hyperfocal distance

When using the concept of hyperfocal distance, do we need to adjust for the
smaller sensor on 300D?

No. It remains the same.

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"leo" wrote in message
k.net...
When using the concept of hyperfocal distance, do we need to adjust for
the
smaller sensor on 300D?

"Tony Spadaro" wrote in news:dJCEc.85007
:

No. It remains the same.

Yes - this is the intuitive answer. But it is not
entirely correct. The formula for hyperfocal distans
is (just as pointed out in another post):

h = (f*f)/(N*c)
f = focal length, N = f-ratio, c = "circle of confusion" diameter.

The crucial factor here is c (circle of confusion). If you search
further on the net you will find that it is 1/1740 of the diagonal
of the sensor. Therefore, h will be bigger for a smaller sensors.

So - the intuitive answer is wrong. The hyperfocal distance
depends on how much you crop your image. Therefore, it is also only
valid for the 35 mm film camera if you don't crop the image.


/Roland

Sorry - the intuitive answer is right.
Yes the more you enlarge the softer the image gets but it's just
plain silly to assume any single size for the final image since as size of
the image increases, viewing distance also increases and they cancel each
other out.

--
http://www.chapelhillnoir.com
home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from my novel "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html
"Roland Karlsson" wrote in message
...
"Tony Spadaro" wrote in news:dJCEc.85007
:

No. It remains the same.

Yes - this is the intuitive answer. But it is not
entirely correct. The formula for hyperfocal distans
is (just as pointed out in another post):

h = (f*f)/(N*c)
f = focal length, N = f-ratio, c = "circle of confusion" diameter.

The crucial factor here is c (circle of confusion). If you search
further on the net you will find that it is 1/1740 of the diagonal
of the sensor. Therefore, h will be bigger for a smaller sensors.

So - the intuitive answer is wrong. The hyperfocal distance
depends on how much you crop your image. Therefore, it is also only
valid for the 35 mm film camera if you don't crop the image.


/Roland

Tony Spadaro wrote:

Sorry - the intuitive answer is right.
Yes the more you enlarge the softer the image gets
but it's just plain silly to assume any single size for
the final image since as size of the image increases,
viewing distance also increases and they cancel each
other out.

What formula are you using to compute hyperfocal
distance that uses increasing image sizes and increasing
viewing distances? I don't see this anywhere.

The formula that I've seen uses focal length,
f ratio, and CoC. The first two are characteristics
of the lens, so image size does not enter. If the
CoC is taken to be the inverse of the resolution factor,
and the rf is taken to be 1525/d, where d is the
diagonal measurement of the sensor. In these
computations, the image size is held constant
at 25 cm, with an 8x10 image size.

In all the discussions I read so far in the last couple
of days, a family of CoCs can be generated for
different sensor/image/viewing distance combinations,
but to compare them across families is of no value.

Don't get all bogged down in formulas. Take an 8x10 print and hold it
where you can see the entire print at one time -- this is proper viewing
distance for an 6x10. Now take an 11x14 and do the same -- it is farther
away, isn't it? A 16x20 will be farther away than the 11x14 and when you get
up to 30x40 you should be halfway across the room.

--
http://www.chapelhillnoir.com
home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from my novel "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html
"M Barnes" wrote in message
...
Tony Spadaro wrote:

Sorry - the intuitive answer is right.
Yes the more you enlarge the softer the image gets
but it's just plain silly to assume any single size for
the final image since as size of the image increases,
viewing distance also increases and they cancel each
other out.

What formula are you using to compute hyperfocal
distance that uses increasing image sizes and increasing
viewing distances? I don't see this anywhere.

The formula that I've seen uses focal length,
f ratio, and CoC. The first two are characteristics
of the lens, so image size does not enter. If the
CoC is taken to be the inverse of the resolution factor,
and the rf is taken to be 1525/d, where d is the
diagonal measurement of the sensor. In these
computations, the image size is held constant
at 25 cm, with an 8x10 image size.

In all the discussions I read so far in the last couple
of days, a family of CoCs can be generated for
different sensor/image/viewing distance combinations,
but to compare them across families is of no value.

On Thu, 1 Jul 2004 08:59:07 -0500, "M Barnes"
wrote:

Tony Spadaro wrote:

Sorry - the intuitive answer is right.
Yes the more you enlarge the softer the image gets
but it's just plain silly to assume any single size for
the final image since as size of the image increases,
viewing distance also increases and they cancel each
other out.

What formula are you using to compute hyperfocal
distance that uses increasing image sizes and increasing
viewing distances? I don't see this anywhere.

The formula that I've seen uses focal length,
f ratio, and CoC. The first two are characteristics
of the lens, so image size does not enter. If the
CoC is taken to be the inverse of the resolution factor,
and the rf is taken to be 1525/d, where d is the
diagonal measurement of the sensor. In these
computations, the image size is held constant
at 25 cm, with an 8x10 image size.

Question:
Using that formula, does it work for *any* sensor size, or the one the
image size on the focal plane was designed for (in the case of the
lenses in question, 35mm)?
Or, to put it a different way, if you take a 35mm flm image at
hyperfocal distance, does cropping that image alter the hyperfocal
distance, or was the HD set when the pic was taken?

I'm wondering, if the CoC formula includes 1525d (and I'm assuming it
does), does d refer to the sensor, or the image on the focal plane,
and the sensor size that image is designed for?
I mean, in a DSLR, the lens uses a smaller part of the image on the
focal plane than 35mm film does. In effect, it crops that image. As I
ask above, does this really change the hyperfocal distance of that
lens?

In all the discussions I read so far in the last couple
of days, a family of CoCs can be generated for
different sensor/image/viewing distance combinations,
but to compare them across families is of no value.


Bill Funk
Change "g" to "a"

"Tony Spadaro" wrote in
. com:

Sorry - the intuitive answer is right.
Yes the more you enlarge the softer the image gets but it's
just
plain silly to assume any single size for the final image since as
size of the image increases, viewing distance also increases and they
cancel each other out.

The formula I gave is the formula for hyper focal distance.
It behaves exactly as I said. The hyper focal distance is
inverse proportional to the size of of the sensor, everything
else kept equal.

You may not like the definition. You may want something else;
but then it is not hyperfocal distance. You may call it Tony
Spadero distance if you want.


/Roland

Roland Karlsson writes:

Yes - this is the intuitive answer. But it is not
entirely correct. The formula for hyperfocal distans
is (just as pointed out in another post):

h = (f*f)/(N*c)
f = focal length, N = f-ratio, c = "circle of confusion" diameter.

The crucial factor here is c (circle of confusion). If you search
further on the net you will find that it is 1/1740 of the diagonal
of the sensor. Therefore, h will be bigger for a smaller sensors.

Assuming that you keep the focal length the same.

On the other hand, if you reduce the focal length in proportion to
the sensor size change, to maintain the same field of view, then
the hyperfocal distance becomes smaller not larger. That's because
it depends on focal length squared.

So - the intuitive answer is wrong. The hyperfocal distance
depends on how much you crop your image. Therefore, it is also only
valid for the 35 mm film camera if you don't crop the image.

Yes - if you don't change the lens focal length.

Dave

(Dave Martindale) wrote in news:cc2lhd$lgt$1
@mughi.cs.ubc.ca:

So - the intuitive answer is wrong. The hyperfocal distance
depends on how much you crop your image. Therefore, it is also only
valid for the 35 mm film camera if you don't crop the image.

Yes - if you don't change the lens focal length.


Ahhh ... but as you yourself said, the hyper focal distance
varies as the focal length squared.

If you crop only - the hyper focal distance is proportional to the
__inverse__ of the cropped image size.

If you crop and compensate with a shorter focal length - the hyper
focal distance is proportional to the cropped image size.

In neither case it is constant - as Tony claimed.


/Roland