[rollei_list] Re: FYI
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 31 Dec 2005 14:10:32 -0800
----- Original Message -----
From: "A. Lal" <alal@xxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Saturday, December 31, 2005 2:00 PM
Subject: [rollei_list] Re: FYI
Not sure what you mean Richard.
These show standard data, i.e. contrast in % (on the Y
axis) as a function of radial displacement from the
optical axis (on the X-axis) for tangential and sagittal
rays at 10, 20 & 40 lppm.
Z did pioneer this, TTBOMK.
The other form for graphing is to show the lines per
millimete plotted against contrast over an interval large
enough to cover the limitations of the lens. Film resolution
is plotted this way. Several graphs are necessary although
plots showing resolution at various image angles for a given
stop can be combined on a single graph or plots for a series
of stops can be combined, in this case several graphs
showing different image angles or hights can be shown.
It is also interesting to have graphs showing spherical
aberration, waveform distortion, and the stimgatic fields. A
lens can be well corrected for astigmatism and still have a
curved field. Astigmatism is the deviation of the tangential
and radial points of focus for various entrance hights.
Ideally, they should overlie each other. The overall field
can still be curved even when astigmatism is small. Field
curvature is sometimes used to aleviate astigmatism by
splitting the error on either side of the flat field.
These may indeed be excellent lenses but the data shown
is not enough to prove it.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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