Aperture limits with high shutter speeds in Panasonic FZ20

measekite wrote:
[]
Even though I do not like it I have the use of a Sony 4mp digital
camera that does produce reasonable results. I also have a Nikon
system.

Ah, so not so much rush, then! It will be interesting to see how things
develop over the summer.

Cheers,
David

On Tue, 19 Jul 2005 14:38:10 +0000 (UTC), (Dave
Martindale) wrote:

Jan Böhme writes:

However, as one decreases the shutter time beyound 1/1000, an aperture
limit is introduced. At 1/1300, the widest accepted aperture is f4.0,
at 1/1600, it is f5.6, and at 2000, it is f8.0, the minimal aperture
of the camera. T

Some of the Canon P&S cameras (e.g. G2) have a similar limitation. It's
because a single mechanism is used as the shutter and aperture. The
blades take a certain amount of time to reach full opening, and that
limits the full-aperture shutter speed.

The way you describe the mechanism, it sounds as if the center of the
image would be considerably more exposed than the edges at high
shutter speeds, giving rise to vignetting. But maybe this only would
occur significantly at the disabled ccombinations of shutter speed and
aperture.

If you're willing to accept a
smaller aperture, you can get a shorter exposure too. This helps the
camera deal with very bright lighting, but doesn't let you use full
aperture at maximum speed.

The alternative, with that shutter mechanism, is to limit the highest
speed to 1/1000. Would that make you happier? Probably not.

No, but not all that much less happy either. If one needs a ND filter
to get shallow DOF in bright light anyway, then of course one can use
the same ND filter under conditions of extremely bright light.

(Canon
does document these limits in the manual).

So do Panasonic, I've discovered, only not at all at place where I
expected it.

If you want very fast shutter speeds at full aperture, you need a focal
plane shutter and separate aperture mechanism. In other words, you need
a SLR.

Wouldn't an electronic shutter do the trick, or are there other
limitations in that case?

The only thing that remains is the
capacity to take properly exposed photos in very intense light - which
would have been equally well catered for by instead including an f11
aperture and doing away with the 1/1000+ shutter times altogether.

No, because at f/8 the image is already losing sharpness due to
diffraction in any of the small-sensor P&S cameras. A higher shutter
speed at f/8 will give you a sharper image. You've already got enormous
DOF at f/8, so there's no reason at all to want f/11.

I suppose not. It might have been more clever to say that it would
have been equally well catered for by including an ISO40 sensitivity.

BTW - is there some table of most favorable apertures for different
sensor sizes, i.e which apertures are the equivalents of f8 for an SLR
for different small-sensor digital cameras?

Jan Böhme
Korrekta personuppgifter är att betrakta som journalistik.
Felaktigheter utgör naturligtvis skönlitteratur.

"Jan Böhme" skrev i meddelandet
...
BTW - is there some table of most favorable apertures for different
sensor sizes, i.e which apertures are the equivalents of f8 for an SLR
for different small-sensor digital cameras?

Jan Böhme

There is nothing equivalent at other scales. F8 is equvalent to F8 for light
inlet, but something else for depth of field, and still something else for
best resolution.
You should try that out yourself with your camera, which aperture is the
sharpest at different zoom lengths.
The new Canon 350 lens (18-55), eg, is sharper at larger apertures and the
old 300 lens, also18-55, is sharper at smaller apertures, so there is really
no rule of thumb.
/per

Jan Böhme wrote:

BTW - is there some table of most favorable apertures for different
sensor sizes, i.e which apertures are the equivalents of f8 for an SLR
for different small-sensor digital cameras?

There is a table to calculate diffraction he
http://www.cambridgeincolour.com/tut...hotography.htm

There is also a link on that page to a DOF calculator, with a dropdown
box to select the common sensor sizes.

Some high mp cameras with small sensors probably have detail loss
starting to occur at close to maximum (widest available) aperture, or at
least some fall-off in contrast will have started. Combine this with
the expectation that most lenses are not sharp at widest aperture -
especially at extremes of the zoom range, and then it seems that often
the high pixel count is wasted.
For high mp small sensor cameras, very fast wide aperture lenses are not
a luxury - they are an absolute necessity - and even then only a few
stops are available with maximum sharpness.

For DOF, you can see that a Canon G6 at f2.8 (one stop off maximimum
wide) at 35mm equivalent has a hyperfocal distance of 2.5 metres.
This is approximately the same as f22 on a typical dslr (and a stop
higher on 35mm). It is a very big difference.
For a hypothetical photo of a person 2.5 metres away from you, with a
background vista, taken at 35mm (equiv focal length) and an expectation
that everything in the frame will be 100% pin-sharp, then it is likely
that a Canon G6 or similar will be able to provide exactly the result
that you want. A dslr will probably not satisfy your expectations - as
at the f22 the image resolution will be well and truly diffraction
limited (but then again maybe not so much that it isn't still quite
acceptable as a 6x4 snapshot).

There is a lot of discussion and arguments about sensor size and noise.
To me, the effect of sensor size on DOF is more important.

David J Taylor wrote:

measekite wrote:
[]


Even though I do not like it I have the use of a Sony 4mp digital
camera that does produce reasonable results. I also have a Nikon
system.



Ah, so not so much rush, then! It will be interesting to see how things
develop over the summer.

Cheers,
David



I do not know if this is relevant but I have downloaded various photos
(that I like for many reasons) that were taken with various cameras with
similar metadata. I then printed 4x6 photos on my IP4000. Maybe I am
having difficulty seeing what I need to see but all of the photos looked
good and there was not that much difference between them. On some
photos I liked the colors of camera x better than y while on others I
thought y was better than x.

What is even more strange was in a 4x6 I compared Pan FZ5, Nikon Cool
Pix 4200 against DRXT, Canon D20, and the Nikon D70 (all of which cost
more than PS) and I was astounded in what I did not see. That is
dramatic differences. I am sure that in an 8.5x11 and up I will see
differences.

I am also wondering how much difference one can see in an 11x14 print
between a Canon 20D and the Canon $8,000 sibling.

Jan Böhme writes:

The way you describe the mechanism, it sounds as if the center of the
image would be considerably more exposed than the edges at high
shutter speeds, giving rise to vignetting. But maybe this only would
occur significantly at the disabled ccombinations of shutter speed and
aperture.

Not at all. If the shutter were a focal plane shutter, then it could
expose some portions of the image and not others. But being located
right inside the lens, even the tiniest shutter opening passes light to
the entire image area.

And what you call the "disabled combinations" are not disabled in the
sense of the firmware not allowing them. The firmware simply knows that
the shutter *physically cannot open and close fast enough* to provide
full aperture at the highest shutter speeds. It takes a finite amount
of time for the shutter to open to f/2 (or whatever max aperture is) and
then close down again.

No, but not all that much less happy either. If one needs a ND filter
to get shallow DOF in bright light anyway, then of course one can use
the same ND filter under conditions of extremely bright light.

You'll probably find that you cannot get a shallow DOF at all, under any
conditions, with this camera. The G2 (which is what I'm familiar with)
has a sensor about 1/5 the dimensions of 35 film. Thus, when the lens
is set to f/2 (wide open), the DOF provided by the camera is equivalent
to a full-frame 35 camera with a lens having the same angle of view set
to f/10, assuming equal print sizes. In other words, the shallowest DOF
available from the G2 is only slightly less than the largest DOF
available on the 35 camera with the lens stopped down to f/16.

If you want very fast shutter speeds at full aperture, you need a focal
plane shutter and separate aperture mechanism. In other words, you need
a SLR.

Wouldn't an electronic shutter do the trick, or are there other
limitations in that case?

Well, what technology of electronic shutter? The LCD and PLZT
electronic shutters I know of aren't actually fully opaque when off -
they need a supplementary mechanical shutter. Nor are they transparent
when on - they eat a lot of light. Not really suitable for a still
camera. Some video cameras have electronically-controlled shutter
speed, but those only have to handle 1/30 second and faster - and
require a CCD designed to do this.

No, because at f/8 the image is already losing sharpness due to
diffraction in any of the small-sensor P&S cameras. A higher shutter
speed at f/8 will give you a sharper image. You've already got enormous
DOF at f/8, so there's no reason at all to want f/11.

I suppose not. It might have been more clever to say that it would
have been equally well catered for by including an ISO40 sensitivity.

You wouldn't want to reduce the fundamental sensitivity of the sensor,
or you'd always have to shoot at ISO 40 for maximum quality, and without
losing a couple of stops at the high end of the ISO range. You can't
just "turn down the gain" electronically, because the lowest ISO is
determined by the point at which the sensor pixel wells overflow. So an
ND filter is actually a pretty good way to handle high brightness in a
small-sensor camera.

BTW - is there some table of most favorable apertures for different
sensor sizes, i.e which apertures are the equivalents of f8 for an SLR
for different small-sensor digital cameras?

You can straightforwardly calculate the amount of diffraction to expect,
and it's proportional to the sensor size ratio. But the optimum
aperture is determined by balancing diffraction and lens aberrations,
and the aberrations do not necessarily scale down at the same rate. So
it depends on each lens.

Dave

measekite wrote:
[]
I do not know if this is relevant but I have downloaded various photos
(that I like for many reasons) that were taken with various cameras
with similar metadata. I then printed 4x6 photos on my IP4000. Maybe I
am having difficulty seeing what I need to see but all of the
photos looked good and there was not that much difference between
them. On some photos I liked the colors of camera x better than y
while on others I thought y was better than x.

Colour is subjective, and all of the current systems (including film) are
an approximation. Even if the colour wasn't "perfect" on a camera all the
time, tweaking after taking is possible.

What is even more strange was in a 4x6 I compared Pan FZ5, Nikon Cool
Pix 4200 against DRXT, Canon D20, and the Nikon D70 (all of which cost
more than PS) and I was astounded in what I did not see. That is
dramatic differences. I am sure that in an 8.5x11 and up I will see
differences.

I am also wondering how much difference one can see in an 11x14 print
between a Canon 20D and the Canon $8,000 sibling.

Some people have a rule of thumb for printing that you need about 300
pixels per inch, so a 4x6 would need 1200 x 1800 pixels to be resolution
limited (2.16MP). Not surprising that you can't see the resolution
differences.

The DSLR cameras differ in having a physically larger sensor, and can
therefore produce lower noise images at higher ISO settings. They also
have interchangeable lenses, dust problems, and are bigger and heavier. A
good point and shoot camera can often equal the quality of a DSLR image,
but it's not as versatile. There are probably a lot of point-and-shoots
at the lower end of the quality range which could never equal a DSLR,
though.

Cheers,
David

David J Taylor wrote:

measekite wrote:
[]


I do not know if this is relevant but I have downloaded various photos
(that I like for many reasons) that were taken with various cameras
with similar metadata. I then printed 4x6 photos on my IP4000. Maybe I
am having difficulty seeing what I need to see but all of the
photos looked good and there was not that much difference between
them. On some photos I liked the colors of camera x better than y
while on others I thought y was better than x.



Colour is subjective, and all of the current systems (including film) are
an approximation. Even if the colour wasn't "perfect" on a camera all the
time, tweaking after taking is possible.



What is even more strange was in a 4x6 I compared Pan FZ5, Nikon Cool
Pix 4200 against DRXT, Canon D20, and the Nikon D70 (all of which cost
more than PS) and I was astounded in what I did not see. That is
dramatic differences. I am sure that in an 8.5x11 and up I will see
differences.

I am also wondering how much difference one can see in an 11x14 print
between a Canon 20D and the Canon $8,000 sibling.



Some people have a rule of thumb for printing that you need about 300
pixels per inch, so a 4x6 would need 1200 x 1800 pixels to be resolution
limited (2.16MP). Not surprising that you can't see the resolution
differences.

The DSLR cameras differ in having a physically larger sensor, and can
therefore produce lower noise images at higher ISO settings. They also
have interchangeable lenses, dust problems,


Are the dust problems on the sensor so bad and so difficult to get rid
of that one does not really want to change lenses? I understand that
you cannot use a can of compressed air. What if you get a stubborn spot?

and are bigger and heavier. A
good point and shoot camera can often equal the quality of a DSLR image,
but it's not as versatile. There are probably a lot of point-and-shoots
at the lower end of the quality range which could never equal a DSLR,
though.

Cheers,
David

measekite wrote:
[]
Are the dust problems on the sensor so bad and so difficult to get rid
of that one does not really want to change lenses? I understand that
you cannot use a can of compressed air. What if you get a stubborn
spot?

Different people seem to report different levels of DSLR dust problem, and
it does seem to depend on both the user and the environment. At least one
camera has a sensor-shaker to remove dust each time the camera is switched
on.

Ask in rec.photo.digital.slr-systems and get a whole set of answers!

Cheers,
David