Digital/Film Dynamic Ranges (long)
2005-12-12 by claudej1@aol.com
Ah yes, B&W in a color world! How shall we truly compare? First of all, one needs to define "film." By way of color ouput capability on every desktop (monitor and printer) the digital capture world is processed to color (Bayer filtered monochrome capture except Foveon X3). So how do we compare that to "film?" Do we compare to the dynamics of tri-filtered B&W film used in the Roy Rogers days with dye transfer prints? Since we view everything processed digitally, RAW or JPG, in POSITIVE color first, should we not compare it to the dynamics of TRANSPARENCY film (Velvia having the SHORTEST scale of all)? Or, should we compare to color negative film, since it outsold transparency or B&W film by several orders of magnitude? Or perhaps do we look only to INFRA RED film dynamic range (DR), since ALL solid state sensors are dismally bad at sensing UV and Blue and are WILDLY sensitive (Quantum Effeciciency) to infra red, where the sensor DR is severy crippled by Cyan filtering in every digital camera in the world? How about duplicating tranparancy film with a Contrast index of 1, closely matching the linear gamma of sensors? Ot, as most people here, the VARIABLE dynamics of B&W film capture with PRE-PROCESS spectral response control via color filters and POST CAPTURE chemical/time controls? Since the answer is, ALL of the above and NONE of the above, we can see that digital image capture can be CONTOLLED by the PHOTOGRPHER in such a way that you can serve all of those masters with a collection of different digital cameras that are optimized for different applications. We never owned just ONE format for film, and used different emulsions for different things. So why the "double standard" for digital capture where only ONE camera is expected to do it all with a single click? Film cameras were nothing more than display pieces when one stopped making the "virtual lease payment" called film. No film, no photography. Now with "re-usable film" we have reduced the "cost per click" down to just pennies here v.s dollars. Economics rule the day. It's in the history books. So what's the real problem?? the PHOTOGRAPHER's unwillingness or incapability to make it work. Whether it be time, attitude, money, technical aptiude. As to the D70 issue, my tests showed that the Sony sensors in the Nikon cameras like the D1X, D1H, etc. inherently blew out highlights worse than others, so that's clearly a worse case scenario comparison to digital capture. Color neg. film with a Contrast Index of less than 0.5 (extreme luminance compression) can hold about 14 stops worth of linear information with a short toe and a shoulder that doesn't kick in until color crossover issues have reared their ugly heads. But linear spectral response doesn't matter to B&W shooter, or does it? The DR argument is a pretty weak one since we are talking about seeing about 6 stops worth of range on PAPER under the best of condiditions. All we need is a good tripod, one stop bracketing, and multi-layers or High Dynamic Range files to do the necessary compression. Let's not forget dodging and burning. Or, for the lazy, processing multiple exposure shifting in RAW output to stretch the dynamics. Even after all that, we sit here and complain the 8-bits isn't smooth enough to contol gray ink levels averged out over 4-8 heads and an ABOLUTE VISUAL DISCRIMINATION QUANTIFICATION than can BARELY detect 100 gray tones under normal viewing conditions. The human eye is a wonderful comparator but a TERRIBLE quantifier. That's why we spectrophotometers and densitometers to sort it all out. The only place left where digital capture ISN'T superior in every way, is in Large Format B&W with standard or specialty films. The emergence of a superior solution in that realm will occur in line with the economics of the demand. As the character Morpheus in the movie "the Matrix" so aptly put it: "I believe it is not a matter of hope, it is simply a matter of time." Claude Jodoin Tech. Editor and Working Photographer Rangefinder Mag. Digital Out since 1986, Digital in since 1995. <<The article in Luminous landscape (at a quick glance) seems to highlight what in my opinion is the biggest drawback of digital cameras -- ie. the limited dynamic range of the sensor. We can burn down blown highlights (eg clouds) with negative film. In fact a C41 process b&w film gives us the ability to record detail in the brightest highlights and deepest shadows. Blown highlights and blocked shadows have no place in landscape photography and as such I am not ready to make the digital leap. I have 300 feet of Tech Pan in the freezer to use on lower contrast subjects and teamed with my Zeiss lenses (35mm) and 5400dpi scanner I have no worries about big enlargements. The only digicam files I have handled came from the D70.>>