hyperfocal distance

Gisle Hannemyr wrote:
"Tony Spadaro" writes:
Sorry - the intuitive answer is right.

No. The intuitive answer (i.e. that you don't need to take the crop
factor into account when figuring hyperfocal distance for a lens) is
wrong.

It may not be obvious that this is wrong as long as we are talking
about a 300D. This camera have 1.6x crop factor, and blur tolerance
is after all subjective.

I don't think that the CoC size it is all that subjective on a digital
camera.

We know exactly what the spatial frequency response of the sensor is
-- in most digital cameras you lose contrast dramatically at about 70%
of the Nyquist frequency. So, a CoC smaller than that is pointless,
but a CoC much larger will reduce contrast. A CoC of about 2 x the
sensor pitch seems about right.

Happily, that's close to the 1/1730 of the "Zeiss formula", at least
on a 6 Mpixel camera.

Andrew.

lid wrote in news:10eabjg8nir0247
@news.supernews.com:

I don't think that the CoC size it is all that subjective on a digital
camera.

We know exactly what the spatial frequency response of the sensor is
-- in most digital cameras you lose contrast dramatically at about 70%
of the Nyquist frequency. So, a CoC smaller than that is pointless,
but a CoC much larger will reduce contrast. A CoC of about 2 x the
sensor pitch seems about right.

Happily, that's close to the 1/1730 of the "Zeiss formula", at least
on a 6 Mpixel camera.

This is no coincidence. A 4 Mpixel camera (or more) is about the
minimum to get perceptive sharp large pictures. So - as long as
we have 4-8 Mpixels, the CoC in the hyper focal distance is
approx one or two pixels.

But his has really nothing to do with digital cameras in general.
If we have a 250 Mpixel camera, the CoC will become 1/1730 again
and not 2 pixels.


/Roland

I'd say the DSLR focal plane. When you are figuring the acceptable
circle of confusion, you must tailor it to to the resolution capability
of the focal plane device being used. We have made up general rules of
thumb for the average film resolution, but that doesn't apply even for
film if it isn't normal res film, let alone a completely different
imaging device.

Big Bill wrote:

On Thu, 01 Jul 2004 10:06:08 -0500, Don Stauffer
wrote:

I don't see how you can compute hyperfocal distance without knowing
something about the format size, resolution, focal length of the lens,
and its f/#, so isn't that already considering the sensor size?

But, that begs a question:
Using DSLRs, which sensor size do you use? The one that's actually
there, or the one that everything else was designed for (35mm)?



--
Don Stauffer in Minnesota

webpage- http://www.usfamily.net/web/stauffer

But dof is NOT just dependent on the lens. One cannot say a lens per se
has a dof. It is the system INCLUDIMG the lens that has a dof.

Gisle Hannemyr wrote:

Don Stauffer writes:
leo wrote:

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

I don't see how you can compute hyperfocal distance without knowing
something about the format size, resolution, focal length of the
lens, and its f/#, so isn't that already considering the sensor
size?

I think the OP's question was not how to compute the hyperfocal
distance for a 300D - but something along the following lines:

If I already own a collection of lenses for my full frame SLR, and
I've worked out the hyperfocal distance for those (on the full frame
camera)- do I need to adjust for the smaller sensor when I put the
/same/ lenes on a DSLR with a smaller sensor?

And the answer is: yes.

(And the adjustment turns out be easy - you should multiply the
hyperfocal distance you've already worked out for full frame SLR with
the DSLR crop factor, and you have the revised hyperfocal distance.)
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
================================================== ======================
«To live outside the law, you must be honest.» (Bob Dylan)

--
Don Stauffer in Minnesota

webpage- http://www.usfamily.net/web/stauffer

Don Stauffer wrote in :

But dof is NOT just dependent on the lens. One cannot say a lens per se
has a dof. It is the system INCLUDIMG the lens that has a dof.

Look here ...

http://tangentsoft.net/fcalc/help/Hyperfocal.htm
http://tangentsoft.net/fcalc/help/DoF.htm

The DOF is a function of hyper focal distance. Therefore, it also
uses the CoC (circle of confusion) as a definition for sharpness.
Therefore, the DOF depends on the focal length, the aperture
and the diagonal of the sensor only.

You don't have to take the entire system into account, in particular
you don't have to take the resolution of the sensor/film into account.

OK - if you have a very low or very high resolution sensor/film you
will end up with having to revise your view of what the DOF and
hyper focal distance really is, but that is outside the definition.

If you have a very low resolution, then the demand on sharpness lowers
and you will accept more unsharpness added by out of focus parts.

If you have a very high resolution, and make a very big picture that
can be viewed nearby, then less unsharpness is accepted.

But hyper focal distance and DOF assumes normal viewing distances
and not to low quality pictures to start with.


/Roland

On Fri, 2 Jul 2004 11:02:34 +0900, "David J. Littleboy"
wrote:


Sorry for the top posting:

The basic idea of DOF that you have to keep in mind is that it's a
perceptual phenomenon that occurs in the mind of the viewer. So it varies
with enlargement and viewing distance.

The CoC at the sensor is back calculated from a given print size, viewing
distance, and assumed visual acuity of a typical viewer for a required DOF
(i.e. we calculate a CoC on the print for a required DOF under given
conditions, and then back calculate the CoC at the sensor required to meet
those conditions).

Note that if you change the viewing conditions, the DOF the viewer will
report seeing will change _for the same image_.

If you hold those conditions constant, then you will find that 1.6x dSLRs
have slightly _more_ DOF than full-frame film or dSLR cameras _for an image
with the same angle of view_, and slightly _less_ DOF if you use the same
lens but print the dSLR image at the same size as you print the full-frame
image.

But the digital age changes the viewing conditions. We inspect and work on
our images at 100% (actual pixels) on the screen, which corresponds to an
enormous magnification. So DOF gets a lot smaller and now depends only on
the focal length, f stop, and pixel pitchg.

David J. Littleboy
Tokyo, Japan

It seems that you're saying that "it's all relative".
In which case, the formulae presented here are nice, but don't mean
much except to 'pixel peepers'.

I kinda agree; it's what you see that counts.

Bill Funk
Change "g" to "a"

On Fri, 02 Jul 2004 09:33:13 -0500, Don Stauffer
wrote:

I'd say the DSLR focal plane. When you are figuring the acceptable
circle of confusion, you must tailor it to to the resolution capability
of the focal plane device being used. We have made up general rules of
thumb for the average film resolution, but that doesn't apply even for
film if it isn't normal res film, let alone a completely different
imaging device.

But Dave wrote:

The one that's actually there, because the actual sensor size determines
the magnification needed to produce a same-size print, and CoC depends
on printing magnification.

Dave

Interesting...
Two exactly opposite answers.

I guess it really is relative. :-)

Bill Funk
Change "g" to "a"

Roland, If anyone ever thought you had a brain, they have long since
switched to the majority opinion.


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"Roland Karlsson" wrote in message
...
"Tony Spadaro" wrote in news:Eh5Fc.93833
:

Viewing distance has NOTHING to do with hyperfocal focusing as .....
Viewing distance cancels out enlargement!!!!
Viewing distance cancels out enlargement!!!!
Viewing distance cancels out enlargement!!!!
Viewing distance cancels out enlargement!!!!
Viewing distance cancels out enlargement!!!!

Entirely right - but viewing does not cancel out cropping.

All things you say does not become right because you write
one true thing 5 times. How old are you? 5? Time to grow up?


/Roland

"Tony Spadaro" wrote in news:7GgFc.93193
:

Roland, If anyone ever thought you had a brain, they have long since
switched to the majority opinion.

Nice try

But you did not suceed - making me angry that is.


/Roland

Roland Karlsson writes:

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.

Yes, exactly. Some of the confusion is because different people assume
different things constant in this situation. Should you assume constant
focal length but variable field of view, or constant field of view and
variable focal length? Both are legitimate starting points, which give
different answers.

In neither case it is constant - as Tony claimed.

Typical Tony. In a situation with two legitimate interpretations, he
picks a third irrelevant one, comes to the wrong conclusion, and then
defends it agressively.

Dave