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Forum: Film SLRs and Compact Film Cameras
10-30-2017, 11:31 AM
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I am still trying to get a feel for the margin between the film MTF curve and what is needed in typical hand held photos.
This photo was with the Ricoh KR-5, Fuji Superia 200 35mm and the SMC Pentax 1:2.8 40mm
The photo .tiff is of lettering on a sign so has lots of edges in it.
The Fuji film rolls off at approximately 40 per millimetre.
The scanner was set to a resolution corresponding to 62.5 lines /mm.
https://app.box.com/s/rrk6aeilqci7mj1wftzsr40vob83ktib
Here is the harmonic content in the photo:
The harmonics are in 16 bit format, so the high order ones are "blocky"
Next time I will put them in floating point.
https://app.box.com/s/7gdxro7wry7y5vxs1gpvkoib7s9gklg8 |
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Forum: Film SLRs and Compact Film Cameras
10-28-2017, 04:12 PM
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I use Fuji Pro 400H C41 which is rated with a corner frequency at about 50 lines per mm, and Ektar 100 which is roughly 40/mm by the data sheets.
On the international 6x7 camera back (eg RH10) the frame width is 67.7mm.
Scan resolution needed for a Nyquist of 50/mm : 2 * (50 * 67.7) = 6770 pixels across.
That corresponds to a nearest scanner setting of 2400 pixels per inch on my PrimeFilm 120Pro.
Here is a scan of Ektar 100 using the vintage (1960's) Super Angulon 65mm on a (1953) 2x3 Graflex with 6x7 back.
(By the way I am finding this old lens difficult to use hand held)
https://app.box.com/s/9qrlw48oqngxx849v6tgrz4l0f129amc
I wanted to quantify how close the higher harmonics of these images are coming to the Modulation Transfer Function (MTF) rating of the film.
The image was converted into the frequency domain, then I extracted the amplitudes of harmonics.
After about the 700th harmonic, the level has tended to zero.
700th harmonic corresponds to a period of about 67 micrometer or 15 lines per millimetre.
So there seems to be reserve, meaning that a hand held photo like this needs a resolution safely below the MTF roll-off of the film and scanner.
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