What next when the hyperfocal is wrong?

Bandicoot wrote:
"DD" wrote in message
...

In article ,
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


This depth of field is constant for a given focal length. You just get a
different size picture. Curiously, the picture you compose with a FF
sensor just adds vignetting to the one you compose with a 1.6 crop
sensor when the aperture closes past about F/10 but the exact same (well
as near as I can see) depth of field is common. The sensor size
difference is just like sticking a 6x4 print over an 8x6 print. Same
picture, just cropped.

Dmac wrote:

This depth of field is constant for a given focal length.


Only if you use the same value for the diameter of the Circle of
Confusion for different sized film formats/sensors, which only an
idiot would do. And that idiot is ...

;-)

Annika1980 wrote:
Like I told ya the other day, D-Mac. The problem with being
self-taught is the teacher!



Douglas J MacDonald, BE. BA, Hon.
Indentured Tradesman Photographer, 1964. Melbourne, Victoria Australia
Mentored by Malcolm Campbell at his St Kilda Studio, Melbourne,
1962 - 1974, R.I.P.

Sorry I don't have any Photoshop qualifications to crop my pics so they
can only be used for postcards the way yours are ...and unlike you,
don't have any experience using freeze spray to stop the action.

I am (for what it's worth - which is basically nothing) a member of
WIPM. For a backwoods boy that's; World Institute of Photographic
Masters. A shonky effort to provide wannabe Photographers with a $30
membership certificate I could have made for the cost of the paper. So
much for modern day "qualifications".

I am however far more qualified than you and probably the only working
photographer in Australia who qualified under the Apprenticeship
Commission and has indentures to prove I can legally claim to be a
qualified tradesman Photographer.

Sometimes Bret, you are a total ******... Read that as most time.

Douglas

Tony Polson wrote:
"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.



It would appear the circle of confusion is the culprit here. I used a
CoC of 0.03 in my calculations. It worked for me with manual 35mm
cameras in the dark old days - which is probably why it worked on the 5D
but according to Russell ( POTD) that calculation is flawed on a 20D.

It's all too easy to just accept Russell's CoC and go on my way. It is
incidentally closer than mine with some tests I just made ...but I use
1.5, 1.6 and FF cameras as well as 2 different size MF cameras. I may
well use something else in the future too. So the question is:

How do you determine the CoC to use in the calculation for any given
lens/camera combination?

Douglas

Dmac wrote:

It would appear the circle of confusion is the culprit here. I used a
CoC of 0.03 in my calculations. It worked for me with manual 35mm
cameras in the dark old days - which is probably why it worked on the 5D
but according to Russell ( POTD) that calculation is flawed on a 20D.

It's all too easy to just accept Russell's CoC and go on my way. It is
incidentally closer than mine with some tests I just made ...but I use
1.5, 1.6 and FF cameras as well as 2 different size MF cameras. I may
well use something else in the future too. So the question is:

How do you determine the CoC to use in the calculation for any given
lens/camera combination?


There are two ways to think about this that will give two different
numbers.
You can choose the CoC that is not large compared to the pixel spacing,
so that you don't soften the image at the pixel level. Or you can
choose a CoC based on a percentage of the sensor/film width you are
using. In either case 0.030mm seems to be pretty larger for a 20D.
You CoC would be 1/750 of the width of the 20D sensor and would be 4.7
times the spaces of the photo sites. The size of the airy disk at
f/11 would be about 0.013mm in diameter (to the first dark ring). Note
that the blurring from an airy disk of 0.013mm is a fair bit less then
the blurring from a out of focus blur circle of the same size.

Note that with a FF camera a CoC of 0.030 is 1/1167 of the width of the
film.

The other point that many people have made is that for the hyperfocal
point to work you have to set the focus point to the right spot,
clearly you did not do this or the people in the foreground would have
been just as blurred as the background. It sounds like you focused at
the near point, which is not what hyerfocal is all about.

Scott

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.



At least 3 web sites offering to explain how to obtain the CoC ...all
differ in what they say it is for a 20D and 50mm lens. All of them,
differ from you Russell.

With so much mis-information out there and idiots like Tony Polson and
Bret Douglas posting barbed comments with no actual contradictory or
factual information, one could be forgiven for presuming no one posting
here in response to my question actually has much of a clue themselves.

The normal range for 35mm format circle of confusion is 0.025 - 0.035
mm. The Leica standard circle of confusion for 35mm format is 0.025. I
obtained this information this morning from 'reliable' (as in published
authors) sources. The CoC for a 20D with a 50mm FL is therefore; 0.048,
not 0.019 as you say. This doesn't answer why using your CoC in my
calculations produces a workable (not ideal) DOF.

So in using a CoC of 0.30 (which I did) It is probably the reason for
the distant part of the shot not focusing as well with the 20D as with a
5D. It still doesn't answer why there are so many varying opinions of
what the CoC should be and how to obtain it.

I have Sigma EX DG lens with DOF markings on it. It saws I should have
infinity focus at about F/10 when focusing on a 20 feet distant object.
This is correct on the 5D but not the 20D. Which answers why there is no
DOF on modern lenses!

Dmac wrote in news:hDnhg.4545$ap3.3028@news-
server.bigpond.net.au:

Annika1980 wrote:
Like I told ya the other day, D-Mac. The problem with being
self-taught is the teacher!



Douglas J MacDonald, BE. BA, Hon.
Indentured Tradesman Photographer, 1964. Melbourne, Victoria Australia
Mentored by Malcolm Campbell at his St Kilda Studio, Melbourne,
1962 - 1974, R.I.P.

Sorry I don't have any Photoshop qualifications to crop my pics so they
can only be used for postcards the way yours are ...and unlike you,
don't have any experience using freeze spray to stop the action.

I am (for what it's worth - which is basically nothing) a member of
WIPM. For a backwoods boy that's; World Institute of Photographic
Masters. A shonky effort to provide wannabe Photographers with a $30
membership certificate I could have made for the cost of the paper. So
much for modern day "qualifications".

I am however far more qualified than you and probably the only working
photographer in Australia who qualified under the Apprenticeship
Commission and has indentures to prove I can legally claim to be a
qualified tradesman Photographer.

Sometimes Bret, you are a total ******... Read that as most time.

Douglas


And yet, you blew hyperfocal distance completely, don't understand
that acceptable CoC is subjective and will depend on *how much of an
enlargement you aim for*, and didn't realize that different sensor sizes
would produce different results.

So, what exactly DO you get from your various titles?


- Al.

--
To reply, insert dash in address to match domain below
Online photo gallery at www.wading-in.net

Scott W wrote:
Dmac wrote:

Annika1980 wrote:

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



Douglas J MacDonald, BE. BA, Hon.
Indentured Tradesman Photographer, 1964. Melbourne, Victoria Australia
Mentored by Malcolm Campbell at his St Kilda Studio, Melbourne,
1962 - 1974, R.I.P.

Sorry I don't have any Photoshop qualifications to crop my pics so they
can only be used for postcards the way yours are ...and unlike you,
don't have any experience using freeze spray to stop the action.

I am (for what it's worth - which is basically nothing) a member of
WIPM. For a backwoods boy that's; World Institute of Photographic
Masters. A shonky effort to provide wannabe Photographers with a $30
membership certificate I could have made for the cost of the paper. So
much for modern day "qualifications".

I am however far more qualified than you and probably the only working
photographer in Australia who qualified under the Apprenticeship
Commission and has indentures to prove I can legally claim to be a
qualified tradesman Photographer.


With all of that you have not yet learned to focus you camera
correctly?

Scott

Really?
If you think this discussion is about my inability, you are a bigger
****** than Bret.

Dmac wrote:

Really?
If you think this discussion is about my inability, you are a bigger
****** than Bret.

Gee, bigger then Bret, wow thanks.

Scott

Al Denelsbeck wrote:
Dmac wrote in news:hDnhg.4545$ap3.3028@news-
server.bigpond.net.au:


Annika1980 wrote:

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



Douglas J MacDonald, BE. BA, Hon.
Indentured Tradesman Photographer, 1964. Melbourne, Victoria Australia
Mentored by Malcolm Campbell at his St Kilda Studio, Melbourne,
1962 - 1974, R.I.P.

Sorry I don't have any Photoshop qualifications to crop my pics so they
can only be used for postcards the way yours are ...and unlike you,
don't have any experience using freeze spray to stop the action.

I am (for what it's worth - which is basically nothing) a member of
WIPM. For a backwoods boy that's; World Institute of Photographic
Masters. A shonky effort to provide wannabe Photographers with a $30
membership certificate I could have made for the cost of the paper. So
much for modern day "qualifications".

I am however far more qualified than you and probably the only working
photographer in Australia who qualified under the Apprenticeship
Commission and has indentures to prove I can legally claim to be a
qualified tradesman Photographer.

Sometimes Bret, you are a total ******... Read that as most time.

Douglas



And yet, you blew hyperfocal distance completely, don't understand
that acceptable CoC is subjective and will depend on *how much of an
enlargement you aim for*, and didn't realize that different sensor sizes
would produce different results.

So, what exactly DO you get from your various titles?


- Al.

Considering no one (you included) here has actually come up with any
definitive information which can be verified as correct - like in having
text book reference or at least a publication to refer to, or provide
information that can be demonstrated to be accurate, your repeated
attempt to belittle me is far from a refreshing divergence. All it does
is show how shallow you really are and how little you actually know.

It highlights your willingness to sink the boots in when someone asks a
question, rather than have the knowledge or ability to answer it. Your's
is just another post from yet another group idiot who flounders when
faced with a technical issue but decides to behave like an immature fool
with a childish retort for some quaint form of keyboard sport.

FYI I didn't "blow the Hyperfocal distance completely". I calculated it
correctly and obtained the picture I needed using my 5D. My question is
all about hyperfocal and a crop factor camera, not my ability or lack of
it. Why don't you crawl back under your rock until you hear another
person you can attack?