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UltravioletPhotography

Filter Transmission Charts #2


Andrea B.

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I've been playing with the Schott filter program so that I can create a new, well-organized filter transmission reference. We've collected many charts from around the web and from various posts with charts made by member Cadmium (who is an expert at the Schott filter program), but the collection is incomplete. So I'm starting over in what I hope is an organized fashion.

 

Here's the old link. Filter Transmission Charts

 

This Trial Topic will provide me with a place to determine sizing and placement and index creation. Please be aware that this topic might eventually disappear. So while comments are welcome here, they might eventually disappear.

 

The initial effort will be for Schott filter glass. Then I will figure out with some help how to import some Hoya data.

 

YOUR INPUT NEEDED. B) What do you want/need to see here?


 

 

INDEX

 

 

Schott UV-Pass: UG1, UG2A, UG5, UG11

These charts show whole-number thicknesses. From them it would be easy to estimate thicknesses like 1.5 or 2.5.

 

UV-Pass UG1 1.0, 2.0, 3.0: linear diabatic

UV-Pass UG2A 1.0, 2.0, 3.0: linear diabatic

UV-Pass UG5 1.0, 2.0, 3.0: linear diabatic

UV-Pass UG11 1.0, 2.0, 3.0: linear diabatic

 

UV-Pass Comparison @ 1.0 mm: linear, diabatic

UV-Pass Comparison @ 1.5 mm: linear, diabatic

UV-Pass Comparison @ 2.0 mm: linear, diabatic

 

 

Schott IR-Block: BG38, BG39, BG40, S8612

I've tried to list the most common thicknesses used for IR-blockers. I can't imagine that one needs to go past 2.0 mm but 2.5mm and 3.0mm are shown in the individual charts.

 

IR-Block BG38 1.0, 1.5, 2.0, 2.5, 3.0 mm: linear, diabatic

IR-Block BG39 1.0, 1.5, 2.0, 2.5, 3.0 mm: linear, diabatic

IR-Block BG40 1.0, 1.5, 2.0, 2.5, 3.0 mm: linear, diabatic

IR-Block S8612 1.0, 1.5, 2.0, 2.5, 3.0 mm: linear, diabatic

 

IR-Block Comparison @ 1.0 mm: linear, diabatic

IR-Block Comparison @ 1.5 mm: linear, diabatic

IR-Block Comparison @ 2.0 mm: linear, diabatic

IR-Block Comparison @ 2.5 mm: linear, diabatic

 

 

Schott UV-Pass + IR-Block Stacks:

yikes - there are a LOT of combos possible. I'm not sure which ones to omit.

Possible combos: 4 UG filter types * 3 UG thicknesses * 4 IR-blocks * 3 IR-block thicknesses = 144

Leaving out 2.5 mm IR-block.

 

16 separate plots for UG1. well geez.

 

Only one done so far.

Link UG1 * 1.0 + S8612 * 1.0, 1.5, 2.0

 

UG1 * 1.0 + BG38

UG1 * 1.0 + BG39

UG1 * 1.0 + BG40

 

UG1 * 2.0 + S8612

UG1 * 2.0 + BG38

UG1 * 2.0 + BG39

UG1 * 2.0 + BG40

 

Maybe leave out the 3.0mm UG thicknesses?

UG1 * 3.0 + S8612

UG1 * 3.0 + BG38

UG1 * 3.0 + BG39

UG1 * 3.0 + BG40

 

UG2A

UG5

UG11

 

Slide from talk:

diabatic.jpg

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Schott UV-Pass Comparison: UG1, UG2A, UG5, UG11 @ 1.0 mm

 

Peaks

  • UG1: 360 nm
  • UG2A: 365 nm
  • UG5: 340 nm
  • UG11: 330 nm

 

UvPass_TDiabatic_1.0mm.jpg

 

UvPass_TLinear_1.0mm.jpg

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Schott UV-Pass Comparison: UG1, UG2A, UG5, UG11 @ 1.5 mm

 

Peaks

  • UG1: 360 nm
  • UG2A: 365 nm
  • UG5: 340 nm
  • UG11: 330 nm

UvPass_TDiabatic_1.5mm.jpg

 

UvPass_TLinear_1.5mm.jpg

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Schott UV-Pass Comparison: UG1, UG2A, UG5, UG11 @ 2.0 mm

 

Peaks

  • UG1: 360 nm
  • UG2A: 365 nm
  • UG5: 340 nm
  • UG11: 330 nm

 

UvPass_TDiabatic_2.0mm.jpg

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Schott IR-Block Comparison: BG38, BG39, BG40, S8612 @ 1.0 mm

 

IrBlockTDiabatic1.0mm.jpg

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Schott IR-Block Comparison: BG38, BG39, BG40, S8612 @ 1.5 mm

 

IrBlockTDiabatic1.5mm.jpg

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Schott IR-Block Comparison: BG38, BG39, BG40, S8612 @ 2.0 mm

 

IrBlockTDiabatic2.0mm.jpg

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Schott IR-Block Comparison: BG38, BG39, BG40, S8612 @ 2.5 mm
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Schott UV-Pass + IR-Block: UG1 * 1.0 + S8612 * 1.0, 1.5, 2.0

 

 

 

 

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2017 version does T diabatic as well as the Ti diabatic that you are showing. 2012 version doesn't do the T diabatic combined graphs, only Ti combined diabatic and T individual graphs.
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Andrea,

Instead of running all combos. Maybe best to either show and compare what is commonly available or what would be needed to match a common blocker.

The BG38 comes at 4mm, that is what I always saw as a microscope filter. I have know Idea how one cuts a filter thickness down. So listing what are easily available may be best.

What I have seen common is S8612 2mm, BG40 2mm, and Bg38 4mm. However Cadmium would be a much better reference, for what are stock thickness and most common ordered thickness.

Also a word of warning, the cheap ebay versions of the more expensive omega filters will not have the same expected curves. My recent 370bp15, filter indicated to have Od4, average od6 ir blocking, looks red when held up to a light and leaks lots of ir. I would say lets at least 10% through. I think it may still be a 370nm filter though, just needs to be stacked with the Baader venus to be useful. You get what you pay for, I guess.

 

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Andy Perrin
This thread is for filter glass not dichroic filters, I assume. Omega filters are mostly dichroic. That said, Omega’s stuff is all high quality and i have never had leakage from one of their filters unless I was pushing it somehow. What is a “cheap ebay version” of an Omega filter? Is it actually Omega?
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Editor's Note: I wanted to highlight some info here so the bolding is mine. It is very interesting stuff to learn! Thanks, Cadmium.


 

Filter glass comes in two varieties, 165mm x 165mm x 4mm thick sheets, and blocks. Blocks require a 'slicer', which is very expensive, however you can cut thicker than 4mm thick slices from a block with a slicer.

 

4mm thick sheets are 'flat lapped' to reduce them down to the thickness desired. So for example,. if you want 1mm thick glass, you flat lap 3mm 'down the drain', so to speak.

 

Thus the price for 1mm is the price for 4mm + the expense of removing the excess material. So in actuality, it cost more to make 1mm than it does to make 2mm, etc.

 

4mm thick BG38 may be common for microscope filters, but 4mm is not common for camera filters. I think most common camera filters are between 2mm and 2.5mm.

Filters you find in scientific places are generally not geared toward photography, and are more commonly 2.5mm or 3mm or more thick.

 

Some filter transmission standards are associated with certain thicknesses. For example, Hoya filters are standard transmission at 2.5mm thick. Schott filters are not all the same thickness/transmission standard,

but for example Schott longpass filters are standard transmission at 3mm thick, and another example, Schott U filters are standard transmission at 1mm thick.

However, in most cased we don't use those filters in those thicknesses.

 

When I say 'standard transmission' (a term I just now made up), I mean the thickness at which they show in their catalogue and data sheets, and which they refer to for their 50%, peak T, etc..

If you want to know more, take a look at their catalogue.

 

When it comes to UV stacking, or any other kind of stacking, we make the thicknesses that we want, so a paired stack will be optimized or adjusted in whatever preferred aspects we want.

So individual thicknesses become much more critical in a paired stack.

A little change in the thickness of one or the other or both stacked filters will change quite a few aspects of the mix.

 

Generally however, anything thicker than 2mm or 2.5mm is unusual for photography use, and even thinner than 2mm is more the normal for individual layers in a stack.

For example, U-340 4mm is available, but highly unusual to use; S8612 3.5mm thick is available but quite an extreme thickness for any BG filter, and would only be used in extreme testing situations.

In short, thickness is quite important, don't just leap out and buy any thickness of a filter, because it will change results quite a bit, used alone or stacked.

 

The most common thicknesses used in photography would be 1mm to 2.5mm thick, but this is a huge generalization, you need to know or ask what you are doing first.

I do this, and think about this stuff all the time, so that is what I am here for, to be asked.

 

I would stay away from microscope filters, they tend to be thicker than what we would want to employ for cameras, even singularly, but certainly in a stack.

Believe me, I have been there, done that... ;)

They may be fun to experiment with if found cheap, but you will not be optimizing anything using those, and often they are sold off because they are already oxidized, and often too deeply to be refurbished.

Not worth the trouble.

 

As far as Omega, they are a fine company, like Andy says, I don't think there are any Omega offerings that are not made BY Omega, however many of the items Omega sells on eBay are surplus and/or rejects,

which can mean a number of things... Out of band data for some of these needs to be checked on before buying, regardless of the listing info, because sometimes listings are copied/pasted/edited...

 

I have had a few Omega BP filters that leaked in higher wavelengths, such as you have noted, but not many, almost all the ones I have ever purchased have quite strong out of band OD.

Omega is very good about returns and refunds if you get something that isn't right, and I doubt they have any time limit about that sort of thing either, so if you have any problems, just message them, they are great people.

Some of their filters are 'roving' around on the surface of Mars... :)

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Dabateman: You get what you pay for, I guess.

 

You most certainly do when it comes to the fake filters sold on Ebay by some vendors! Be very careful! I've said before and will say again that there is no cheap way to do good UV photography. You have to spend something!

 


 

I am not yet attempting to collect new charts for manufactured filters from Baader or Omega or other places. We already have a few of those manufacturers' charts. And of course you can always find such charts on the manufacturers' websites.

 

This initial chart creation effort is only for filter glass from Schott and eventually from Hoya.

 


 

Cadimium: 2017 version does T diabatic as well as the Ti diabatic that you are showing. 2012 version doesn't do the T diabatic combined graphs, only Ti combined diabatic and T individual graphs.

 

Thanks, Steve!!!

I have the 2015 program and the 2017 program. This initial effort was simply to learn how to use the programs and figure out their messy edits because, as I'm sure you know, the tutorial tells you nothing about how to change ranges and so forth! And the programs are locked against other changes we might want to make.

 

The 2015 version does both T & Ti linear & diabatic for single filters. And it does Ti linear & diabatic for combos, but no T.

 


 

Dmitry: There are wrong graphs - one for BG and other for UG

 

Thanks for catching that! I removed it and will replace later with the correct chart.

 

 


 

Steve, thanks for the interesting info about filter glass thicknesses! B)

 

 

.

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I hate that Schott program for not letting me do what I want !! I think I'll just transfer the data into a spreadsheet and make my own charts. Growl, grrrrrr........
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Andy Perrin

Andrea, doing T when you have more than one piece of glass is a fairly involved mathematical endeavor (I know, cause I wrote a MATLAB code to do it!). The issue is that when you have multiple glass layers you have to account for the (infinite) reflections between each layer. This can be done via a nifty trick called the Matrix Method, but you do need to know some linear algebra. This version even includes surface roughness effects but the basic method works for smooth surfaces also:

https://www.osapubli...i=ao-34-10-1678

 

Schott has good reasons for not including this feature in their program. It adds quite a bit of additional complexity if you want to do it properly.

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