aperture and fixed zoom lens non DSLR

Desert Dweller wrote:

> I keep reading about apertures of F/22 for story-telling photos,
> showing foreground grass in focus as well as background mountains in
> focus. My shiny new non-DSLR digital camera I bought (Panasonic Lumix
> FZ8) only can close the aperture down to F/8. Does this mean I can't
> get those story-telling, landscape shots with my camera? Do I need a
> better camera? When I try to take those shots, the camera's auto-focus
> finds something to focus on and everything else is out of focus. If I
> choose manual focus, then whatever I do not focus on is still out of
> focus. How do I get everything in focus? And can F/8 do it? Is that
> the problem?
>
Compact non-interchangeable lens cameras such as the FZ8 have tiny
sensors (IIRC yours is about 7mm diagonal), which gives vast depth of
field - at f/8 and the wide end of the zoom you should be able to get
everything from about half a metre away to infinity in focus if you
focus at about 1 metre, the hypofocal distance.

For a more detailed explaination of depth of field & hypofocal distance
focussing, have a look here:

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm
http://www.cambridgeincolour.com/tutorials/DOF-calculator.htm

If you want to use the online calculators, remember that the FZ8 has a
1/2.5" sensor, which is slightly smaller than the 1/1.8" that some of
the calculators go down to. Also, the focal length used is the actual
focal length (6-72mm), not the 35mm equivalent (36-432mm).

The pictures that you've been looking at were probably taken on 35mm,
medium format (6x6cm etc.) or large format (up to 10x8") cameras, so
they need much smaller apertures to get the depth of field.

> In contrast, to get those macro shots of the subject popping out of
> the image so that everything else is totally out of focus, I've been
> seeing those images with apertures of F/1.4. My camera won't go that
> big, as its biggest setting is F/2.8. When I take the macro shots, the
> background is out of focus slightly, but not as much as the images I
> see
> in magazines, books, and on the web that claim to be at F/1.4. Do I
> need a better camera? Or is there more technique in getting those
> shots that I haven't learned?
>
This is the opposite to the problem you described above, getting a
narrow depth of field is difficult with a small sensor. However, to
some extent you can sometimes improve things by zooming to a longer
focal length and stepping back, since DoF is related to focal length.
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

In article <4ipr93dqb7jstrta4btuo5pa7hrc4l736k RemoveThis @4ax.com>, BaumBadier
says...

> Look up "hyperfocal distance" on the net. At f/8.0, widest zoom, and manually
> focused on about 3 ft, everything from 18 inches to infinity is in focus.

How much is that in metres and cm?
--

Alfred Molon
------------------------------
Olympus 50X0, 7070, 8080, E3X0, E4X0 and E5X0 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

On Jul 22, 10:57 pm, Ilya Zakharevich <nospam-ab... DeleteThis @ilyaz.org> wrote:
> [A complimentary Cc of this posting was sent to
> Alex Monro
> <al... DeleteThis @pobox.com>], who wrote in article <469debe0$0$641$5a6ae...@news.aaisp.net.uk>:
>
> > This is the opposite to the problem you described above, getting a
> > narrow depth of field is difficult with a small sensor. However, to
> > some extent you can sometimes improve things by zooming to a longer
> > focal length and stepping back, since DoF is related to focal length.
>
> BS. Depth of focus is related ONLY to magnification and f-number.
>

Well then: magnification and f-number are both dimensionless; so how
can a distance depend only on these two? How can you form a quantity
with units of length out of two (dimensionless) numbers?
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

On Jul 22, 11:27 pm, Ilya Zakharevich <nospam-ab....TakeThisOut@ilyaz.org> wrote:
> [A complimentary Cc of this posting was NOT [per weedlist] sent to
> acl
> <achilleaslazari....TakeThisOut@yahoo.co.uk>], who wrote in article <1185131076.227326.321....TakeThisOut@o61g2000hsh.googlegroups.com>:
>
> > > > This is the opposite to the problem you described above, getting a
> > > > narrow depth of field is difficult with a small sensor. However, to
> > > > some extent you can sometimes improve things by zooming to a longer
> > > > focal length and stepping back, since DoF is related to focal length.
> > > BS. Depth of focus is related ONLY to magnification and f-number.
> > Well then: magnification and f-number are both dimensionless; so how
> > can a distance depend only on these two? How can you form a quantity
> > with units of length out of two (dimensionless) numbers?
>
> Good question. You forgot about wavelength; this is easy to do; I do
> not think I saw places where this is done 100% correct. So let's look
> through the math (I hope it is correct .

I was just pedantically pointing out that the "ONLY" in your statement
renders it incorrect . Obviously another length is needed, even from
dimensional arguments.

>
> Magnification determines "depth magnification". f-number determines
> the angle of the cone of incoming light. E.g., if your 2 subjects are
> separated by 10cm depth-wise, their images near the focal plane will
> be separated by 10cm/M^2 depth-wise (here magnification is 1/M).
> Assuming the focal plane is in the middle, this would give 5cm/M^2
> off-focus distance.
>
> With f/8, this translates to 5cm/M^2/8 diameter of circle of confusion.
>
> Now return to depth of focus: we want the circle of confusion due to
> off-focus to be related to the circle of confusion of in-focus
> objects. The latter one is due to diffraction (depends only on
> f-number, and wavelength), and "lens quality". Since there is no
> other "reasonable" assumption - assume that the lens quality is the
> same (measured in the ratio of diameters of the actual circle of
> confusion to the circle of confusion of same-f-number
> diffraction-bound lens).
>
> So you get that magnification and f-number determine the depth of
> focus via the wavelength.

Well that's because you arbitrarily decided to use wavelength. All
you're doing here is ray optics, which is essentially geometrical.
This is why you can argue the way you do about magnifications and so
on: you could draw a ray diagram and then enlarging everything by two
and it would still be correct (if it was correct to start with),
precisely because wave effects are neglected.

So you should be able to reason without invoking wavelengths or
anything like that. Of course in the end you need to decide about the
acceptable COC and this is where you bring in diffraction disks and
hence the wavelength, but this is external to the theory: I could just
as well decide to use 100 microns COC, independent of everything.
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

I was wondering why you were so polite

On Jul 23, 12:13 am, Ilya Zakharevich <nospam-ab....TakeThisOut@ilyaz.org> wrote:
> [A complimentary Cc of this posting was NOT [per weedlist] sent to
> acl
> <achilleaslazari....TakeThisOut@yahoo.co.uk>], who wrote in article <1185133617.028715.66....TakeThisOut@57g2000hsv.googlegroups.com>:

> > I was just pedantically pointing out that the "ONLY" in your statement
> > renders it incorrect . Obviously another length is needed, even from
> > dimensional arguments.
>
> In context of r.p.d, the wavelength is a fixed parameter. So without
> <pedantic></pedantic> markers, your "pointing out" was confusing.

Let me be explicit then: you wrote that (I quote) "Depth of focus is
related ONLY to magnification and f-number.". Well that's wrong;
furthermore, it's impossible, and obviously so. Now I know what you
mean and normally wouldn't say anything, but...


> > Well that's because you arbitrarily decided to use wavelength. All
> > you're doing here is ray optics, which is essentially geometrical.
>
> Nope. Diffraction is not "essentially geometrical".

Yes, that's what I said: all your reasoning is geometrical, until you
introduce diffraction. Please concentrate.

>
> > This is why you can argue the way you do about magnifications and so
> > on: you could draw a ray diagram and then enlarging everything by two
> > and it would still be correct (if it was correct to start with),
> > precisely because wave effects are neglected.
>
> This argument of yours is complemente misplaced. Doubling the focal
> length and the object distance is NOT "enlarging everything by two";
> it is a much finer effect: e.g., note M *squared* in the initial
> argument, and that the size of the image does not change.

I did not say that doubling everything by 2=doubling f and s. I said
that if I draw a correct ray diagram and enlarge it by 2, it remains
correct. This is meant to illustrate the fact that we are reasoning
geometrically to arrive at the conclusion that magnification and f-
stop are important (rather than eg f by itself). Except that COC
wasn't mentioned anywhere, which is what made your statement wrong.

Again, please concentrate.

>
> > So you should be able to reason without invoking wavelengths or
> > anything like that. Of course in the end you need to decide about the
> > acceptable COC and this is where you bring in diffraction disks and
> > hence the wavelength, but this is external to the theory: I could just
> > as well decide to use 100 microns COC, independent of everything.
>
> Of course you can decide on discussing anything you like. However, I
> was discussing depth of focus.

Ha! Wouldn't it have been easier to say "oops yes, the COC also comes
in somewhere"?

>
> Hope this helps,

I'm sure you do
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

[A complimentary Cc of this posting was sent to
Alex Monro
<alexm.DeleteThis@pobox.com>], who wrote in article <469debe0$0$641$5a6aecb4@news.aaisp.net.uk>:
> This is the opposite to the problem you described above, getting a
> narrow depth of field is difficult with a small sensor. However, to
> some extent you can sometimes improve things by zooming to a longer
> focal length and stepping back, since DoF is related to focal length.

BS. Depth of focus is related ONLY to magnification and f-number.

Hope this helps,
Ilya
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

[A complimentary Cc of this posting was NOT [per weedlist] sent to
acl
<achilleaslazarides RemoveThis @yahoo.co.uk>], who wrote in article <1185131076.227326.321350 RemoveThis @o61g2000hsh.googlegroups.com>:

> > > This is the opposite to the problem you described above, getting a
> > > narrow depth of field is difficult with a small sensor. However, to
> > > some extent you can sometimes improve things by zooming to a longer
> > > focal length and stepping back, since DoF is related to focal length.

> > BS. Depth of focus is related ONLY to magnification and f-number.

> Well then: magnification and f-number are both dimensionless; so how
> can a distance depend only on these two? How can you form a quantity
> with units of length out of two (dimensionless) numbers?

Good question. You forgot about wavelength; this is easy to do; I do
not think I saw places where this is done 100% correct. So let's look
through the math (I hope it is correct .

Magnification determines "depth magnification". f-number determines
the angle of the cone of incoming light. E.g., if your 2 subjects are
separated by 10cm depth-wise, their images near the focal plane will
be separated by 10cm/M^2 depth-wise (here magnification is 1/M).
Assuming the focal plane is in the middle, this would give 5cm/M^2
off-focus distance.

With f/8, this translates to 5cm/M^2/8 diameter of circle of confusion.

Now return to depth of focus: we want the circle of confusion due to
off-focus to be related to the circle of confusion of in-focus
objects. The latter one is due to diffraction (depends only on
f-number, and wavelength), and "lens quality". Since there is no
other "reasonable" assumption - assume that the lens quality is the
same (measured in the ratio of diameters of the actual circle of
confusion to the circle of confusion of same-f-number
diffraction-bound lens).

So you get that magnification and f-number determine the depth of
focus via the wavelength.

Hope this helps,
Ilya
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

[A complimentary Cc of this posting was NOT [per weedlist] sent to
acl
<achilleaslazarides.DeleteThis@yahoo.co.uk>], who wrote in article <1185133617.028715.66630.DeleteThis@57g2000hsv.googlegroups.com>:
> > > > BS. Depth of focus is related ONLY to magnification and f-number.

> > > Well then: magnification and f-number are both dimensionless; so how
> > > can a distance depend only on these two? How can you form a quantity
> > > with units of length out of two (dimensionless) numbers?

> > Good question. You forgot about wavelength; this is easy to do; I do
> > not think I saw places where this is done 100% correct. So let's look
> > through the math (I hope it is correct .

> I was just pedantically pointing out that the "ONLY" in your statement
> renders it incorrect . Obviously another length is needed, even from
> dimensional arguments.

In context of r.p.d, the wavelength is a fixed parameter. So without
<pedantic></pedantic> markers, your "pointing out" was confusing.

> Well that's because you arbitrarily decided to use wavelength. All
> you're doing here is ray optics, which is essentially geometrical.

Nope. Diffraction is not "essentially geometrical".

> This is why you can argue the way you do about magnifications and so
> on: you could draw a ray diagram and then enlarging everything by two
> and it would still be correct (if it was correct to start with),
> precisely because wave effects are neglected.

This argument of yours is complemente misplaced. Doubling the focal
length and the object distance is NOT "enlarging everything by two";
it is a much finer effect: e.g., note M *squared* in the initial
argument, and that the size of the image does not change.

> So you should be able to reason without invoking wavelengths or
> anything like that. Of course in the end you need to decide about the
> acceptable COC and this is where you bring in diffraction disks and
> hence the wavelength, but this is external to the theory: I could just
> as well decide to use 100 microns COC, independent of everything.

Of course you can decide on discussing anything you like. However, I
was discussing depth of focus.

Hope this helps,
Ilya
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

Ilya Zakharevich wrote:

> [A complimentary Cc of this posting was sent to
> Alex Monro
> <alexm DeleteThis @pobox.com>], who wrote in article
> <469debe0$0$641$5a6aecb4@news.aaisp.net.uk>:
>> This is the opposite to the problem you described above, getting a
>> narrow depth of field is difficult with a small sensor. However, to
>> some extent you can sometimes improve things by zooming to a longer
>> focal length and stepping back, since DoF is related to focal length.
>
> BS. Depth of focus is related ONLY to magnification and f-number.
>
Sorry, I missed the bit about macro, so obviously the close up rules
apply.

http://en.wikipedia.org/wiki/Depth_of_field
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

On Jul 22, 2:57 pm, Ilya Zakharevich <nospam-ab....TakeThisOut@ilyaz.org> wrote:
> [A complimentary Cc of this posting was sent to
> Alex Monro
> <al....TakeThisOut@pobox.com>], who wrote in article <469debe0$0$641$5a6ae...@news.aaisp.net.uk>:
>
> > This is the opposite to the problem you described above, getting a
> > narrow depth of field is difficult with a small sensor. However, to
> > some extent you can sometimes improve things by zooming to a longer
> > focal length and stepping back, since DoF is related to focal length.
>
> BS. Depth of focus is related ONLY to magnification and f-number.
>
> Hope this helps,
> Ilya


You are incorrect. Ever wonder why Ansel Adams often stopped down to
f32 and beyond to achieve large DOF? He was working on large format
material and thus needed to use tiny apertures to combat the fact that
the COF of such large formats is appreciable (.2mm for an 8x10).
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

[A complimentary Cc of this posting was sent to
ajamess DeleteThis @gmail.com
<ajamess DeleteThis @gmail.com>], who wrote in article <1185212328.428843.310250 DeleteThis @n2g2000hse.googlegroups.com>:
> > BS. Depth of focus is related ONLY to magnification and f-number.

> You are incorrect. Ever wonder why Ansel Adams often stopped down to
> f32 and beyond to achieve large DOF?

Why would somebody "wonder" about this?

> He was working on large format material and thus needed to use tiny
> apertures to combat the fact that the COF of such large formats is
> appreciable (.2mm for an 8x10).

I do not think that your sentence makes any sense.

Anyway, since "Depth of focus is related ONLY to magnification and
f-number", you get the same DoF for 16mm film and 8x10in film - as far
as you use the same magnification and f-number.

I suspect that the reason why you are so confused is that TYPICAL
MAGNIFICATIONS used with different sizes of film/sensors are very
different; this is why typical f-numbers must be very different - if
you want to achieve similar DoF. [The other, somewhat related, reason
is the question of quality of lenses - for smaller formats it is
easier to make lenses which are diffraction-bound at significant
f-numbers; it looks like some recent 1/2.5in cameras have lenses which
are diffraction-bound at f/4.]

Hope this helps,
ILya
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

Ilya Zakharevich wrote:
> [A complimentary Cc of this posting was sent to
> Alex Monro
> <alexm RemoveThis @pobox.com>], who wrote in article <469debe0$0$641$5a6aecb4@news.aaisp.net.uk>:
>> This is the opposite to the problem you described above, getting a
>> narrow depth of field is difficult with a small sensor. However, to
>> some extent you can sometimes improve things by zooming to a longer
>> focal length and stepping back, since DoF is related to focal length.
>
> BS. Depth of focus is related ONLY to magnification and f-number.
>
> Hope this helps,
> Ilya

BS. Depth of field is related to focal length and f:stop. Nobody asked
about Depth-of-focus which is a different item.

Small sensor cameras have a lot of Depth of field because they have
short lenses. Common is 5-7mm at the short end. Even APS size sensor
dSLR appear to have more DoF because users keep wanting to translate the
crop factor into a magnification factor. They take a 1.5/1.6 factor and
assume they are working with a longer lens. Then they comment, oh
digital has more DoF than film.
 >> Stay informed about: aperture and fixed zoom lens non DSLR 

[A complimentary Cc of this posting was sent to
Not Disclosed
<nospam DeleteThis @invalid.not>], who wrote in article <46b1f31c$0$11988$88260bb3@unlimited.teranews.com>:
> > BS. Depth of focus is related ONLY to magnification and f-number.

> BS. Depth of field is related to focal length and f:stop.

Since depth of focus is related ONLY to magnification and f-number,
the focal length comes into equation ONLY if a change in focal length
changes the magnification.

If you shoot the same subject with 50mm and 100mm lens with the same
f-number, AND choose the distance so that the subject fills the frame
both times, the depth of focus will be the same.

> Small sensor cameras have a lot of Depth of field because they have
> short lenses.

This is very misleading. It is possible to make *exactly* the same
shots with different form-factors of sensors (see my posts on the
scaling laws, if you do not know the details). Just changing the
format of the sensor would not change the depth of field - if you
accompany it with appropriate changes in other parameters.

"Small sensor cameras have a lot of Depth of field" makes sense ONLY
in the following context:

Given a 12mm sensor, to make an equivalent of a shot made at f/4
with 25mm sensor, one needs to use f/2. The lens may not provide
f/2 (or the aberrations at f/2 of a smaller lens may be more
pronounced that at f/4 of a larger lens), so an equivalent shot
could be not possible WITH THE GIVEN lens/sensor COMBINATION.

Hope this helps,
Ilya
 >> Stay informed about: aperture and fixed zoom lens non DSLR