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Pushing the limits of B&W macrophotography
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Lou Jost



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PostPosted: Sat Dec 30, 2017 4:53 am    Post subject: Reply with quote

Yes, that's a good suggestion. I should at least check to make sure they are not fluorescing.
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Pau
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PostPosted: Sat Dec 30, 2017 9:03 am    Post subject: Reply with quote

If your sensor has good sensitivity for violet light and the lens good transmittance (as it seems at least in the second case) and the subject is not highly fluorescent like white paper I think that fluorescence will not be an issue:
Typically fluorescence emission light is much weaker that excitation light, often several orders of magnitude.
Anyway testing with emission filters will be interesting.
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Lou Jost



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PostPosted: Sat Dec 30, 2017 11:42 am    Post subject: Reply with quote

The appropriate filters are hard to find.....
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Pau
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PostPosted: Sat Dec 30, 2017 12:12 pm    Post subject: Reply with quote

Lou Jost wrote:
The appropriate filters are hard to find.....


Not so much, you just need an adequate yellow filter, just now at Ebay:

- This one will be excellent for sure, the price is ridiculously low but it is 25mm diam
https://www.ebay.com/itm/Chroma-HHQ460LP-25mm-Long-Pass-Emission-Fluorescence-Microscope-Filter/263382420904?epid=848434842&hash=item3d52d0cda8:g:IgwAAOSwTVtZZdiu

- This one likely would also work well:
https://www.ebay.com/itm/Bigblue-Fluorescence-Filter-Yellow-58mm/253335886148?hash=item3afbfed944:g:sqcAAOSwdGFYuIuO
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Lou Jost



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PostPosted: Sat Dec 30, 2017 2:26 pm    Post subject: Reply with quote

Pau, I need the opposite of the one you indicated; I need to pass deep blue and cut off longer wavelengths. The goal is to eliminate fluorescence.
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Pau
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PostPosted: Sat Dec 30, 2017 4:33 pm    Post subject: Reply with quote

The emission filters I linked are to see the fluorescence and so could be useful for you to see and eventually study or image it.

To eliminate it if it is enough intense that could damage your pictures (likely it couldn't) you want just the opposite: an excitation filter but placed between the subject and the sensor. It can be a short pass filter or a pass band filter. Pass band filters are in many cases more expensive and have lower transmission factors.

This pass band one will be fully adequate:
https://www.ebay.com/itm/Chroma-ET402-15X-25mm-Fluorescence-Microscope-Excitation-Filter/263411178177?hash=item3d54879ac1:g:HhMAAOSwjUhaR3hM

see the spectrum at:
https://www.chroma.com/products/parts/et402-15x
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Lou Jost



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PostPosted: Sat Dec 30, 2017 5:49 pm    Post subject: Reply with quote

Yes, that would do it for this laser, thanks. Are there larger filters though? This is a big lens....
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Pau
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PostPosted: Sun Dec 31, 2017 1:40 am    Post subject: Reply with quote

25mm is the most standard size for fluorescence microscopy. Bigger will be hard to find and extremely expensive if ordered to have it custom made, Chroma can do it, you could contact them, and maybe they could have someones in stock.

What's the diameter of the rear lens element of your objective? If close to 25mm this will be the adequate position for the filter to get minimum image degradation.

Again, I would take the easier way with an inexpensive emission LP filter to test: if the autofluorescence of your samples is low enough, just don't worry.
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Lou Jost



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PostPosted: Sun Dec 31, 2017 4:46 am    Post subject: Reply with quote

I will take the latter route. I don't think the things that interest me fluoresce....
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kds315*



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PostPosted: Tue Jan 02, 2018 5:14 pm    Post subject: Reply with quote

Lou Jost wrote:
Yes, that would do it for this laser, thanks. Are there larger filters though? This is a big lens....


Asahi Optical filters I use, availabe in 50mm size:
http://asahi-spectra.com/opticalfilters/detail.asp?key=ZBPA405
Their high transmission Shortpass filters unfortunately are not ideal:
http://asahi-spectra.com/opticalfilters/detail.asp?key=ZHS0425

They do offer custom made filters, bit pricey though, but very good.
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Klaus

http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
http://photographyoftheinvisibleworld.blogspot.com/ my UV diary


Last edited by kds315* on Tue Jan 02, 2018 5:24 pm; edited 2 times in total
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Lou Jost



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PostPosted: Tue Jan 02, 2018 5:19 pm    Post subject: Reply with quote

Thanks for the information. They do look good, but are very expensive and inconveniently square.

I see they have round mercury-line filters here
http://asahi-spectra.com/opticalfilters/photolithography_filters.html
but I bet they are even more expensive...
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kds315*



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PostPosted: Tue Jan 02, 2018 5:24 pm    Post subject: Reply with quote

Lou Jost wrote:
Thanks for the information. They do look good, but are very expensive and inconveniently square.

I see they have round mercury-line filters here
http://asahi-spectra.com/opticalfilters/photolithography_filters.html
but I bet they are even more expensive...


Edmund Optivs also has one in 50mm, looks better, cut off at 410nm:
https://www.edmundoptics.com/optics/optical-filters/shortpass-edge-filters/400nm-50mm-diameter-od-4-shortpass-filter/
Transmission is here:
https://www.edmundoptics.com/document/download/359503
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Klaus

http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
http://photographyoftheinvisibleworld.blogspot.com/ my UV diary
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Lou Jost



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PostPosted: Tue Jan 02, 2018 5:32 pm    Post subject: Reply with quote

Those are perfect but even more expensive. That's 50% of the cost of the lens. I will search for simpler solutions, since I suspect that my subjects don't even fluoresce.
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kds315*



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PostPosted: Tue Jan 02, 2018 5:36 pm    Post subject: Reply with quote

Lou Jost wrote:
Those are perfect but even more expensive. That's 50% of the cost of the lens. I will search for simpler solutions, since I suspect that my subjects don't even fluoresce.


Here from China, they make custom sizes, I'm sure 50mm is doable and won't be that expensive:
https://www.ebay.com/itm/405nm-Narrow-Band-Filter-Violet-High-Flux-Filter-color-Film-Laser-Lasers-Filter-/263369251015


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Klaus

http://www.macrolenses.de for macro and special lens info
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http://photographyoftheinvisibleworld.blogspot.com/ my UV diary
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Lou Jost



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PostPosted: Tue Jan 02, 2018 5:57 pm    Post subject: Reply with quote

That seller has more reasonable prices. I will get this one, which is big and round, though it might not be narrow enough. (The one you indicated is not for sale now.)

https://www.ebay.com/itm/QB29-type-Glass-Filter-film-Optical-Detection-Glass-sheet-Filter-color-Film-50mm/263407990589?hash=item3d5456f73d:g:IEYAAOSwuhFaGj8m
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