Blur Circle



NB.. I am aware that recently a blur circle of 200microns (0.2 mm) is often quoted as the standard; however just as there are variations between individual humans optical systems there are variations in what manufacturers use or claim.
A 35mm frame requires approx 8 x magnification to give a standard 8x10 print which means that the blur circle on the chip of film needs to be less than 25um (0.025mm) if it is to appear sharp on the print; film is capable of achieving resolutions of less than 5um (0.005mm) the latest CMOS chips are approaching 9um however this is over a 30 x 40mm chip still some way to go to achieve the information content of sheet film.

We must also not forget that capture is by a CCD or CMOS array, in the form of a Bayer Matrix so interpolation is required even in RAW capture, for full colour. The exceptions being Multi-Shot or Scanning Backs and the Foveon chip which give 'Full Colour' without interpolation ref:

Foven Direct Image Sensor

BetterLight Scanning Backs

Seitz Digital Scan Back

Hasselblad Multi-Shot Back


ref Virtual Parish Project Image Capture Protocol by Phil Gee 2005