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Re: filmscanners: Nikon IV Depth of Field Test

Hello Mike
I think I was the first to try out LS4000 in mars 2001 and reported some
bad scans with curved film, and depth of field problem on my Ls4000 scanner.
I wrote that the scanner was sharp in the middle and unsharp out against the 
sides and corner . Please give me a fully conclusion of your figures.
Best regard Mikael Risedal

>From: Mike Duncan <mgduncan@esper.com>
>Reply-To: filmscanners@halftone.co.uk
>To: Filmscanners@halftone.co.uk
>Subject: filmscanners: Nikon IV Depth of Field Test
>Date: Wed, 29 Aug 2001 14:18:08 -0400
>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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