Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Digital Photography > Another Depth of Field Question

Reply
Thread Tools

Another Depth of Field Question

 
 
Jules Vide
Guest
Posts: n/a
 
      07-16-2006
minnesotti wrote:
> 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.


I admit that I'm a pixel peeper, or least that I have been so far.
What I'm wondering now is if a new DSLR obsession isn't just a costlier
version of pixel peeping.

 
Reply With Quote
 
 
 
 
Jules Vide
Guest
Posts: n/a
 
      07-16-2006
jeremy wrote:
>
> 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.


I snipped a lot of another great post. But what I'd like to know
here--in fact, the reason I made the original post--is if what you (and
luminous-landscapes) says about digital cameras and depth of field is
true, then WHY is it called depth of field, when it results in the
opposite?

ANother poster on another thread I have going said the term I'm
actually seeking is "Contrast." I thought Contrast and Depth of Field
were pretty much interchangeable; and I realize that DOF deals with
spatial elements as opposed to color and light. However, I'll return
to my original point: if small digital sensors create MORE
depth-of-field, isn't the term therefore either an oxymoron or in need
of changing (for neophytes, at least) in order not to confuse the heck
out of them?

 
Reply With Quote
 
 
 
 
Kulvinder Singh Matharu
Guest
Posts: n/a
 
      07-16-2006
On Sat, 15 Jul 2006 11:42:01 -0400, Marvin <(E-Mail Removed)>
wrote:

[snip]
>The meaning of depth of field in optics and photography is
>rather precisely defined. See, for example,
>http://en.wikipedia.org/wiki/Depth-of-field/.


Indeed, but the link is:
http://en.wikipedia.org/wiki/Depth_of_field

Always cut n paste

--
Kulvinder Singh Matharu

Website : www.metalvortex.com
Contact : www.metalvortex.com/contact/
 
Reply With Quote
 
John Bean
Guest
Posts: n/a
 
      07-16-2006
On 16 Jul 2006 04:15:28 -0700, "Jules Vide"
<(E-Mail Removed)> wrote:

>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.


Zoom usually has nothing whatsoever to do with focus, though
it may affect the minimum distance the camera can focus.

You're using an autofocus camera so *you* don't focus at
all, the camera does. You do of course need to get the
camera to focus on what you want to be sharp. It's very
necessary to get to know the basic operation of any camera
before trying to do anything "clever" with it; I'm honestly
not being condescending, we were all beginners at some time,
but the old adage of not attempting to run before you can
walk seems very appropriate here.

A good first step is to learn how to get clear focus on a
subject close to the camera, rather than just pressing the
shutter and hoping for the best. It usually involves aiming
at the subject and *half* pressing the shutter to lock
focus, then with the shutter still half-pressed re-compose
as necessary and press the shutter fully to take the
picture. I'm sure the manual will describe this somewhere
and it's a lot easier to do than to describe


--
John Bean
 
Reply With Quote
 
John Bean
Guest
Posts: n/a
 
      07-16-2006
On 16 Jul 2006 04:25:42 -0700, "Jules Vide"
<(E-Mail Removed)> wrote:
>But what I'd like to know
>here--in fact, the reason I made the original post--is if what you (and
>luminous-landscapes) says about digital cameras and depth of field is
>true, then WHY is it called depth of field, when it results in the
>opposite?


Of course it doesn't.

Depth is a measure of distance, whatever sense it's used. In
the case of DoF "depth" is the distance between the nearest
and furthest points in the field [of view] that are
acceptably sharp. You can make the depth [of field] less
("shallower") by using wide apertures and/or longer focal
lengths, or for most landscapes you'd probably want to make
the depth [of field] as great as possible.

You will often see terms like "shallow depth of field" which
means just what it says.


>if small digital sensors create MORE
>depth-of-field, isn't the term therefore either an oxymoron or in need
>of changing (for neophytes, at least) in order not to confuse the heck
>out of them?


No, they simply need to learn what it actually means

--
John Bean
 
Reply With Quote
 
J. Clarke
Guest
Posts: n/a
 
      07-16-2006
Jules Vide wrote:

> 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.


Stop. What, physically, were you touching? Where was it located on the
camera? What markings did it bear? It sounds like you were adjusting the
zoom, not the focus.

> 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?


Autofocus does not change shutter speed or aperture on any camera I've ever
seen. If those are changing then it's almost certain that you are
adjusting something other than focus.

> 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.


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
 
Reply With Quote
 
Jules Vide
Guest
Posts: n/a
 
      07-16-2006
John Bean wrote:

> A good first step is to learn how to get clear focus on a
> subject close to the camera, rather than just pressing the
> shutter and hoping for the best. It usually involves aiming
> at the subject and *half* pressing the shutter to lock
> focus, then with the shutter still half-pressed re-compose
> as necessary and press the shutter fully to take the
> picture. I'm sure the manual will describe this somewhere
> and it's a lot easier to do than to describe


No, you've been very kind, and you're right in what you say. But
there's no reason I shouldn't achieve the simple exercises suggested on
this thread and others--with this particular camera--i.e., opening the
aperture wide and manual focusing on the subject, for attractive blurry
portraits/still lifes, with "blurry backgrounds." Attempting this, I
found that the PowerShot would not allow me to keep the f stop open
wide while also allowing me to focus on the subject...and capture a
clear portrait.

I had my choice either of 1) remaining at an "unportrait-like"
distance, and keeping the aperture wide, or 2) zooming in on the
sitter, focusing manually--and having the camera "choose" the f stop
for me.

 
Reply With Quote
 
Jules Vide
Guest
Posts: n/a
 
      07-16-2006
J. Clarke wrote:
>
> Stop. What, physically, were you touching? Where was it located on the
> camera? What markings did it bear? It sounds like you were adjusting the
> zoom, not the focus.


As I said in another follow-up on this subject, even while in aperture
priority mode, if I set the f stop to 2.8 (for this experiment in
"sharp subject/fuzzy background" photo-taking), then focused manually,
the digital photos ALL turned out blurred. ALL of them.

So then I used the zoom, at which point the zoom overrode the AP mode
and changed the f stop to 3.5, 4.1, or something.

This suggests that--at least with my particular camera, which I am
almost surely going to return, either for a Rebel XT or
nuthin'--aperture priority, like shutter priority, is something that
really doesn't exist or exists within such narrow parameters as to be
virtually worthless.

Of course, being as new to this as I am, perhaps there is yet another
aspect I'm overlooking; but I've read all posted responses to my
questions closely, and I honestly don't think I am.
>
> Autofocus does not change shutter speed or aperture on any camera I've ever
> seen. If those are changing then it's almost certain that you are
> adjusting something other than focus.


Cross my heart and hope to die, autofocus *did* change aperture on this
camera. It disallowed certain f stops, and I wasn't touching anything
else.

 
Reply With Quote
 
jeremy
Guest
Posts: n/a
 
      07-16-2006

"Jules Vide" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>
> Cross my heart and hope to die, autofocus *did* change aperture on this
> camera. It disallowed certain f stops, and I wasn't touching anything
> else.
>


If you still want to use a P&S camera, you should insist upon one that
offers various picture modes. If you cannot completely override the
automation, then you need a Portrait Mode, that will blur the backgrounds.

But, as I noted in an earlier post, if you really want that shallow
depth-of-field, along with smooth bokeh, a lens with a maximum aperture of
f/2.8 that is used on a small-sized CCD is not going to give you enough of
what you want. If you could compare the results of a film camera with an
f/1.4 normal lens against your digicam, you would immediately see the
difference.

One way to try to maximize shallow depth of field on a digicam is to shoot
at a long focal length. Telephoto lenses have shallower depth of field than
normal or wide angle lenses. To use that technique, be prepared to move
farther away from your subject, so as to offset the additional magnification
that the use of a long focal length will introduce.

I have the suspicion that your present camera simply will not allow you to
achieve the results you are seeking, no matter how many hoops you jump
through. My digicam is the same way. When I want to exploit the effects of
shallow depth of field I use one of my film bodies, typically with a 50mm
f/1.4 normal lens mounted on it. P&S cameras are jackknives. Jacks of all
trades but masters of very few.

You may require more than one camera. No single camera, not even the
costliest SLR or DSLR, can do everything.


 
Reply With Quote
 
Dave Martindale
Guest
Posts: n/a
 
      07-16-2006
"Jules Vide" <(E-Mail Removed)> writes:

>> 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.


It sounds like you are somewhat confused about the operation of the
camera. Are you in manual focus or autofocus mode? On some Canons,
in manual focus mode, you use left/right on the directional controller
for *both* focus and aperture control (when in Av), but only one at a
time. If you're in Av and manual focus modes, the "Set" button allows
you to switch between adjusting aperture and adjusting focus.

>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?


Now it sounds like you're trying to use autofocus, not manual. Which is
it?

Also note that, even if you get the controls worked out, a P&S camera
simply isn't capable of really shallow depth of focus. On a camera like
the Canon G series, with f/2.0 lens and relatively large sensor for a
P&S camera, f/2 will give you about the same depth of field as you'd get
at f/11 with the same field of view on a full-frame camera (either film
or digital). Most P&S cameras don't open up to f/2.0, and many have
even smaller sensors than the G series, so their minimum DOF is even
larger.

Dave
 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
javascript validation for a not required field, field is onlyrequired if another field has a value jr Javascript 3 07-08-2010 10:33 AM
Depth of Field Preview Question: Michael P Gabriel Digital Photography 6 06-25-2004 10:29 PM
Question on depth of field Bob Digital Photography 16 06-15-2004 08:23 PM
D10 question - depth of field preview Bryce Digital Photography 52 02-27-2004 07:18 PM
Question on depth of field jean Digital Photography 14 02-25-2004 06:36 PM



Advertisments