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UVIVF Possible Visible Light Leak?


cdhgamer

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I called their USA branch, twice, no answer, left a message, no word, so I have no idea what the UV/Visual ~400nm~ cutoff point is for their UV IR MC filter. I can't find the info about that anywhere.

So... If you missed the first show, your ticket is good for the second show.

 

This is my test, shooting down from above at a Convoy S2+ filtered with U-340 2mm.

Same exposure, settings, and white balance for all shots.

This might lead me to believe that the UV IR MC has better UV cutoff than the UV 400 MC, and that the Baader UV/IR-Cut has better UV cutoff than either of the Firecrest filters.

However, it can be a sticky wicket or problematic and deceptive to shoot tests of LED's, they can be intensively powerful, intensive enough to burn through strong OD blocking and cutoff, even into ranges that are not associated with the LED.

So I can't say for sure if what we see is UV or even IR, because I think I might be able to do about the same thing with an IR longpass filter.

For what it's worth, here is a comparison.

I think Firecrest needs graphs. Maybe their UV400 isn't exactly 400nm, if we go by this comparison.

By the way, the bright violet/blue/white circle in the background is the paper under the Convoy, fluorescing from the reflected UV off the front of the camera lens filters, which was always about the same with each filter, And that might be another aspect to consider, the UV reflected back at the front of the Convoy, but maybe some other time...

 

post-87-0-96394800-1550874009.jpg

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Steve or anyone else, have you ever had to repair a Convoy S2+? I switched out the battery last night, and now it won't turn on with any of my 4 batteries.

 

Edit: Disregard, the center shaft where the battery is got flipped around, didn't realize the direction mattered.

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Ok thanks Steve, and I fully I agree we need charts for these Firecrest filters. I have the feeling it isn't going to be a nice vertical drop at 400nm for their 400 one, and like wise for the 370 one. If I end up getting any I will of course post my findings.

 

EDIT - ordered one of the 400nm UV filters, so will see what it's like when it gets here.

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Sorry to revive the topic again, but I shot more photos last night, and the colors just aren't matching up with any sort of white balancing I do to what I visually see, which is a bit confusing and frustrating.

 

Here is the shot with daylight white balance.

 

post-227-0-34513000-1550990010.jpg

 

Here's an edit that is much closer to what I visually see, although the stamen should be red from chlorophyll, and I can't really get a white balance to reflect that aspect. This is at Temp - 50,000, and Tint - 50

 

post-227-0-89510700-1550991664.jpg

 

I'm really at a loss for why these photos seem to be so blown out in the blue/purple spectrum if that's not what I'm visually seeing. I'm also still confused why I'm able to shoot at such a low shutter speed. I'm stopping down for the depth of field that I want, but if I opened the lens I'm using wide, I'd be shooting at 1/8 s at ISO 500, shouldn't it be closer to 10 to 15 seconds? I apologize if these are bad questions at all. I'll attach a photo of the flower in normal light with a correct white balance below too.

 

 

post-227-0-62567900-1550992148.jpg

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OK, you are using a D810, stock camera, right? Not converted.

Any UV blocking filter on the lens at all?

If you are seeing the red then I don't know exactly why the red is absent in your photo.

I don't know the advised way to white balance for UVIVF, like I said, I just try to match it up with what I see, but you are seeing the red.

You might want to ask Dave or Mark, they both do UVIVF on a fairly regular basis and seem to be pretty precise with their captures.

I don't think any usual white balance setting in the camera is going to work that well, to get close you will probably need to do a custom white balance, and the fastest way to play around with that would be from RAW, like with NX-D or Ninja.

I also have a D810 stock, but I have never used it for UVIVF so far.

I would think that if you are seeing red, then it should show up with a stock camera if the lens is not filtered.

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OK, you are using a D810, stock camera, right? Not converted.

Any UV blocking filter on the lens at all?

If you are seeing the red then I don't know exactly why the red is absent in your photo.

I don't know the advised way to white balance for UVIVF, like I said, I just try to match it up with what I see, but you are seeing the red.

You might want to ask Dave or Mark, they both do UVIVF on a fairly regular basis and seem to be pretty precise with their captures.

I don't think any usual white balance setting in the camera is going to work that well, to get close you will probably need to do a custom white balance, and the fastest way to play around with that would be from RAW, like with NX-D or Ninja.

I also have a D810 stock, but I have never used it for UVIVF so far.

I would think that if you are seeing red, then it should show up with a stock camera if the lens is not filtered.

 

Yep, my Nikon D810 is stock, and I also tested my D750 which is stock as well. I tried some other lens combos just incase my macro lens was somehow leaking more blue/purple than other lenses but they all seemed the same. And I have been shooting in RAW and messing with custom white balances in Lightroom, but I think it does have a more limited white balance compared to those programs doesn't it?

 

Some flowers do seem to be fluorescing somewhat close to what I can see visually, but it's seeming like any flower that fluoresces blue or purple for the most part, those colors are washing out reds/oranges, but not yellows.

 

What are Mark and Dave's usernames by the way?

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Yep, my Nikon D810 is stock, and I also tested my D750 which is stock as well. I tried some other lens combos just incase my macro lens was somehow leaking more blue/purple than other lenses but they all seemed the same. And I have been shooting in RAW and messing with custom white balances in Lightroom, but I think it does have a more limited white balance compared to those programs doesn't it?
Any UV blocking filter on the lens at all?

As Cadmium said, you need a FILTER on the lens to block UV. It sounds like the answer to his question here is "no" and that may be the issue. It's not about the lens, it's about not having a filter.

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I was kind of asking in the reverse, because I was wondering if whatever UV/IR cut filter on the lens might be cutting off too much of the red...

My thinking is that if there camera is stock and there is no lens filter, then it should be recording visible red if seen by the eyes.

So I don't have any idea about that, given the scenario.

But a lens filter that blocks UV would be something to try/test, who knows.

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As Cadmium said, you need a FILTER on the lens to block UV. It sounds like the answer to his question here is "no" and that may be the issue. It's not about the lens, it's about not having a filter.

 

Alright, thank you Andy, that's what I've been trying to figure out, I heard from various people that I don't "really need" it and I keep feeling like I should really get one but I was hearing conflicting things, or at least that's what I was taking from it, maybe I was misunderstanding some people

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Once again, I didn't mean to say you need a filter on the lens, I was kind of saying the opposite.

Since you are using a stock camera, and a non-UV friendly lens, then you may not be getting much UV to your sensor.

I see a huge difference in UV between shooting the Convoy with the full spectrum D7000 + the Kuribayashi UV friendly lens, and the D610 or D810 stock cameras with modern kit lenses.

I just now tried all of this.

 

Camera Sensor < (Internal UV/IR-Cut filter) < Lens < (UV blocking filter) < < < < < U-340 (visual blocking filter) < Convoy S2+ 365nm Nichia LED

 

Shooting head-on at the U-340/Convoy, I see very weak UV with the D810 and D610 using modern Nikon lenses.

Using the Kuri lens instead, I see more UV with the D810 and D610.

Shooting with the D7000-UV/IR with Kuri, I see a LOT of UV.

 

So, the lens has a lot to do with how much UV is getting to the sensor.

When I put the Firecrest UV IR MC on the kit lens the UV becomes almost undetectable using my stock cameras.

I do believe the UV IR ME cuts more UV at a higher nm than does their UV 400 MC filter, regardless of the numbers, but I am not saying either of those filters should be used for cutting UV,

there are others, but I am not saying you absolutely need it either, given your stock visual equipment.

On the other hand if someone is using a full spectrum camera they pretty much need to cut the UV at 400nm to 435nm.

I am not familiar with the Tokina 100 mm Macro f/2.8, but it looks pretty modern, so it probably doesn't transmit UV well, of course, a lot of lenses will transmit some UV, down to 380...more? Don't know, they are all different.

If I were you, I would first try white balancing with NX-D, it is made for Nikon, and it would be rather handy to have, and it is free I think still. Try that first.

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The problem might be a white balance issue, but also an uv leakage in the stock camera's internal filtering.

If white balancing fails the next step would be to put a suitable filter on the lens.

 

From the graph of the filter transmission it is clear that the D810's UV-blocking is done by a dichroic filter:

https://diglloyd.com...sion-curve.html

 

For normal photography this filtering is good enough as the sensor's UV-sensitivity is low too.

However the light levels from fluorescence are low and then it might not be enough.

 

Sometimes dichroic filter are not blocking that good in their reject bands.

We know that from earlier versions of the Baader U-filter.

That filter had an IR leakage causing problems for UV-photography with full spectrum cameras.

 

The small wiggle in the article about the transmission graph for the D810 near 400nm can be an indication that this filter too might leak a bit into the UV.

If the leakage exist and is strong enough it might allow enough UV-light to overwhelm the weak VIS-fluorescence.

 

The UV-blocking of modern lenses is not a main design issue when creating the coatings and no safe way to eliminate UV during fluorescence-photography.

They are optimised to transmit maximally and flat in the VIS and to do that the blocking can begin a bit into the UV-range.

Modern lenses are also often built with many lens elements causing an UV-cutoff, but that can sometimes give a cutoff further into the UV.

For UV-photography this is very important and cause problems, but might not solve all UV-cutoff needs for fluorescence-photography.

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Once again, I didn't mean to say you need a filter on the lens, I was kind of saying the opposite.

Since you are using a stock camera, and a non-UV friendly lens, then you may not be getting much UV to your sensor.

I see a huge difference in UV between shooting the Convoy with the full spectrum D7000 + the Kuribayashi UV friendly lens, and the D610 or D810 stock cameras with modern kit lenses.

I just now tried all of this.

 

Camera Sensor < (Internal UV/IR-Cut filter) < Lens < (UV blocking filter) < < < < < U-340 (visual blocking filter) < Convoy S2+ 365nm Nichia LED

 

Shooting head-on at the U-340/Convoy, I see very weak UV with the D810 and D610 using modern Nikon lenses.

Using the Kuri lens instead, I see more UV with the D810 and D610.

Shooting with the D7000-UV/IR with Kuri, I see a LOT of UV.

 

So, the lens has a lot to do with how much UV is getting to the sensor.

When I put the Firecrest UV IR MC on the kit lens the UV becomes almost undetectable using my stock cameras.

I do believe the UV IR ME cuts more UV at a higher nm than does their UV 400 MC filter, regardless of the numbers, but I am not saying either of those filters should be used for cutting UV,

there are others, but I am not saying you absolutely need it either, given your stock visual equipment.

On the other hand if someone is using a full spectrum camera they pretty much need to cut the UV at 400nm to 435nm.

I am not familiar with the Tokina 100 mm Macro f/2.8, but it looks pretty modern, so it probably doesn't transmit UV well, of course, a lot of lenses will transmit some UV, down to 380...more? Don't know, they are all different.

If I were you, I would first try white balancing with NX-D, it is made for Nikon, and it would be rather handy to have, and it is free I think still. Try that first.

 

NX-D got me a tiny bit closer to what I saw but not quite all the way there. I did order a Firecrest UV 400 to try out though since it wasn't too costly, and I can always use it on my other camera when it comes back from a full spectrum conversion. I'll report back whether or not it helps in any way

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Here is a graph for the Firecrest UV IR MC below.

There are other alternatives for blocking UV. Just ask, and people will suggest what to use.

 

Frankly, Ulf's graph of the D810 internal cut filter that he linked to above seems to cut at about 420nm, for the most part, and that looks pretty good to me.

Regardless, it is good to have an external cut filter, but I don't know if very low amounts of UV leaking into your camera would keep your camera from seeing the fluorescing visual red you see.

Often you will find that green leaves will fluoresce red, and they can be used as a good red fluorescence test subject. You could find a leaf that fluoresces to your eyes, and test that with your camera,

if you can't get the camera to record a red fluorescing leaf, then I don't know...?

 

post-87-0-76845000-1551106235.jpg

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I heard from various people that I don't "really need" it and I keep feeling like I should really get one but I was hearing conflicting things, or at least that's what I was taking from it, maybe I was misunderstanding some people

 

A stock Nikon D810 has a UV/IR blocking filter. But we do not know how much UV or IR that filter blocks. So if that filter is letting any UV light pass between 390-400, then you might be getting some blue/purple contamination. Our cameras record stray UV around 400nm as either blue or purple.

 

If anybody has told you it is OK to shoot UVIVF without a UV-blocker on the lens, well then, they are not correct. Proper fluorescence photography always requires double filtration: a filter on the illumination source and a filter on the taking lens. This is certainly not to say that we here on UVP all follow proper procedure all of the time. :D I experimented with UVIVF for a long time without using a filter on my UV-LED flashlight. Always did use the Baader UV/IR-Cut on my lens.

 

Scientific fluorescence photography uses very narrowband filtration for UVIVF. Our foto filters are very broad by comparison. So we will never get an absolutely, totally "pure" fluorescence photo. But we can and should attempt to minimize the leakage.

 

 

1) Your blue/purple overload may result from the converter you are using? What are you using to convert your raw NEFs from the D810?

 

2) For shooting, set the D810 white balance to K10000 and use a Standard [0] picture control. (Okay to add sharpening).

Yes, I know that internal settings only apply to the jpg, but you do need to check what you are recording while doing it. So getting as close as possible to fluor neutrality is helpful.

 

3) While in the dark shooting fluor, your vision may change. So be sure to observe the emitted colors at the very beginning of your shooting session while you still have some photopic vision working. I don't really know if our eyes ever convert to total scotopic vision when shooting fluor in the dark because, after all, there is some emitted visibile light from the subjects. But best to observe at the beginning, not the end of the session. And then hope your mental color map holds well enough so that you can aim for it during raw conversion. :rolleyes:

 

Hope this helps. Don't give up! We'll figure it out.

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Addition to preceding.

 

Todd, two things.

 

I have a D810. I could try to make a UVIVF white balanced NEF with my Convoy and make it available for you to load into your camera to use as a WB setting. (Do you know how to do that?) I wonder if this would be useful or help?

 

If you can arrange for me to download a raw NEF of your flower, I'll run it through Raw Digger and see whether any red is being recorded in the chlorophyll area. And I can try other converters for you to see if they bring out the red. Let me know.

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hmm.....turns out we can post raw nefs here on UVP.

TEMPORARILY.

They cannot be displayed. But can be downloaded.

 

Posting NEF files eats up a huge amount of space. So I would have to remove such a link after 24-hours or so. This does let us share NEFs or other raws if we want to.

 

So I might try to make that D810 WB foto and post it. Gotta wait til dark though. B)

 

Obligatory cat photo.

[Added: Linked as a NEF upload trial. TEMPORARILY.]

[attachment now removed]

chaiCatInABox_20190112wf__16759.nef

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And we hope that the chart is accurate. Unless someone (Kolari or whoever) is willing to explain their spectro setup, then we take all such charts with the proverbial grain o salt because so many people do not make proper spectral measurements.

 

I know -- I'm always such a skeptic! Let's say that the chart probably is reasonably accurate.

 

In which case the problem lies in the finish not the effort. I.E., Todd's fluorescent colors, red in particular, are not being brought out by the conversion.

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I agree with you, you are right technically, all I was saying previously is that I don't think his red problem is caused by the lack of a lens barrier filter given the lens he is using and the D810 graph.

 

Not sure what you mean about his red is not being brought out by the conversion?

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And we hope that the chart is accurate. Unless someone (Kolari or whoever) is willing to explain their spectro setup, then we take all such charts with the proverbial grain o salt because so many people do not make proper spectral measurements.

 

I know -- I'm always such a skeptic! Let's say that the chart probably is reasonably accurate.

 

In which case the problem lies in the finish not the effort. I.E., Todd's fluorescent colors, red in particular, are not being brought out by the conversion.

I'm just doing some work at the moment using a Canon EOS 5DSR (unmodified) for fluorescence. I am pretty certain the stock filters over the sensor are not blocking all the UV, and lead to a sizable contribution from reflected UV in fluorescence images, if a suitable UV blocking filter is not added to the lens. Once I have finished it I'll share my findings on here. Also, looking at the Kolari sensor filter transmission profiles, they look to be measurement points every 5nm. From what I'm seeing, that could lead to issues with averaging of the data, and be underestimating the potential problem of leaks. It'll make more sense when it's written up and shared (I hope).

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Ok thanks Steve, and I fully I agree we need charts for these Firecrest filters. I have the feeling it isn't going to be a nice vertical drop at 400nm for their 400 one, and like wise for the 370 one. If I end up getting any I will of course post my findings.

 

EDIT - ordered one of the 400nm UV filters, so will see what it's like when it gets here.

My Firecrest 400nm UV filter turned up and I have measured the transmission on it. Used my Ocean Optics FX spectrometer. Measured spectra in two halves - up to 410nm with the Deuterium lamp only, and above 410nm with both lamps. Then pasted the two halves together (they matched up very well at the join). This was done to minimise stray light effects at the short wavelength side of the cut off. Here's how it looks;

post-148-0-83392100-1551628124.jpg

 

Steve - looks very similar to the graph you shared (where did you get from?). On mine there is a little more tail on the short wavelength side of cut-off. While I tried to minimise stray light effects, if I'm still getting any that would account for the tail I saw.

 

I stand corrected - I fully expected this not to be a sharp cut off, but I am pretty impressed. If I get one of the 370 ones I'll test that too.

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Jonathan-

 

To further examine the tail below 400nm of the Firecrest 400nm UV you could pre-filter the deuterium light with your SEU2-filter, and use that as the modified light source.

The stack of SEU2 and Firecrest 400nm UV will not transmit any unwanted light causing much stray light errors.

Naturally the data will only be valid for the transmission range of the SEU2.

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