Is digital 6x9cm quality as good as 5x4" film"

**Mattg** · 13-Jul-2008, 14:40

Good on you Bob, any plans to open an Elevator Sydney?

**Gordon Moat** · 13-Jul-2008, 15:00

Originally Posted by gari beet

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I have no direct experience but have read that there is also an issue of colour fringing with digital backs when movements such as swing and tilt are used, depending on what you are shooting this may have a bearing also, it seems that it is an issue with LF and MF sensors but not APS or FULL FRAME.

Microlenses or diffusion layers simply are not efficient enough guiding light beyond a certain angle (somewhat dependent upon design). There was an excellent write-up about these technology issues in LFI a few issues ago, though mostly relating to the Kodak work on the Leica M8. Each photosite is more like a well or pit, and light needs to fall (or be guided) down that well. Fringing can occur as a result of guidance issues combined with Bayer pattern interpolation errors.

Why you see this (generally) more with larger sensors is that the photosites tend to be physically larger, though this is not always a good generalization. As photosites become physically smaller, the potential optical resolution improves, but there are more likely to be colour issues from Bayer interpolation, or noise intruding upon accumulated charge at each photosite.

Possible solutions are in the works, through a variety of different approaches. In video cameras, interpolation issues can be solved by having three separate sensors, and no Bayer pattern; unfortunately cost is a huge barrier to doing that in stills cameras. Three chips also creates a separate issue in that lenses need to be more optimized to focus on each chip the same. Blue filtration can still cause the most problems, since the chips are often receiving the least light under blue filtration (much worse than green, though only slightly worse than red).

Ciao!

Gordon Moat Photography