MicrobeHunter.com Microscopy Forum

I was interested in ordering a set of Rheinberg filters such as these off of eBay to play with:

https://www.ebay.com/itm/Rheinberg-Filt ... %7Ciid%3A1

But then read this article suggesting that the diameter of the inside color disc should specifically match the diameter of the condenser iris, which changes with each objective if you follow the author's instructions:

http://www.quekett.org/resources/rheinberg

So the question is, has anyone used the eBay filter sets with success and will they work optimally for different magnifications? Are the measurements from the above article necessary for success? I did see this thread below and it seems like they worked without any mention of complications:

viewtopic.php?f=28&t=6701

I note that the filters on eBay are 3mm thick, which is probably too fat for my filter holder (could probably do a mod to remedy this) so maybe it would be better to custom-make filters for each objective, albeit more time consuming and not less expensive once the acetate paper is purchased.

Custom made filters how to from Oliver:
https://www.youtube.com/watch?v=Pku4T8s-0lg

Thank you for this timely video. I wonder why that other article suggests the disc diameter is so important and yet, it appears not to be necessarily true.

Sauerkraut wrote:Thank you for this timely video. I wonder why that other article suggests the disc diameter is so important and yet, it appears not to be necessarily true.

I has to do with obtaining the max NA from each objective. You can achieve similar lighting results with a smaller disk diameter by stopping down the diaphragm, but it is at the loss of some resolution.

Sauerkraut wrote:I was interested in ordering a set of Rheinberg filters such as these off of eBay to play with:



But then read this article suggesting that the diameter of the inside color disc should specifically match the diameter of the condenser iris, which changes with each objective if you follow the author's instructions:

http://www.quekett.org/resources/rheinberg

Really nice link about stop sizes. Thanks.

fibreoptix wrote:

Sauerkraut wrote:
http://www.quekett.org/resources/rheinberg

Really nice link about stop sizes. Thanks.

I'm glad you reminded me about this link (had forgotten about it. Oops). I ended up ordering that stock Rheinberg set from eBay and finally today got decent results with the off-the-shelf discs through 10x. But for 20x, so far I'm having to use handmade discs with a smaller central diameter.

I wonder how hard it would be to custom cut a set of glass discs - maybe just a few favorite combos. Perhaps there would be better overall resolution (less distortion) than plastic gives?

Heather

Sauerkraut wrote:I wonder how hard it would be to custom cut a set of glass discs - maybe just a few favorite combos. Perhaps there would be better overall resolution (less distortion) than plastic gives?

I doubt that the material makes a significant difference, but the direct answer to the question is: not hard if you have the appropriate equipment, which is:
1. Drill press
2. Glass drilling bit
3. A shallow pan of water
4. A few 6"x6" (say) pieces of flat scrap glass, thickness 3-6mm ("base").
5. Safety equipment - good goggles.
The drilling bits look like small cylinders with a shaft. They are coated with diamond powder. I remember someone pointing to a commercial source on this forum.

Supposing that the colored glass you want to cut is thin - say, 1-3mm. You put the base plate in the pan, place the colored glass on top of it, fill the pan with water so it covers the top plate. Don the goggles. The rotation speed of the drill should be medium-low. It is "underwater" drilling. Press on the colored glass with a finger (precaution - you do it at your own responsibility), and drill through the glass until the bit reaches the base. Drill through, such that you fill that the colored plate has been drilled and the base has been just marked by the bit. Carefully knock the circle out of the bit. A new bit will be good for about 10 circles, I guess.
Warning - do not press hard on the drill, work gently. It works by abrasion of the glass by the diamond particles, nothing else. Do not stop in the middle.

Thanks Hobbyst46. Good to know. I will keep it in mind and store it in my mental 'maybe to try someday' list. Sounds like glass over plastic is not a major improvement but still would be interesting to compare.

Heather

The Rheinberg filters on Ebay are excellent I have purchased and used them on several of my microscopes. They cost about $30 which is cheap in my opinion. You do need to adjust the height of the filters under the condenser for different objectives. What I did with my research microscope is create a small cardboard box that fits over the bottom lamp and cut a hold in the top to fit the Rheinberg filters. I now found that metal holders for inverted microscopes (cost about $30) fit the filters and use it. I can vary the height a little bit, but it works with most of my objectives.

I have posted an article here: https://www.canadiannaturephotographer. ... s2017.html

I don't show my carboard box, but they are easy to make with a little imagination, some tape, and cardboard or balsa wood.

A photo showing the results I get with different filters I purchased from ebay.