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I've got a SP-94 compound microscope. It seems very similiar or the same as the SP100.

All I know about microscopy, I've learnt in the last couple of days. I have played with the scope a fair bit but I am unsure as to where it lies in terms of darkfield and phase contrast.

It has a ring under the condensor in which I can place one of two different coloured discs, one blue the other white. You can swing the disc holder in and out, with each colour giving a different effect. However, if the holder is half way in, I get a darkfield type effect. Is this "true" darkfield, all that seems to be happening is the disc holder edge is blocking out the light under the specimen as I swing it back and forth.

This effect doesn't work so well with the x40 objective and not at all at x100.

Any help appreciated...

Hi sWozzAres,

I am not familiar with your microscope so I looked up the SP100 on Brunel's web sight. Reading the specifications this microscope does not come with phase contrast as standard, if you want phase contrast you will need to replace your objectives and condenser.
The effect you get when swinging the condenser filter carrier is a partial darkfield, to get a better darkfield make or obtain some clear disks to fit into the filter carrier, fix a opaque disk to the center of these and place in the carrier to use. The opaque disks will need to be different sizes for the different objectives, experiment for optimum results. When you have found the sizes you may like to experiment with Rheinberg illumination, to do this replace the opaque disk with a transparent but coloured one (say blue ) and place a contrasting coloured annulus (say red ) around this, viewing with this filter should show reddish objects on a blue field. Dark field and Rheinberg illumination will not be available with the 100x objective as these forms of contrast need a condenser with a higher NA than the objective.

I hope this helps.

Good luck.

Peter.

Alot of stuff I have been reading recently now makes alot more sense! I have a dark field condensor/objectives and I can upgrade it to support phase contrast. Different filters sound very interesting and I will certainly have a play with that.

Thanks for your help