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UltravioletPhotography

How to WB this (or maybe the filter I have is bad)


bsas

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Bernardo, I have UG11 in a 2.00 mm thickness and BG40 in a 2.00 mm thickness. When stacked this will not precisely match your stack thickness, but it might offer us some additional information. So I propose to test it and post the results. I'll include some white and black standards and a flower with a known UV signature. Then I will make a test with a UG11 x 2 + S8612 x 2 stack for comparison.

 

{stay tuned....I'll do this asap, but I need to finish my coffee first! And water some plants.}

 

And I downloaded your raw files to run through Raw Digger. Perhaps we will observe something from that. :cool:

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Both filters are glued :(... I even thought about getting some kind of dissolvent to try to unglued them but I have no idea what can I use that will not destroy the chemicals on the glass.

 

The vendor on ebay was the guy called “image-laboratory” that people here in the forum told me to not trust, and clearly you were right :(

 

Anyway, if anyone has any idea how to unglue those so I can test them separate with the S8612 glass I am up for it. I don’t care if it doesn’t work and one of them gets destroyed, I am fully open for suggestions :)

 

Cadmium will know. But I would guess acetone should do it. Also these are ionic glass types. The glass is a solid block of filter. So you can polish, cut or clean them without much worry.

The Baader venus filter is dichroic filter. If you polish it you would remove all the IR blocking layers.

 

As far as I have tracked down, they are a USA distributor for China company. I can't remember off the top of my head which one. But most likely you have ZWB1 and QB stack there.

I also have an image laboratory "bg40" filter 77mm x 2mm thick. I may be able to test it in 2 weeks when I get some time.

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Here's a deeper look at the photo.

I cropped away some background and shadow irrelevant to the discussion.

 

As Shot

This is where we start.

I think it is good to look at what you started with for comparison to what you end up with. :cool:

DSC01391asShot.jpg

 

 

Raw Digger :: Raw Composite

You can say that this is the raw demosaiced data before white balance multipliers have been applied.

There is some under-exposure in the shadows, as is common.

There are a few bits of specular highlight from the wet sunscreen, also no surprise.

DSC01391rawComp.jpg

 

 

Photo Ninja

This is where Photo Ninja starts.

PN applies more saturation and curve adjustment to the raw data as do most other converters at the start.

DSC01391pnNoEdits.jpg

 

 

Photo Ninja :: White Balanced

Because I/we know from other work that sunscreen would be neutral and dark in a reflected UV photo,

I averaged the white balance dropper over the sunscreen area.

Seeing that there was a very blue result, I then went back to Raw Digger to retrieve the 3 channels.

DSC01391pnWbOnSunScr.jpg

 

 

Raw Digger :: Raw Blue Channel

So, there's where I think the UV went because the sunscreen is darker here in the blue channel.

We might then be able to conclude that the contaminating light was red??

I'm not entirely sure we can made that conclusion although it does seem right

given what we all know about contamination by IR.

DSC01391rawBlue.jpg

 

 

Raw Digger :: Raw Red and Green Channels

The sunscreen is very much lighter than in the blue channel. Red is lightest.

DSC01391rawRed.jpgDSC01391rawGreen.jpg

 

 

Raw Digger :: Raw Histogram

The "spikes" happen because older Sony cameras compress 12-bit data in a certain lossy way.

I'm thinking that in the typical UV photo, red leads green & blue more than is shown here.

The left-most combing/humps in the histos are mostly the underexposed shadows.

DSC01391rawHisto.jpg

 

 

ok, done.

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D610 + Vivitar 35/3.5 + Various Filters + Sunlight

All were exposed at f/8 and ISO-800 for various times.

I wanted to shoot with a non-dedicated UV lens.

 

Conversion: Photo Ninja, Photo Mechanic and NX2

I was back & forth between these apps for white balance, resizing, etc.

These are somewhat quick 'n' dirty.

 

 

Visible Reference: Baader UV/IR-Cut

The wide-angle scene. My late summer garden is beginning to fade.

610_7780pn.jpg

 

 

UV+IR: Schott UG11 x 2.00mm + Schott BG40 x 2.00mm

This is the closest I have to what Bsas is shooting with.

Clearly, Schott BG40 does not block the UG11's IR hump.

And did you happen to notice that I forgot to refocus? I'd be embarassed but what's the point? Too funny that focus shift bites the user of the UV-Nikkor. :lol: One forgets to remember such things as focus shift after a while I suppose.

Ok, maybe it is a little embarassing.

Fortunately, my back focus here does not alter the fact that this stack is not supressing the IR hump of the UG11 glass.

610_7788pn.jpg

 

 

UV: Schott UG11 x 2.00mm + Schott S8612 x 2.00mm

The S8612 blocks the IR leak. S8612/2 is a good multi-purpose IR-blocker.

The S8612 thickness could be refined (up or down) if you wanted to keep a permanently stacked filter set.

610_7794pn.jpg

 

 

 

Force Tests

I ran some 30" force tests on the faulty stack to try to trap the leak.

 

NO EDITS.

These are the JPG straight-from-camera.

 

All RG filters are 2.0 mm in thickness.

 

UG11/2 + BG40/2 + Baader UV/IR Cut

Quite a bit getting through here. Probably high Red.

610_7799.jpg

 

UG11/2 + BG40/2 + Schott RG695

The dual bandpass UG11 has a IR passage bump around 700 as can be seen from preceding trans charts.

Here it is, blasting its way through 6mm of glass.

610_7806.jpg

 

UG11/2 + BG40/2 + Schott RG715

More of the same.

610_7808.jpg

 

UG11/2 + BG40/2 + Schott RG730

And so, the IR leakage is almost gone by 730 nm -- as we would expect.

610_7810.jpg

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OMG Andrea, thank you so much for all those tests and work! That helped me a lot!

 

By the way, after talking to Cadmium on PM he was able to make an S8612 52mm x 2mm and an U-360 52mm x 2mm for me! So, I cannot be more excited and anxious for those to arrive :D

 

I just received his S8612 58mm x 2mm (from eBay) on mail right now and I am going to send it back to him because it was part of our deal to exchange the big 58mm filter with both 52mm and pay the difference. But, I couldn't resist to test it before shipping it back and I have to say: WHAT A DIFFERENCE!

 

Now I know what a good filter can do! And UVIR Optics craftsmanship is outstanding. The filter is so clean and well cut!

 

Just using his S8612 filter on the top of my cheapo ZWBs I was able to get the "promised" black sunscream photo right away! Here are the RAW files for you Andrea:

 

https://www.dropbox.com/s/5n13dr7513ssbu3/DSC01423.ARW?dl=0

https://www.dropbox.com/s/8muzowcv1ocra6c/DSC01424.ARW?dl=0

 

So, I can just imagine how much better the results will be with the U-360 from him. Super happy now!

 

I want to test the "weird stack" with the S8612 but I am first trying to unglue them with acetone :P

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Andrea, Nice tests .

 

Really toxic and nasty stuff (I think it is banned in Europe?), depending on the glue, but it is probably UV curable adhesive, the best way to dissolve the glue is Dichloromethane (DCM) AKA methylene chloride.

https://en.wikipedia...Dichloromethane

 

Basically, put it in a seal-able screw top glass jar, submerse the filter on the liquid... and run! OK, sorry, actually I should not joke, the stuff IS extremely flammable, but that is the safe part...

It is clear, it is liquid, it is order-less, it takes no prisoners... OK, sorry... does it sound like I am trying to scare you? I am.

...OK, where was I... OK, you put it in the jar, screw it tight, and leave it there for a few days, it can take a while for the solvent to work into the middle of the thin layer of glue.

DO ALL OF THIS OUTDOORS!

Stay way back away, 'upwind', so the air if not blowing from the solvent toward you, but in the other direction, do it in a spray booth (what I use, and still outdoors) or other ventilation if you have such.

DON'T DO IT INDOORS even with ventilation.

You don't want to breath or touch this stuff.

Once the jar is closed and the DCM can is closed back up, then you are cool. But when you open the jar back up again... take all the same precautions.

Interestingly enough, this is the same stuff they put in common paint stripper that you can buy at any hardware store (here in the USA anyway).

I treat this stuff with much more caution than I ever would have known to with paint stripper, but I consider both the same thing now.

Once the DCM reaches the center of the glue layer, then the two glass circles should slide part easy, you can test this with something long, without having to pull it out of the liquid.

You can kind of see this visually also if you have done it before.

Then pull the glass out with some tongs or tweezers or such, put it on some soft towel/PEC pad, etc., and they will slide apart, wash them off.

Screw the lid back on the glass jar with the DCM you used, and leave it outside in some secure place.

There may be some residue left, but it should wipe off or use alcohol.

Read the warnings, this stuff is bad.

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Andrea, great shots. The true BG40 + UG11 reminds me of a UG5 or U330 type photo. Its not but you could probably push the red down and the pattern would be more green like a UG5. So could be an interesting UV+ stack. Eka was using something similar to get a UV brown, that worked well with trees and people.

 

Cadmium, good to know that DCM is best. I also didn't know it was main ingredient in paint striper. I grew up in Canada and ours were mostly Toluene. Which may also work. I used to be able to smell DCM, it does have slight odor. But now that I am older and have used many other solvents, I may have lost that. My favorite solvent was ethyl acetate. Very nice smell and dangerous end product if you let your wine fermentation go too long past the acetic acid (vinegar) stage.

Its great that many controlled solvents I used to use when working at 3M are commonly available in the hardware and grocery store in the US. I recently got a bottle of pure Ammonia, because you always need that and pure bleach.

 

You can add a 1/4 teaspoon of pure bleach to a gallon of water to make it drinkable. But you may need to first sanitize that container were you use 1 teaspoon of pure bleach to a quart first, to clean your surfaces.

 

Also if you do end up using DCM make sure to use a glass box like container. DCM is used in many modelling glues to glue plastic together. If you place it in a disposable plastic container, you will get a mess.

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Let me just say, if anyone has anything they bought on eBay, that they are in any way not happy about, the standard these days is 30 day return with full refund, maybe minus shipping.

Don't let an eBay seller push you around.

Some sellers still use the 15 day time, but that is not standard eBay these days, to be a top notch eBay seller these days you have to offer the 30 day return policy.

Regardless, even if the seller uses 15 days, you can get full refund.

If the seller says anything else, CALL eBay voice, tell them the situation, they will make it happen.

You will get full refund -shipping, for no other reason that "I decided I didn't want the item", and if the item didn't work or was in any way falsely advertised, then you will get a full refund including shipping costs.

Don't keep things from eBay that you are not happy with. Return them, that is BASIC eBay policy, use it.

eBay wants sellers to make customers happy, that means you, so call eBay if any seller doesn't accept a return with full refund within their listed time limit.

Even outside the listed time limit... call eBay, get your money back for something you can use it on that makes you happy.

Making people happy is what makes the world go around.

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If an eBay item doesn't work, send it back. eBay WILL back you up on that.

You do NOT have to keep eBay items that you decide you do not want, you don't need any excuse, call eBay, and send it back.

Get your refund, and use it for something else.

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OK, interesting development :)

 

I was able to de-glue the stack with a 50-50 mixture of pure acetone and isopropyl alcohol, so now I have both glasses on separate 58mm frames.

 

I want to test those to figure it out maybe what they are and what are their characteristics. So, can anyone point out the best or at least easiest way to test them?

 

Thanks!!!

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I am amazed you got that apart so fast using acetone if the glue had a full cure. I have used acetone before, but it took much longer than DMC.

I am skeptical that the alcohol had much to do with it other than raising the depth of your liquid.

I should have mentioned that it can be done with acetone given enough time.

Alcohol is good for removing the glue if it just pre-cured.

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The cheapest way I have used to test filters is to build the following.

1. Buy 1000 line/mm film $7:

https://www.ebay.com/itm/Diffraction-Grating-Roll-Sheet-Linear-1000-lines-mm-Laser-Holographic-Spectrum/280859388704?hash=item4164862b20:g:Po4AAOSwWxNYosl8

 

2. Cut it into an old circular polarizers filter holder. You will need to be able to spin it. This $4 one would work:

 

https://www.ebay.com/itm/58mm-CPL-PL-CIR-Lens-Filter-Circular-Polarizing-for-Digital-Camera-DSLR-SLR-DV/322175249378?hash=item4b03242be2:g:Z5EAAOSwv9hW38xs

 

3. Add to pinhole pro lens. This is best to avoid glass filtration. But could use a high transmission lens like the Nikkor 80mm EL or Kuri 35mm f3.5.

 

4. Get a ExoTerra UVB bulb and place in desk lamp.

 

Image the filter stacked on the film using a full spectrum conversion camera. You will see distinct bands for the mercury lines. You can also image using the sun to get wider spectrum.

This will let you know if you see the 405nm mercury lines or the 708nm IR line to see where the filters cut.

 

This testing looks like this:

 

https://www.ultravioletphotography.com/content/index.php/topic/3213-%d1%81omparison-of-uv-filters-for-lamp-exo-terra-reptile-uvb150/page__view__findpost__p__26720

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Cool test procedure! I will try out something similar later.

 

But here is what I have right now:

 

I have three UV pass filers: the mysterious one from the stack, the cheapo ZWB1 and the cheapo ZWB2. The problem is that, there is NO marks on those ZWBs so I don't know which one is which. So, let's call it UV1 (stack), UV2 (one ZWB) and UV3 (the other ZWB).

I also have two IR cut filters: the amazing S8612 from UVIR and the mysterious one from the stack (let's call it IR1)

 

I just setup and open bottle of sunscream and an a PTFE card that I used for the custom WB.

So, here are some tests with multiple stacks:

 

UV1 + IR1 (https://www.dropbox.com/s/hijvthlhobughhb/DSC01435.ARW?dl=0):

post-268-0-71868700-1567464432.jpg

 

UV1 + S8612 (https://www.dropbox.com/s/5sv26cgynxfzfng/DSC01436.ARW?dl=0):

post-268-0-89345800-1567464452.jpg

 

UV2 + IR1 (https://www.dropbox.com/s/oe2dqrx1eees483/DSC01437.ARW?dl=0):

post-268-0-12655200-1567464471.jpg

 

UV2 + S8612 (https://www.dropbox.com/s/pekrtj6vv6v2oin/DSC01438.ARW?dl=0):

post-268-0-30349400-1567464487.jpg

 

UV3 + IR1 (https://www.dropbox.com/s/sfjp2fvzs6dxrdl/DSC01439.ARW?dl=0):

post-268-0-28627400-1567464506.jpg

 

UV3 + S8612 (https://www.dropbox.com/s/vdegqwwdyytuuu7/DSC01440.ARW?dl=0):

post-268-0-05425700-1567464525.jpg

 

And here are some tests of the UV filters by themselves:

 

UV1 (https://www.dropbox.com/s/w39sthfjmrjzcht/DSC01441.ARW?dl=0):

post-268-0-09144900-1567464543.jpg

 

UV2 (https://www.dropbox.com/s/nna72f03vfaxqkv/DSC01443.ARW?dl=0):

post-268-0-34885400-1567464553.jpg

 

UV3 (https://www.dropbox.com/s/kl536tj214d85km/DSC01442.ARW?dl=0):

post-268-0-22039700-1567464564.jpg

 

So, here are my basic conclusions:

 

1) Obviously the issue with the stack was the IR cut filter. It is clearly not sufficient since it leaks the nasty orange color on the sunscream, but as soon as I use the S8612 instead all problems are solved and I get the beautiful "black sunscream" :D

2) Looks like the UV filter from the stack is very similar to the UV3 filter. They show very similar colors and exposure with the S8612 and by themselves on the tree and sky.

3) Clearly the UV2 filter gives me the best exposure times. Interesting enough, it shows more false colors. Don't know why, but the colors look natural for me.

 

I will give more test and compare those with the U-360 when it arrives! :D

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Bsas, Important question. What are the thinkness of your filters.

By your sunscreen test I would say UV1 is ZWB1 at thicker than 2mm. UV2 is ZWB2 at about 1.8mm. UV3 is ZWB1 at 2mm thickness.

 

That is my guess.

 

Here are some of the spectra I got using the Pinhole pro, Exo Terra UVB bulb method I described to you:

 

BaaderVenus Filter:

post-188-0-39121000-1567472427.jpg

 

ZWB1 1.8mm thick

post-188-0-23393900-1567472576.jpg

 

ZWB2 2mm thick:

post-188-0-43531500-1567472589.jpg

 

GRB3 2mm thick:

post-188-0-30825700-1567472602.jpg

 

UG1 1mm thick:

post-188-0-17861400-1567472654.jpg

 

UG1 2mm thick:

post-188-0-02081500-1567472671.jpg

 

BW486 UV/IR block filter:

post-188-0-22630500-1567472684.jpg

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I think you probably hit the nail in the head!

 

UV1 is about 2.5mm, UV2 is about 1.8mm and UV3 is about 2mm.

 

So, probably UV1 and UV3 are both ZWB1 with different thickness. Very bad since UV1 was sold to me as UG11 :(

 

I am quite happy with the ZWBs, they’re quite cheap and they are usable, but clearly the stack from eBay is not UG11 and BG40. I am actually curious to find out what is the IR1. I know it’s 1.75mm and based on the tests leaks A LOT. Any idea? Supposed to be BG40 but clearly it’s not.

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Very bad since UV1 was sold to me as UG11 :(

I think most of us have gotten bad glass at one point or another. I'm a tutor, so I tell my students, "Think of it as a learning experience!" :wink:

 

I will say that I very much prefer knowing what the exact glasses are that I have because it makes predicting the effect of stacks and things much easier if you have a known spectrum. I rarely use my Chinese filters for that reason -- just don't know what I'm getting out of them.

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I think your ZWB glass is good and most likely equivalent to the Hoya glass, which is a tad faster than the Schott glass.

You will know when your real U360 2mm arribes if it equals the exposure settings of your ZWB2 filter.

In the past some ZWB glass had bubnles in it, wasn't flat, or leaked into the visible spectrum, all bad things not correctable. But your seem good.

 

The thing that is different is mine transmit twice as much IR as I would expect. So you need to use a S8612 to knock them down. The weaker BG38 and BG40 will not cut it.

 

The Chinese BG40, BG38, BG39, still don't seem good. They leak far too much IR.

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ZWB1 is not as efficient ad UG11, it requires more exposure time.

If you mean that Hoya is faster than Schott, not really.

It is true (my opinion) that U-360 is more efficient for UV stacking than UG1, however, when it comes to UG11 and U-340, then UG11 is better, and if you use those at 1mm thick then U-340 is problematic when it comes to leaking visual in the 550nm+ range.

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