## Equations

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All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

### Equations

I am at the starting of a very ambitious project that might take me a lot of time and effort.
The only thing I want from you is to contribute your methods/equations/formulas you use to estimate :
1. The magnification
2. The step size
Also the DOF ones [if you believe that applies in our kind of microphotography (using microscope objectives)].
The ones I have are for the magnification:
1. magnification=(sensor width)/(frame width)
2. magnification=(tube length)/(focal length of the objective)
3. magnification = (Marked magnification X the new tube lens focal length)/(the system tube lens focal length)
And the ones for step size :
1. DOF (in mm)=0.00055/((NA*NA))
2. Step size=2cn(m+1)/(m*m)
I`d like to hear whatever is plusable and reliable enough to fit in a mathematick approutch .
Thank you.
All--Ex

Posts: 1165
Joined: Mon Nov 30, 2015 1:09 pm

### Re: Equations

Hi AllEx,
DOF (in mm)=0.00055/((NA*NA)) is really good for the microscope lenses.
But I would recommend to measure the magnification it you needed the right values.

rjlittlefield
Posts: 21037
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

### Re: Equations

With microscope objectives, the second equation for step size is not appropriate. It can be made to work, but only in conjunction with other equations that calculate "n" based on NA, and adjust "c" for diffraction blur.

The most reliable equation is your first one, DOF (in mm)=0.00055/((NA*NA)) .

However, for critical work there is no good substitute for experimentation. The formulas consider only blur circles and diffraction. But the required step size can also depend on the nature of the subject and the style of illumination. Some cases give significantly better results with step size that is much smaller than the formula predicts -- perhaps half the calculated value, sometimes even smaller. The calculated DOF should always be considered just a starting point.

--Rik

All Ex
Posts: 261
Joined: Mon Jul 20, 2015 3:54 am
Location: Greece Thessaloniki

### Re: Equations

In my aims, it is highly possible to play an important role except for the equations the lists containing step sizes too, beyond the list in Zereene Stacker & the Weelmacro one do anybody has in mind any other one?
Rik, the second equation is the base of Johan J Ingles-Le Nobel calculator if I recall right, of course, he (as very thoroughly refers in his site) and everybody of us knows the role that experimentation plays in the all procedure.
I`m just wondering if something else worths considering.
All--Ex