New DoF online calculator

enricosavazzi · Post by **enricosavazzi** » Sun Nov 20, 2011 5:01 am

I made a new DoF calculator available on my web site at

http://savazzi.freehostia.com/photography/applet.htm

It is pre-configured with sensor data from several current cameras, but its real strength is being fully configurable in almost all respects I can think of.

Some debugging might still be needed.

Charles Krebs · Post by **Charles Krebs** » Sun Nov 20, 2011 10:33 pm

Enrico,

Nice piece of work... I've bookmarked it... Thanks!

elf · Post by **elf** » Sun Nov 20, 2011 11:24 pm

Service Temporarily Unavailable when I try to connect.

Harold Gough · Post by **Harold Gough** » Mon Nov 21, 2011 1:30 am

I see it for a second and am diverted to a java download site.

Harold

enricosavazzi · Post by **enricosavazzi** » Mon Nov 21, 2011 2:20 am

Harold Gough wrote:I see it for a second and am diverted to a java download site.

Harold

This is probably because you don't have a compatible Java runtime system installed. After installing it, you should be able to use the applet.

ChrisR · Post by **ChrisR** » Mon Nov 21, 2011 7:19 am

It works well for me

I was looking for somewhere to input "NA" for the higher magnifications.
Is it reasonable to only use F(effective) = 1/2*NA?
I'm thinking that the PMF of many scope objectives would be far from unity, but I don't know.

rjlittlefield · Post by **rjlittlefield** » Mon Nov 21, 2011 9:58 am

ChrisR wrote:Is it reasonable to only use F(effective) = 1/2*NA?

Correction: F(effective) = magnification/(2*NA)

Example: 10X at NA 0.25 gives F(effective) = 10/(2*0.25) = f/20.

Or you can go the other direction that F(nominal) = (m/(m+1)) * (1/(2*NA)).

Example: 10X at NA 0.25 gives F(nominal) = f/1.8

I'm thinking that the PMF of many scope objectives would be far from unity, but I don't know.

They are, but that's already incorporated into the NA specification when the objective is used at rated magnification. If you push them far off rated magnification then the calculations will go astray.

--Rik

enricosavazzi · Post by **enricosavazzi** » Mon Nov 21, 2011 11:17 am

ChrisR wrote:It works well for me
I was looking for somewhere to input "NA" for the higher magnifications.
Is it reasonable to only use F(effective) = 1/2*NA?
I'm thinking that the PMF of many scope objectives would be far from unity, but I don't know.

It is already implicit in Rik's answer, but to be clear, the NA of an objective is already an effective aperture, specified for the magnification for which the lens/objective is designed. So there is no good reason to have a table of values, because the lens preferably should be used at just one magnification (and in addition there is no need to enter a pupil ratio because, as Rik says, it is already included in the NA figure).

rjlittlefield · Post by **rjlittlefield** » Mon Nov 21, 2011 11:23 am

enricosavazzi wrote:It is already implicit in Rik's answer, but to be clear, the NA of an objective is already an effective aperture, specified for the magnification for which the lens/objective is designed.

To further clarify (I hope!), the NA actually specifies effective aperture on the subject side. The effective aperture on the camera side will be different from that by the magnification factor. If you have an infinity objective, there is no problem adjusting the magnification by changing the length of the tube lens, but in that case the effective aperture (as seen by the camera!) will change in proportion also.

--Rik

pierre · Post by **pierre** » Mon Nov 21, 2011 11:49 am

Bookmarked too

It is very nice Enrico, thanks !

ChrisR · Post by **ChrisR** » Mon Nov 21, 2011 2:13 pm

I got that wrong by a word and a typo then -
I meant to write
f(nominal) = 1/(2*NA)

but still would have been wrong by M/(M+1). (Actually not too big an error for M>=10 or so)
Nominalish?

The chart uses marked lens apertures, not effective apertures. I can't see how it's to be used at all for microscope objectives. I can use it with a nominalish aperture but they're awkward for M< 10 or so

If I think of a 10x NA 0.25 lens as behaving like an f/2 lens - as given by 1/(2*NA), I get the right number - ish.

For larger M lenses 1/(2*NA) also works, I believe.

For a 2x NA0.1 lens,
2/(2+1) * (1/(2*0.1)) gives f(nominal) = 3.33

So there is no good reason to have a table of values

Would it not be useful, for anyone using whichever type of lens the situation suits?

Harold Gough · Post by **Harold Gough** » Mon Nov 21, 2011 2:26 pm

enricosavazzi wrote:
Harold Gough wrote:I see it for a second and am diverted to a java download site.

Harold
This is probably because you don't have a compatible Java runtime system installed. After installing it, you should be able to use the applet.

Installed and working. Thanks.

Harold

naturephoto1 · Post by **naturephoto1** » Mon Nov 21, 2011 2:43 pm

Enrico,

Thank you. But we need more cameras listed like my Panasonic Lumix G1 micro 4/3.

Rich

enricosavazzi · Post by **enricosavazzi** » Mon Nov 21, 2011 10:07 pm

naturephoto1 wrote:Enrico,

Thank you. But we need more cameras listed like my Panasonic Lumix G1 micro 4/3.

Rich

It can be done by adding data to a configuration file, no need to change the code itself. Will probably extend the list in the next release. In the meantime, it is always possible to manually enter the sensor data in the configuration panel.

enricosavazzi · Post by **enricosavazzi** » Sat Dec 03, 2011 3:30 pm

I uploaded a new version of the applet at

http://savazzi.freehostia.com/photography/applet101.htm

Links and bookmarks to the earlier version no longer work (this is necessary to make sure you are running the new version, not the original version that is probably still cached in your web browser or Java runtime system).

Changes:
- Fixed a localizaton bug that caused the applet to crash on some non-English systems.
- Added a few camera models.