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Mystery IR filter - transmission spectra and images

Infrared
128 replies to this topic

#21 Andrea B.

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Posted 12 September 2019 - 00:49

Or it is possible that Hoya has sold different versions of the R72 over time?
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#22 Andy Perrin

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Posted 12 September 2019 - 01:11

I don't know. What I think we need is for someone else with a spectrometer to run their R72 and try to confirm Jonathan's spectrum. Or Jonathan could run a second R72 if he has one or can borrow one.

Edited by Andy Perrin, 12 September 2019 - 01:16.


#23 dabateman

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Posted 12 September 2019 - 02:48

What I think is funny is that the Hoya USA links show the Hoya R72 as a LP filter.
But Jonathan's Hoya Japan link shows it as a bandpass filter and states:
"ATTENTION: BE AWARE OF COUNTERFEIT FILTERS
In order to avoid purchasing one of those counterfeit filters we highly recommend to purchase only from official retailers that are recognized by HOYA's official global distributors. Prior the purchase kindly inquire and verify whether a retailer is authorized by HOYA global distributors."

The only USA distributor on the list is:
U.S.A.
KENKO TOKINA USA, INC

Our USA links don't say to watch out for counterfeit products. So are we in the US just getting counterfeit Chinese filters?

All the super cheap UV filters I get off ebay to mount 50mm or 25mm filters are labeled Kenko. They seem to always have retaining rings. We may just have counterfeit products here.

Edited by dabateman, 12 September 2019 - 02:52.


#24 Cadmium

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Posted 12 September 2019 - 03:14

The link I posted is Japan, not USA and it shows the longpass version.
http://www.hoyacande...o/color/01.html

Jonathan's link is "hoyafilter", there is nothing about that link suggesting it is a Japan link/site. Right? Why do you say it is Japan?
https://hoyafilter.c...t/r72_infrared/

Kenko:
https://hoyafilter.com/company/

I am confused now.
I was confused to start with. :-)
I find it strange that one of these R72 filters is a bandpass type and the others are shown as longpass.
I have never seen R72 graphed as bandpass before, always longpass, so this is news to me...
And why does the Kenko site show a different plot from the Hoya Japan site.
Given Jonathan's scan, which matches the Kenko "hoyafilter" site graph, it would seem that they have changed glass type, if you ask me.

Edited by Cadmium, 12 September 2019 - 03:24.


#25 dabateman

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Posted 12 September 2019 - 03:19

Sorry I have no idea where Jonathan's link was from, now that I look at it. Its not clear.

I was going from this USA link:
https://hoyafilterus...infrared/#tab-2

It shows the R72 as a LP filter.
Maybe then Jonathan has the counterfeit filter?

#26 Cadmium

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Posted 12 September 2019 - 03:34

Yes, there is also the hoyafilterusa site, like you link to there. Yet another site.
That is why I went to Hoya.com first, then paged my way to their filters. Thinking it would give me the "real deal", but who is to say if that info is outdated compared to what they are manufacturing now?
Regardless, Jonathan has something that matches the graph on the site he posted, and that site seems to be a Kenko site, given the Kenko info on the info page for that site.
However, I suppose we don't even know for sure that side is really Hoya or Kenko? But that might be a stretch. But...these days? I tell ya, what can you believe these days? You can believe a spectrometer.
I don't know... the mystery plot thickens.

Edited by Cadmium, 12 September 2019 - 03:36.


#27 Cadmium

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Posted 12 September 2019 - 03:56

Now, you want to get even MORE confused? I know you do. :-)
OK, so go to the site Jonathan posted first:
https://hoyafilter.c...t/r72_infrared/

Then go to the "support/distributors" link on the above site top menu:
https://hoyafilter.c...t/distributors/

Then scroll down to the North America/U.S.A section, and go the site for that:
https://www.kenkotokinausa.com/

OK, now click on the top menu there, "brands/Hoya Filters", and that takes you to hoyafiltersua:
https://www.kenkotokinausa.com/

Then select "shop/specialized", then scroll down and choose R72, and you are at the same page showing the longpass graph.
https://hoyafilterus...a-r72-infrared/
(I think that is the same link that David posted above)

See what I am saying, these are all connected, yet one shows a bandpass and most show a longpass, and I am wondering... have they changed something, perhaps?
That is what I think, Hoya has some new glass they are starting to use for the R72.

#28 Cadmium

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Posted 12 September 2019 - 04:03

Oh, and Jonathan, may I ask what vendor? I mean did you get it from that site you posted? Or where?

#29 Cadmium

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Posted 12 September 2019 - 04:18

So... I wrote them, not holding my breath, but want to know what they say.
---
I need to know which is accurate, has Hoya changed the type of glass they are using. Why are these two graphs different? Which graph is correct for the R72 you are selling?

Hoya R72 showing a bandpass type transmission graph plot:
https://hoyafilter.c...t/r72_infrared/

Hoya R72 showing a longpass type transmission graph plot:
https://hoyafilterus...a-r72-infrared/

#30 Cadmium

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Posted 12 September 2019 - 04:36

By the way, the Hoya filter catalog I just downloaded from the Hoya filter (.jp) site shows the R72 as being the old standard longpass type transmission plot.
Of course, that catalog is dated April 2014.

http://www.hoyacande...f/catalog_e.pdf

p. 49/50


Edited by Cadmium, 12 September 2019 - 04:38.


#31 Cadmium

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Posted 12 September 2019 - 04:54

Furthermore... sorry, but just looked through that entire catalog, and the only bandpass type IR range filter they show is the RT830 (like I mentioned on the previous page), similar but not the same as Jonathan's scan or the graph shown on the page like he posted. So I don't know what is going on.

#32 UlfW

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Posted 12 September 2019 - 05:00

View PostAndrea B., on 11 September 2019 - 16:47, said:

Here is something interesting that I was reading on Jonathan's Hoya link from above: https://hoyafilter.c...t/r72_infrared/ [The R72] can be paired with colored black and white contrast filters such as the R25 (red), K2 (yellow), O (orange) or other color filters to change the color rendition or contrast effects. But how could stacking the R72 with, say, a K2 make any change in color/contrast? The filter with the fartherest-out cut-in, the R72, would be the filter controlling the transmission, right? What am I missing here?
You are only missing that the maketing departments don't need technical understanding of their products.
The statement might generate some extra sales.

Your analysis is otherwise perfect. The fartherest-out cut-in, is controlling the transmission.
The pairing statement above is true for some other filters, like the two green filters on their program.
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#33 dabateman

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Posted 12 September 2019 - 06:54

Cadmium,
Whats truely funny is the only site, the one Jonathan linked to) with the only bandpass filter spectrum is also the only site that says to watch out for counterfeit products.

Lets see what they tell you. If Kenko now controls Hoya, I would say its gone to Chinese glass. This maybe why Zwb glass got better?

#34 JMC

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Posted 12 September 2019 - 12:50

Blimey this has moved on since I left it last night. Mine was bought from ebay from a private seller, who had it and a U-360 from when he worked in forensics. I doubt it's counterfeit, but it could well be quite old.

My guess, is that they have changed materials at some point.
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#35 Andrea B.

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Posted 12 September 2019 - 17:57

Someone could politely call up Hoya and ask whether there have been two versions of the R72. :lol:
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#36 Cadmium

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Posted 12 September 2019 - 21:01

This is quite perplexing. Especially given Jonathan's scan.
Hoya is a very excellent filter company, and is it not good to have variation in their products.
Disconcerting to anyone using their glass for filters. We want to know what we are buying. We want consistency.
These are the kinds of things that military specifications are based on.

In my opinion, it appears that this filter that Jonathan has and the graph that is shown on that link he posted are not actual Hoya glass.
I don't think Kenko owns Hoya, if anything it is the other way around, more likely Kenko is licensed to make/sell Hoya camera filters.
Hoya sells glass sheets, I don't know if they make camera filters themselves these days or not.
It seems strange that anyone making filters under license from Hoya would then use some other brand of glass and sell it as being Hoya,
and it seems strange that they would show a graph revealing such a discrepancy.
Jonathan has discovered something that I doubt anyone else has.
I can't find any actual Hoya glass that has that transmission curve.
Very weird.

Edited by Cadmium, 12 September 2019 - 21:25.


#37 Cadmium

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Posted 12 September 2019 - 21:41

OK, this just back from Hoya, basically:
They don't make camera filters, "call Kenko Japan".
So you see, Hoya makes glass, Kenko uses the glass to make filters with Hoya on the ring... That part is actually good, I like knowing what exact glass is in the ring, and having a real graph to go with that.
I like that part, I mean if the graph and glass were what was on the ring...
However, I don't like what is going on here, Kenko making the Hoya R72 out of some other brand and even type of glass...
This is unreal, how is this any different than someone on eBay making a filter out of some Chinese ZWB glass and labeling it Schott,
and this is Kenko doing it?! And seemingly, Hoya doesn't sound like they care...?

Edited by Cadmium, 12 September 2019 - 21:46.


#38 JMC

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Posted 13 September 2019 - 08:44

When I get chance I will run my Heliopan 715 - just to make 100% sure this is not a glitch or a result of my measurement setup.
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#39 JMC

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Posted 13 September 2019 - 13:52

This is getting silly now.

I ran my Heliopan 715 filter, expecting it to be a simple long pass filter. But, I get the same thing - it's not a pure long pass filter, and transmission drops towards 880nm. Thinking I am going mad, I get out my B+W091 red filter, and run that. No drop at the high end. I also ran no filter, light on (+ve control) and no filter, light off (-ve control), just to make sure the device was behaving as it should.

Attached Image: Hel 715 and BW091.jpg
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#40 Andrea B.

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Posted 13 September 2019 - 15:07

However, I don't like what is going on here, Kenko making the Hoya R72 out of some other brand and even type of glass...

I don't think we can make that assumption just yet!

First of all, Hoya would never permit their glass to be misrepresented by a major company like Kenko.

Secondly, it is becoming apparent that the IR bandpass glass cutting in just before 700 nm and hitting its height at about 715-720 nm is of two forms: one is longpass and one is bandpass. Both types of glass could fairly be labeled and sold and sold as IR-pass filters under names such as Heliopan 715 or Hoya R72 (or some other similar designation). I would only worry if bandpass glass is mis-labeled longpass.

The question which immediately occurs to me here is this: How is that right shoulder created for the 720/IR-bandpass type of glass? Is there some kind of natural glass formula being used? Or is the drop-off created by some kind of coating or layering?

The formulas for the glass being poured seem to be quite standard across the various glass manufacturers. You see in the product brochures or online pages that all they all offer the same stuff (mostly). The IR-bandpass filters I have from MaxMax are quite obviously coated (dichroic, shiny side). But my Hoya R72 does not have that shiny side. It's coated with something, I assume, because I've never had to clean it for oxidation. But I don't think I can see whether it is layered or stacked unless I try to take it out of the filter ring.

Thanks for the measurements, Jonathan. I'm sure we will figure this out.
Andrea G. Blum
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