DOF of a Nikon 10x 0.25 Objective

[axle01]

Can someone tell me is the DOF of this objective 0.25

Alan

[Alan Wood]

My Nikon brochures do not specify depth of field.

One old Olympus brochure quotes 18 microns DOF for a 10x 0.25 objective with 10x eyepiece.

Alan Wood

[Ichthyophthirius]

Hi Alan,

That also depends a bit on the final magnification.

For a microscope, have a look at this graph: http://www.mikrofotografie-digital.de/O ... haerfe.jpg

"Gesamtvergrößerung" = final magnification
"Tiefenschärfe" = DOF (here in µm)

For an aperture of 0.25, DOF is somewhere between 25 and 8 µm, and approx. 18 µm at 100x, as Alan said.

Regards, Ichty

[ray_parkhurst]

I usually refer to the Zerene table of microscope objectives here:

http://www.zerenesystems.com/cms/stacke ... romicrodof

According to that page, In the case of microscope objectives, "step size is determined almost entirely by the NA rating (Numerical Aperture) of the objective. "

Here is the data from that page:

Table 2-C – Determine DOF (step size) from Numerical Aperture (NA)
Microscope Objectives
NA DOF
0.1 0.055 mm
0.14 0.028 mm
0.2 0.014 mm
0.25 0.0088 mm
0.3 0.0061 mm
0.4 0.0034 mm
0.5 0.0022 mm
0.55 0.0018 mm

[axle01]

Appreciate that info thank you.

Alan

[JH]

Normaly I use the "lambda/(na^2)" formula, but for high na I use the formula from the article "Depth-of-Focus in Microscopy" written by I.T. Young, R. Zagers, L.J. van Vliet, J. Mullikin, F. Boddeke, H. Netten

https://www.researchgate.net/publicatio ... Microscopy

To get the two sided depth multiply the formula with the factor 2.

The "lambda/(na^2)" formula used for "low" na in air (n=1) is practically the same up to na 0.5. (0.0022 vs 0.0021 at lambda 0.000550). Above that the difference increase between the formulas, at na 1.0 the difference is a factor 2.

Best regards Jörgen



[Edit: lambda 0.000550 thanks Rik!]

[lonepal]

Hi;

There is an important point here.

DOF changes with sensor type, camera brand and magnification.

I also use coinimaging.com calculator and I had any ?ssues, I advice using it for precise calculations. It is trustable.


http://coinimaging.com/calculator.html

[lonepal]

Sorry for triple posting.
I couldn't understand why it happened

[rjlittlefield]

Sorry for triple posting.

No worries, I deleted the extra copies.

DOF changes with sensor type, camera brand and magnification.

Most of all, DOF changes depending on what is meant by the term.

If you select the "Depth of Field" option at http://coinimaging.com/calculator.html, then you have to specify an acceptable "Circle Of Confusion" (COC). The COC is a number that ultimately depends on the amount of blur that you're willing to tolerate in the final image. That can vary over a wide range, depending for example on whether you plan to reproduce the image at 800 pixels wide on a web page, or you want to pixel-peep within a camera resolution image at 5000 pixels wide.

In contrast, the lambda/NA^2 formulation, and the more accurate refinement shown by JH, essentially assume that you're not willing to tolerate much more blur than what is unavoidable from diffraction. Roughly speaking, those formulations are equivalent to the circle-of-confusion formulation if you use the Airy disk diameter as an acceptable COC.

In the table that ray_parkhurst mentions, I use the lambda/NA^2 formulation specifically because it does not depend on sensor type, camera brand, magnification, and so on. The numbers produced by those formulas remain valid no matter how good of a sensor you use, or how closely you look at the captured image.

If your requirements are less stringent, then the COC formulation might be a better predictor of the larger DOF that you're willing to accept.

--Rik

Edit: added URL tag to correct invalid link

[JH]

Even with more "normal" lenses than microscope objectives it is always best to test. I have ruined stacks because what I thought was ok DOF in single pictures turned out to be clearly visible focus banding after stacking. The resultat was useful for webb and smal prints but not anything else.

Regards Jörgen

[lonepal]

Sorry for triple posting.

No worries, I deleted the extra copies.

DOF changes with sensor type, camera brand and magnification.

Most of all, DOF changes depending on what is meant by the term.

If you select the "Depth of Field" option at http://coinimaging.com/calculator.html, then you have to specify an acceptable "Circle Of Confusion" (COC). The COC is a number that ultimately depends on the amount of blur that you're willing to tolerate in the final image. That can vary over a wide range, depending for example on whether you plan to reproduce the image at 800 pixels wide on a web page, or you want to pixel-peep within a camera resolution image at 5000 pixels wide.

In contrast, the lambda/NA^2 formulation, and the more accurate refinement shown by JH, essentially assume that you're not willing to tolerate much more blur than what is unavoidable from diffraction. Roughly speaking, those formulations are equivalent to the circle-of-confusion formulation if you use the Airy disk diameter as an acceptable COC.

In the table that ray_parkhurst mentions, I use the lambda/NA^2 formulation specifically because it does not depend on sensor type, camera brand, magnification, and so on. The numbers produced by those formulas remain valid no matter how good of a sensor you use, or how closely you look at the captured image.

If your requirements are less stringent, then the COC formulation might be a better predictor of the larger DOF that you're willing to accept.

--Rik

Thanks for the explanations Rik;

You can find the COC values if you click on the question mark near it.

Do you think the DOF will be same for a microscope lens on an APSC and a FF camera?

[rjlittlefield]

You can find the COC values if you click on the question mark near it.

Clicking the question mark shows commonly accepted COC values, such as 0.029 mm for full-frame.

That's about 1/1240 of the frame width, about 1/4 mm on an 8"x12" print, a completely reasonable value for many purposes.

But on my D800E (full frame, 36 megapixels), that number also corresponds to a blur circle that is just under 6 pixels wide, definitely not sharp when pixel-peeping, and a guarantee of focus banding when stacking with a sharp lens.

So, if I want to pixel-peep and focus stack, and to use that calculator, all with the D800E, then I need to plug in a smaller value for COC, which will produce a correspondingly smaller value for DOF.

Do you think the DOF will be same for a microscope lens on an APSC and a FF camera?

Yes or no, depending on exactly what question is being asked.

Most of the people that I deal with are concerned with DOF because they want to avoid focus banding in stacked images, no matter how close they look. For those people the answer I give is "yes, DOF is the same for all cameras", because with typical objectives and typical cameras, the cameras are more than good enough to capture all the detail that is present in the optical image. The relevant DOF in that case is the diffraction-limited value calculated by the lambda/NA^2 formulation and its refinement shown by JH.

If the person asking the question has other interests, then the answer may be "no", but I wouldn't be able to know that without finding out exactly what those interests are.

--Rik

[lonepal]

Thanks Rik!

If I had a FF camera I would try but unfortunately I have no.

But once I accidentally used the FF (Sony A7II) DOF values on my APSC (Canon 100D) which are calculated from coinimaging calculator for Mitutoyo M Plan APO 20X and I had banding after stacking near 450 images that was terrible!

When you calculate from coinimaging; the DOF is always narraower on APSC camera.

But I will try the JH values to check.