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UltravioletPhotography

Mystery IR filter - transmission spectra and images


JMC

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https://shashinki.com/blog/2014/09/25/detecting-fake-hoya-filter/

That is an old link which discusses fake versus real Hoya filters. Quite interesting.

 

 

If you buy brand name (Hoya, B+W, Heliopan) filters from one of the big reputable sellers (such as B&H here in the US),

then you have a reasonable certainty of not getting a fake. Brand name filters sold on Ebay or Amazon

might be chancy.

 

I'm also thinking that for some products, different versions of the product are sold in different countries. Now whether that applies to brand name photographic filters, I do not know. But it is certainly possible that the R72 we are all trying to figure out is sold/marketed differently in US than in, say, Japan.

 

Cadmium, I hope you hear back from Kenko. :smile:

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So what have we learned?

The Real Hoya R72 and 715 filters are long pass, right. But Hoya nor Schott make camera filters you can screw on to a lens.

 

So some other company is licencing the Hoya name and stamping that on the filter ring.

So looks like if a company has a whole bunch of rings, you may get anything in that ring, bandpass or longpass.

 

I guess that make sense as I read that Quantaray CP filters were Hoya glass.

 

I guess what would matter is do we see a difference in the IR images taken with bandpass 720 vs long pass 720? That is with our normal cameras, not Andy's rare expensive IR camera.

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The Real Hoya R72 and 715 filters are long pass

 

Do we actually know this yet? :smile:

 


 

The differences between RG9 bandpass and its nearest neighbors is minimal. It is too late tonight to go searching for examples. But I will look tomorrow.

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Andrea,

I now no longer believe those spot the fake type posts.

Hoya doesn't make filters. So that link may just be comparing a Tokina licensed Hoya glass to an other company that skimps on details but may in fact still have Hoya glass inside.

Some reputable seller on ebay that actually uses Hoya glass may just print a label and add it to a digital frame. That will still be genuine Hoya glass.

 

That is why this is a problem. The consumer really doesn't know unless they have a spectrometer.

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To answer both Andrea and David,

The graphs on the Hoya site, which I linked to in my last post above, are the actual transmissions for the Hoya filter glass types.

I would doubt strongly that those graphs are wrong for Hoya glass. You should not need a spectrometer if the glass is from Hoya.

They make tightly controlled standardized filter glass, used in many industrial and critical applications which require more precision and reliability than what we use filters for.

 

I don't get the impression here that this has anything to do with 'fake' filters. Not like some knock off type thing. Yet the glass is not Hoya R72, that is obvious, because Hoya R72 is longpass.

I don't know the history of Hoya camera filters, who made them, how many companies were making them, or if Hoya originally made them themselves or not.

I don't know if there are multiple companies making Hoya camera filters, other than Kenko.

It would seem that Kenko is the only company that makes the Hoya Branded camera filters, but I don't know that.

Nevertheless, it would seem that given Kenko's R72 graph is not R72 longpass, and that Jonathan's test of a randomly obtained R72 looks the same as the Kenko graph,

then this suggests that perhaps a large percentage of what people think are Hoya R72 longpass filters may not be actual Hoya R72 longpass filters at all,

but instead some other filter glass, which looks and works essentially the same as real Hoya R72 longpass filter glass when using it for usual IR photography.

For all I know, the 'fake' R72 glass may work even better for IR photography, by slightly muting the higher IR...

But I don't know, all I know is it is not Hoya R72 glass in that filter that Jonathan has. And now he has the Heliopan that looks the same also...

It's like ice-nine.

 

My guess, Kenko will not answer me, and Hoya probably wants to avoid the subject.

It would be a can of worms.

 

Hoya R72 data sheet:

http://www.hoyacandeo.co.jp/english/products/eo_pdf/R72.pdf

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Chinese knock-offs - interesting business model, they figure no one would know the difference. deceptive advertising, I'd be blaming Kenko supply chain that supplies Hoya with their glass.
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I'm home at last and had an opportunity to take a closer look at my R72. Apparently mine is made by Tokina?! So if mine is a knockoff of anything, it would appear to be Japanese rather than Chinese.
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I'm home at last and had an opportunity to take a closer look at my R72. Apparently mine is made by Tokina?! So if mine is a knockoff of anything, it would appear to be Japanese rather than Chinese.

 

Kenko is Japanese also. It is not about the manufacturer, it is about the glass used.

Unless your have a spectrometer, or do some pretty thought out fancy stacking with other filters, I think you will have a very hard time differentiating the real Hoya R72 filter glass from some bandpass fake,

that is the case between RG715 and RG9 also. Again, Hoya doesn't make the filter glass that is being used in the two filters that Jonathan has scanned.

Chinese glass, probably, but certainly not Hoya glass.

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Cadmium, can you get real R72 glass from Hoya so I can buy a filter whose identity I’m sure of?

 

Absolutely you can! I will get a sheet. It should still be tested, given all this, we need to make sure where the problem originates.

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Kenko is Japanese also. It is not about the manufacturer, it is about the glass used.

Unless your have a spectrometer, or do some pretty thought out fancy stacking with other filters, I think you will have a very hard time differentiating the real Hoya R72 filter glass from some bandpass fake,

that is the case between RG715 and RG9 also. Again, Hoya doesn't make the filter glass that is being used in the two filters that Jonathan has scanned.

Chinese glass, probably, but certainly not Hoya glass.

Yes, but there is the question of where each manufacturer is getting their glass from. Suppose we have several manufacturers, each originally making a filter called "Hoya R72" but one starts substituting a different glass. Could we be looking at a situation like that?

 

Absolutely you can! What do you think I am doing on Monday? It should still be tested, given all this, we need to make sure where the problem originates.

Yes! Okay, then put me down for one, if you like, tell me when you are ready and I will purchase on ebay.

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Andi, so far we have two camera filter manufacturers, One is making "Hoya R72" filters, the other is making "715" filters, and both are making them out of something other than Hoya R72 filter glass.

Neither manufacturer is using longpass type filter glass.

We have no idea who makes the filter glass, but we know it is not any glass that we know of that is made by Hoya.

The primary question is why is a Hoya R72 labled filter made out of something that is not Hoya R72 glass.

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There use to be a website called heliosoptical.net, and it had filters made out of Schott and Hoya glass, but it is gone. I don't know if it was a Heliopan site or not.

http://www.heliosoptical.net/html/

 

I looked up Heliopan 715 IR filter on Heliopan's site, and they don't show a graph, but they do call it RG 715 (88A), RG implying it is made from Schott RG717, and 88A referring to the Wratten 88A IR filter,

both of which have a flat longpass plot. My Wratten book shows the 88A has a 50% transmission at about 750nm, however, that isn't important here since we know the 50% of RG175 is 715nm (at 3mm thick).

Some camera stores show a small graph, which is longpass.

 

1494433906_IMG_797258.jpg

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Here is an overlay I did to help compare all the filter glass mentioned in this topic so far with Jonathan's Hoya R72 and Heliopan 715 scans.

What stands out is that the same glass is obviously being used for both the Hoya R72 and Heliopan 715 camera filters,

and how much different that glass is from what it is suppose to be, and from any other glass mentioned so far.

 

post-87-0-33630500-1568677109.jpg

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While I'm not normally one to cast doubt on my own work, I must point out that observations should be repeated by someone else. I cannot see an issue with what I've done, but that doesn't mean there isn't one.
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I understand, but given the comparison between your scan of the B+W longpass filter and the other two scans, I would have to say that something is amiss about those other filters being longpass filter glass.

Not to worry, I will have some of the Hoya R72 sheet scanned when I get it, might be a while, takes time.

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While I'm not normally one to cast doubt on my own work, I must point out that observations should be repeated by someone else. I cannot see an issue with what I've done, but that doesn't mean there isn't one.

Jonathan, if I am "someone else" I'll happily repeat the measurement.

 

However your spectrograms look quite realistic.

If there is any deviation, it would be a slight general amplitude error due to drift or calibration. I do not think such error would be big.

The fast upper drop would be difficult to get sometimes due to method errors.

The longpass spectra proves that the methods are sound.

 

These kinds of filter high level filter measurements are easy compared to measuring transmission of lenses.

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I can't figure out how the B+W would scan as a normal longpass, and the Hoya and Heliopan would not. Seems like everything is working correctly for the B+W, so why wouldn't it be working for the other two?
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Yeah, your scans look fine, Jonathan. As everyone has pointed out, if everything were showing up as “band pass” that might suggest something is wrong, but to have the B+W show the expected behavior but not the others makes me think your work is okay and it is the filters’ fault.

 

I would like to see more tests of more alleged R72 filters, though. I want to know how deep the rabbit hole goes...

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Is the R72 designation really strictly defined?

It could be that we just assumed it to be a longpass filter, as the majority of available glass-types are of longpass type.

 

The designation might instead indicate a filter cutting the visual part of the spectra at ca 720nm, suitable for NIR photography.

As the sensor sensitivity is dropping above 850nm the difference between longpass- and bandpass-versions is mostly irrelevant.

 

EDIT:Stupid mistake please ignore all above!!

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Hoya R72 filter glass is strictly defined, it is a longpass filter, and it has a defined data sheet, with defined tolerances:

http://www.hoyacande.../eo_pdf/R72.pdf

 

All of the Hoya and Schott filter glass is strictly defined, each having strictly defined data sheets, and strictly defined tolerances.

That is saying a lot more for those filter glass brands than any other filter glass brand, especially those filters from China, and many other brands of camera filters which have poorly defined data,

unreliable and inaccurate data, or no real data at all (the REAL mystery filters).

Schott and Hoya filter glass are much more defined than any other filter glass on the planet, and Schott has the absolute best and most complete filter data.

Can you say that about Zomei filters, for example? Do they even show graphs? I don't see any Zomei graphs, just mystery Chinese glass.

What do we need graphs for? What do we need spectrometers for?

 

This is why I appreciate Schott and Hoya filter glass more than any other, they provide highly defined data sheets and graphs, they make that data public, they stand by their data sheets,

they put them selves on the line, and it is used in critical applications for that reason.

There is a reason why many camera filter companies don't even show a graph.

If some company is labeling and selling Hoya R72 filters as such, but using some other filter glass which is not real Hoya R72, then people should know.

If Hoya is making R72 out of some new recipe that isn't what they show on their data sheets, people should know that also.

However, I will be quite surprised if a sheet of Hoya R72 doesn't scan to show the same graph as they provide in their data sheet.

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Really, seriously?!

Hoya R72 filter glass is strictly defined, it is a longpass filter, and it has a defined data sheet, with defined tolerances:

http://www.hoyacande.../eo_pdf/R72.pdf

 

All of the Hoya and Schott filter glass is strictly defined, each having strictly defined data sheets, and strictly defined tolerances.

That is saying a lot more for those filter glass brands than any other filter glass brand, especially those filters from China, and many other brands of camera filters which have poorly defined data,

unreliable and inaccurate data, or no real data at all (the REAL mystery filters).

Schott and Hoya filter glass are much more defined than any other filter glass on the planet, and Schott has the absolute best and most complete filter data.

Can you say that about Zomei filters, for example? Do they even show graphs? I don't see any Zomei graphs, just mystery Chinese glass.

What do we need graphs for? What do we need spectrometers for?

 

This is why I appreciate Schott and Hoya filter glass more than any other, they provide highly defined data sheets and graphs, they make that data public, they stand by their data sheets,

they put them selves on the line, and it is used in critical applications for that reason.

There is a reason why many camera filter companies don't even show a graph.

If some company is labeling and selling Hoya R72 filters as such, but using some other filter glass which is not real Hoya R72, then people should know.

If Hoya is making R72 out of some new recipe that isn't what they show on their data sheets, people should know that also.

However, I will be quite surprised if a sheet of Hoya R72 doesn't scan to show the same graph as they provide in their data sheet.

SORRY, SORRY!!

I deeply apologise for my ignorance. :sad:

 

I did not find that information when I looked for Hoya filter glass online.

Must blame my dyslexia that i didn't notice the last label R72 after R70 in their transmission overview

 

Therefore I thought it just was a general label.

I am more familiar with Schott's filter glass.

Now I better understand the worries about the different transmission results.

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Quick update.

 

Heliopan got back to me, with the graph that Steve posted in post #63 and nothing helpful. So, no answer from them about the Heliopan 715.

 

I'm getting hold of a new Hoya R72 filter (from a UK dealer). Once I've run it myself, I'm sending it to Ulf to confirm my findings.

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The next step is for someone to build or buy an ICP-MS instrument. Then just sand off a gram around the edges of the glass and tell us the true elemental composition. Then we will know the real make up of the real glass formula.

 

There not too hard to build if you have a mass spectrometer, just need a lot of argon.

 

I think yes they are cheating. But does it matter? I would like to see a normal camera image with both real Hoya long pass and Tokina fake bandpass IR filter. Except for Andy's triwave, I bet they will look the same. That is most likely why they are cheating us.

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