What next when the hyperfocal is wrong?

According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't get
the measuring tape out but I have a fair idea of how far away 25 feet is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Douglas

Dmac wrote:

According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't get
the measuring tape out but I have a fair idea of how far away 25 feet is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Douglas

Presuming your couple were at 25 feet and the church was near enough to
infinity, then the hyperfocal distance - your focus point - should be 50
feet. Focus on 50 feet and the dof will extend from half the HD, i.e. 25 ft
to infinity, at the correct stop, of course. If you focused on 25 feet then
there's your problem. Dof when focused at 25 ft and f/11 extends from 13.5
ft to 174 ft, so the foreground and couple will be sharp, but the church will
probably be outside the 174 ft limit (from Dofmaster calculator).

From the DofMaster website calculator for APS-sized sensors with a CoC of
0.025mm, focusing on 50 ft at f/8 will give a dof of 22.6 feet to infinity.
If you focused directly on the couple for maximum sharpness (which is what I
would do), and wanted the church in as well, then your HD is 25 ft, the point
you focused on, and the aperture to extend the dof to infinity will be
f/13.5. This would also extend the dof in front of the couple to 12.4 feet -
so your total dof would be 12.4 ft to infinity when focused on 25 ft, which
obeys the rule of acceptable sharpness from half the HD to infinity.

But, as I well know, doing this in your head while shooting a wedding is all
but impossible.

Did you not think of using the 'A-dep' function on the camera?

Colin D.


--
Posted via a free Usenet account from http://www.teranews.com

In article ,
p says...
According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't get
the measuring tape out but I have a fair idea of how far away 25 feet is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Ah, to have HF markings on your lens... God bless 'em old manual focus
lenses. I was actually using this method of focussing at a German Bazaar
I attended on the weekend. I simply put the infinity sign at the marking
for my aperture and made sure that the subject was within the distance
indicated at the other marking for that aperture.

Interesting that you are getting different results with the same lens on
different DSLR's...

--
http://www.nikongear.com/

"Dmac" wrote in message
...
According the Lord of math, the hyperfocal distance of my 50mm lens is 25
feet at F/11. Supposedly everything from 25 feet to infinity will be in
focus. Unfortunately you can't tell if this is the case until you examine
the image on a computer.


The hyperfocal distance for a 20D with 50mm @ f11 is 38.3 feet. This is
the minimim distance at which you could focus while maintaining a far focus
limit of infinity.


Last week, I shot a wedding where I wanted the couple at about 25 feet and
a church at infinity plus all in between to be focused. I didn't get the
measuring tape out but I have a fair idea of how far away 25 feet is.

If you focused at 25 feet (20D + 50mm @ f11) your near limit of acceptable
sharpness was 15.1 feet, while the far limit was only 71.6 feet.... this may
have resulted in your church softness.

To get a far limit of infinity to cover the church, you would need to focus
at the hyperfocal as mentioned above. This focus distance would also give
you enough DOF to cover your subject with a near limit of 19.2 feet.


The picture is OK. The foreground is sharp but the church in the distance
is not as sharp as I'd have thought it would be considering the maths of
the matter. I reasoned any smaller than F/11 and the image would start to
lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D was
spot on. Have I missed something with the crop factor or are there other
considerations when the lens is on 1.6 crop camera?

Douglas

Different CoC (circles of confusion) must be considered for these cams, due
to their different sensor sizes and their need to be enlarged by different
amounts to get to the same size print. A 20D has a CoC of 0.019, while the
5D is 0.030.


Naturally the above comparisons are based on the same subject distance,
where is reality these would be different between the two cams if you wished
to compose the same within the frame. Moving closer to the subject with the
5D would mean a whole new set of calcs whould have to be made and these
would pretty much resemble the 20D near and far limit results.

"C J Donoghue" wrote in message
...


Dmac wrote:

According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't get
the measuring tape out but I have a fair idea of how far away 25 feet is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Douglas

Presuming your couple were at 25 feet and the church was near enough to
infinity, then the hyperfocal distance - your focus point - should be 50
feet. Focus on 50 feet and the dof will extend from half the HD, i.e. 25
ft
to infinity, at the correct stop, of course. If you focused on 25 feet
then
there's your problem. Dof when focused at 25 ft and f/11 extends from
13.5
ft to 174 ft, so the foreground and couple will be sharp, but the church
will
probably be outside the 174 ft limit (from Dofmaster calculator).

From the DofMaster website calculator for APS-sized sensors with a CoC of
0.025mm, focusing on 50 ft at f/8 will give a dof of 22.6 feet to
infinity.
If you focused directly on the couple for maximum sharpness (which is what
I
would do), and wanted the church in as well, then your HD is 25 ft, the
point
you focused on, and the aperture to extend the dof to infinity will be
f/13.5. This would also extend the dof in front of the couple to 12.4
feet -
so your total dof would be 12.4 ft to infinity when focused on 25 ft,
which
obeys the rule of acceptable sharpness from half the HD to infinity.

But, as I well know, doing this in your head while shooting a wedding is
all
but impossible.

Did you not think of using the 'A-dep' function on the camera?

Colin D.


--
Posted via a free Usenet account from http://www.teranews.com


Our numbers differ

I used a CoC of .019 for the 20D (as shown on dofmaster), but you used
..025???

Like I told ya the other day, D-Mac. The problem with being
self-taught is the teacher!

"DD" wrote in message
...
In article ,
p says...
According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't get
the measuring tape out but I have a fair idea of how far away 25 feet
is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Ah, to have HF markings on your lens... God bless 'em old manual focus
lenses. I was actually using this method of focussing at a German Bazaar
I attended on the weekend. I simply put the infinity sign at the marking
for my aperture and made sure that the subject was within the distance
indicated at the other marking for that aperture.

Yes, the omission of this from so many current lenses is a real pity. DoF
preview helps, but isn't a panacea either. Bring back properly marked
lenses I say! (But then, most of mine are...)


Interesting that you are getting different results with the same lens on
different DSLR's...

Different size sensors would mean different DoF for a given aperture, just
as different film formats do. A smaller sensor will give more DoF
(sometimes annoyingly much) but it will also show the effects of diffration
at larger apertures than can be used with a larger format / sensor size.



Peter

"POTD.com.au" wrote:

Different CoC (circles of confusion) must be considered for these cams, due
to their different sensor sizes and their need to be enlarged by different
amounts to get to the same size print. A 20D has a CoC of 0.019, while the
5D is 0.030.


The idea that a Circle of Confusion is somehow defined to be a certain
value is highly misleading. The Circle of Confusion is actually what
you decide it is going to be, based on your experience and equipment
and the type of photography you do.

The depth of field figures for a given focal length, aperture and
focusing distance are therefore highly subjective. It is amusing to
see them quoted with such precision as in this thread. Quoting
figures of 13.5 feet to 174 feet is a joke.

Precision of this sort is complete nonsense. It suggests that some
element of the shot located at 175 feet will be out of focus, whereas
an identical element located at 173 feet will be sharp. In practice,
there will be no difference in sharpness between the two that anyone
can discern. They will both have the same perceived level of
unsharpness.

By using hyperfocal distances that are based on depth of field
calculations as if they were definitive, we are actually throwing away
sharpness. The greatest sharpness is at the plane of focus and
sharpness drops away as the element under consideration gets further
from the plane of focus. It is easily possible to use differential
focus between elements that are all well within the calculated depth
of field, whereas the calculation would appear to imply that
everything within the calculated depth of field would be adequately
sharp, when it isn't.

The idea that depth of field is the same for all lenses of the same
focal length and chosen aperture focused at the same distance might
look good in theory. It is in practice untrue, as the sharpest lenses
will show a greater apparent loss of sharpness with distance than
lenses that are less sharp.

This shows the danger of relying on a formula. Just because it
appears to give you a definitive answer doesn't make that answer
meaningful. The answer is in fact highly misleading, as anyone with
the slightest interest in understanding the chronic weaknesses behind
the assumptions that led to its derivation will soon know.

"Bandicoot" wrote in message
...
"DD" wrote in message
...
In article ,
p says...
According the Lord of math, the hyperfocal distance of my 50mm lens is
25 feet at F/11. Supposedly everything from 25 feet to infinity will be
in focus. Unfortunately you can't tell if this is the case until you
examine the image on a computer.

Last week, I shot a wedding where I wanted the couple at about 25 feet
and a church at infinity plus all in between to be focused. I didn't
get
the measuring tape out but I have a fair idea of how far away 25 feet
is.

The picture is OK. The foreground is sharp but the church in the
distance is not as sharp as I'd have thought it would be considering
the
maths of the matter. I reasoned any smaller than F/11 and the image
would start to lose sharpness and produce vignetting.

Anyway... Can someone offer a suggestion as to why the technical
details
were right and the results with my 20D off? The same image from my 5D
was spot on. Have I missed something with the crop factor or are there
other considerations when the lens is on 1.6 crop camera?

Ah, to have HF markings on your lens... God bless 'em old manual focus
lenses. I was actually using this method of focussing at a German Bazaar
I attended on the weekend. I simply put the infinity sign at the marking
for my aperture and made sure that the subject was within the distance
indicated at the other marking for that aperture.

Yes, the omission of this from so many current lenses is a real pity. DoF
preview helps, but isn't a panacea either. Bring back properly marked
lenses I say! (But then, most of mine are...)


Interesting that you are getting different results with the same lens on
different DSLR's...

Different size sensors would mean different DoF for a given aperture, just
as different film formats do. A smaller sensor will give more DoF
(sometimes annoyingly much) but it will also show the effects of
diffration
at larger apertures than can be used with a larger format / sensor size.



Peter



Given that all other variables remail the same (eg, FL, subject distance and
f-stop ....as in the case of the OP) smaller sensors actually provide less
DOF because extra enlargement to a given print size means extra enlargement
of the CoC.

However, what normally happens is that we compose the image the same in the
view finder regardless of the type of camera used. But because of the
different sized sensors and their different FOV, we will be shooting from
different subject distances or using different focal lengths (smaller sensor
cams will either be shooting a shorter FL or from a greater subject
distance) and it is this that increases the DOF.

So raw statement of "A smaller sensor will give more DoF" is not true,
unless it is accompanied by the extra info as above.

"Tony Polson" wrote in message
...
"POTD.com.au" wrote:

Different CoC (circles of confusion) must be considered for these cams,
due
to their different sensor sizes and their need to be enlarged by different
amounts to get to the same size print. A 20D has a CoC of 0.019, while
the
5D is 0.030.


The idea that a Circle of Confusion is somehow defined to be a certain
value is highly misleading. The Circle of Confusion is actually what
you decide it is going to be, based on your experience and equipment
and the type of photography you do.

The depth of field figures for a given focal length, aperture and
focusing distance are therefore highly subjective. It is amusing to
see them quoted with such precision as in this thread. Quoting
figures of 13.5 feet to 174 feet is a joke.

Precision of this sort is complete nonsense. It suggests that some
element of the shot located at 175 feet will be out of focus, whereas
an identical element located at 173 feet will be sharp. In practice,
there will be no difference in sharpness between the two that anyone
can discern. They will both have the same perceived level of
unsharpness.

By using hyperfocal distances that are based on depth of field
calculations as if they were definitive, we are actually throwing away
sharpness. The greatest sharpness is at the plane of focus and
sharpness drops away as the element under consideration gets further
from the plane of focus. It is easily possible to use differential
focus between elements that are all well within the calculated depth
of field, whereas the calculation would appear to imply that
everything within the calculated depth of field would be adequately
sharp, when it isn't.

The idea that depth of field is the same for all lenses of the same
focal length and chosen aperture focused at the same distance might
look good in theory. It is in practice untrue, as the sharpest lenses
will show a greater apparent loss of sharpness with distance than
lenses that are less sharp.

This shows the danger of relying on a formula. Just because it
appears to give you a definitive answer doesn't make that answer
meaningful. The answer is in fact highly misleading, as anyone with
the slightest interest in understanding the chronic weaknesses behind
the assumptions that led to its derivation will soon know.


Calculators are intended as a guide, just as the lines the manufacturers
place on the lens are intended as a guide.... while "acceptable" results are
always subjective, neither of the guides are "meaningless".