sensor and the light qualities that hit it.

Highlight blowout is due to sensor saturation, ie, the sensor cannot 
register the actual number of photons that have hit it as it's a 
number that's bigger than what it's maximum. Near the actual 
highlight, where every channel is blown out, is a region where some 
channels are saturated, but not other(s). That will give areas or 
rings around the highlights of colours that have not yet saturated. 
Because some channels have saturated in this region, the colours will 
be false as the saturated channels cannot provide the proper value.

All digital sensors will do this, but unless the highlight areas are 
large with gradual transition areas, it won't be a problem. There are 
some workarounds, but they involve 'creating' some colour values in 
this region.

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    *            Henning J. Wulff
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