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Old Nov 29, 2004, 3:15 AM   #1
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Hi all,
There was a post a while back about f8 and 1/2000s bot being useful. Thought I would share this pic hot off the press taken with these settings.
Just thought I would share it, been a while since my last photo post.
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Old Nov 29, 2004, 9:35 AM   #2
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Perfect. I like how these settings keep the detail in the bright areas around the perifory of the clouds without blowing them out. I will keep these setting in mind. I try not to venture into F-8 territory as a rule of thumb with digitals but here the results speak for themselves.
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Old Nov 29, 2004, 4:37 PM   #3
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I was also at full zoom, so f8 really is the best. Nick, why would you not usually use f8 in digital cams?
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Old Nov 29, 2004, 6:24 PM   #4
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Treemonkey wrote:
Quote:
I was also at full zoom, so f8 really is the best. Nick, why would you not usually use f8 in digital cams?
(Well... in the case of your photo, since you were pointing it directly at the sun, you didn't have a choice. F-8, 50 iso, and the cam set the shutter speed as quick as possible. So I stand corrected. However, apart from this...)

To avoid lens diffraction, and optimize the the resolution capabilities of the lens is the short answer. That is every lens has a "sweet spot" F4 (my opinion) seems like it's it for the Lumixes. The "sweet spot" is the F-stop that minimizes diffraction and optimizes the resolution capabilities of the lens. The f-stop where this occurs is relative to the size of the focal plane. Quite small in most digitals, which is why they don't "give you" f-11, f-16 (excluding DSLRs) like 35mm film cams. I set the f-stop to f-4 and iso 50 whenever possible on my FZ-1, and let the cam adjust the shutter speed accordingly when shooting outdoors, unless circumstance dictates another setting. More below (Sorry, forgot to get the Q/A link...)
__________________________________________________ _______
http://www.normankoren.com/digital_cameras.html

1. Lens Diffraction...
Small sensors run into problems with lens diffraction, which limits total image resolution at small apertures. The f-stop where the image becomes diffraction-limited is proportional to format size (sensor diagonal). It's around f/16-f/22 for the 35mm format (43.3 mm diagonal). At large apertures-- f/4 and above-- resolution is limited by aberrations. There is a resolution "sweet spot" between the two limits, typically between f/5.6 and f/11 for good 35mm lenses. A 22 mm diagonal sensor becomes diffraction-limited around f/8 and an 11 mm diagonal sensor becomes diffraction-limited around f/4-- the same aperture where it becomes aberration-limited. There is no "sweet spot;" the total image resolution at optimum aperture is considerably less than for larger formats.

2. Stay in the Camera's Sweet Spot
The larger the format, the larger the sweet spot.
Lenses have their optimum aperture— their highest total resolution— near the center of the sweet spot, typically around f/8 for 35mm, f/11 for medium format, f/16 for 4x5, and f/22 for 8x10. In practice, f/16 may be more practical for 4x5 and f/32 is more practical for 8x10 because depth of field is severely limited for large formats. Testing and experience will teach you which apertures are sharpest for your individual lens, but these numbers are good estimates. Optimum aperture is not sharply defined: for example, a good 4x5 lens with an optimum aperture around f/16 should produce excellent image quality between f/11 and f/32. Since large format lenses tend to be diffraction-limited at optimum aperture.

__________________________________________________ ____
Q21. What is diffraction?

A. When a beam of light passes through any aperture it spreads out.
This effect limits how sharp a lens can possibly be.

The diffraction is caused by the limiting of the beam to the size of
the aperture, not primarily by sharp edges of the aperture. Even if
one made a "soft edged" aperture that faded slowly from clear to
opaque, there would still be diffraction, and the size of the central
part of the diffraction pattern would not change much compared with
the sharp-edged case.


Q22. What is the diffraction limit of a lens.

A. All lenses are diffraction limited to no more than about 1500/N to
1800/N line pairs per mm. See below under the question "What is
MTF?".


Q23. What are aberrations?

A. Aberrations are image defects that result from limitations in the
way lenses can be designed. Better lenses have smaller aberrations,
but aberrations can never be completely eliminated, just reduced.

The classic aberrations are:

* Spherical aberration. Light passing through the edge of the lens is
focused at a different distance (closer in simple lenses) than light
striking the lens near the center.

* Coma. Off axis points are rendered with tails, reminiscent of
comets, hence the name. It can be shown that coma must occur if the
image formed by rays passing near the edge of the lens has a different
magnification than the image formed by rays passing near the center of
the lens.

* Astigmatism. Off-axis points are blurred in their the radial or
tangential direction, and focusing can reduce one at the expense of
the other, but cannot bring both into focus at the same time. Think
of it as the focal length as varying around the circumference of the
lens. (Optometrists apply the word "astigmatism" to a defect in the
human eye that causes *on-axis* points to be similarly blurred. That
astigmatism is not quite the same as astigmatism in photographic
lenses.)

* Curvature of field. Points in a plane get focused sharply on a
curved surface, rather than a plane (the film). Or equivalently, the
set of points in the object space that are brought to sharp focus on
the film plane form a curved surface rather than a plane. With a
plane subject or a subject at infinite distance the net effect is that
when the center is in focus the edges are out of focus, and if the
edges are in focus the center is out of focus.

* Distortion (pincushion and barrel). The image of a square object
has sides that curve in or out. (This should not be confused with the
natural perspective effects that become particularly noticeable with
wide angle lenses.) This happens because the magnification is not a
constant, but rather varies with the angle from the axis.

* Chromatic aberration. The position (forward and back) of sharp focus
varies with the wavelength.

* Lateral color. The magnification varies with wavelength.


Q24. Can I eliminate these aberrations by stopping down the lens?

A. The effect of all aberrations except distortion and lateral color
is reduced by stopping down. The amount of field curvature is not
affected by stopping down, but its effect on the film is. But note
that stopping down also increases diffraction.

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Old Nov 29, 2004, 8:30 PM   #5
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Well, that answers it doesnt it! Thanks for that Nick, ive often wondered what the FZ10's sweet spot was. When I get some more time I will do a analysis of image sharpness at diffrent f values and zoom for the FZ10.
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Old Nov 29, 2004, 9:22 PM   #6
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Heres one I took this morning at f8.0, 1/2000


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Old Nov 29, 2004, 9:27 PM   #7
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Bob -

I'm really seeing improvement in composition... not that I'm an expert or anything like that but your photos are getting more and more interesting with each post. This one SCREAMS for an ir filter...:lol:

Nick
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Old Nov 29, 2004, 9:29 PM   #8
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Treemonkey wrote:
Quote:
Well, that answers it doesnt it! Thanks for that Nick, ive often wondered what the FZ10's sweet spot was. When I get some more time I will do a analysis of image sharpness at diffrent f values and zoom for the FZ10.
One of the things I've ordered for outdoor shots for this are a couple ND filters. Basically, they're gray filters that reduce the light coming into the lens for outdoor shots. Looking forward to trying them...
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Old Nov 29, 2004, 9:30 PM   #9
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Oh well, thanks for sharing your pics
I really thought those settings are pretty useless, Im gonna try to get something similar this weekend.

P.D. Valuable information Nick - I printed it.
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Old Nov 29, 2004, 9:34 PM   #10
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NickTrop wrote:
Quote:
Bob -

I'm really seeing improvement in composition... not that I'm an expert or anything like that but your photos are getting more and more interesting with each post. This one SCREAMS for an ir filter...:lol:

Nick
Thank you Nick..

I ussually keep a UV Haze filter on to protect my lense but did not have it on for this shot.

I did'nt even start getting into filters yet, as I am trying to get better with the camera.

What Does an IR filter do?

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