ZS20 / TZ30 Users: Any tips on 'best' setting for shooting pictures?

Started Dec 30, 2012 | Questions thread
Ianperegian
Senior MemberPosts: 2,715
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Re: Ian, Jimmy #1
In reply to Erik Ohlson, Jan 3, 2013

Hi Erik,

I couldn't really see where the figure of 3mm came from as the effective aperture is not constant in relation to the degree of diffraction, since diffraction depends on the f number.

As far as the effect of wavelength goes, I think it can be assumed that the average wavelength is practically constant for daylight scenes and therefore it is not an issue in relation what we are discussing. That is, considering the resolution and diffraction effects, in daylight, as the aperture and FL are changed on the cam.

As I tried to convey in my reply above, but I don't think I made it very clear, because the diffraction effect is independent of FL (assuming a constant wavelength average) then it can be generally said that for any FL setting, diffraction only really becomes a practical issue above about f/5.6, and it is worst at f/8.

However, that is not to say that "f/8 should never be used" because it might be quite appropriate in many situations. In my dragonfly shot, it does represent the degree of diffraction that occurs at f/6.4, and to my mind it is not a problem.

Quite separate to the diffraction effect there is the issue of the change in resolution of the lens as the aperture and focal length are changed. I've copied below the summary table of my tripod tests using controlled conditions on a test chart (the tests are shown in full at http://www.ianperegian.com/My_FZ35_38_Webpage/ZS20_Resolution_Testing.html )



The results showed that with change in FL the resolution of the ZS20 is generally somewhat higher at shorter and medium FLs than at the tele end.

The resolution at a given FL is generally highest at or near the widest aperture but I think in practical terms narrower apertures can be used in most situations.

That's just my own take on it, and as they say: "your mileage may vary".

Ian

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