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Another Depth of Field Question

 
 
tomm42
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      07-15-2006

> > You're wrong. It's not as easy or flexible to do with
> > small-sensor cameras but if the point of focus is close
> > and/or a longer focal length is used it's perfectly
> > possible, and something I do quite often.

>
> I took the camera out of the box and tried to do this. I set the
> aperture for its lowest setting, then tried to focus on my exquisite
> Subaru. Whenever I touched the focus, even though I was in the "Av
> Priority" setting, the aperture setting changed. How else are you
> supposed to focus if not with the auto focus; and if the auto focus has
> dominance over the other customized settings, is this not just another
> way of saying the p&s can only autofocus?
>
> I'm not being rhetorical. I don't know any other way to focus outside
> of bodily getting the subject in focus by waltzing with myself, at
> which point my neighbors will have all the proof they need I've finally
> gone over the edge.


Your asking some basic yet fair deep photo questions. You are talking
about two variables that are interdependent on each other.
Depth of field and exposure.
Exposure is a relationship between, sensor sensitivity (ISO) shutter
speed aperture, and ambient light. So for a given sensor ISO in a
given lighting situation there is a a unique set of shutter speeds and
apertures. The easiest one to explain is a sunny day at noon, your
exposure in the sun will be 1/ISO at f16 so if you have an ISO of 125
your exposure will be 1/125 @ f16, 1/250 @ f11, 1/500 @ f8, 1/1000 @
f5.6. Vary the shutter speed you have to vary the aperture. What
happened to you was the aperture was too large for the shutter speed of
your camera. It also could be there is a preset that is set on your
camera for groups or landscapes etc, check the menus and ditch that if
you want to learn anything.
Depth of field
For every focal length there is a distance in front and in back of the
focal point that will appear to be in sharp focus. So if you want a
narrow depth of field in bright sunlight you better have 1/4000 or up
on your camera cause if we go back to the earlier example the f stop
for 1/4000 will be f2, a very wide aperture. But if you are
photographing inside under artificial light I will be difficult to get
alot of depth of field so say the exposure is 1/30 @f2.8 and you want
to photograph a group, to even get f5.6 you are at 1/8 of a second,
difficult to hand hold at that speed, a tripod, image stabilization or
a flash (to get more light) is necessary.
You should get a good photo book, be it film or digital based, the
basics are the same. I also find a basis manual camera easier to get
the concepts. Go find a second hand pentax K1000 and a 50mm lens and
some ISO 100 film, find a pro lab to get contact sheets made and just
shoot a couple of rolls using a match needle meter, you start to
understand. If there was a cheap digital camera you could do the same
thing with I'd say get that.


Tom

 
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Paul Mitchum
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      07-16-2006
Jules Vide <(E-Mail Removed)> wrote:

> Paul Mitchum wrote:
> >
> > Actually, depth of field is the extent to which objects appear sharp in
> > the print. But your definition is close enough for practical purposes.

>
> [SNIP HELPFUL CLARIFICATION]
>
> > A narrow depth of field focused on a near-field object, with the
> > background all fuzzy is a standard technique. To use it, you open up the
> > aperture and focus on the near-field object.

>
> Am I right or wrong in assuming you can't do this with a p&s camera, even
> if the camera has a setting called aperture priority?


You can do this with any lens that lets you set a small enough aperture.
You'd have to use aperture priority if you wanted automatic metering.

Some point-and-shoot cameras have a closeup or macro mode (usually shown
on the mode selector as a little flower) you could try using instead.
This works best for close, small objects (like, say... flowers), but try
experimenting and see what else it'll do.
 
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Paul Mitchum
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      07-16-2006
Paul Mitchum <(E-Mail Removed)0m> wrote:

> Jules Vide <(E-Mail Removed)> wrote:
>
> > Paul Mitchum wrote:
> > >
> > > Actually, depth of field is the extent to which objects appear sharp in
> > > the print. But your definition is close enough for practical purposes.

> >
> > [SNIP HELPFUL CLARIFICATION]
> >
> > > A narrow depth of field focused on a near-field object, with the
> > > background all fuzzy is a standard technique. To use it, you open up the
> > > aperture and focus on the near-field object.

> >
> > Am I right or wrong in assuming you can't do this with a p&s camera, even
> > if the camera has a setting called aperture priority?

>
> You can do this with any lens that lets you set a small enough aperture.


I did, of course, mean BIG enough aperture.

> You'd have to use aperture priority if you wanted automatic metering.
>
> Some point-and-shoot cameras have a closeup or macro mode (usually shown
> on the mode selector as a little flower) you could try using instead.
> This works best for close, small objects (like, say... flowers), but try
> experimenting and see what else it'll do.

 
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minnesotti
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      07-16-2006

Jules Vide wrote:
> ... tried to focus on my exquisite Subaru.


Aha... you like your equipment... this is a characteristic of a "pixel
peeper". If you are one, you need a camera better than Canon A620.
Canon of cameras is a Toyota of cars. Get yourself a Panasonic LX1 or
Ricoh GR-Digital.



 
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jeremy
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      07-16-2006
"Jules Vide" <(E-Mail Removed)> wrote in message

>> A narrow depth of field focused on a near-field object, with the
>> background all fuzzy is a standard technique. To use it, you open up the
>> aperture and focus on the near-field object.

>
> Am I right or wrong in assuming you can't do this with a p&s camera,
> even if the camera has a setting called aperture priority?
>


The degree to which you can shoot with shallow depth-of-field depends upon
the lens you are using. Two specific factors are involved.

1: Some lenses have wider maximum apertures than others. For example, my
50mm f/1.4 lens will give me shallower depth-of-field when opened to maximum
aperture than will my 35mm f/3.5, because the 50mm lens can open up wider.

2: The focal length of the lens matters. Telephoto lenses have shallower
depth of field than wide angle lenses. Wide angle lenses won't give you the
shallow depth-of-field that you will get from telephoto lenses.

So, if your objective it to blur the background, use a fast normal lens,
opened to full aperture or close to full aperture, or use a telephoto lens.
Don't use a wide angle lens and expect to have shallow depth-of-field.

DIGITAL CAMERAS, with their typically-small sensor size, add another factor
to the equation. Small sensor sizes result in MORE depth-of-field, all
other things being equal. So you probably will not be able to get as
shallow a depth-of-field on a digicam as you can on a film SLR with a fast
normal lens.

And many digicams do not allow the photographer to manually set the
aperture. The cameras control aperture and shutter speed. If you own such
a camera you will not be able to control the amount of depth-of-field at
all.

There are other digital cameras that have things like "portrait mode," where
the camera will open up the lens to a wide aperture to achieve some degree
of shallow depth-of-field. Check your camera manual to see if it has such a
mode.

Shallow depth-of-field is one of my favorite techniques to visually isolate
the main subject from its surroundings, and I feel that I have the greatest
degree of control by using it with one of my film cameras and 50mm f/1.4
normal lenses. My digicam does not offer the ability to control aperture,
so most of my shots naturally have a lot of depth-of-field. That is great
for landscape shots, where I would want everything to be in sharp focus, but
not good for times when I want shallow depth-of-field, such as for
portraits.


 
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jeremy
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      07-16-2006

"Jules Vide" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> John Bean wrote:
>> >
>> >> A narrow depth of field focused on a near-field object, with the
>> >> background all fuzzy is a standard technique. To use it, you open up
>> >> the
>> >> aperture and focus on the near-field object.
>> >
>> >Am I right or wrong in assuming you can't do this with a p&s camera,
>> >even if the camera has a setting called aperture priority?

>>
>> You're wrong. It's not as easy or flexible to do with
>> small-sensor cameras but if the point of focus is close
>> and/or a longer focal length is used it's perfectly
>> possible, and something I do quite often.

>
> I took the camera out of the box and tried to do this. I set the
> aperture for its lowest setting, then tried to focus on my exquisite
> Subaru. Whenever I touched the focus, even though I was in the "Av
> Priority" setting, the aperture setting changed. How else are you
> supposed to focus if not with the auto focus; and if the auto focus has
> dominance over the other customized settings, is this not just another
> way of saying the p&s can only autofocus?
>
> I'm not being rhetorical. I don't know any other way to focus outside
> of bodily getting the subject in focus by waltzing with myself, at
> which point my neighbors will have all the proof they need I've finally
> gone over the edge.
>


Not to want to keep beating a dead horse, but if you had a simple, manual
camera with a fast normal lens, you could achieve your objective with ease,
any time you wanted.

Automatic digital cameras, with their small sensors and factory-programmed
exposure settings, make it difficult or impossible for the photographer to
stay in control. Most people that use P&S cameras--film or
digital--probably do not even know that there is such a thing as being able
to control depth-of-field at all. Automation is a double-edged sword.

Ideally one's camera should offer manual override. My film SLRs, the Pentax
P3n and the P30t, both have automatic exposure but they allow me to manually
set my shutter speed and aperture openings. If I open my aperture up full
and that requires a shutter speed that is faster than my camera's maximum of
1/1000, I just need to fit a neutral density filter onto the lens.


 
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Peter Irwin
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      07-16-2006
jeremy <(E-Mail Removed)> wrote:
>
> 2: The focal length of the lens matters. Telephoto lenses have shallower
> depth of field than wide angle lenses. Wide angle lenses won't give you the
> shallow depth-of-field that you will get from telephoto lenses.


That's true for the case where you are shooting at the same
istance for each lens. If you are shooting for the same
reproduction ratio, the DOF will be similar for different
focal length lenses. So if you shoot from 1 meter away with
a 35mm lens and 5 meters away with a 175mm lens so that the
image size is the same in both cases, you will get similar
DOF at the same aperture.

Peter.
--
http://www.velocityreviews.com/forums/(E-Mail Removed)
 
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Paul Mitchum
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Posts: n/a
 
      07-16-2006
Peter Irwin <(E-Mail Removed)> wrote:

> jeremy <(E-Mail Removed)> wrote:
> >
> > 2: The focal length of the lens matters. Telephoto lenses have shallower
> > depth of field than wide angle lenses. Wide angle lenses won't give you the
> > shallow depth-of-field that you will get from telephoto lenses.

>
> That's true for the case where you are shooting at the same
> istance for each lens. If you are shooting for the same
> reproduction ratio, the DOF will be similar for different
> focal length lenses. So if you shoot from 1 meter away with
> a 35mm lens and 5 meters away with a 175mm lens so that the
> image size is the same in both cases, you will get similar
> DOF at the same aperture.


This is illustrated here: <http://www.dofmaster.com/dofjs.html>

Plug in the numbers you want.
 
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Jules Vide
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      07-16-2006
John Bean wrote:
> On 15 Jul 2006 14:21:37 -0700, "Jules Vide"
> <(E-Mail Removed)> wrote:
> >
> >I took the camera out of the box and tried to do this. I set the
> >aperture for its lowest setting, then tried to focus on my exquisite
> >Subaru. Whenever I touched the focus, even though I was in the "Av
> >Priority" setting, the aperture setting changed. How else are you
> >supposed to focus if not with the auto focus; and if the auto focus has
> >dominance over the other customized settings, is this not just another
> >way of saying the p&s can only autofocus?

>
> You're not confusing AF with zoom are you? If you "zoomed
> in" on the car the lens may have been forced to stop down;
> most P&S cameras don't have the same maximum aperture across
> the whole zoom range.


Obviously I am. As I posted on another thread, I just realized that I
don't know how to--and my user's manual doesn't tell me how to--focus
without the zoom.

 
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Jules Vide
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Posts: n/a
 
      07-16-2006
tomm42 wrote:
>
> Go find a second hand pentax K1000 and a 50mm lens and
> some ISO 100 film, find a pro lab to get contact sheets made and just
> shoot a couple of rolls using a match needle meter, you start to
> understand. If there was a cheap digital camera you could do the same
> thing with I'd say get that.


Tom, you are a Usenet "find." I'm going to try to do exactly this but
with an old Nikon my "art school" Dad, now deceased, left us, among
Rollies and other cameras. I need a specific manual that will first
tell me which control is which, and then my July free-time project is
going to be what you suggest. I've had enough!

 
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