hyperfocal distance

"Dave Martindale" wrote in message
...
SNIP
The preprinted tables are not valid. But calculated DOF tables
that allow you to change the CoC size cover all possible situations.
You can even build your own tables using a spreadsheet.

Or use the tools at http://dfleming.ameranet.com/dofjs.html to print a
personalized one.

Bart

Thanks for the comments. You are right and I also mentioned in
my original statement that CoC is not hard number which depends
on many factors, real and/or conceptual. (my original statement had
a typo, "only" should "on").

I think my description may serve as starting point in setting
the CoC value according to different requirements or needs.
By adjusting the printing quality criteria and changing the
the ppi value defining the size of CoC, I think you can achieve
all the effects/requirements you mentioned. My point is really,
in digital photography, it is better define CoC in number of
pixels rather than the physical size. I believe this is more
consistent and repeatable on the same camera or different cameras.
If you want to set CoC approximately proportional to the picuture
size or to achieve some artistical DOV effect, it is still better to use
pixel numbers. Of course you have to convert the pixel number to
the physical dimension according to the sensor size for the final
hyperfocal distance and DOV calculations. I think your statements
are generally correct. I just feel that using pixel as a unit
may be more consistent.



In article ,
Roland Karlsson wrote:
(Charlie Ih) wrote in
:

DOF questions/topics come up quite frequently and naturally lead
to hyperfocal distance and then to CoC. We all know that the CoC is
not hard number which depends only many factors including
"enlargement". For digital cameras and using "digital" printers, we
may be able to define CoC more scientifically. The following is a post
I made almost exactly one year ago. It is slightly edited and repeated
below. I hope this will clear some of the CoC issues.

...

Hi ... nice analysis!

Yes - you can choose CoC according to a fixed resolution, e.g. 50 ppi.
Then you can use that to calculate DOF and hyperfocal distance if you want.

But - this is not how it is done. CoC is not based upon acceptable
sharpness in general - it is based upon percepted sharpness for out
of focus details. Out of focus details may be unsharper than what
is unacceptable for in focus detail; and the basis for CoC is that
the CoC is really independent of how sharp the sharper parts are;
it is approx. proportional to the picture size.

Of course, this assumption may be wrong. If the tendency is towards
super sharp pictures in general, the the CoC migh be what you propose.
If the tendency is to use DOF artistically, then it is rather the old
CoC method that is valid IMHO.


/Roland


--
Charles S. Ih
302-831-8173, FAX 302-831-4316

Thanks for the comments. You are right and I also mentioned in
my original statement that CoC is not hard number which depends
on many factors, real and/or conceptual. (my original statement had
a typo, "only" should "on").

I think my description may serve as starting point in setting
the CoC value according to different requirements or needs.
By adjusting the printing quality criteria and changing the
the ppi value defining the size of CoC, I think you can achieve
all the effects/requirements you mentioned. My point is really,
in digital photography, it is better define CoC in number of
pixels rather than the physical size. I believe this is more
consistent and repeatable on the same camera or different cameras.
If you want to set CoC approximately proportional to the picuture
size or to achieve some artistical DOV effect, it is still better to use
pixel numbers. Of course you have to convert the pixel number to
the physical dimension according to the sensor size for the final
hyperfocal distance and DOV calculations. I think your statements
are generally correct. I just feel that using pixel as a unit
may be more consistent.



In article ,
Roland Karlsson wrote:
(Charlie Ih) wrote in
:

DOF questions/topics come up quite frequently and naturally lead
to hyperfocal distance and then to CoC. We all know that the CoC is
not hard number which depends only many factors including
"enlargement". For digital cameras and using "digital" printers, we
may be able to define CoC more scientifically. The following is a post
I made almost exactly one year ago. It is slightly edited and repeated
below. I hope this will clear some of the CoC issues.

...

Hi ... nice analysis!

Yes - you can choose CoC according to a fixed resolution, e.g. 50 ppi.
Then you can use that to calculate DOF and hyperfocal distance if you want.

But - this is not how it is done. CoC is not based upon acceptable
sharpness in general - it is based upon percepted sharpness for out
of focus details. Out of focus details may be unsharper than what
is unacceptable for in focus detail; and the basis for CoC is that
the CoC is really independent of how sharp the sharper parts are;
it is approx. proportional to the picture size.

Of course, this assumption may be wrong. If the tendency is towards
super sharp pictures in general, the the CoC migh be what you propose.
If the tendency is to use DOF artistically, then it is rather the old
CoC method that is valid IMHO.


/Roland


--
Charles S. Ih
302-831-8173, FAX 302-831-4316

(Charlie Ih) wrote in :

I just feel that using pixel as a unit
may be more consistent.

I think this is just a matter of choice, you can do whatever
that you feel comfortable with.

/Roland

(Charlie Ih) wrote in :

I just feel that using pixel as a unit
may be more consistent.

I think this is just a matter of choice, you can do whatever
that you feel comfortable with.

/Roland