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Pushing the limits of B&W macrophotography
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Tue Jan 02, 2018 6:47 pm    Post subject: Reply with quote

Here's a better one, though not so big, it has a narrow band. I bought it just now instead of the one above.
https://www.ebay.com/itm/263407977643
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kds315*



Joined: 02 Feb 2009
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PostPosted: Wed Jan 03, 2018 12:15 am    Post subject: Reply with quote

Lou Jost wrote:
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


Yes this 405nm filter is for sale, seller just responded that for $120 he would do a 50mm round one. I had asked him for you.

The filter you bought has a center wavelength of 400nm, which might be a bit critical as your lasers have 405nm center.


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Klaus

http://www.macrolenses.de for macro and special lens info
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Pau
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Joined: 20 Jan 2010
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Location: Valencia, Spain

PostPosted: Wed Jan 03, 2018 1:47 am    Post subject: Reply with quote

Yes, that 400nm passband seems a bit too narrow and will cut at half of light (54% T at 405nm).

Because your source is monochromatic and your application not so critical I think that the Chroma I linked or the Asahi 425 proposed by Klaus could be more convenient.

Because these filters are very reflective it's possible that you could have reflections of the sensor, if so try mounting it with a small angle, although this could alter the spectrum of interference filters some microscope makers do it.

Please keep us informed on how it works, it's a very interesting project
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kds315*



Joined: 02 Feb 2009
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PostPosted: Wed Jan 03, 2018 2:00 am    Post subject: Reply with quote

Pau wrote:
Yes, that 400nm passband seems a bit too narrow and will cut at half of light (54% T at 405nm).

Because your source is monochromatic and your application not so critical I think that the Chroma I linked or the Asahi 425 proposed by Klaus could be more convenient.

Because these filters are very reflective it's possible that you could have reflections of the sensor, if so try mounting it with a small angle, although this could alter the spectrum of interference filters some microscope makers do it.

Please keep us informed on how it works, it's a very interesting project


A small angle does not cause that much shift in my experience...

I measured it here with my classic UV Transmitting filter, a highly reflective Baader-U dichroitic filter which I use very often:
http://photographyoftheinvisibleworld.blogspot.de/2011/06/uv-influence-of-ray-angle-when-using.html

In an older ZEISS brochure about their metal interference filters, they state that max 10 degrees should be used.
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Klaus

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Pau
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PostPosted: Wed Jan 03, 2018 2:11 am    Post subject: Reply with quote

Very interesting, Klaus

I've not done true tests but visually with some fluorescence interference filters for visible light the effect is much more important: at 45º the color can be completely different than the expected at 0º, but about 5º doesn't alter it much
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kds315*



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PostPosted: Wed Jan 03, 2018 2:20 am    Post subject: Reply with quote

Pau wrote:
Very interesting, Klaus

I've not done true tests but visually with some fluorescence interference filters for visible light the effect is much more important: at 45º the color can be completely different than the expected at 0º, but about 5º doesn't alter it much


In line with my own results Pau and with the Zeiss Statement!

Here the graph from the CZJ document:

(the two lines show the splitting up of the two polarized beams)
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Klaus

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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Wed Jan 03, 2018 5:49 am    Post subject: Reply with quote

Thanks for the interesting advice, and for asking about the 50mm filter. That price is reasonable. But since I already bought the other one, I will see how well it works first. The specs on the filter I bought are that the center of the passed band is 400+/- 5nm; the 5nm figure is the uncertainty in the center of the bandwidth, if I am reading it correctly. The stated half-bandwidth is 20nm. So it should do alright, and if I angle it a bit, I will increase the peak a bit, according to the Zeiss graphs. I have lots of light so some cutoff is fine. I just want to check to make sure fluorescence is not affecting my photos (and I think it isn't, since the photos are very sharp).
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kds315*



Joined: 02 Feb 2009
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PostPosted: Wed Jan 03, 2018 9:25 am    Post subject: Reply with quote

Lou Jost wrote:
Thanks for the interesting advice, and for asking about the 50mm filter. That price is reasonable. But since I already bought the other one, I will see how well it works first. The specs on the filter I bought are that the center of the passed band is 400+/- 5nm; the 5nm figure is the uncertainty in the center of the bandwidth, if I am reading it correctly. The stated half-bandwidth is 20nm. So it should do alright, and if I angle it a bit, I will increase the peak a bit, according to the Zeiss graphs. I have lots of light so some cutoff is fine. I just want to check to make sure fluorescence is not affecting my photos (and I think it isn't, since the photos are very sharp).


Press thumbs that it'll work out for you Lou. Btw. the peak will be shifted slightly towards shorter wavelengths if tilted, not increased (it actually decreases a little). 20nm HBW should give you enough wiggle room to get enough laser light through.
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Klaus

http://www.macrolenses.de for macro and special lens info
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Lou Jost



Joined: 04 Sep 2015
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Location: Ecuador

PostPosted: Wed Jan 03, 2018 10:08 am    Post subject: Reply with quote

Thanks, and yes, I wasn't thinking when I saw that graph from Zeiss...I was so accustomed to see the x-axis as wavelength that I did not even notice the axis labels.
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