Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Darkfield Condenser vs Filter

  • Please log in to reply
20 replies to this topic

#1 Ezzz

Ezzz

    Vostok 1

  • *****
  • topic starter
  • Posts: 123
  • Joined: 18 May 2015
  • Loc: Cochrane, Alberta, Canada

Posted 01 June 2021 - 09:00 AM

Hey Folks,

Is there any reason why someone would buy a dedicated darkfield condenser ($200) vs making your own darkfield filter?

Thanks,

Ezzz



#2 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 01 June 2021 - 06:45 PM

I have found that making your own darkfield filters is a frustrating endeavor quite often resulting in less than desired results.  

 

Patrick


  • Ezzz likes this

#3 Ezzz

Ezzz

    Vostok 1

  • *****
  • topic starter
  • Posts: 123
  • Joined: 18 May 2015
  • Loc: Cochrane, Alberta, Canada

Posted 01 June 2021 - 10:53 PM

Thanks for your input, Patrick. I appreciate it. I think I will just splurge and buy a dedicated DF condenser.

Question - Do you know if you can use the oil immersion DF condenser at lower magnifications?

Eric



#4 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 02 June 2021 - 07:19 AM

I believe that no matter which route you go...  condenser or filters...  darkfield works best at low magnifications such as 4x, 10x, 40x.  I don't have a darkfield condenser though so I'm not absolutely certain on this point.  Hopefully someone with some experience with darkfield condensers will follow up on this.  

 

Patrick



#5 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 02 June 2021 - 07:25 AM

I just checked a few darkfield condensers online and it appears as though you can go with oil immersion higher than 40x.  I suspect your biggest issue will be getting enough light though since this is all reflected light.  I had the same problem with filters at low power so I installed a more powerful bulb in my microscope.  I could still use more light though.

 

I swore that my next microscope will have both lightfield and darkfield condensers...   I don't see that happening anytime soon though.

 

Patrick



#6 db2005

db2005

    Apollo

  • *****
  • Posts: 1,329
  • Joined: 23 Dec 2017
  • Loc: Living in Denmark, under Bortle 5/6 skies.

Posted 03 June 2021 - 04:15 AM

I have never had much luck achieving darkfield illumination with a patch stop using objectives above 20x magnification. It's a small loss, as most of the things I enjoy looking at in darkfield (diatoms, water critters and the like) tend to look better with fairly low magnification anyway.


  • Ezzz likes this

#7 Ezzz

Ezzz

    Vostok 1

  • *****
  • topic starter
  • Posts: 123
  • Joined: 18 May 2015
  • Loc: Cochrane, Alberta, Canada

Posted 03 June 2021 - 11:46 AM

I have never had much luck achieving darkfield illumination with a patch stop using objectives above 20x magnification. It's a small loss, as most of the things I enjoy looking at in darkfield (diatoms, water critters and the like) tend to look better with fairly low magnification anyway.

Did you buy a darkfield condenser? If so, was it dry or oil? 



#8 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 03 June 2021 - 01:50 PM

A patch stop = filter, so, I suspect db2005 is using his usual lightfield condenser with various filters.  

 

I agree with him in that up to the 20x objective is pretty much it most of the time.  If you make your own filters that are perfect for your particular scope, you can sometimes get the 40x objective to produce something appealing.  The big problem here is just like in astronomy...  the more magnification, the less light.  Getting enough rim light on your subject at high magnifications (40x and up) is difficult to accomplish.  One option is to get more powerful lighting.  The option most people go for is just using up to 20x with a few homemade darkfield filters of the right size for their microscope.

 

I happened to increase the wattage of my lighting and made an awful lot of various filters to try.  Out of dozens of tries of various sizes and shapes, only a very few (maybe a half dozen) work well enough to be considered darkfield.  Having brighter lighting has helped with a bit more magnification but it still turns out quite dim at 40x.  

 

Patrick


  • db2005 likes this

#9 db2005

db2005

    Apollo

  • *****
  • Posts: 1,329
  • Joined: 23 Dec 2017
  • Loc: Living in Denmark, under Bortle 5/6 skies.

Posted 04 June 2021 - 12:17 AM

Did you buy a darkfield condenser? If so, was it dry or oil? 

I don't own a darkfield condenser. Most of my microscopes have been second-hand for which darkfield condensers are hard to come by. And relatively expensive for new scopes.


  • Ezzz likes this

#10 SearchingForLife

SearchingForLife

    Lift Off

  • -----
  • Posts: 3
  • Joined: 15 Oct 2021

Posted 15 October 2021 - 06:12 PM

A patch stop = filter, so, I suspect db2005 is using his usual lightfield condenser with various filters.  

 

I agree with him in that up to the 20x objective is pretty much it most of the time.  If you make your own filters that are perfect for your particular scope, you can sometimes get the 40x objective to produce something appealing.  The big problem here is just like in astronomy...  the more magnification, the less light.  Getting enough rim light on your subject at high magnifications (40x and up) is difficult to accomplish.  One option is to get more powerful lighting.  The option most people go for is just using up to 20x with a few homemade darkfield filters of the right size for their microscope.

 

I happened to increase the wattage of my lighting and made an awful lot of various filters to try.  Out of dozens of tries of various sizes and shapes, only a very few (maybe a half dozen) work well enough to be considered darkfield.  Having brighter lighting has helped with a bit more magnification but it still turns out quite dim at 40x.  

 

Patrick

Hey Patrick,

So you increased the wattage of your lighting. What did you go from and to? I have a 100w halogen setup on order right now and I'm anxious to try it out. I was told that the 100w would make it really nice in darkfield at 40x. We'll see...



#11 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 15 October 2021 - 06:34 PM

My microscope came with a 20W halogen bulb.  I changed it to a 30W bulb.  Both of these get incredibly hot so I could not imagine a 100W halogen inside a microscope.  

 

Patrick


  • SearchingForLife likes this

#12 SearchingForLife

SearchingForLife

    Lift Off

  • -----
  • Posts: 3
  • Joined: 15 Oct 2021

Posted 15 October 2021 - 08:43 PM

I'm new to this and just buying my first scope. I have been shown the ropes a bit on two different scopes that belong to other people. One is 10w and the other is 20. Neither does a good job at 40x and both of those guys told me that if I want to get very high quality darkfield, I need to get a setup with at least 50w and preferably 100w so I chose this exotic scope because it is said to do a fantastic job at darkfield. I'm doing live blood analysis so a clear darkfield at 40x is necessary. The light bulb has it's own housing that is vented and away from everything else ( at back of scope ). This thing is a beast.

 

I couldn't afford to get a modern scope with these specific features so after much searching, I found a retired microscope tech with 30+ experience who rebuilds older, high quality scopes and sells them . I got this AO Series 20 with all accessories, filters, condensers etc,,

 

The big black cylinder on the back left is the light carrier and it slips into the housing.

Attached Thumbnails

  • Scope Ad CL.jpg

Edited by SearchingForLife, 15 October 2021 - 09:13 PM.

  • vertex2100 likes this

#13 EJN

EJN

    Fly Me to the Moon

  • *****
  • Posts: 5,097
  • Joined: 01 Nov 2005
  • Loc: Between eigenstates

Posted 16 October 2021 - 12:55 AM

My microscope came with a 20W halogen bulb.  I changed it to a 30W bulb.  Both of these get incredibly hot so I could not imagine a 100W halogen inside a microscope.  

 

Patrick

 

Swap it out for LEDs. I only use LED illumination, you can get incredibly bright illumination and it remains cool.

 

As far as darkfield, I use patch stops with up to a 20x objective. Beyond that they lose contrast.

 

 

Click on images for uncompressed view

 

Paramecium, 200x

 

para-cr2-df.jpg

 

 

Daphnia, 40x

 

daphnia-df.jpg


Edited by EJN, 16 October 2021 - 01:03 AM.

  • Javier1978, db2005 and vertex2100 like this

#14 EJN

EJN

    Fly Me to the Moon

  • *****
  • Posts: 5,097
  • Joined: 01 Nov 2005
  • Loc: Between eigenstates

Posted 16 October 2021 - 12:57 AM

Continued...

 

Hydra, 40x

 

hydra-df.jpg

 

 

Copepod (Cyclops), 40x

 

cyc-df.jpg

 


  • db2005 and vertex2100 like this

#15 EJN

EJN

    Fly Me to the Moon

  • *****
  • Posts: 5,097
  • Joined: 01 Nov 2005
  • Loc: Between eigenstates

Posted 16 October 2021 - 01:13 AM

All these were taken with a vintage Bausch & Lomb Dynoptic, and an LED flashlight as an illuminator, with a Canon 400D DSLR.

 

IMG_7726p1.jpg


  • sarastro, Javier1978, db2005 and 1 other like this

#16 PatrickVt

PatrickVt

    Apollo

  • ****-
  • Posts: 1,044
  • Joined: 20 Apr 2018
  • Loc: Vermont, US

Posted 16 October 2021 - 07:15 AM

I attempted to swap the halogen bulb for LED but I could not find 6v LEDs with the correct pin configuration so I stuck with the halogen bulbs.

 

Patrick



#17 SearchingForLife

SearchingForLife

    Lift Off

  • -----
  • Posts: 3
  • Joined: 15 Oct 2021

Posted 16 October 2021 - 10:00 AM

All these were taken with a vintage Bausch & Lomb Dynoptic, and an LED flashlight as an illuminator, with a Canon 400D DSLR.

 

attachicon.gifIMG_7726p1.jpg

EJN,

 

WOW. Very impressive. Talk about doing a lot with just a little. Very clever setup.


  • vertex2100 likes this

#18 vertex2100

vertex2100

    Vostok 1

  • -----
  • Posts: 158
  • Joined: 25 Mar 2019
  • Loc: Magic kingdom

Posted 17 October 2021 - 03:59 PM

Amazing ! 



#19 RocketScientist

RocketScientist

    Mariner 2

  • -----
  • Posts: 277
  • Joined: 28 Aug 2008
  • Loc: Vermont

Posted 30 October 2021 - 06:28 PM

I use a commercial dark field condenser, and it works extremely well with a 10X objective, but starts to lose contrast above that.

A video put out by Amscope suggests that an oil condenser can go to higher magnification objectives, but it may require an expensive objective with a built-in iris to keep the glare and contrast under control.

I typically stick to my 10X objective for dark field, sometimes combined with a 20X eyepiece.

However, I have made my own Rheinberg filters using a color printer and transparency material. Again, these work well at low magnification. I find yellow-violet to be the most effective.
  • PatrickVt likes this

#20 Javier1978

Javier1978

    Apollo

  • *****
  • Posts: 1,402
  • Joined: 12 Feb 2009
  • Loc: Buenos Aires, Argentina.

Posted 31 October 2021 - 06:19 AM

I use a commercial dark field condenser, and it works extremely well with a 10X objective, but starts to lose contrast above that.
 

 

I have been trying to get decent dark field videos at 200x with a homemade filter and found that lowering the condenser a bit sometimes helps to find a sweet spot. I got some decent-to-me results using this technique:

 

https://www.youtube....h?v=3BS57ll2KpE



#21 RocketScientist

RocketScientist

    Mariner 2

  • -----
  • Posts: 277
  • Joined: 28 Aug 2008
  • Loc: Vermont

Posted 03 November 2021 - 06:33 PM

I definitely agree that adjusting the height of the condenser can improve dark field views.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics