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Is VLC 3.0.3 for Windows 7?



 
 
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  #151  
Old August 15th 18, 05:06 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
NY
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Posts: 586
Default film vs CMOS

"nospam" wrote in message
...
That goes against everything I've ever learned about photography,


it's a common myth.

and the
fringe benefit of using larger film (the main one being finer level of
detail for the same type of film).


in other words, different image quality.


I hadn't appreciated that image quality affected DOF. So same lens, same
camera, same aperture (but different shutter speed) on very slow
fine-grained film and very fast coarse-grained film will produce different
DOF?

Well, well.

this explains it exceptionally well:
http://www.clarkvision.com/articles/dof_myth/
A commonly cited advantage of smaller digital cameras is their
greater depth-of-field. This is incorrect.


Interesting article. The reason for the myth is that we are comparing the
wrong things and keeping the wrong things constant in the comparison. The
longer lens needed to produce the same field of view on the camera with the
larger sensor needs to be stopped down further make the *absolute* aperture
the same as for the camera with a smaller sensor and correspondingly smaller
focal length to give same field of view. Comparing f5.6 on the longer lens
with f5.6 on the shorter lens is wrong in terms of DOF. Understood!

Of course, in practical photographic terms, we tends to constraint aperture
to *roughly* the same range of f numbers for any lens. A lens that is 10x as
long doesn't have apertures which are roughly 1/10 (in f number terms) - on
all lenses, they will always be around f2 - f16 give or take a couple of f
numbers either way. That's so the light-gathering abilities of the lenses
are comparable.

So a camera with a small sensor will have a lens that has usable apertures
in terms of light-gathering capabilities which equate to a camera with a
larger sensor and hence a longer lens that has much smaller apertures and
therefore needs much longer exposures if film speed / CMOS sensitivity is
the same.


So a smaller camera doesn't inherently produce a greater depth of field, but
when it used in the same conditions of image brightness and film speed, and
the need to avoid diffraction due to excessively small apertures, the
smaller camera's range of *available* apertures produce a greater DOF than
the *available* range of apertures on a longer lens on a larger camera.

In other words, it's the age-old difference between theory and practical
usability.

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  #152  
Old August 15th 18, 05:32 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
NY
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Posts: 586
Default film vs CMOS

"NY" wrote in message
o.uk...
Interesting article. The reason for the myth is that we are comparing the
wrong things and keeping the wrong things constant in the comparison. The
longer lens needed to produce the same field of view on the camera with
the larger sensor needs to be stopped down further make the *absolute*
aperture the same as for the camera with a smaller sensor and
correspondingly smaller focal length to give same field of view. Comparing
f5.6 on the longer lens with f5.6 on the shorter lens is wrong in terms of
DOF. Understood!


The only thing that I'll need to read a few more times is the issue of
number of photons. I can see that this affects how much light the
film/sensor receives and therefore the brightness of the image. But I can't
see how it has any effect on the DOF of that image which is a purely
optical, lens issue: a dim image and a bright image will still have the same
objects in sharp focus and the same objects blurred by some amount.

So if in some way you halve the number of photos reaching the sensor (by
making the aperture smaller, by using a neutral density or by dimming the
illumination of the subject) then as long as you make the sensor twice as
sensitive or double the exposure time then the recorded image will be the
same. Of these, only altering the aperture alters the DOF. As long as the
aperture doesn't change, you can change all the other parameters and as long
as you do so proportionally, the image will be identical, both in brightness
and in DOF.

To think of it another way, suppose you have two sensors which have pixels
which are same size. In one case, the pixels border each other, without any
space between them; in the other case the pixels are the same size but
spaced more widely.

Sensor 1
x x x
x x x
x x x

versus

Sensor 2
x x x

x x x

x x x

The pixel size (the x) is the same size. So the size of the buckets is the
same.

But if the pixels are spaced more widely, the sensor will be physically
larger and will need a longer lens to capture the same field of view (and so
will need a smaller f number to give the same absolute size of aperture and
hence DOF).

But if we replace Sensor 2 by the more normal situation where the pixels are
bigger although their spacing hasn't altered (Sensor 3), the same lens is
needed and for the same aperture the DOF will be the same. I presume...

Sensor 3

X X X

X X X

X X X

The spacing is the same but the pixel size has increased from x to X which
means the larger buckets can gather more pixels.


I'm still struggling to see how altering the "size of the buckets" has
affected the DOF, if the pitch of the buckets is the same.


My brain hurts. I'm probably over-thinking all this :-)

  #153  
Old August 25th 18, 10:55 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
+++ATH0
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Posts: 5
Default film vs CMOS

On 2018-08-14 09:08, nospam wrote:
In article , NY
wrote:

One other factor to bear in mind: the depth of field varies with lens focal
length, not field of view of the subject.


actually, it's aperture.


actually, it's the ratio of focal length to aperture.
  #154  
Old August 25th 18, 11:06 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
nospam
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Posts: 4,718
Default film vs CMOS

In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with lens
focal length, not field of view of the subject.


actually, it's aperture.


actually, it's the ratio of focal length to aperture.


nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes, and
in some cases (usually movies), t/stops are used, which is actual light
transmission through the lens, not a simple ratio.
  #155  
Old August 25th 18, 11:56 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
+++ATH0
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Posts: 5
Default film vs CMOS

On 2018-08-25 15:06, nospam wrote:
In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with lens
focal length, not field of view of the subject.

actually, it's aperture.


actually, it's the ratio of focal length to aperture.


nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes, and
in some cases (usually movies), t/stops are used, which is actual light
transmission through the lens, not a simple ratio.


Are you claiming that focal length has no bearing on depth of field?
That's an interesting viewpoint.
  #156  
Old August 26th 18, 12:23 AM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
nospam
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Posts: 4,718
Default film vs CMOS

In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with lens
focal length, not field of view of the subject.

actually, it's aperture.

actually, it's the ratio of focal length to aperture.


nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes, and
in some cases (usually movies), t/stops are used, which is actual light
transmission through the lens, not a simple ratio.


Are you claiming that focal length has no bearing on depth of field?


for the same subject size and same image quality (coc), no.

That's an interesting viewpoint.


not really. it's just math.
  #157  
Old August 26th 18, 02:05 AM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
Tim[_10_]
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Posts: 249
Default film vs CMOS

+++ATH0 wrote in
:

On 2018-08-14 09:08, nospam wrote:
In article , NY
wrote:

One other factor to bear in mind: the depth of field varies with
lens focal length, not field of view of the subject.


actually, it's aperture.


actually, it's the ratio of focal length to aperture.

That is correct. For any given focal length, the smaller the aperature, the
greater the depth of field. That is why pinhole cameras focus from closeup
to infinity without a lens.
  #158  
Old August 26th 18, 02:13 AM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
Tim[_10_]
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Posts: 249
Default film vs CMOS

nospam wrote in
:

In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with
lens focal length, not field of view of the subject.

actually, it's aperture.

actually, it's the ratio of focal length to aperture.

nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes,
and in some cases (usually movies), t/stops are used, which is
actual light transmission through the lens, not a simple ratio.


Are you claiming that focal length has no bearing on depth of field?


for the same subject size and same image quality (coc), no.

That's an interesting viewpoint.


not really. it's just math.


No matter what the focal length of the lense is, the further away the
focal plane is, the greater the depth of field will be for any aperature.

As an example, if one is taking a head and shoulders portrait with a
large aperature, it is quite likely that part of the subject will be out
of focus slighty. Moving back a few feet with the same lense and
aperature will result in a deeper depth of field, so that all of the
subject should be in focus. The drawback is that the image size will be
smaller, and thus require more enlargement to obtain the same size image,
with the resulting loss of resolution with the enlarged image.
  #159  
Old August 26th 18, 06:52 PM posted to alt.windows7.general,alt.comp.os.windows-10,alt.comp.hardware.pc-homebuilt,alt.comp.os.windows-10,sci.electronics.basics
Phil Hobbs
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Posts: 7
Default film vs CMOS

On 08/25/2018 06:06 PM, nospam wrote:
In article , +++ATH0
wrote:

One other factor to bear in mind: the depth of field varies with lens
focal length, not field of view of the subject.

actually, it's aperture.


actually, it's the ratio of focal length to aperture.


nope. depth of field is a function of physical aperture.

what you describe is f/stop, which is used for exposure purposes, and
in some cases (usually movies), t/stops are used, which is actual light
transmission through the lens, not a simple ratio.


For an ideal optical system, the depth of _focus_ (on the image side) is
a function only of wavelength and numerical aperture, i.e. the sine of
the half-angle of the cone defined by the rim rays (i.e. the illuminated
cone). That's where wave properties come in.

On the object side, the depth of _field_ equals the depth of focus
scaled by the square of the magnification. Magnification is of course
the ratio of the object distance to the image distance.

Aberrated optical systems degrade a bit more slowly because they're not
as good to begin with.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 




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