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Old Jul 1, 2005, 7:32 PM   #11
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The lack of a distance reading (which should be readily able to be provided in the screen display) is one of the two main design failings of the (otherwise well-designed) FZ series...
(the other main problem of course being the EVF - with it's limited resolution and darkening in manual mode).

Though just a pun, the above post's reference to BUZ is ironically apt here - since the FZ20 does have a final focus ofslightly BEYOND INFINITY! That is, just keeping on turning the barrel lots and lots to make sure you get to infinity focus will not necessarily work - because, to allow for manufacturing variations in the optics, Panasonic/Leica have allowed for the lens to actually go slightly past its theoretical point of 'sharpest infinity focus'.

So it will vary from camera to camera - where some people will get infinity focus with maximal focus dial rotation, while others will need to somehow know where to stop turning before then.....

If only Panasonic would have given a distance reading (+ DOF and hyperfocal reading while I am wishful thinking????), critical photo-composition would have been so much easy!!!!

(BTW, FZFUN if you want me to critique your math, it would be better if you expressed your view a bit more clearly. I find the current post rather unclear - and I have a degree in theoretical optics....
eg what do you mean by "max. focus"?
At 6mm (aperture at wide) and the lens focussed sharply at 2m, the acceptable DOF is approx from 1.1 to 9.2 m (for 10mm and f8 the DOF is a similar range for a 2m focus). Wide open and at wide zoom (ie 6mm), the lens has a hyperfocal distance of just under 3m, so as far as the camera is concerned, 'infinity' is practically anything beyond 1.5m - ie if you focus at 3m away everything between 1.5m and far distant is all in adequate focus (but not 'maximal' focus).

For f8 and 6mm the hyperfocal distance of the FZ lens is below a metre!
While for max zoom,stopped down (72mm at f 8.0, the hyperfocal distance is probably something like 120m (ie 'infinity' toapprox 60m away are in reasonable focus).

Problem is, without a distance reading, it's hard to use this knowledge adequately anyway!)
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Old Jul 2, 2005, 12:42 PM   #12
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according to the calculator on the DOFmaster website, the hyperfocal distance for the FZ20 ad max optical zoom is about 425 feet at f8, and 1200 feet at f2.8. as the zoom factor decreases, of course, this distance becomes less, till at max WA, it's only about 3 feet at f8 and a bit over 8 feet at f2.8.

am i confusing "focus on infinity" with hyperfocal distance? it's beginning to look that way... :?
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Old Jul 2, 2005, 11:40 PM   #13
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8OK...max focal distance of 6.56 in this case is the farthest it will focus at F2.8 and still be considered 1X.

The other thing I realized is that I was cheating and being a little lazy with how the 6mm distance between 11X and 12X really breaks down. I divided it evenly, but thats not actually the correct way to do it. I could be totally wrong here, but the last magnificiation from 11X max focus, to 12 max focus should have a magnification factor of 1.090909. 6mm, so, X^6=1.090909 Which means the each mm has and the final magnification at the end of the last mm is .00002338196528. From there I can't seem to make the math work out, but technically, if you multiply .00002338196528 (lost train of thought)

2*1.5*1.33333333*1.25*1.2*1.16666667*1.42857143*1. 125*1.111111*1.1=total magnification at 11X.grrr..too tired for this...I'll come back to it again later..

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Old Jul 3, 2005, 2:19 AM   #14
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How exact the "focus on infinity" is required depends on the final output - eg how big the image or print is to be viewed and how good the eyesight of the viewer is likely to be.

It all depends on how big a Circle of Confusion (CoC) the photographer is prepared to accept - standard CoC values for 35mm cameras assume reasonably large print sizes and average eyesight, and usually lie around 0.03mm. This means a standard CoC for the FZ lens (with its small CCD) is around 0.005mm.
However for poster size prints (or for viewing by people with very good eyesight), the CoC should be as much as 3 times smaller - meaning the actual lens focus has to be setmuch closer to the calibrated'infinity' focus point of the barrel (for that zoom setting) to get horizons of acceptable sharpness.

Focussing at the usually given hyperfocal distances thus means that 'infinity' is only just in focus, for people of average eyesight. Actual 'maximal 'focus for distant objects is actually well beyond such average CoC hyperfocal distances.

FZFUN - unless I am misunderstanding what you are trying to say, it appears you are confusing some of the standard optics terminology, so that your calculation is significantly off mark. eg the hyperfocal distance for the FZ lens at max zoom is at least 120m, and in mostlighting cases (ie possible f settings) will be well beyond this. So the 'infinity' focus of the lens (at 72mm) is over 5 times the value you have calculated.

Of course it's always fun to spend time on numerical anaysis (but most people would probably say that's weird theoretical physicisttalk lol) :lol:

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