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[Filter Test SEU Gen2 #6] Monochrome Museum Comparison


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[Filter Test SEU Gen2 #1] Introduction to the SEU Gen2

[Filter Test SEU Gen2 #2] White Balance, Raw Histogram & Andrea's "White Signature"

[Filter Test SEU Gen2 #3] Filter Speed & A Windy Bull's-eye

[Filter Test SEU Gen2 #4] Dealing with the Usual Dichroic Effects

[Filter Test SEU Gen2 #5] Landscape Interlude

[Filter Test SEU Gen2 #6] Monochrome Museum Comparison

[Filter Test SEU Gen2 #7] Measured Filter Transmission

[Filter Test SEU Gen2 #8] Dichroic Reflection Detour

[Filter Test SEU Gen2 #9A] Longpass Stack Wandering Discussion. See #9B for results.

[Filter Test SEU Gen2 #9B] Longpass Stack Results

[Filter Test SEU Gen2 #10] What good is a filter test without a Rudbeckia?

[Filter Test SEU Gen2 #11] A Fascinating New Rudbeckian View

[Filter Test SEU Gen2 #12] Summary


 

Monochrome Museum Comparison

I recently visited Speyer in Germany, and went to the Technik Museum there. I had with me my monochrome converted EOS 5DSR and 85mm Asahi Ultra Achromatic lens, as well as Baader U, StraightEdgeU Gen 2, and Heliopan 715 filters.

 

MONOCHROME MUSEUM TEST: Photograph a museum exhibit in sunlight using the Canon EOS 5DSR UV-Monochrome Camera with different filters, and compare the results.

 

Question: How does a museum exhibit look with a monochrome camera with the new SEU Gen2?

 

Answer: Differences were observed between the Baader U and StraightEdgeU Gen 2 filter rendering, in terms of exposure and reflection from the surfaces imaged. StraightEdgeU Gen 2 filter shows some UV and some visible characteristics. On the monochrome camera conversion the StraightEdgeU Gen 2 filters appears to let slightly more light through than the Baader U, but this consists of visible as well as UV.

 

Subject: Aircraft, building and sky.

 

Location: Speyer, Germany (Lat 49.32N, Long 8.44E)

 

Gear: Canon EOS 5DSR monochrome conversion + 85mm Asahi UAT + Baader U, StraightEdgeU Gen 2 and Heliopan 715 filters + Sun

 

UV-Pass Filters:Baader U, StraightEdgeU Gen 2 and Heliopan 715 filters

 

Exposure: f8 @ ISO-400

 

Conversion: Taken as JPEGs directly in the camera, using custom white balance based on PTFE tile.

 

Comment_1: All shots done with direct sunlight, although some cloud cover was present in the sky.

 

Comment_2: Did not do a control shot with UV/IR blocking filter. Control shot was done with no filter, so contains information from UV, visible and IR.

 

Comment_3: Shots were hand held, hence the slight change in alignment between each one.

 

Unfiltered - UV, visible and IR

1/1600th s exposure time

post-148-0-88344900-1532109958.jpg

 

Baader U

1/25th s exposure time

post-148-0-72240700-1532109955.jpg

 

StraightEdgeU Gen 2

1/25th s exposure time

post-148-0-17279600-1532109964.jpg

 

StraightEdgeU Gen 2

1/40th s exposure time

post-148-0-51909100-1532109966.jpg

 

Heliopan 715

1/250th s exposure time

post-148-0-37391900-1532109961.jpg

 

There were some strong differences in the rendering of parts of the image with the Baader U and StraigthEdgeU Gen 2 filter. Notably the lettering on the main plane, along with the chequer patterning on the engine intake, and the arrow on the fuselage, where they became almost indistinguishable from the main paint odf the plane with the Baader U. Not all lettering behaved the same way though - at the bottom of the image one another plane was the word 'Texans'. Although not visible in the full spectrum image, it appeared dark against the plane body in both UV and IR images.

 

The painted lettering on the museum wall was interesting - the letters were lighter in colour than the surrounding painted section in the UV and IR images, comapred to the full spectrum one. This suggest the paint used for them is dark in the visible spectrum but more relfective in the UV and IR, perhaps due to the pigments used.

 

The StraightEdgeU Gen 2 filter lets some short wavelength visible light through in addition to UV.

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A quick question for you....

I do not have a Monochrome camera, so I'm curious about your white balancing step? Presumably it is needed or you would not have done that? :D

Perhaps sometime you will make a short comparison for us using one filter with different in-camera WB settings on the MonoCam.

 

We all hate tripods. Almost required for UV photography though. :rolleyes:

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I've been wondering about whitebalancing Andrea, and hope to look at that systematically in the future. I left it to the camera for these, but I did recorded them as RAW files as well, and also took pictures of the PTFE disk with each filter as well. I intend to look at these when I have a little more spare time, and see what if any impact it does have.
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Jonathan,

 

You mention that the SEU Gen2 "filter lets some short wavelength visible light through in addition to UV." What part of the image shows this visible light?

 

Do you have an explanation for the BaaderU not capturing the text and the arrow on the lead aircraft? Why is the arrow completely dark in the SEU Gen2 images, but not in the Vis image?

 

Curiouser and curiouser.

Thanks.

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Jonathan,

 

You mention that the SEU Gen2 "filter lets some short wavelength visible light through in addition to UV." What part of the image shows this visible light?

 

Do you have an explanation for the BaaderU not capturing the text and the arrow on the lead aircraft? Why is the arrow completely dark in the SEU Gen2 images, but not in the Vis image?

 

Curiouser and curiouser.

Thanks.

 

For me, Reed, the writing on the plane shows the visible plus the UV. It can't be IR, as the filter is very good at blocking that. With the Baader U, the writing on the plane looks like the paint around it. With the SEU there is some contrast between the writing and the surrounding paint. I am open to other suggestions as to what would cause that effect.

 

Looking at the pictures again, this effect is also seen on the chequering on the engine intake.

 

I could test this using my glasses as well. They have an anti UV coating on them. So I would expect the Baader U image of them to look black, while I would expect the SEU image of them to make them look tinted, but not completely black. I'll try this if I get chance.

 

With regards to the arrow, I presume it's down to the pigments in the sticker or paint that is the arrow.

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The canopy of the plane is black for the BaaderU and darkly tinted for the SEU2.

That is as expected for the different transmission peak wavelengths.

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eye4invisible

The canopy of the plane is black for the BaaderU and darkly tinted for the SEU2.

That is as expected for the different transmission peak wavelengths.

That's the first thing I noticed - more so than the lettering on the side of the plane.

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I think the frontmost plane looks like a McDonnell Douglas F-4 Phantom II but I'm not really sure.

Does anyone else know?

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Andy Perrin

This suggest the paint used for them is dark in the visible spectrum but more relfective in the UV and IR, perhaps due to the pigments used.

 

Might it also be a question of what the background is doing in addition to the paint?

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A Vis image is helpful Here is a MD Phantom F-4 image from the net:

http://uvroptics.com/images/Phantom%20F4.jpg

 

You will notice the arrow has a yellow background. Yellow pigments are often low UV reflective.

The U.S. Air Force lettering is a deep blue decal 21" high. I read it as #05111f. Full marking specs are here http://www.oldwings.nl/content/o0/USAF_TechOrder_TO_1-1-4.pdf

 

I assume the canopy is "tinted" because the SEU Gen2 was able to capture more of the 380-400nm than the Baader U, or as ULf said "That is as expected for the different transmission peak wavelengths."

 

So, I see no evidence of a visible light leakage, other than a low possibility of violet in the 400-407nm range. Ulf's spectrophotometric results show no leakage. If you have evidence, Jonathan, to support your statement "The StraightEdgeU Gen 2 filter lets some short wavelength visible light through in addition to UV." I would be very interested to see it. What wavelengths does it let through, specifically?

 

Thank you.

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Andy Perrin
Ulf’s results did seem to show a tiny bit past 400nm? It was not a lot and I don’t know how significant it would be in practice given that the filter is transmitting so much 380-400nm also, which would drown out the tiny bit extra.
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As for visible contributions. As a basic test, I can see through it. In a darkened room with the curtains open slightly and a sunny day outside, I can see the gap in the curtains through the filter. I wear glasses which have a UV blocking filter on them, so I'm pretty sure what I'm seeing is visible light.

 

Ulf has already shown a transmission spectrum for the filter. I've also measured the transmission spectrum for my filter. Something I have also done previously is measure a solar spectrum and the response of my monochrome camera as a function of wavelength. Using this the solar spectrum and cameras response I have come up with a formula for correcting the filter transmission for camera response and sunlight, as both the camera response and sunlight intensity drops with wavelength. I can then multiply this correction factor by the filter transmission to give me an idea of the effective filter profile for the camera and lighting. Thus the relative contribution of small amounts of transmission in the 400nm to 420nm region gets amplified, as the sensor is more sensitive and there is more light there.

 

Below is is the SEU MkII transmission graph of my filter as measured on my OO spectrometer between 280nm and 480nm. On the same graph is the same filter, multiplied by the correction factor for sunlight and camera sensor response.

post-148-0-00446500-1532158857.jpg

 

And the same graph plotted between 380nm and 420nm.

post-148-0-72416200-1532158855.jpg

 

I wouldn't call this leakage (if I have anywhere in the thread, I'll correct that), it's light coming from the top end of the transmission band.

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A slightly more refined version of the experiment I suggested with my glasses, to try and explain the small amount of visible light transmission. This time 2 images with the Baader U and 2 with StraightEdgeU Mk2 - one with the filter alone, then a second with a GG400 3mm as well. 'TEST' written on white card with a black ball point pen. All images taken with my monochrome 5DSR and 85mm UAT lens. f8, 1/40th s, ISO400, direct sunlight for all images.

 

Baader U alone

post-148-0-39817200-1532169450.jpg

 

StraightEdgeU MkII alone

post-148-0-95513200-1532169455.jpg

 

Baader U + GG400 3mm

post-148-0-17886500-1532169459.jpg

 

StraightEdgeU MkII + GG400 3mm

post-148-0-87650200-1532169461.jpg

 

The word 'TEST' can be seen faintly through the SEU MkII but not the Baader U.

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Jonathan,

Your spectrum above I see two bumps around 470nm. I wonder if those are real. You could grab a lens, place the SEU2 on then the gg455 on top and see if you can photograph a tree or something in full sun. Similar to Andrea IR leak test comparison between Baader venus and the original SEU.

 

I may be mistaken, but thought the Gg400 had small tail into uv, approximately around 398, which for this filter would matter.

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Yes, the GG400 3mm transmits 49.1% at 400nm.

http://uvroptics.com/images/GG400%203mm.jpg

 

It is possible that the additional light was from the 400nm+ area, but the probability is higher that it is from the 392-400nm range which, according to the Schott catalogue transmits from 2% to 49.1%. However, that is the Schott value, the particular melt of Jonathan's GG400 may be different.

 

As for the glasses, unless the glasses are tested with a spectrophotometer, we have no idea of the UV blocking. And the subjective viewing of the Mark I eyeball is even more random. All children start life with UV vision. Over time, the yellow pigments in the lens is heavier in some adults than others. Some adults can see quite a bit in the <400nm range.

 

Clearly, Jonathan, you are determined to attribute the difference between the Baader U and the SEU Gen2 to visible light, where logic would tell us that though there is a small amount of transmission in the violet from 400-407nm for the SEU Gen2, there is much higher transmission in the UV intensive 370-400nm range for the SEU Gen2 as compared to the Baader U. So far you have used your eyesight, your glasses, and a GG400, to suggest problems with the SEU Gen2. Ulf tested the filter extensively with a spectrophotometer. Ulf did not find the "two bumps around 470nm".

 

Thank you.

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I've come into this discussion on the SEU after a request to share the data that I found. I have done so, and been open as to what I am testing and how I am testing it. I have drawn conclusions based on my interpretation of what I am seeing in the images. If I can see something through the filter when I hold it up to a light source with my eye then I call that visible light, random or not.

 

As for the 470nm features Dabateman mentioned, I have made no comments about bumps at 470nm, nor would I do given the size of the features in my chart, as I have no idea whether that is in the noise or not.

 

Mods, if you feel there is anything in this thread that goes against the data I have share feel free to remove it, as I have no wish to muddy the water.

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Well UlfW also sees the 470 peak, its just quite small. So maybe not an issue. But the 524nm peak, that is show I think maybe an issue. I have slightly smaller peaks in IR range on my Baader venus filter and that IR at 720nm does have an effect on my SD14. Which is really an IR camera.

But we will not know until someone tests the filter with a GG455 infront.

I have no vested interest either way. Just posting my thought. If this too is deemed inappropriate please delete. I try not to cause trouble and hope to be corrected when I come close. I typically live off 2 hours sleep, so I may miss speak at times.

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Well, I do not wish to cause contention or disunity.

I confess that I do not understand why someone would say " If I can see something through the filter when I hold it up to a light source with my eye then I call that visible light, random or not." Yes, the light is visible to the viewer, but that does not indicate that the light is not UV wavelengths as we use the term, i.e., 320-400nm equals UVA.

 

"The sensitivity of the human eye to light of a certain intensity varies strongly over the wavelength range between 380 and 800 nm." (https://light-measurement.com/spectral-sensitivity-of-eye/)

 

I can see light through 1mm of Schott UG1 and Schott UG11. Does this mean I am seeing "Visible light" (400nm-700nm)?

 

Anyway, I should not have responded to this thread. I do have a dog in this hunt. :)

 

I do appreciate all the submissions to this thread.

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I'm in the middle of Longpass testing now.

Can't do it all in one day! Patience grasshoppers !! :rolleyes: :blink: :lol:

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Andy Perrin
Hah, Andrea. I think people (in this thread at least) just have to be careful to say which definition of visible light they mean — “light from 400-700(?)nm” versus “light that they can personally see with their eyes.” Probably the first is better for quantitative purposes because we all have different vision.
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I can see light through 1mm of Schott UG1 and Schott UG11. Does this mean I am seeing "Visible light" (400nm-700nm)?

 

With 1mm UG1 and 1mm UG11, alone and unsuppressed, then yes of course you are seeing visible light, even if you delineate that range at 700nm.

You are seeing some red with both, and you are also seeing some blue with the 1mm UG1.

 

T graph

post-87-0-30079500-1532197061.jpg

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Please nobody should get upset because questions are asked or issues are raised when testing new gear (or performing any kind of technical experiment).

 

If you are the one to present data, then you naturally defend the data and methodology.

 

If you are the one to create the new gear, then naturally you defend its performance.

 

We all have our natural biases in these situations. But I know every one of you respects the principle that we should follow the data and the experimental outcomes to wherever they lead us. What else could we do really? :D

 

I see nothing so far to concern me about any "green bumps" in the SEU Gen2, but I'm not done testing. I just had a little card problem which has delayed things, but when the weather clears here I'll get right back on the testing.

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I've been mulling this over, over the past week. Is it visible or isn't it, and how to test it? It may seem a petty question to some, after all, if the images are pretty, what's the issue. However for me, if I get asked to recommend equipment for research, and someone asks me "so am I looking at a UV image or one with other wavelengths too?", I need to be able to give an answer for that. If a company uses my advice to image sunscreens on skin, and makes claims about "UV image of skin and sunscreens", then a competitor comes along and challenges that with, "ah but 2% of the image is composed of visible light, how do you know what you're seeing is truly UV related", while it may sound obvious it can make claims challenges in court very difficult and expensive.

 

I tell it as I see it. So apologies if that comes across badly at times.

 

Anyway, back to trying to figure out what is happening. I ran a transmission spectra measurement of my GG400 3mm filter. Interestingly it did not hit 50% max transmission at 400nm, it was actually nearly 403nm. I hadn't realised the tolerance on max transmission of these was so wide, but when I checked the specs it stated 400+/-6nm for 50% max transmission. Potentially a 12nm spread, seems to be huge and really surprised me. Is it normal for filters to have such a range?

 

In theory, the image I presented with the GG400 above with the word "TEST" just barely showing through should be effectively from a 6mm GG400 filter, as the light had to pass through it twice before being imaged (sunlight to card, and then reflected from the card to camera). I cannot rule out fluorescence from the UV hitting the card and then passing back through the GG400 as visible light, as I guess the card has plenty of optical brighteners in it like paper. Although I did not see anything for the Baader U, so I think it's unlikely to be UV induced fluorescence.

 

I do have another couple of filters in my Sparticle that may be useful here as well - there are two, one with a max transmission at 404nm and the other at 405nm, so perhaps an assessment with the Sparticle is in order, as that would rule out fluorescence and reflection from a card/paper target.

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