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I was wondering if the addition of Kohler illmination which for me would be around 90$cdn would be worth the expense in better resolution
Hi steve,
This rather depends on your microscope, I have a book in which the author admonishes people who pay the price of a car for their microscope but balk at paying the price of a bicycle for a light source. The microscope is all about the control of light, without Köhler illumination you may be loosing 50% of your resolution. Modern microscopes usually come with Köhler illumination facilities built in you may be better off buying one of these.
Good luck.
Peter.
Steve,
It's not only about resolution, important as this may be. Without Köhler you may get foggy images due to internal reflections of the optics. With the Köhler diaphragm, you can limit the light to only the part of the specimen which you look at, reducing stray light. Köhler therefore also improves the contrast of the images.
Here is a blog post about this: http://www.microbehunter.com/2…..flections/
Oliver.
Just to update this thread. Simply put for those of you who were wondering, Koehler illumination is a method used to provide even illumination of a specimen without having your focus distracted by the illumination source. (such as by a filament from the light bulb in the base of your scope when your attempting to focus on your specimen).
Companies like Nikon, Leica, and Olympus have "pre-centered" and aligned their illumination sockets so that you don't need to use Koehler illumination field diaphragms.
And just when you thought it couldn't get any better, "Voila!", the microscope industry is working to replace halogen (UV Output Light Sources) with eco friendly variable light emitting diode sources (LED) which gives a full bright white light across the entire field of view with no damaging UV rays to your eyes. Plus no need for color compensation filters (the blue filter) and most LED scopes are rechargeable and run during power outages.
Some LED scopes already on the market.
The Olympus CX 21
Nikon Eclipse 100 and 200
Labomed LX 400
Koehler illumination while a thing of the past, may still come in handy for those of us with an appreciation and collection of the Pre 2000 microscopes.
Problem is, at least in my case, that the LED illuminator casts everything blue, and pictures taken with (some) digital cameras are thus seriously compromised. Post-processing helps a bit, but not nearly enough. Additionally, the white LED bulb also emits in a certain UV band, and repeated efforts on my part to find out the exact LEDs used in my illuminator have failed. More interestingly, not all white LEDs are created equal. So for me, for the time being, this remains an open topic. (Should add that my only experience with microscopes is with this LED illuminator.)
If I may, I would like to respectfully disagree with a couple of points raised in jacinadante's post. (1) I don't think that Koehler illumination is a "thing of the past", it is just more expensive to implement, and so it is not usually implemented in low cost microscopes. (2) Built-in illumination is not necessarily Koehler illumination: if a microscope does not incorporate a field diaphragm, it does not have Koehler illumination.
Regarding johvog's problem with LEDs and cameras: I believe most compacts and all DSLRs can be set to "custom" white balance, which should do a vary good job of balancing the LEDs' blue light. An inexpensive camera UV filter or two ($2 to $5 on Ebay) somewhere below the condenser might help reduce UV levels to the eyes if that is a concern.
Gekko,
I have been experimenting with some UV filters (photo, sunglasses, those attached to the halogen bulbs, plain glass) and if I use an iPhone, then nothing really helps. The iPhone is not spectacular in performance but for quick videos it might be good enough… except the heavy blue casting. My Nikon DSLR and a Canon P&S don't have this issue, which makes me believe that the LEDs must be emitting in a certain band that some camera sensors pick up. I will update this story if I find anything that works.
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