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Lee 729 IR - West Green House garden

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#21 JMC

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Posted 03 September 2019 - 09:24

I'm not planning on trying this with KG3 at the moment. I rear mounted the Lee 729, and it was on my wide angle which has a 77mm filter thread.

I think I can get to 850nm with my spectrometer, but no higher than that.

#22 Cadmium

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Posted 03 September 2019 - 10:59

View Postdabateman, on 03 September 2019 - 07:05, said:

Actually based on the Lee plot for 729, I bet it shoots straight up. Most Lee filters don't block any IR. I think the material used for the 729 is the same. So I would expect 50% at 850nm and near 100% just after 900nm.

Yes, your right, I was thinking of the other plot, the 729 is headed UP not down at 800nm.
I have never seen any transmission data on any Lee filter above 800nm. Do you know of any?

Edited by Cadmium, 03 September 2019 - 11:02.


#23 UlfW

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Posted 03 September 2019 - 11:00

I found that my filter transmission measurement components sat untouched on its own Arca-rail, ready to be used. :smile:
The transmission of my sheet of Lee Scuba-blue 729 looks like this:
Attached Image: Screen Shot 2019-09-03 at 12.45.23.png
The curve is a result of 1000 spectra, with 37ms measurement time each.
I verified that 0% and 100% was OK before and after the measurement.

I suspect that the result below 400nm is partly due to crosstalk and the lowest values in vis below 1% might also be offset slightly upwards.
Neither of these limitations to the accuracy are affecting the result for the Aerochrome-like images we are trying to get with this type of filter.

Linear scale to be easier to compare with the Lee diagram:
Attached Image: Screen Shot 2019-09-03 at 13.01.57.png

The last bit beyond 1000nm can be compromised too. I have never really looked into that end for accuracy issues.
I guess that if I combined the light source with a RG850 I would be able to focus on that end only.

Edited by UlfW, 03 September 2019 - 11:20.

Ulf Wilhelmson
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#24 Cadmium

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Posted 03 September 2019 - 11:05

Ulf, Thanks! Very nice to see that!

Edited by Cadmium, 03 September 2019 - 11:07.


#25 UlfW

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Posted 03 September 2019 - 11:16

I have the Lee sample book and can measure other filter-types, if I find a good way to mount them, without taking the book apart.
I want to keep the book intact.
Ulf Wilhelmson
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#26 Timber

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Posted 03 September 2019 - 12:07

View PostCadmium, on 02 September 2019 - 22:14, said:

We are only using KG3 to reduce the higher IR, without removing the lower range IR that 729 transmits.
And I use the Hoya 80C for the same reason. No idea about transmission, but I know that the results are better with it than without it. I will do an experiment with Hoya 80C and IR960 filter to see how much it reduces. But with the Hoya I am not getting red tinting on concrete. KG3 is just way out of my budget.

#27 dabateman

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Posted 03 September 2019 - 12:30

Wow only 2 hours wait. Thats fast! Thank you Ulf, I am on a roll firstguessed Bassa filters to the thickness and now the IR profile of the Scuba. Should bought a lottery ticket before all the luck wore off. But I am pretty sure too late for that. I just have to be care not too get hit with lightning in the same spot twice.

I will look forward to seeing your Tiffen 2A haze scan. I just got a 52mm one from KEH as part of the labour day clearance. Also got a rare canon sync cord A and 2 199A flashes. Sadly one 1 of the 2 fully works. The other lights up, just no humm and the flash will not fire.
Most likely the capacitor needs to be refreshed, as it looks to have never been used. As in never, the end contacts were clean and not scrapped as it seems to have never been placed on top of a camera.



#28 UlfW

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Posted 03 September 2019 - 15:06

Here comes the result from the measurement of my Tiffen Haze 2A filter.

The general passband transmission above 400nm:
Attached Image: Screen Shot 2019-09-03 at 16.12.10.png
The blue graph is the result averaged from 1000 spectra á 32ms, measured using full bandwidth of the light source.
No boxcar averaging as the data is above the noise floor.
The toe to the left of 400nm is as usual crosstalk from the passed strong light at longer wavelengths.

Measurement with improved crosstalk, valid around the transition area at 400nm - 425nm:
Attached Image: Screen Shot 2019-09-03 at 16.17.51.png
Averaged from 5000 spectra á 37ms.
No boxcar averaging as the data is above the noise floor.

With light only from the deuterium lamp and more averaging I can decrease the crosstalk a bit.
The red graph show that the filter has almost OD 3 at 400nm.
It is likely that the decay continues a bit further at shorter wavelengths.
The orange graph, related to the red graph, is the dark noise at current configuration, almost one magnitude lower.


Maybe we should start a series of more formal individual topics with more detailed analysis of different filters.
Is that a good idea?
To make it easier to find the information they might be placed in a separate subsection of the forum.
I could suggest a tentative template for that kind of topic.
The naming of the topics maybe also should be in a suitable format.
If this post was such a topic I would have named it [Filter transmission, Tiffen Haze 2A].
I would like a more complete format of such a topic than this one above, but it could possibly be something to build on.

Edited by UlfW, 03 September 2019 - 15:08.

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#29 Cadmium

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Posted 04 September 2019 - 05:41

Thanks Ulf :-)
Do you happen to have a Hoya 80C you can scan above 750nm? Or even an 80A?

Edited by Cadmium, 04 September 2019 - 05:41.


#30 dabateman

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Posted 04 September 2019 - 06:32

Thank you Ulf.
Yes your filter scans should probably be completely different posts.
The 2A looks great. A good filter for UVIVF. I was using a kodak 2A wratten 2 gel, most likely polyester. But I scratched the surface. So have been using a 2E gel. I am glad I got the Tiffen looks like maybe the best to just snag 400nm.

#31 Cadmium

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Posted 04 September 2019 - 06:46

However, I think the 729 scan is quite appropriate included in this topic.

#32 UlfW

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Posted 04 September 2019 - 09:58

No I have none of the Hoya 80 A-, B- or C-filters.
I have all six Hoya 81- and 82-filters.
I also have a Nikon B12, that might be using some blue Hoya filter glass type.
Ulf Wilhelmson
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#33 Cadmium

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Posted 10 September 2019 - 03:54

Jonathan, was your test made using the 729 sample I sent you? Or maybe from the swatch book I sent?
If so, the surface quality of the material seems a bit poor to me,
dents, and such, what do you think of the surface, optically?
I have purchased the 729 from two separate sources, one seemed only slightly better, not much. The samples in the swatch book seems the best.
Just wondered if you have had any thoughts on all that?

Edited by Cadmium, 10 September 2019 - 05:09.


#34 JMC

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Posted 10 September 2019 - 08:15

View PostCadmium, on 10 September 2019 - 03:54, said:

Jonathan, was your test made using the 729 sample I sent you? Or maybe from the swatch book I sent?
If so, the surface quality of the material seems a bit poor to me,
dents, and such, what do you think of the surface, optically?
I have purchased the 729 from two separate sources, one seemed only slightly better, not much. The samples in the swatch book seems the best.
Just wondered if you have had any thoughts on all that?

I used the piece you sent me Steve, not the swatch book. And yes, the quality wasn't great, with plenty of dings and dents. I presume because it's mainly used as a lighting gel, the quality control isn't as high.

#35 UlfW

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Posted 10 September 2019 - 13:46

View PostCadmium, on 04 September 2019 - 05:41, said:

Thanks Ulf :-)
Do you happen to have a Hoya 80C you can scan above 750nm? Or even an 80A?

I found the Hoya filter glass data for some of the filter materials I suspect are used for their 80A - 80C filters.
http://www.hoyaoptic...m/color/06.html
They all surpress light less efficient in NIR above 750nm.
Ulf Wilhelmson
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#36 Cadmium

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Posted 10 September 2019 - 21:47

Thanks Jonathan. :-)

Ulf, thanks! Indeed, those don't suppress IR any more above 750nm than they do at 750nm, even less. So those don't taper the IR down, and they don't create a 780nm peak like the KG3 does,
however they do act as a kind of neutral density filter for the IR, attenuating it to a lower level across the entire range. This has the same % of lower IR to higher IR however.
http://www.hoyaoptic...g_graph_6-2.png

#37 Nisei

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Posted 06 January 2020 - 23:22

Pardon my ignorance but when I combine the KG3 graph and the 729 graph Ulf posted above, there's not much IR being transmitted with this stack.
729 blocks up to 750 and KG3 only transmits 30% at that wavelength, going down to 0 at little over 900. If the purpose is to only block higher wavelengths, wouldn't a short pass 850 or 900 be better in this case?

Edited by Nisei, 07 January 2020 - 20:36.


#38 Cadmium

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Posted 07 January 2020 - 03:53

Nisei, Interesting question. A shortpass filter like that would be dichroic, and I don't have such filter to test. The closest filter I have to that would be the Baader UV/IR-Cut, and that it cuts at 700nm.
Here is the composite graph of 729 + KG3 2mm (up to 800nm).

Attached Image: 729_full_stack_t.jpg

KG3 2mm is handy for attenuating the IR content of other longpass and dualband IR filters also.
I have tried using 1mm, and other KG#'s also, but KG3 2mm seems to work best to my preference with the filters I have tried pairing it with.

#39 dabateman

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Posted 07 January 2020 - 06:27

View PostNisei, on 06 January 2020 - 23:22, said:

Pardon my ignorance but when I combine the KG3 graph and the 729 graph Ulf posted above, there's not much IR being transmitted with this stack.
729 blocks up to 750 and KG3 only transmits 30% at that wavelength, going down to 0 at little over 900. If the purpose is to only block higher wavelengths, wouldn't a short pass 850 or 900 be better in this case? (Sorry, could only find a pic for an 800nm)

Yes a shortpass filter should work. The Original David Twede article, he mentioned using an inefficient hot-mirror glass, called the Permacolor #8000 that should also work.
https://next-eyes.bl...tal-ir.html?m=1


#40 Nisei

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Posted 07 January 2020 - 11:39

Hmmm, I think I finally get what this is about now.
I thought the idea was to block higher wavelength IR but that's not the case. It's about bringing down IR to around the same transmittance value as blue so IR doesn't get overexposed (or blue getting underexposed).
The Lee 729 + KG3 stack is not very efficient. 729 only transmits around 40% peak for blue and we therefore have to use KG3 to lower the IR curve to match it to the low blue transmittance value.
Is that the idea?

When looking for filter graphs I came across Kopp 5031
The curve looks close to Lee 729 but with a much higher transmittance value for blue so blue and IR are well balanced here.
No idea about price but I'd love to see the results of this sooc.
Perhaps stacked with a 450 long pass filter?
Or, if it's indeed your goal to block higher wavelength IR, stacked with short pass 800 or 850.

Attached Images

  • Attached Image: 5031.gif

Edited by Nisei, 07 January 2020 - 21:09.