MicrobeHunter.com Microscopy Forum

In the past I had made a few by hand using black construction paper. These looked so nicely made I couldn't resist. I bought the largest sets at 35mm diameter. These fit on the annular shelf just above the iris diaphragm on my 4 Series 'scope. The opening is a hair over 36mm diameter, so after dropping these in they are carefully centered with a toothpick, then the lens block is screwed back into place. If the block is screwed in just until it touches the stops, it holds them in place without interfering with the function of the iris.

They are a bit thicker than I anticipated, at around 0.080" or roughly 2mm thick. The group on the left are for some exotic illumination effects, the group on the right are more standard for darkfield and oblique. The only one I've tried so far is the one in the upper left corner. It seemed to enhance contrast a bit in unstained objects.
Below is a link to the seller's items on Ebay. He has these in a lot of different diameters, plus some illumination accessories for certain makes and models of microscopes.

https://www.ebay.com/sch/optitec2020/m. ... pg=&_from=

Rick,

Please kindly let me know how well stop #8 and #11 works (if you number them according your photo above, firstly from left to right and then top to bottom).

I have bought lots of filter stops from that eBay seller. Great guy. He even custom-made some filters for me for specific diameters.

Of those I tried, I personally do not like the ones that let in too much light towards their center. I have not tried your #1 and #7, but based on my past experience, I probably would not like them on my scope. #3, #4, #5, #6 and #9 should be safe bets, if diameter fits about 80% of objective back focal plane.

Now I use and prefer simple circular stop with specific diameters (COL) combined with Dave Johnson's "Radial 3D mask" (COL+Radial 3D): http://bettermicroscopy.blogspot.com/20 ... rt-iv.html
I often de-center the COL filter slightly, based on subject appearance at eyepiece. I prefer this oblique method over my Leitz Heine 's COL (which produces too much halos for thick subjects).

Would the best objects be unstained, like Klaus Kemp's 8 form test plate?

Rick,

I guess it depends on your interest. For stained slides, you may prefer less contrast offered by shadows, so stops #1, #3, #10 and #10 may work better than #6 and #9.

I know I would prefer to use #6 and #9 for transparent subject, becuase produce more shadow and contrast.

I have tried and failed DIY black paper darkfield stops and "arrows" and other "obliques" circles like that, possibly because of inaccurate centration. I placed them in the filter holder, which in the Zeiss Standard is about 30mm below the height of the condenser aperture iris. The nominal filter size is 32mm. I wonder if anybody succeeded with such stops on the Standard. Insertion of the stops in the empty positions of the phase contrast condenser turret, instead, would be possible and perhaps yield results, but is not a wieldy arrangement.

Hi Doron,
I have a GFL but I can't really remember how I got on with the condenser. What I found was that different microscopes and condensers are not the same when it comes to dark field/COL/oblique stop use. With a Lomo Abbe condenser and filter holder directly below it works fine. With a Zeiss Jena NF and n.A. 1,4 achromatic aplanatic condenser not. With a phase revolver condenser I would expect the perfect place for stops to be in the revolver, not below. You might put a stop into the opening of the phase condenser from below.

When I had to specify my perfect microscope it would be high on the list that manipulation of the lighting would have to be easy.

Bob

Some of the books on use of the microscope from the beginning of the 20th century recommend putting darkfield and oblique stops next to the condenser iris.

My 4 series condenser has a filter holder well below the iris. I suspect it's for filters only. That's why I unscrew the lens block to put the stops right above the iris. My antique Spencer monocular scopes have a slot in the condenser body right below the iris. I think it would work for illumination stops, as the width of the opening is too thin for filters. It's even too thin for the stops I just bought.

MicroBob wrote:You might put a stop into the opening of the phase condenser from below.Bob

Thanks. So I did, but centration is very difficult and replacement is cumbersome. Not worth the trouble IMO.

Putting filters at condenser iris is ideal, but not always niece. Directly at condenser bottom is good enough. Centration is not always necessary, unless one needs darkfield.

I usually use mounting putty and microscope slide to hold filters. I would putty the filter to slide, then putty slide to condenser bottom. Firstly center filter by peeping down eye tube without eyepiece. Then decenter it and mov eit around, based on eyepiece appearance. I usually do not like perfectly centered COL, unless subject is a super tiny and thin diatom.

thanks for this post. i want to experiment with my AO model 110 which has the 1087 condenser. I'm assuming I put the filter in the slot in the bottom of the condenser. Does anyone know what diameter best fits the 1087? Thanks!