Rheinberg filter test

Jan l'Amie · Post by **Jan l'Amie** » Tue Nov 15, 2011 8:38 am

The first tests of a blue spot Rheinberg filter I just made.
I'm very satisfied, and you ?

Mitch640 · Post by **Mitch640** » Tue Nov 15, 2011 8:49 am

Very nice colors and detail.

Litonotus · Post by **Litonotus** » Tue Nov 15, 2011 12:25 pm

looks good (:
it is a great fun to make filters, and sometimes (usually by accident) you discover something that works very good. mixing rheinberg and obligue light can give really interesting effects.

Jan l'Amie · Post by **Jan l'Amie** » Tue Nov 15, 2011 1:24 pm

And they are very easy and cheap to make. I found a site at the internet where you can buy a set home-made filters for allmost 100 dollars but I make them for about 25 cents each. I don't sell.

Franz Neidl · Post by **Franz Neidl** » Tue Nov 15, 2011 1:41 pm

I think that the blue color is too strong. It requires a lot of attention and then the worm is only in the background (specially in the first picture). Personaly I prefer gray. But it's good that there are different likings.

Franz

Jan l'Amie · Post by **Jan l'Amie** » Tue Nov 15, 2011 2:05 pm

Your right Franz but Rheinberg filters are used for special effect.
I used a very high contast to get this colour effect. You can see it like using pola filters. It gives nice colour effects but you don't see the real colour. A Rheinberg filter is a combination of oblique light and colour.
In this case I used a transparant filter with a blue colour spot in the middle. That gives a ,,real,, colour of the object with a blue background.
I made these filters with blue, red, green and yellow spots. Blue gives the nicest effect for this worm. Yellow gives nice effect at desmids.
I also made one with a black solid spot. This gives a nice darkfield effect.
Very nice and cheap to make filters for experimenting.

Charles Krebs · Post by **Charles Krebs** » Tue Nov 15, 2011 2:38 pm

Franz,

I think that the blue color is too strong.

Blue was always my favorite color for Rheinberg with water creatures (and a clear outer ring). But I can see what you mean... although naturally it is all subjective.

Jan... these are nice. (It's too bad that it is so hard to use Rheinberg filters with the microscopes that hold the condenser at the bottom and no longer have a filter tray. With my older stand there was a nice "swing-out" filter tray just below the condenser diaphragm and I used Rheinberg much more frequently). With subjects that have a large amount of clear or semitransparent parts, my experience was that the center colored stop needed to be much darker than I expected to provide a deeper color and not allow too much of the color to "bleed through" the translucent sections (Also a good reason to not have the colored center much larger than it needs to be). Frequently it was necessary to use 2 or 3 layers of the colored gel material to increase the density of the center stop.

If you can afford to give up some light, a fun thing to try is to get some polarizing "film" and cut a circle the same size as the colored center stop. Put it together with the colored center stop. Then, if you rotate a polarizer placed over the base light, you can vary the density of this center stop (as the polarizers cross to "extinction") and produce very different effects without needing to change filters as often.

Wim van Egmond · Post by **Wim van Egmond** » Wed Nov 16, 2011 1:41 am

They are very good, Jan. The colour of the organism looks pretty o.k., perhaps a bit too red and over saturated but that could be adjusted in the computer. Blue is always nice for an aquatic feel.

Oblique Rheinberg with natural colours is one of the most interesting cheap techniques. I have used it many times. I make the central stop with a polarised filter cut from 3D glasses. They are easy to find and cheap. They darken to a blue but you can alter the colours with a piece of plastic. In polarised light it gives all kinds of colours. But the center stop, like Charles says, has to be very dark so you may need some extra filtering to create that. You can use a black marker pen to make your filter darker.

Wim

Jan l'Amie · Post by **Jan l'Amie** » Wed Nov 16, 2011 1:46 am

Thans Charles. I have a swingout filter tray unther the condenser.
I make my filters with transparant not coloured acrylat foil and blue, red, green and yellow transparant sticky foil. The size of the tray is 32 mm and the size of the blue spot is 16 mm. I will make some other size spots.
Thanks for the idea of the combination with pola-foil. I have a little piece of it (hard to find here). I made these pictures with this blue-spot Rheinberg filter in combination with a oblique light filter so there is only a small segment left for the light going thru the condenser.
Diafragma wide open. Microscope light is 6V 20W Halogen.
The objective I used is a Plan 10x in combination with a 2.5x photo-oculair.
I used a Canon EOS 50D with Canon software at the PC. Camera in Live View, automatic white-balance, ISO 100, speed 0.4 sec.
Added some extra contrast with Photoshop.
This is my first test with Rheinberg. I will make some more different types of these filters.

Thanks Wim. This is my first try with Rheinberg so every idea is welcome.
I have a few pola glasses so I will make some filters with it.
To get darker colours I can combine some spot filters. I can use 3 filters together in the tray.

BJ · Post by BJ » Wed Nov 16, 2011 9:54 am

Hi,

just a small comment. This discussion about Rheinberg filters illustrates what is so valuable about this forum. A contributor generously shares his images, and others contribute / comment with their expertise and experiences - freely given without any wish to "score points" or show off.

It is what a forum should be about - I feel privilged to be a member.

Thank you all.

Brian

Litonotus · Post by **Litonotus** » Wed Nov 16, 2011 10:21 am

Wim van Egmond wrote:

I tested these kind o filters and made a lot of modifications (before I discovered my version). it does not work very good; moreover it reqiures to be changed everytime when the objective is changed so it has no 'universality' factor. But it was a base for me and thanks to that I started my experiences.

and the center part must be very dark indeed - at least 3 or 4 layers of colour foil.

Jan l'Amie · Post by **Jan l'Amie** » Wed Nov 16, 2011 12:32 pm

So I have to make some other versions before I reach your level I think.

Wim van Egmond · Post by **Wim van Egmond** » Wed Nov 16, 2011 1:32 pm

That makes sense Litonotus. Your filter seems excellent for tweeking and manipulating until you get a nice effect.

Wim

Litonotus · Post by **Litonotus** » Wed Nov 16, 2011 11:21 pm

So I have to make some other versions before I reach your level I think.

just play with it and maybe you discover something I missed (:

here is one of my first modifications of the filter posted by Wim:

the moon shaped part did not work well, I changed it. I made many versions for different objectives and with number of the colour stop modifications, and it gave nice 'dic like' effect, but, as I said befeore, it had to be changed on and on.

Wim van Egmond · Post by **Wim van Egmond** » Thu Nov 17, 2011 1:16 am

That is a smart modification. I wonder how much it differs. And indeed the size has to be larger for higher magnifications.

Wim