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Bold claim - Hitech ND filters and UV capability

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#1 JMC

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Posted 04 January 2019 - 15:37

Just been reading about Firecrest ND filters from Hitech, and they are making a pretty bold claim about them;

"The Firecrest Soft Edge ND Grad uses Firecrest technology to create the world’s most neutral grad filter, and is the perfect complement to the Firecrest ND filters. Soft edge grads are versatile filters used to balance the luminosity of a bright sky with the terrain below. The soft edge makes it easy to place the filter in the scene, especially over undulating horizons (such as mountains).

Firecrest is a revolutionary new type of ND filter from Formatt-Hitech. Rather than dyed resin, Firecrest is a rare earth metal coating used to create hyper neutral NDs. The filters are made from 2mm thick Schott Superwite glass, and the multicoating is bonded in the middle to increase scratch resistance. Firecrest Filters are neutral across all spectrums, including UV, visible, and infrared."

It's the last sentence that got me - these are neutral across all spectrums including UV.

This was taken from here - https://www.formatt-...ium-format-film

Has anyone got these or ever tried these with UV?

Edited by JMC, 04 January 2019 - 15:39.

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#2 Andy Perrin

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Posted 04 January 2019 - 15:45

I haven’t, but what do we need an ND filter for in UV anyhow? We have so little light to begin with.

Edited by Andy Perrin, 04 January 2019 - 15:45.


#3 JMC

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Posted 04 January 2019 - 16:00

View PostAndy Perrin, on 04 January 2019 - 15:45, said:

I haven’t, but what do we need an ND filter for in UV anyhow? We have so little light to begin with.

Indeed, but perhaps as a grad it could be useful for bringing some detail into clouds for instance. Just surprised that they talk about UV behaviour in the blurb for it.
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#4 dabateman

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Posted 04 January 2019 - 16:59

I am with Andy. I am resisting spending $1000 on a ZWO 1600mm camera just to gain 2 stops. I don't think I will throw an ND filter on there.
But to each there own. If anyone has too much UV exposure for wide depth of field, please send it to me.

#5 Cadmium

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Posted 04 January 2019 - 20:05

'Bringing detail to clouds', pondering here...
You mean, reduce UV at the same amount as the visual sky to reduce far away UV fogginess? Maybe I don't follow the idea here.
Wouldn't that be already prevented by the internal UV/IR filter or whatever...?
Wouldn't using Schott regular ND filters (NG1, NG3, NG4, NG5, NG9, NG11) tend to attenuate UV even more than whatever ND density you choose, of course those filters are not graduated from top to bottom.
Trying to see a reason to use a ND filter for UV.

#6 JMC

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Posted 04 January 2019 - 21:04

Yep, a bit of an odd thing to mention in the advertising blurb (about it being useful in UV). Only mentioned it in case anyone had one or had ever tried it.
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#7 Cadmium

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Posted 04 January 2019 - 22:11

Interesting.
Most ND filters will attenuate UV more then the rest of the rang. Visual and IR are fairly even with the Schott NG filter, not flat, but pretty good.
Here:
oops, out of file allocation... help help, I am sinking into the abyss! OK, resolved, Thank you Birna for the O2 refill...

Attached Image: Schott_NG_ND_Filters.jpg

Edited by Cadmium, 05 January 2019 - 01:58.


#8 Pedro J. Aphalo

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Posted 05 January 2019 - 23:26

I do have two Firecrest ND filters (not the Ultra ones), and not the graduated ones, just simple ND 1.2 and 1.8. Somewhere they tell they use rare-earth metal deposition and then sandwich this between Schott glass for protection. The company was recently bought by Tokina, so they may have some patents or some technology worthy of a takeover. I will try to find time to measure these filters next week. I do have their UV400, and it does sharply cut at 400 nm vs. Zeiss UV T* which cuts at 405 nm or so. Their Firecrest UVIR cuts at 400 nm and 700 nm almost exactly. As far as I can remember, I think they started quite many years ago as a spin off from Kodak UK.

#9 Cadmium

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Posted 06 January 2019 - 04:22

"Firecrest Filters are neutral across all spectrums, including UV, visible, and infrared."
Without a graph...?... Do they show a graph somewhere? I couldn't find one. I like to look at graphs, a bit of a habit, I know, but they usually work for me. :-)
I don't buy filters unless I see the graph first. Too many layers of mystery involved.
I showed a Schott graph above, now you show me a graph, Mr. Firecrest, which I can use for comparison.

Edited by Cadmium, 06 January 2019 - 04:27.


#10 Terry

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Posted 06 January 2019 - 09:35

View PostCadmium, on 06 January 2019 - 04:22, said:

"Firecrest Filters are neutral across all spectrums, including UV, visible, and infrared."
Without a graph...?... Do they show a graph somewhere? I couldn't find one. I like to look at graphs, a bit of a habit, I know, but they usually work for me. :-)
I don't buy filters unless I see the graph first. Too many layers of mystery involved.
I showed a Schott graph above, now you show me a graph, Mr. Firecrest, which I can use for comparison.

https://www.formatt-...recrest-nd-1316

mid page or so
Terry
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Sony and Minolta lenses

#11 dabateman

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Posted 06 January 2019 - 12:23

I think I understand this graph now. The amount of light emitted from a tungsten lamp and reflected off a barium target very slightly increases from 0.001 to 0.005 as wavelength increases. These filters are shown to elimate that reflected light from 380nm to 780nm. The firecreast is best with only slight leakage of reflected IR.
However, they think uv is only 380nm to 402nm to make the UV claim. Their IR cuts off at 780nm, which is way too low and you do see it increasing. I don't think they can make an IR claim unless they go out to at least 900nm. 1100nm would be ideal.

All though pretty graphs. These tell us nothing about the absorption of the glass that Cadmium asked about. That curve may look like a typicall 'n' like other filters when placing transmission on the y axis.

Edited by dabateman, 06 January 2019 - 12:38.


#12 Cadmium

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Posted 06 January 2019 - 23:56

Thanks Terry, I guess I missed those.
Is it just me, or am I looking at those graphs from a few light years away? Can't read them, and one is on a slant also, no wait, both are on a slant, guess that is suppose to make them look fancy (?) or something,
I can live without the fancy stuff, I just want to be able to read them, but I can't read them from my planet, anyone live on a closer planet?

Seriously?

Edited by Cadmium, 06 January 2019 - 23:58.


#13 Andy Perrin

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Posted 07 January 2019 - 00:20

Cadmium, you think the slant is bad, how about this?
Attached Image: 1428964089935.jpg

Yes, it's NEGATIVE. I'm thinking that this whole graph thing has more to do with the marketing department than engineering...

Edited by Andy Perrin, 07 January 2019 - 00:21.


#14 dabateman

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Posted 07 January 2019 - 00:27

@Andy,
I actually don't have an issue with that. They are only measuring the reflective light. So if the filter scatters light back to the Barium target, then it would be negative. They would be adding light back.

#15 Andy Perrin

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Posted 07 January 2019 - 00:41

Then how do you explain where the curve crosses the axis and goes positive? Also, I've never heard of anyone using negative numbers to represent reflected light on this sort of graph.

Edited by Andy Perrin, 07 January 2019 - 00:43.


#16 Cadmium

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Posted 07 January 2019 - 02:34

I have to admit, I am confused about what all is going on with those graphs...

Still... "The Academy of Motion Picture Arts and Sciences (AMPAS).... The test measured the spectral power distribution of tungsten light reflected off a spectralon target made of barium sulfate using a Photo Research SpectraScan Model 705 spectroradiometer..."
Sounds pretty impressive, definitely a mouthful. Not sure if anyone here has all of that stuff.

Hmm...
http://www.cs.unc.ed...ter/705spec.pdf

I think I like the PR-670 better, maybe?
http://www.photorese...troradiometer-0

#17 Cadmium

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Posted 07 January 2019 - 02:53

Jonathan, What power supply is that you are using there?
Oops, wrong topic...

Edited by Cadmium, 07 January 2019 - 02:54.


#18 dabateman

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Posted 07 January 2019 - 05:38

@Andy,
A positive number would be light going through the filter. A negative number would be light bouncing off the front of the filter and going back to the target, adding light.

Back to what I said above. These are pretty graghs, but tell us nothing about the absorption of the glass.

#19 Andy Perrin

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Posted 07 January 2019 - 05:51

dabateman: no. You have one line that has both positive and negative values at different wavelengths. There's no way you can get some positive and some negative numbers. It can't bounce off at some wavelengths and not at others.

Attached Image: 1428964089935 asdf.jpg
--

Edit: " It can't bounce off at some wavelengths and not at others." - not what I intended to say. Obviously it CAN, but you won't get a negative reading if you are measuring reflected light and some of it happens to get transmitted.

Edited by Andy Perrin, 07 January 2019 - 06:22.


#20 dabateman

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Posted 07 January 2019 - 06:02

I think the best explanation is they paid their third party too much and some interesting data was needed.
Look back at the site of the second graph. All my discussion is mute as it is not negative but really 0.000045 at the point you highlight. However at 402nm on the second graph we hit negative again.
So made up data?
Would have been better to buy a usb spectrometer then pay this third party.