Green Interference Filter for Phase Contrast

[microb]

What is a good transmission for a phase contrast green filter?

Here's a graph of a glass filter I have. But it's one bought off of ebay and not a microscope company. So I'd like to check:

[MichaelG.]

That doesn’t look like an Interference Filter plot should ...

Is that the one you have purchased ?

MichaelG.
.
Edit: for comparison https://midopt.com/filters/bi550/

[75RR]

Here's a graph of a glass filter I have. But it's one bought off of ebay and not a microscope company. So I'd like to check:

Did you make the graph and if so how?

[Hobbyst46]

The above spectrum represents a not very selective filter.
Here are example spectra of two filters that I have. Both are green (when you look through). The transmittance (0-100%) is plotted against the wavelength (nm). Green is 546nm.
The absorption filter is way more selective than the one shown at the top of the post. The interference filter is even more selective.
Since the absorption filter provides decent transmittance (say, >30%) at a relatively wide range of wavelengths, it can comply with fairly bright illumination.
The interference filter, that allows the passage of only a narrow wavelength range, accordingly needs a very bright lamp to make the image visible (to the eye or camera).
Hence, the better filter "quality" (interference, narrow wavelength range, much higher cost), the stronger illumination is required. A tradeoff.
A green laser provides both an extremely narrow wavelength range around 546nm, and high intensity... but that is not for the human eye, just to a light detector.

Often, transmittance spectra of commonly available commercial filters (from Kodak, Schott, Corning, Chroma) are downloadable.

Note, that I am not saying that the interference filter is significantly better for phase contrast. Most phase contrast scopes that I have seen, for tissue cultures at least, had just absorption filters.

[microb]

So where does one get a good deal on a more narrowed green filter?

What's the spec on one of these? LEICA GREEN FILTER PART NO. 512077

Or maybe Edmund Optics 50mm dia -- but I'd lke 32mm: https://www.edmundoptics.com/p/50mm-dia ... ter/10613/ (https://www.edmundoptics.com/document/download/353834)

[microb]

Here's a graph of a glass filter I have. But it's one bought off of ebay and not a microscope company. So I'd like to check:

Did you make the graph and if so how?

This was done with an Ocean Spectrometer. A baseline spectrum was built up with a RGB LED, two UV LEDs, and one IR LED. Snapshots were saved to CSV files of the spectrum (baseline and filter in front).

Loading the two .csv files into Excel, a new graph column was added with a formula to drop baseline values to that are too low to be trust worthy (return 0), and otherwise AVERAGE(after[0..10])/AVERAGE(before[0..10]) is the percentage for a transmission graph.

[microb]

That doesn’t look like an Interference Filter plot should ...

Is that the one you have purchased ?

MichaelG.
.
Edit: for comparison https://midopt.com/filters/bi550/

It was just one of those cheap 32mm glass filters on e-bay. I thought I try it. Maybe I can Reinberg it.

[MichaelG.]

It was just one of those cheap 32mm glass filters on e-bay. I thought I try it. […]

.
Ah ... that’s O.K. then

Sorry, I misinterpreted the title of your topic.

MichaelG.

[microb]

Looks like a Zeiss Axiomat filter I have might work:

[MichaelG.]

That’s more like it !!

MichaelG.

[Hobbyst46]

The width of the Zeiss Axiomat green band (measured at half-height) is ~25nm.
The width of the Edmund optics as well as my interference filter, shown above, is 40-50nm.
So the Axiomat filter provides "purer" green. And blocks a lot of the light. That means that a powerful white light lamp (guessing - at least 20W) is required to achieve reasonable exposure times for the camera..

Whereas the LEICA GREEN FILTER PART NO. 512077, being an absorption filter, probably looks more like my absorption filter shown above, or your green filter shown at the top of the post, or something in between... and, at an eBay cost of 30$, is quite expensive for an absorption filter.

[75RR]

Here's a graph of a glass filter I have. But it's one bought off of ebay and not a microscope company. So I'd like to check:

Did you make the graph and if so how?

This was done with an Ocean Spectrometer. A baseline spectrum was built up with a RGB LED, two UV LEDs, and one IR LED. Snapshots were saved to CSV files of the spectrum (baseline and filter in front).

Loading the two .csv files into Excel, a new graph column was added with a formula to drop baseline values to that are too low to be trust worthy (return 0), and otherwise AVERAGE(after[0..10])/AVERAGE(before[0..10]) is the percentage for a transmission graph.

Thanks!

[microb]

So this is a price quote for a green interference filter from MidOp -- yeah the Edmund Optics one at $35 is far cheaper:

[NinetySix]

I've had some success using a narrow-band astrophotography filter intended for use with a monochrome camera, an "O-III" filter, 7nm centred on around 500nm from memory. Transmission is quite low though so I have to run my led at full power (10w) but it really cleans up the image and improves contrast.

At about US$150 I wouldn't suggest buying one, but if you happen to have one already, give it a shot I mounted mine in a 31mm to T2 filter holder screwed into a T2 female-female adaptor and sit it on to of the field lens. You can bet your beans I'm careful not to scratch it, to the point that it's no longer fun


Here's a quick smartphone eyepiece video of my saliva using a 40x Nikon cf 0.65 ph3 (from memory)

https://photos.app.goo.gl/ikMUAPFKKkP8ZqgDA