infinity focus

On Apr 7, 8:02 pm, "Mr.Bolshoyhuy" wrote:
> I really do hate to pre-focus and hold the shutter button half-way and
> wait for the subject
> to be where I want it. Also, if using f/8, it takes longer to focus,
> thus the moment is gone
> by the time you take the pic.

can't you just use set focus, aperture, and shutter in manual mode?
 >> Stay informed about: infinity focus 

On Sun, 08 Apr 2007 00:08:33 -0700, Bucky wrote:

>
> can't you just use set focus, aperture, and shutter in manual mode?

He can't. He has to learn how to.
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On Apr 8, 3:54 am, Neil Ellwood
wrote:
> On Sun, 08 Apr 2007 00:08:33 -0700, Bucky wrote:
>
> > can't you just use set focus, aperture, and shutter in manual mode?
>
> He can't. He has to learn how to.

funny. I was referring to P&S cameras.
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"Mr.Bolshoyhuy" wrote in message


> infinity focus

> whats the opinion here of it?

It's particularly useful if you're photographing scenery through a window,
to ensure that the camera doesn't mistakenly try to focus on reflections in
the window.
 >> Stay informed about: infinity focus 

On 8 Apr 2007 09:16:53 -0700, "Mr.Bolshoyhuy"
wrote:

>On Apr 8, 3:54 am, Neil Ellwood
>wrote:
>> On Sun, 08 Apr 2007 00:08:33 -0700, Bucky wrote:
>>
>> > can't you just use set focus, aperture, and shutter in manual mode?
>>
>> He can't. He has to learn how to.
>
>funny. I was referring to P&S cameras.

Owning a P&S camera does not automatically limit the user to no
control.
But, to answer your question, these cameras aren't limited or set to
"infinity". The aperture and focus are set such that infinity is
included in the DOF. How close the focus will go to is up to the
designers.

--
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the Swift Boat Veterans, a recess
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Nothing ever changes. John Kerry
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before he was against the appointment.
 >> Stay informed about: infinity focus 

Kevin McMurtrie wrote:
<snip>
>
> No-focus cameras have the focus set a moderate distance out. With a
> tiny enough aperture and a low enough resolution, infinity is within the
> depth of field.
>


Many years ago there was a term for the point at which a set focus would
yield an acceptable sharpness for an object at "infinity" and also
provide that same acceptable sharpness (circle of confusion) at the
nearest point, for any given focal-length/f-stop combination. I have
wracked my brain trying to remember that term, with no success; does
anyone recall it? It _might_ have been "Hyperfocal distance".
Allen
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On Apr 9, 6:20 am, Paul J Gans wrote:
> Allen wrote:
> >Kevin McMurtrie wrote:
> ><snip>
>
> >> No-focus cameras have the focus set a moderate distance out. With a
> >> tiny enough aperture and a low enough resolution, infinity is within the
> >> depth of field.
>
> >Many years ago there was a term for the point at which a set focus would
> >yield an acceptable sharpness for an object at "infinity" and also
> >provide that same acceptable sharpness (circle of confusion) at the
> >nearest point, for any given focal-length/f-stop combination. I have
> >wracked my brain trying to remember that term, with no success; does
> >anyone recall it? It _might_ have been "Hyperfocal distance".
> >Allen
>
> I suspect "hyperfocal distance" is the term.
>
> It is the distance such that at a given f stop with a given
> lens anything from the hyperfocal distance to infinity was
> in "focus".
>
> This, of course, depends on the acceptable sharpness of the circle
> of confusion. In other words folks milage may vary. The hyperfocal
> distance is fairly close by for wide angle lenses.
>
> Back in the Good Old Days (tm) when lenses had distance scales
> on the barrels and f stop range marks opposite them, you could set
> infinity at one range mark and read the hyperfocal distance off
> the other range mark. It was a great setting for grab shots.
>
> That was then. This is now.

You can still get lenses like that but they tend to be primes. My
28mm f/2.8 has those markings and I make a fair bit of use of them.
However I find they are a bit optimistic about what is in focus, so I
use the markings that are about 1 stop wider then what I am shooting
at. As an example if I am shooting at f/11 I would use the marks for f/
8.

Scott
 >> Stay informed about: infinity focus 

Allen wrote:
>Kevin McMurtrie wrote:
><snip>
>>
>> No-focus cameras have the focus set a moderate distance out. With a
>> tiny enough aperture and a low enough resolution, infinity is within the
>> depth of field.
>>


>Many years ago there was a term for the point at which a set focus would
>yield an acceptable sharpness for an object at "infinity" and also
>provide that same acceptable sharpness (circle of confusion) at the
>nearest point, for any given focal-length/f-stop combination. I have
>wracked my brain trying to remember that term, with no success; does
>anyone recall it? It _might_ have been "Hyperfocal distance".
>Allen

I suspect "hyperfocal distance" is the term.

It is the distance such that at a given f stop with a given
lens anything from the hyperfocal distance to infinity was
in "focus".

This, of course, depends on the acceptable sharpness of the circle
of confusion. In other words folks milage may vary. The hyperfocal
distance is fairly close by for wide angle lenses.

Back in the Good Old Days (tm) when lenses had distance scales
on the barrels and f stop range marks opposite them, you could set
infinity at one range mark and read the hyperfocal distance off
the other range mark. It was a great setting for grab shots.

That was then. This is now.

--
--- Paul J. Gans
 >> Stay informed about: infinity focus 

Allen wrote:
[]
> Many years ago there was a term for the point at which a set focus
> would yield an acceptable sharpness for an object at "infinity" and
> also provide that same acceptable sharpness (circle of confusion) at
> the nearest point, for any given focal-length/f-stop combination. I
> have wracked my brain trying to remember that term, with no success;
> does anyone recall it? It _might_ have been "Hyperfocal distance".
> Allen

Correct.

http://en.wikipedia.org/wiki/Hyperfocal_distance

They give an example of focussing a 50mm lens working at f/16 to 5.2m,
when everything from 2.6m to infinity is then "in focus".

David
 >> Stay informed about: infinity focus 

On Mon, 09 Apr 2007 14:33:04 GMT, David J Taylor wrote:

>> Many years ago there was a term for the point at which a set focus
>> would yield an acceptable sharpness for an object at "infinity" and
>> also provide that same acceptable sharpness (circle of confusion) at
>> the nearest point, for any given focal-length/f-stop combination. I
>> have wracked my brain trying to remember that term, with no success;
>> does anyone recall it? It _might_ have been "Hyperfocal distance".
>> Allen
>
> Correct.
>
> http://en.wikipedia.org/wiki/Hyperfocal_distance
>
> They give an example of focussing a 50mm lens working at f/16 to 5.2m,
> when everything from 2.6m to infinity is then "in focus".

That's probably a useful definition for 4"x6" snapshooters, but
maybe not so good for others that occasionally make larger prints.
Maybe a better way to put it with that example would be that for a
specific print size, focus would be best at 5.2m, but at infinity
and 2.6m, sharpness would still be pretty good, but noticeably
inferior with closer than normal examination, or not very sharp in
larger size prints. For larger print sizes where a "smaller circle
of confusion" would be needed, the hyperfocal distance would move
slightly closer to infinity from 5.2m, and the DOF would also
decrease slightly with the "near" DOF border moving slightly closer
to infinity from 2.6m (by 1/2 the change in the h.d.) and the "far"
border remaining at infinity. And of course if you give pictures to
one of our professed pixel peepers whose places his proboscis
against the prints for perusal, all bets are off.
 >> Stay informed about: infinity focus 

David J Taylor wrote:
> Allen wrote:
> []
>> Many years ago there was a term for the point at which a set focus
>> would yield an acceptable sharpness for an object at "infinity" and
>> also provide that same acceptable sharpness (circle of confusion) at
>> the nearest point, for any given focal-length/f-stop combination. I
>> have wracked my brain trying to remember that term, with no success;
>> does anyone recall it? It _might_ have been "Hyperfocal distance".
>> Allen
>
> Correct.
>
> http://en.wikipedia.org/wiki/Hyperfocal_distance
>
> They give an example of focussing a 50mm lens working at f/16 to 5.2m,
> when everything from 2.6m to infinity is then "in focus".
>
> David
>
>

Thanks! Just before I hit "send" Hyperfocal distance entered my
thoughts, but I wasn't sure. It was probably 45 or 50 years ago that I
last heard or read the term. The arrival of the SLR and then autofocus
pretty much eliminated much of the discussion of such issues.
Allen
 >> Stay informed about: infinity focus 

ASAAR wrote:
> On Mon, 09 Apr 2007 14:33:04 GMT, David J Taylor wrote:
>
>>> Many years ago there was a term for the point at which a set focus
>>> would yield an acceptable sharpness for an object at "infinity" and
>>> also provide that same acceptable sharpness (circle of confusion) at
>>> the nearest point, for any given focal-length/f-stop combination. I
>>> have wracked my brain trying to remember that term, with no success;
>>> does anyone recall it? It _might_ have been "Hyperfocal distance".
>>> Allen
>>
>> Correct.
>>
>> http://en.wikipedia.org/wiki/Hyperfocal_distance
>>
>> They give an example of focussing a 50mm lens working at f/16 to
>> 5.2m, when everything from 2.6m to infinity is then "in focus".
>
> That's probably a useful definition for 4"x6" snapshooters, but
> maybe not so good for others that occasionally make larger prints.
> Maybe a better way to put it with that example would be that for a
> specific print size, focus would be best at 5.2m, but at infinity
> and 2.6m, sharpness would still be pretty good, but noticeably
> inferior with closer than normal examination, or not very sharp in
> larger size prints. For larger print sizes where a "smaller circle
> of confusion" would be needed, the hyperfocal distance would move
> slightly closer to infinity from 5.2m, and the DOF would also
> decrease slightly with the "near" DOF border moving slightly closer
> to infinity from 2.6m (by 1/2 the change in the h.d.) and the "far"
> border remaining at infinity. And of course if you give pictures to
> one of our professed pixel peepers whose places his proboscis
> against the prints for perusal, all bets are off.

Indeed, yes! I wrote "in focus" (with quotes), not 'in focus', to cover
the very situation you mentioned. I wonder if with digital, because of
the finite pixel size, the variation of focus might be less noticeable?
It might be useful to update the wikipedia entry to cover digital
photography as well as film photography. However, I have seen lots of
people here get very confused over this whole issue, so that's not a task
I'm prepared to take on!

What's the approximate number of pixels implied by CoC 0.03 with a 35mm
format? Would it be 36/0.03 x 24/0.03 pixels - i.e. 1200 x 800 pixels?
Today that probably does fit into the 6 x 4 inch category!

Cheers,
David
 >> Stay informed about: infinity focus 

On Mon, 09 Apr 2007 17:10:33 GMT, David J Taylor wrote:

> Indeed, yes! I wrote "in focus" (with quotes), not 'in focus', to cover
> the very situation you mentioned. I wonder if with digital, because of
> the finite pixel size, the variation of focus might be less noticeable?

I don't think so. For the pixel size to matter the sensor's
resolution would have to be so low, or the magnification so high
that you'd be able to see individual pixels in a print. Somewhat
like not being able to easily distinguish between in-focus and
slightly out-of-focus parts of a high quality glossy magazine
picture because you're using a loupe to examine half-tone dots. If
the pixels aren't large enough to see, by definition they're already
smaller than the CoC size which is small enough so that the eye
can't easily distinguish between the most in-focus and most
out-of-focus objects within the DOF.


> What's the approximate number of pixels implied by CoC 0.03 with
> a 35mm format? Would it be 36/0.03 x 24/0.03 pixels - i.e. 1200 x 800
> pixels? Today that probably does fit into the 6 x 4 inch category!

That represents quite a small crop from a FF sensor, slightly less
than 1mp. With 12.8mp, the 5D has about 13x the number of pixels,
and 13x the 6 x 4 size == 13 * 24, or 312 square inches for a
comparably sharp picture using the entire sensor. That's about 50%
larger than a 12" x 18" print. DPReview's glossary entry for Circle
of Confusion comes up with a CoC size of 0.033mm, virtually the same
as your 0.03mm.


> Circle of Confusion
> By Vincent Bockaert
>
>
> This term usually brings up "circles of confusion" around
> people's eyes. But this does not need to be the case as it is
> actually rather simple. Depth of field defines the distance
> range where things have an acceptable level of sharpness.
> Although sharpness is very subjective, it is in general based
> on an 8" x 10" print viewed from a one feet distance. You can,
> for instance, define that an 8" x 10" print is sharp until
> you can still distinguish 4 lines per mm. That would represent
> dots of 0.25mm each or 100 dots per inch (DPI), a fair approx-
> imation. Other areas of the image would of course be sharper.
> In other words, 0.25mm or 250 µ (micron) is the cut-off point
> where we decide things are no longer sharp and is called the
> Maximum Permissible Circle of Confusion. An 8" x 10" print
> measures 203mm x 254mm and has a diagonal of 325mm, while
> 35mm film measures 36mm x 24mm and has a diagonal of
> 43.27mm or 7.5 times smaller. Since 35mm film needs to be
> enlarged 7.5 times to obtain an 8" x 10" print from it, the
> diameter of the Maximum Permissible Circle of Confusion must
> be 7.5 times smaller or 0.25/7.5 = 0.033mm. If you use 8" x 10"
> large format film, then the CoC remains at 0.25mm as the
> information on the negative does not need to be enlarged to createa
> an 8" x 10" print.


http://www.dpreview.com/learn/?/Glossary/Optical/Circle_of_Confusion_01.htm


After a recent flurry of messages trying to see if the number of
shutter actuations was contained in EXIF data, I downloaded Exiftool
and applied it to some of my Fuji S5100's images. It shows
considerably more information, but not the number of shutter
actuations. Where Irfanview shows only "FocalLength - 8.4000 mm"
for one particular , Exiftool shows:

> Circle Of Confusion : 0.005 mm
> Focal Length : 8.4mm (35mm equivalent: 54.5mm)
> Hyperfocal Distance : 3.38 m

Considering the very small sensors used in P&S cameras, they've
got some really hard working lenses. I don't think that in this
case that focusing the camera at the hyperfocal distance would be a
good idea since the camera was well focused on a niece's face which
was probably no more than 1m from the camera. Had it been focused
several meters behind her I'm pretty sure that her face would have
been considerably out of focus. As it is, the small print on a can
of Pepsi held only a couple of inches in front of her face as well
as the wallpaper about 2 to 3 feet behind her isn't particularly
sharp. The aperture was f/4.5, btw. Of course this is from looking
at it on a monitor. The small print on the can might be barely
readable if a 4"x6" print was made, but what could be seen probably
would appear to be nicely sharp on such a small print.
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