Digital BW, The Print

Yes the histogramme is a histo of the inbuilt jpeg conversion.  The inherent
problem is the metering which is still "multi-point expose for mid grey" (if
that's an appropriate abbreviation).  For digital things become a little
more complex.  Ideally the metering system would determine the brightest
portion in the frame and expose that at white or just fractionally under -
letting the other points fall as they may. (Think of a right-justified
histogramme with nothing blown.)  The issue with this is a specular
highlight (which should be blown) could upset the overall exposure and
detail could be lost in the shadows where there are so few levels.  [But
personally I would rather see a non-blown histo displayed and then choose to
blow the specular highlights if necessary with exposure compensation.]  The
conversion to jpeg (and hence the histogramme formation) would require
something more like ACR's auto exposure adjustment to rebalance the image
levels to a more normal (multi-point expose for grey) exposure.  Then we
have many more levels in the lower half of the histogramme to work with.


> From: "Paul D. DeRocco" <pderocco@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 25 Aug 2005 02:28:07 -0700
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] 1Ds Mk III prediction (was new canons)
> 
>> From: Peter Marshall
>> 
>> The essential tool is built into the digital camera I use and is called
>> a histogram! 
>> 
>> I use it all the time, and I think it will remain the only way to get
>> optimum exposure. Incidentally I think Nikon have tweaked their
>> auto-exposure system to give better results from digital, certainly my
>> experience suggests that the D70 is an improvement in this respect on
>> the D100.
> 
> Trouble is, it only works _after_ shooting. If you want to know if individual
> pixels are clipped, you can't deduce that from a conventional exposure
> meter--you have to look at all the pixels coming off the sensor, which
> basically means you have to take the picture.
> 
> I'd like to see an indicator in the viewfinder that tells if more than a
> certain small fraction of pixels have clipping in them.
> 
> -- 
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@...