Re: TECH-3D digest 213

[T3D John Ohrt <johrt@xxxxxxx>]

T3D Eric Goldstein wrote:

>  Tangential to that... is it possible that lens
> resolution 2 or 3 times greater than that of the film is still considered
> desireable and yields visible benefits? I seem to recall this from somewhere...

 As, I understand it, you want a lens resolution of at least 3 times the film
resolution as a rule of thumb.

eg if film res = lens res = 100 lpm  ->  .01 mpl

camera mpl = sqrt ( .01^2 + .01^2) = sqrt .0002 = 0.014 mpl

thereffore camera lpm =  70 lpm

however if lens lpm =300  -> .003333 mpl then

Camera mp;l = sqrt ( .01^2 + .003333^2) = sqrt ( 0.0001111) = .01054 mpl

then camera lpm =  95 lpm.

So you can see why 3 is a common rule of thumb.

If you had a lens of 300 lpm resolution were combined with the film resolution of
100 lpm, the camera performance is less than 5% from the performance of a lens of
infitie resolution.

However, if the lens and film resolution are equal, then the camera is functioning
at only 70% of the theoretical maximum.

So going from lens = film res to len = 3x film res, you see an improvement of
25/70 = 36%.

Now, what are you willing to pay for such an improvement?

That's how I understand it.

Comments from the pro's please.

--

John Ohrt * Toronto * ON * Canada






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