MicrobeHunter.com Microscopy Forum

Hello, i'm new here.
I have a question about color filters.

I always use a blue one. But i also own a red, green and yellow one.

When are these filters usefull?

Halogen lighting is very red and when dimmed, the field becomes yellow. The blue filter counteracts that effect, making it seem more white. Other filters can enhance the appearance of images. When using polarization or oblique lighting, colored filters cause a measureable retardation of the light wavelength, creating enhanced imaging.
Red = 0
Orange = 1/4
Yellow = 1/2
Green = 3/4
Blue =1.0
Anyone can enhance imaging with a computer. I think that's cheating. The computer produced the final result but not you.
With different filtering and colors, the enhancement is seen in the eyepiece, and You did it. It makes You the artist and a master of light.
Greg

Greg Howald wrote: ↑

Tue May 24, 2022 3:02 pm

Anyone can enhance imaging with a computer. I think that's cheating. The computer produced the final result but not you.

Would it not be the same as saying "The filter produced the final result but not you"? There's definitely some skill and understanding required to process images and get good results, see any of mine as examples where little of that is done.
Seriously though, I think if we compare our earliest attempts with our most recent there should be a quite discernable difference unless there's either little time or effort between the two examples.

A green filter has use in monochromatic imaging with achromat objectives the achromat when looking at a function of focal length and wavelength has a dish shape. You can have a red and blue wavelengths of particular frequencies in exact focus simultaneously, but the function at these points will be at it's steepest. The green section in the middle i.e. the bottom of the bowl will be the flattest so a green filter will produce a range of frequencies but a narrow range. Putting that narrow range right at the bottom of the bowl means that essentially all the light I'm that range will be simultaneously focused.

Also the calculations done in phase contrast setups use green light as the reference frequency, so some advise the use of a green filter to maximize contrast. Phase is a bit artful as your subject will retard light waves about a quarter wave but never exactly a quarter wave, so experimentation with different types of phase lenses and setups for different subjects is warranted.

Also if you want you can light plants with ultraviolet and use the red filter before a camera (maybe not your eyeballs with uv) to capture some auto-fluorescence

Uses are endless.

Thanks for answering the question. I'll try something.

Inexpensive

https://www.ebay.com/itm/255495582241?h ... SwUG1hGC8B

Greg Howald wrote: ↑

Tue May 24, 2022 3:02 pm

When using polarization or oblique lighting, colored filters cause a measureable retardation of the light wavelength, creating enhanced imaging.

Why would filtering out specific wavelength of light slow it down?

Not exactly sure what Greg is referring to but plastic film itself can act as a waveplate. The color difference may be referring to the idea that a crude device such as stretched plastic is sensitive to wavelength

Yeah, it's just the layer of plastic.