Wavelength and resolution (image embedding fixed)

[75RR]

Not sure why the address you have is that long - here is a shorter one that links to the same article:

https://www.researchgate.net/publicatio ... lorida_USA

It may be because I am using the iPad and/or because of the numerous underscores in the address.

All I did was copy and paste the URL from the web page ...

Thanks for posting the shortened form of the link.
How do you make it do that ?

MichaelG.

I can't seem to reproduce that long address.

Perhaps if you scroll down this page to the article* it will give you a more direct link: https://www.researchgate.net/profile/Peter_Siver

*Article is 5/6 of the way down

I am using yosemite + firefox

[MichaelG.]

I can't seem to reproduce that long address.

The long address is simply the direct URL for the PDF of the paper
... which you will find by clicking the blue button near top-right of the page that you linked

[ Download full-text PDF ]

MichaelG.

[75RR]

I can't seem to reproduce that long address.

The long address is simply the direct URL for the PDF of the paper
... which you will find by clicking the blue button near top-right of the page that you linked

[ Download full-text PDF ]

MichaelG.

Got it. You are copying link location - what you want is to copy the direct address from the browser window.

[MichaelG.]

Learning point:

https://www.researchgate.net/publicatio ... lorida_USA

https://www.researchgate.net/profile/Pe ... ion_detail

Those two links ^^^ are the result of pasting the two addresses directly into this message
... without using the url and /url codes to enclose them !!

HTML seems to work in mysterious ways, these days

MichaelG.

[MichaelG.]

Got it. You are copying link location - what you want is to copy the direct address from the browser window.

Sorry, but no

I did copy the direct address [URL] from the browser window.

The mysterious behaviour is 'explained' in my follow-up post

Thanks for joining me on this voyage of discovery

MichaelG.

[Wes]

The first comparison I posted wasn't not very well controlled. To improve the demonstration of the relationship between wavelength and resolution I isolated 3 relatively equidistant wavelengths. I made a mistake in the original post as the blue filter is 445 not 447 nm. I think now its much clearer and convincing how shortening the wavelength improves the resolving power of the microscope. You can open the image in a new tab for full resolution to get a better glimpse of the striae.

[MicroBob]

Hi Wes,
very impressive comparison, obviously you picked just the right diatom for this demonstration!

How did you apply the filters and what type were they?

Bob

[Hobbyst46]

IMO the difference between the 531 and 445nm appears to be in contrast rather than resolution. Hence, in agreement with Sauerkraut above, it would be nice to see a similar test with brightfield. DIC enhances contrast, but, could it not bias, if optimized (by design) for green light ?

[Wes]

Hi Wes,
very impressive comparison, obviously you picked just the right diatom for this demonstration!

How did you apply the filters and what type were they?

Bob

Thanks Bob, I chose the diatom that I could barely resolve by eye so I figured it must be on the limit of what this particular objective can deliver. All three filters are short pass interference filters with the following wavelength and FWHM (Full width at half maximum) bandpass: 641/75, 531/40, 445/50. I simply put them on top of the field diaphragm.

IMO the difference between the 531 and 445nm appears to be in contrast rather than resolution. Hence, in agreement with Sauerkraut above, it would be nice to see a similar test with brightfield. DIC enhances contrast, but, could it not bias, if optimized (by design) for green light ?

I have no idea whether the "new" DIC system from Zeiss was optimized for a particular wavelength but if it was green would be a good guess. Contrast in brightfield was very poor but I did not try hard enough to be honest.

[Wes]

For diatoms I have done this occasionally and the resulting image of one colour channel changed to b/w was somewhat better than all colour channels together. The method makes an apochromat from a simple achromat in a way.

I tried this and I concur, there is a visible improvement of the green and blue channels over the red channel. I took an image of the diatom in standard mode, then split it into its three component channel, converted each to a gray scale image and stacked them on top of each other.

[MicroBob]

Hi Wes,
when I split the image I posted into the colour channels I liked the green channel best, red was quite ok, but blue was a lot worse. I can't remember which objective I used to take the image, maybe an old achromat on the Biolamini. So it is possible that the ecpected effect of use of the different wavelenghts is overlapped by an unexpected effect.

Your use of interference filters seems to combine well with the DIC. I just overhauled a Standard 18 and equipped it with the old DIC for an honoured member of our group and used a diatom slide to test out a set of suitable objectives. The image was very nice, contrasty but not too many artefacts, so I plan to spend some time with diatoms and DIC old and will look for suitable interference filters to make use of this effect. As far as I know the old DIC condenser limits the aperture to ca. 0,9 which will be a bit if a drawback for diatoms.

Bob

[Hobbyst46]

...I just overhauled a Standard 18 and equipped it with the old DIC for an honoured member of our group and used a diatom slide to test out a set of suitable objectives.

Bob, would you maybe consider posting the details of the "overall", in a separate thread of course ?

[Wes]

I just overhauled a Standard 18 and equipped it with the old DIC for an honoured member of our group and used a diatom slide to test out a set of suitable objectives.

I too would be very interested to see/learn more about this setup as well as see some diatom images.

[MicroBob]

...I just overhauled a Standard 18 and equipped it with the old DIC for an honoured member of our group and used a diatom slide to test out a set of suitable objectives.

Bob, would you maybe consider posting the details of the "overall", in a separate thread of course ?

Hi Doron and Wes,
I have started to assemble a document on the old DIC as it is so difficult, expensive and painful to assemble such a set. Spread over some documents and a lot of threads in different forums I found quite a bit of information, but also quite a bit of rumors on this over 50 years old rare system. I already thought about compiling an english version so more people can profit from it and my document will not become the source of more myths through over enthusiastic google translations. I will post a link here when it is up on our site.
I have two systems running now but at least one more to do that has been cobbled together inexpertly. So far I didn't have unexpected problems (after thorough study of the available information) but this was luck because the parts were used together and thrown away together, no ebay parts that have been passed on due to problems.

Bob