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[Filter Test] 340/10 #6 Progress was made, finally. UPDATE: Progress was then lost.


Andrea B.

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[Filter Test 340/10 #1] Gotta work out a problem or two, but here is a 340/10 result anyway

[Filter Test 340/10 #2] Cured the flare but it's ring around the posy here

[Filter Test 340/10 #3] Trying again with the 340/10

[Filter Test 340/10 #4] Edmund Hard-coated 340/10 Rear-mount Experiment

[Filter Test 340/10 #5] Edmund Hard-coated 340/10, Sunflower, Sun

 

My previous tests with the Edmund Optics Hard-coated 340BP10 UV-pass filter were full of flare, reflection rings and washout. I pretty much had given up on using this filter.

 

However, today when I stacked an AR-coated S8612 over the Edmund 340/10, I FINALLY got some good results in the sense that there was no flare, no washouts and no reflection rings.

 

The white balance problem remains, but at least some progress was made.

 

D610-fullSpec + UV-Nikkor 105/4.5

SB-140 UV-Flash

Edmund 340BP10 + S8612-ARx2.0mm

Both frames f/11 for 2.5" @ ISO-400

 

Peak transmission of the Edmund 340/10 is above 95% with OD4 or better outside the 10 nm bandpass. I could have shortened the exposure time of 2.5" if I had let the camera control the flash instead of firing it manually.

 

The flower in the photo is a Chocolate Flower.

You can see what it looks like in Visible light by scrolling down here--> LINK.

 

The following pairs feature:

  • flower against dark background
  • flower (drooping!) against Spectralon background

.

The raw composite shows that this filter's raw color is orange.

No white balance has been applied.

610_1710rawComp.jpg

610_1708rawComp.jpg

 

 

White balance in Photo Ninja against the Spectralon produced this blue mess.

610_1710pnBkg.jpg

610_1708pnBkg.jpg

 

 

White balance in Capture NX2 against the Spectralon produced this yellow & dark blue mess.

Dark areas are blocked.

Note that the marquee WB tool did not turn the Spectralon white or grey.

610_1710nx2Bkg.jpg

610_1708nx2Bkg.jpg

 

 

The best version I got was produced by applying the Photo Ninja WB tool

to the shadow behind the flower. Go figure. :blink: :wacko: :rolleyes:

610_1710pnShadow.jpg

610_1708pnShadow.jpg

 


Now that I've figured out that an AR coated filter "fixes" the Edmund 340BP10, I'm going to try to get a clear AR-coated piece of glass to put over it or behind it.


 

 

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Roughly speaking, the white balance problem with the Edmund 340/10 is that is pretty much impossible to white balance a monochrome color photo. That's what I think is the problem anyway. Could be wrong!
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Andrea, this is very similar to what I get with my 340/10 filter and my 340-345 nm LED (individually, not together). The raw color is orange and white balancing the image gives a blue mess. My camera cannot set an in-camera white balance with those tight LED/filter. Probably as you say the images are very monochromatic with very little color information, and you cannot white balance them. I prefer to just shoot in B&W with that filter.
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Andrea, I've been doing a lot of work with these type of narrow band pass filters for a client. Despite having high blocking, I was getting the same issues that you saw (flaring, rings etc) when used with broadband light sources. What worked for me was using something like Hoya U340 4mm in combination with them to get rid of most of the unwanted visible and IR from the light source. And yes whitebalance is pretty much a moot point with such a narrow bandpass.

 

Something to check. Take the filter and look through it at something like a normal LED light. Then still looking at the light, twist the filter. The blocking falls apart very quickly as you go off axis with those filters.

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Colin Nikon cameras seem to be the worst at doing a custom white balance.

However, your trick might work.

 

Andrea with camera, lens and filters that you are going to use. Place a thin sheet of PTFE in front of it all. Best if you have a 52mm or 72mm PTFE filter thats 3mm thick or little less that you can screw stack all together. Now try in camera one touch white balance or custom white balance. That has been working for tricky WB. Its just like the Expo disc method.

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Thanks Dave

My PTFE film is about 0.14mm or 6 thousands of an inch thick.

I haven't tried any other thickness.

To get the CWB I set-up the camera for the shoot with filters & lighting then set the exposure etc, then place the film in front of the lens / filters & do the CWB.

Sometimes the CWB doesn't take & I need to change the exposure, but it is close to what I will be shooting with.

And it is then close to what Photo Ninja want too.

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andreatestmember

Thanks all for the comments!

I'm temporarily logged on under a test ID. Just testing.


 

Stefano: This is very similar to what I get with my 340/10 filter and my 340-345 nm LED (individually, not together)...I prefer to just shoot in B&W with that filter.

 

I often also shoot in monochrome with narrowband or color filters because it gives one a better feel for where the exposure is placed when looking at the camera histogram. I try to expose long enough to place the histogram "hill" in the center.

 

The raw orange colors did make a nice photo though. I could live with that raw color for the Edmund 340/10. A Raw Digger conversion needs some additional tweaks of micro-contrast/contrast/sharpening as it is a bit weak on details, but as you can see above I did get a good result from the raw composite.


 

Jonathan: What worked for me was using something like Hoya U340 4mm in combination with them to get rid of most of the unwanted visible and IR from the light source.

 

With this Edmund hard-coated filter having OD>= 4 there are not really any vis/IR leaks to worry about when used with the SB-140 UV-flash. Even without UV-flash, this filter hasn't shown any evidence of vis/IR leaks. It is a really tight filter. But the silver hard-coating creates monster reflections.

That is a good suggestion though for leakier filters - to combine a tight wide-band over a less-tight narrow-band.


 

Colin: Don't you or Nikon cameras like doing a Custom White Balance in Camera before the shot ?

 

:lol: :lol: :lol: Well, Col, *I* like to do an in-camera white balance, but those pesky Nikon converted DSLRs refuse to white-balance properly under dark filtration. This is a known problem. However, it is easily enough dealt with during the raw file conversion. And given that I've found the occasional inaccuracies in other brands' white balance efforts under dark filtration, I'd say that any in-camera white-balance has to be confirmed during raw file conversion anyway.

 

I have pushed the white balance multipliers in the D610 to a near UniWhiteBalance. So I am able to compose and shoot without any red overload that obscures details. Or I shoot in monochrome, as mentioned above.

 

Now I'm getting ready to test my S1R conversion (which has been sitting here for about a year unused!! Bad girl.) and I know it has much better capabilities for in-camera WB under dark filters. That will be interesting for me.


 

Dabateman: Place a thin sheet of PTFE in front of it all.

 

I have a couple of thin PTFE "expo style" front filters. One of them kindly sent by JC Dowdy. However this doesn't work for Nikon DSLRs. If the D610 + BaaderU won't white balance against the 99% reflection from a slab of Spectralon, it isn't going to white balance through a PTFE film.


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Andrea,

Off of and through for some magical reason that I can't explain are different. I tried for 30 minutes to try and get a custom WB off PTFE reflectance and got nothing.

I than added my home made 3mm thick PTFE 52mm filter in front of it all on my camera and adjusted the exposure time to hit zero on my histogram. Then magic3al it locked on and gave me a custom WB profile.

I can't explain it but its different and you should give it a shot.

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PTFE doesn't have a diffuse reflection so it is easily overexposed. Was that the problem?

 

Also, what camera are you talking about? Thx.

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Well flappedly-dang-doodle.

 

The AR coated S8612 + Edmund 340BP10 combination did NOT work at all outdoors.

 

The photo is of a hollyhock flower & bud. It is a washout. Only the red channel looked good.

 

This is the raw composite from Raw Digger.

D610 + UV-Nikkor + S8612-AR x 2.0mm + Edmund 340BP10

f/8 for sec @ ISO-400

610_1713rawComposite01.jpg

 

This is the red channel of the raw composite from Raw Digger.

I added some detail sharpening but no other adjustments.

610_1713redChannel01pn.jpg

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Andy Perrin
Andrea, it seems like (unless you have a huge light leak) the only difference is the spectrum of sunlight vs the flash. I wonder what wavelength is washing it out?!
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Andy Perrin
Andrea, you were not having this reflection problem indoors with the same equipment. I did see all prior posts on the topic. If the only thing that changed was the spectrum then that must be the cause. But maybe also check for light leaks in case the light is getting in some other way.
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We know 340 nm looks orange, so that blue-green color is something else.

 

I know you have a 4 mm thick U-340 filter, that is perfect to stack with a 340 nm bandpass filter.

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Okie dokes, here are two stacked fotos for the beginning of the Jonathan/Stefano suggestion to stack the Edmund 340/10 with some U-340.

 

This is the indoors test first using flash. Next I'll try again outdoors.

 

Note that the focusing errors are *mine*.

I am having a bit of trouble working out the focus under 4 to 7mm of 340 filtration because I don't have any 340 torch to use. By trial and error I could work it out and make note of the adjustment if I were going to use this combo regularly in the future. But for now let it ride if that's ok, OK? "-}

 

There is nothing surprising with the two indoors, flashed, stack foto.

They look like the previous 340BP10 foto.

These are straight-out-of-camera.

 

D610 + UV-Nikkor.

Both f/8 @ ISO-400.

Flash was controlled by the camera.

 

Metering doesn't work, so exposure times are just a guess.

Again refinement of exposure length could happen with experimentation.

 

I took care to hold the flash the same distance from the Chocolate Flower.

(Which, btw, is smelling like chocolate right now. Weird but cool.)

 

The raw composites look the same as before, so I'm not going to post them right now.

 

 

Edmund 340BP10 stacked with U-340 x 4.0mm with SB140 UV-flash

610_1716_340x4.jpg

 

Edmund 340BP10 stacked with U-340 x 1.0mm with SB140 UV-flash

610_1717_340x1.jpg

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Andy: If the only thing that changed was the spectrum then that must be the cause

 

Andy, I hear you. WIll try to figure this out after I do the remainder of this stacking test.

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Geez. There was a tarantula out there. Slightly creepy because I couldn't see where it went.

Let me move to the nice tarantula-free driveway to complete this test so the tarantula can

continue free-range in my garden for now.

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BINGO!!

 

The double 340 stacking worked. Results on the way. WOO !!!

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Andy Perrin
Sounds like we can conclude that the filter’s OOB blocking either has a weak spot or the sunshine just does not have enough 340nm in it to prevent the OOB stuff from punching through without extra help.
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The double stacked 340s worked !!! Thank you Jonathan for discovering this. Thank you Stefano for urging me to go find my U-340 glass.

 

It looks as though the 1.0 mm thick U-340 works so I might not have to go to the 4.0 mm thick U-340.

 

The Big Question: why in the world does stacking U-340 over the Ed 340BP10 work to suppress the Ed's reflections, rings and washouts?

 

Pros and Cons

 

Pro: the stacking worked to reduce reflection/flare/rings while maintaining the narrow bandpass.

 

Con: the incredible 95% transmission of the Edmund 340/10 is greatly reduced. Can't have everything I suppose. :rolleyes:

 

 

 

[i always feel the need to apologize for bad exposures. I can't see a thing with these stacked 340s and did not want to take the time to refine focus and exposure lengths. Kinda hot out there today.]

 

 

marigold_vis_sun_20210701laSecuela_24791pn01.jpg

 

f/8 for 2" @ ISO-800

marigold_ed340bp10_u340x1_20210701laSecuela_24800.jpg

 

 

f/8 for 4" @ ISO-800

marigold_ed340bp10_u340x4_20210701laSecuela_24811.jpg

 

 

f/8 for 8" @ ISO-800 with flash

Even under strong sunlight, a boost from the SB-140 was helpful with stacked filters.

marigold_ed340bp10_u340x4_sb140_20210701laSecuela_24815.jpg

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A color sampler for one of the raw composites.

Still orange. :grin:

 

marigold_ed340bp10_u340x1_20210701laSecuela_24800rawComp01.jpg

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There's a lot of difference between 1 mm and 4 mm of U-340. Given the difference is mainly the IR blocking in the ~700-800 nm range, that's at least one place where the filter leaks.

 

OD 4 for a tight UV bandpass filter is probably not enough. I think at least OD 5 is required, better OD 6.

 

U-340 is one of my favourite glasses. Very versatile.

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Andy, I have to look at the light leak around my upper LCD again. I wonder if I didn't have it properly covered?
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