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filmscanners: Nikon IV Depth of Field Test

Using the film strip adapter SA-21 with the Nikon IV and NS3.1, I obtained
the following focus Nos. on a relatively flat Max400 negative (Landscape):

End Frame:
        L       Mid     Right
Top     221     228     219
Mid Top 217     225     217
Mid     213     217     212
Low     212     221     214
Bottom  214     223     220

Center Frame:
        L       Mid     Right
Top     219     226     224
Mid     206     216     218
Bottom  211     222     223

Right faces the scanner front.

Next the focus was changed at the center of the negative and the SFR was
measured at 50% response and 10% response.  Note that SFR is the spectrum
of a slanted edge and gives a more conservative number than MTF using
sinewaves.  For comparison the 50% response is 500 cycles/in using MTF and
290 cycles/in using SFR.  Also note these numbers include the response of
Kodak Max400 and my Canon FD 50mm F3.5 macro lens stopped down to F9.5 and
tripod mounted.  The 50% SFR indicates sharpness, while the 10% SFR
indicate resolution.

Nikon Focus     50% SFR 10% SFR
214             283.6   690
226             238.5   580
238             158.6   450

For comparison, my Minolta Dual (SCSI, fixed focus) has 50% SFR in the
center of the negative at 170 cycles/in and 10% SFR at 570 cycles/in. So
the depth of field to equal the Minolta best SFR is just under +/- 24.
Grain is soft at this limit.

Mike Duncan


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