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Best way to construct a filter


motorhead9999

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motorhead9999

Hello all,

 

I've been following the threads here on the aerochrome filter options and am starting to get what I need to make one. So the idea is to get the Roscoe E-Colour+ Scuba blue filter and a piece of KGS3 IR glass and put them into a 52mm filter. My question is: What's the best way to actually physically construct the filter so that it'll last? The glass is 1.75mm thick. My thought was to get a piece of clear optical glass and sandwich the scuba blue filter between that and the KGS3 glass. Someone on another forum suggested I disassemble a circular polarizer, and put the gel filter in the rotating portion there, with the glass in the screw in portion.

 

Anybody have a good or better suggestion?

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eye4invisible

It depends on the thickness of the filters you plan to sandwich together, along with how "deep" the 52mm filter's inner thread is.

 

I've purchased various brands of cheap clear UV filters, just to re-use the filter ring to mount different types of glass. Most UV filters are "slim" ones, so you don't have a lot of space to fit in multiple layers of glass/gell under the retaining ring. And even if you do, that leaves no inner thread left to attach anything else in front (may not be important to you, but something to think about)..

 

For example, most of my clear UV filter rings have an inner depth of 4.5mm to 5mm. The Hrommagicus filter that I got from uviroptics on ebay has a depth of 7.5mm (with some inner threading still available).

 

You may have to consider stacking 2x 52mm filters, and grind/dremel out the inner flange of the top ring to give you more space.

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motorhead9999

It depends on the thickness of the filters you plan to sandwich together, along with how "deep" the 52mm filter's inner thread is.

 

I've purchased various brands of cheap clear UV filters, just to re-use the filter ring to mount different types of glass. Most UV filters are "slim" ones, so you don't have a lot of space to fit in multiple layers of glass/gell under the retaining ring. And even if you do, that leaves no inner thread left to attach anything else in front (may not be important to you, but something to think about)..

 

For example, most of my clear UV filter rings have an inner depth of 4.5mm to 5mm. The Hrommagicus filter that I got from uviroptics on ebay has a depth of 7.5mm (with some inner threading still available).

 

You may have to consider stacking 2x 52mm filters, and grind/dremel out the inner flange of the top ring to give you more space.

 

Thanks.

 

At least for test purposes, I have a deep threaded 52mm filter I can use to try this out on. So here's another question: Basically, the sandwich will consist of the sheet of Scuba Blue between a piece of the KG3 (or Roscoe 8000) glass, and another piece of clear glass (probably scavenged from one of those standard UV protection filters we all get). Is there a particular order the sandwich should be? Should the IR blocking glass be closer to the lens, or should it be the front piece, with the clear UV glass being closer to the lens?

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For best performance and longevity, cementing the components is recommended. You can purchase 0.5mm thick fused silica or quartz in 50.8mm diameter online. If you clad both sides of your filter with this using a good cement from Norland, you won't need to worry about oxidation of the ionic glass. Then cement together the final filter pieces.

 

Cementing filters takes practice. Have some acetone handy to undo mistakes immediately.

 

Good luck.

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If you stack two optical components in close contact without cementing them, you are likely to get an interference phenomenon called Newton's rings, resulting in light and dark banding. If you are not cementing them together, you should ensure that they don't actually come in contact with each other. I know this is true for two glass surfaces, and I assume it would be true for glass/plastic.
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dabateman

The filter combination you want is easier than most glass filter stacks.

The Lee 729 filter is polyester and acts as a separator.

The order I use is glass (what ever you want as long as not optically garbage). The lee 729 gel, then finally KG3 2mm thick.

I like this order as junk comes from outside, rarely from the lens itself. So dirt an finger prints will end up on the easily replaced glass, not the others.

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When you say "KGS3" do you mean KG3?

KG3 1.75mm is going to be slightly different, 2mm is what I use.

If you simply put the KG3 in one filter ring, and the polyester film in a separate ring, stack them, it works just as well as gluing everything together, and also makes the KG3 more versatile to stack with other filters,

because many filters can be altered by stacking with KG3. The polyester filter is cheap and expendable, a standard small sheet of it will last you forever (Lee #729 is about $7+).

If you want to glue everything together in one stack, then you need to use glue that will work with polyester, but not the the one that they make specially for polyester.

Polyester film filters are made of clear polyester film that is dyed on the surface. The special polyester glue will smear the surface dye and leave a somewhat uneven color.

Call them, they will tell you which glues to use instead. These glues are UV cured glues, you will need a UV light source, even a Convoy S2+ for curing the glue, there is info about that at Norland.

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motorhead9999

When you say "KGS3" do you mean KG3?

KG3 1.75mm is going to be slightly different, 2mm is what I use.

If you simply put the KG3 in one filter ring, and the polyester film in a separate ring, stack them, it works just as well as gluing everything together, and also makes the KG3 more versatile to stack with other filters,

because many filters can be altered by stacking with KG3. The polyester filter is cheap and expendable, a standard small sheet of it will last you forever (Lee #729 is about $7+).

If you want to glue everything together in one stack, then you need to use glue that will work with polyester, but not the the one that they make specially for polyester.

Polyester film filters are made of clear polyester film that is dyed on the surface. The special polyester glue will smear the surface dye and leave a somewhat uneven color.

Call them, they will tell you which glues to use instead. These glues are UV cured glues, you will need a UV light source, even a Convoy S2+ for curing the glue, there is info about that at Norland.

 

Sorry about that...KGS is an acronym I use a lot of at work, so it's habit. And to further confuse things, I actually did not buy KG3 glass. I bought Dichroic Filter Rosco Permacolor #8000 IR/UV Filter, which I saw mentioned on David Twede's blog (and looking back now, probably makes me wish I read his comments section, as he talks about wide angles being an issue with that glass...oh well.). Meh...after how much I've sunk into IR modification and cameras and lenses, what's a few more dollars?

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KG3 is very handy for stacking with many other filters, that is why I prefer using separate filters most of the time. You don't need to clad the polyester, not worth it. The KG3, I haven't used it long enough to know, but I rather doubt it would need cladding either.
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Stacking different glass types with air gaps between them does not work "just as well as gluing everything together". With each air gap you are introducing two air/glass interfaces. Each of these represent an approximate 4% loss of UV transmission. Just as we wish to use few groups and few lens elements in our UV lenses in order to lose less transmission of the UV, we should do the same with our filters. Another significant reason to cement filters is the oxidation of many ionic glass types. Some glass oxidizes very quickly. The Schott filter calculator provides the rate of oxidation of the glass, by type.

 

If anyone shows you the output of the Schott Calculator for a combination of filters, remember that is only true for a "Calculation of cemented glass filter combination (up to 5 types)" as stated by Schott on the combi input page.

 

Vignetting is another reason to avoid stacking filters, according to some photographers.

 

A very significant aspect of using stacked filters is cleanliness. A cemented filter with three layers of glass has two surfaces exposed to dust or fingerprints. Stack three filters and you have six surfaces that need to be cleaned prior to each use. How many of us are going to take the time to do all that cleaning?

 

If you leave your filter stack together between uses, you invite condensation between the filters. This is not an issue with a cemented filter.

 

Thanks.

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eye4invisible

Just as we wish to use few groups and few lens elements in our UV lenses in order to lose less transmission of the UV, we should do the same with our filters.

Some great points. Another reason to avoid air gaps would be to reduce the amount of internal reflections between each surface.

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eye4invisible

If you stack two optical components in close contact without cementing them, you are likely to get an interference phenomenon called Newton's rings, resulting in light and dark banding.

Does Newton's rings happen between 2 flat surfaces? I was under the impression this phenomenon only happens between a curved surface and a touching flat one.

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Andy Perrin
Other Andy- that’s correct but as a practical matter, the “flat” filter surfaces are not really flat at the nanoscale. Remember, the interference becomes an issue on the scale of the wavelength, so in UV that will be a few hundred nanometers separation.
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OK, not just as well, but darn close, hard to tell. There are improvements when gluing, but I shoot stacks all the time, and they work great, look just as good to me.

There are benefits of both methods, and glued stacks will cost more.

 

For example, let's say I wanted to shoot reflected UV, UV+Blue+Green ('bee vision'), some other UV stacks... etc., then I would just need ONE S8612 (unless I want to change the S8612 thickness).

The same goes with let's say various dual band and/or false color IR Longpass filters stacked with KG3, then I would only need ONE KG3.

Having just ONE S8612 and just ONE KG3, gives me a lot of versatility to explore other combinations.

Gluing will cost a lot more, mostly because you would need more than one of each S8612, or KG3 (in those examples), and you can't explore or test anything outside that box.

It is always handy to have a separate S8612 or KG3 around that isn't glued and dedicated to some other filter.

Personally, I would start out that way, and if you find a stack you like so much, then get a glued version.

Using separate filters not only permits you to use the same filter in different stacks, it also permits you to change the formulas, using multiple thicknesses.

For example, let's say I have several thicknesses of U-360, and/or several thickness of S8612, this permits me to mix them in many ways to adjust various factors and change the transmission recipe and resulting look.

If you glue, then you will have improved transmission, but I see great performance with two separate filters stacked.

So do what you like, if you want to save money and have more versatility, then separate filters are a great way to go.

Or, if you wish, you can have glued stacks. Either way.

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For example, I am pretty sure that ALL of the shots I posted in the topic below are using simple two filter stacks, except the La La U.

https://www.ultravioletphotography.com/content/index.php/topic/3859-common-lawn-flowers/page__fromsearch__1

There are two versions of the U-340 8mm stack, one glued, one air gaped, using UV-Nikkor, can't tell the difference between them.

Anyway, have no fear of using two filter stacks they work great.

You want glued? I do that, I got glue. You want separate filters, got them, what I use mostly, because I am always changing things around to see what might happen.

Either way, you gotta start with separate filters, even if you glue them.

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The matter of cost savings by buying filter components rather than a UV filter is only true if you wish to mix components. Our more experienced floral photographers on the forum tend to use one filter for all their floral shots. This way they have consistency over the years (decades? ).

 

If however, you desire a UV bandpass filter, you may find yourself creating it from components or buying a finished filter. If you wish to build your own filter, then it is most practical, and yields the best performance, to cement it for all the reasons stated above.

 

However, do not buy components thinking you are saving money over purchasing an established UV bandpass filter, you are not. Buying on ebay will have you paying, from one supplier, $89.95 for an S8612 of 1.5mm thickness in a 52mm filter ring. The same seller markets a UG11 of 2.0mm thickness in a 52mm filter ring for $185.95. Just the two pieces of glass will cost you $275.90 plus shipping. Then you need to purchase the correct cement, a 52mm ring deep enough for the finished filter, tools (UV light, spanner, etc.), and disposable supplies, before you build your filter.

 

So, you can spend approximately $300.00 on ebay to build a filter from components, or you can pay $269.95 (plus shipping) to purchase an absorbent, or dichroic/absorbent, filter, with useful accessories, from a provider of tested UV bandpass filters.

 

Cadmium's statement "Either way, you gotta start with separate filters, even if you glue them." is not true. Look at the list of UV bandpass filter makers - https://www.ultravio...vvisir-filters/ . Many of these filters have been rigorously tested by Andrea.

 

Just an fyi.

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Our more experienced floral photographers on the forum tend to use one filter for all their floral shots. This way they have consistency over the years (decades? ).

 

I do not agree with the conclusions in your post, Reed.

 

 

If you are curious, as I am, and might want the possibility to expand and experiment beyond the simple pure UV-imaging, separate filters are sometimes the only way to go.

 

There are a few filters that work well as base filters for stacks.

If you get one S8612, 2mm that can be combined with very many other filters for interesting results.

The filters to use together with the S8612 can be purchased over a long time. It is very true that that filter's glass is sensitive to degradation over time, but with proper care it can get a long life.

I bought mine three years ago and it is still pristine. By checking and cleaning it from time to time it has been kept fine.

 

Even if our most experienced photographers seams to mostly use one filter for documenting floral UV-signatures, that does not mean that other filter combinations are uninteresting.

You can find very interesting patterns, with other filter combinations, that are hidden in the grey or black in typical Baader U image.

 

I am not that experienced yet and often find new, interesting details with different filters with different motives and characteristics of light sources.

Normally I'm going through at least 10 different filter combinations when exploring new flowers.

It is quite often that the most interesting images are not from pure UV in Baader U-style.

 

To be able to do that I must use separate filters as many of the combinations are not available as cemented stacks.

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Our more experienced floral photographers on the forum tend to use one filter for all their floral shots.

This way they have consistency over the years (decades? ).

 

Actually, this is almost always true for me. I almost always use the BaaderU for documentary UV floral signatures. It is fast and sharp.

 

Of course, I do also use other filters for comparative purposes. And I make use of *all* the other filters for photographing other subjects. I usually would not use the BaaderU for wide angle landscapy stuff these days. But everybody has a different take on what filter to use where.

 

Reminder: make sure you know what happens when you stack.

Air gaps: how might this affect transmission.

No air gaps: possible Newton rings.

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Ulf,

 

I do, and did, not deny the usefulness of mixing and matching different filter types. I, like you, have often tried different combinations of filter elements. And I have had dichroic filters made in batches, hoping to eek out just the transmission curve that I wanted. So, you needn't question my curiosity regarding the subject.

 

You said "
I do not agree with the conclusions in your post, Reed."

 

Which conclusions are those? My conclusions were based upon physical facts, not anecdotal evidence.

 

1/ Will not 6 surfaces usually take longer to clean than 2 surfaces of the same size?

 

2/ Is the Schott Calculator not designed for
"Calculation of cemented glass filter combination(s)"?

 

3/ Is Vignetting not sometimes a problem arising from stacking filters?

 

4/ Does not leaving stacks together invite condensation between the filters?

 

5/ Don't we generally avoid a large number of air/glass interfaces in our lenses? Why then introduce them in our filters?

 

6/ Is $300.00 more than $269.95?

 

and so on.

 

The title of this thread is "Best way to construct a filter". I answered this question. I did not address the business of playing with different filter glass, I simply answered the question the OP posed.

 

So, Ulf, what conclusions of mine do you disagree with?

 

Warm regards,

Reed
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3/ Is Vignetting not sometimes a problem arising from stacking filters?

 

Sometimes vignetting is a problem, esp on wide angle lenses. Depends on the thickness/thinness of mounting rings and whether filter mount is in front or in rear. But you can get vignetting from almost any front mounted filter regardless of purpose, whether stacked or not.

You get vignetting anyway from the lens itself.

 

4/ Does not leaving stacks together invite condensation between the filters?

 

Most of the stacking we do here is with separate filters. So I always just unstack filters before storage.

Stacked, cemented filters don't have condensation problems.

 

5/ Don't we generally avoid a large number of air/glass interfaces in our lenses? Why then introduce them in our filters?

 

The question I suppose is what constitutes "a large number" of air/glass interfaces in lenses?

My big old Nikkor 24-70 AFS had 11 groups !!!

 

As for filters, much of the fluorescent and multispectral photography practiced by members here makes use of filter stacks because no manufactured ionic or dichroic filter is available. Not referring to UV-pass filtration with this remark, of course.

 


 

We have been over all this many times before. I've written summaries in the Filter Sticky. So again, there can be some possible problems with air-gapped stacked filters. Some of the following problems I've also seen with cladded filters or dichroic filters.

  • Possible reflection problems might happen with air-gapped stacks, but you can also get that with dichroic filters because of the mirrored shiny surface. When it happens with either type of filtration, you just deal - change angle of shooting, angle of illumination, etc.

  • The minor transmission loss (requiring longer exposures) with air-gapped stacked filters is usually not so much that it makes the photography difficult. Some stacks are faster than the KUV for example. Trans loss could play a larger role when shooting closer to, say, 320 nm. But around 365 nm, you don't see more than 1/2-1 stop loss in some, not all, UV-pass stacks, for example.

  • Sharpness loss. You won't notice it much because detail sharpening during conversion can restore the illusion (which is all "sharpness" is anyway.) Everyone will *kindly* note that I am going to totally avoid a deep discussion of sharpness here. Not nearly enough years to fully discuss Airy disks, distance from photo, detail and texture, edge acutance, effects from diffraction and so on, ad infinitum.

 

A lot of this is hairsplitting. Just go make some nice photographs.

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motorhead9999

Just as the innocent bystander who started this, as of this time, I was really just trying to get a handle on getting started. I'm still testing out the aerochrome examples I've found online out, so once I settle that and am happy with the results, then maybe I'll start considering cementing. Right now I just need to get an image that (roughly) works! I have rolls of the 729, and I have some Roscoe 8000 dichroic glass on order. Once that comes in (hopefully end of this week or monday), I can do a full test. I (hopefully) should also have my new full spectrum S1R delivered by then too.

 

One other question: Is there any sort of gel or polyester filter that does the same as the KGS3 or Roscoe 8000 IR? I've used them for my fisheye and ultra-wide lenses in the past, but haven't tried any sort of IR cutting material.

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Andy Perrin
Just as the innocent bystander who started this, as of this time, I was really just trying to get a handle on getting started.

Hahahaha, welcome to UVP! :grin: I hope the discussion was at least informative.

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motorhead9999

Hahahaha, welcome to UVP! :grin: I hope the discussion was at least informative.

 

It certainly has. Makes me look forward to the replies I get when I post the inevitable "But I did what you did and my images didn't come out the same" thread ;-)

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Yep, we all do get intense sometimes. But that is only because we love this stuff and really enjoy talking about it. :lol:

 

Mike, I am *really* looking forward to seeing photos from your new full spectrum S1R. That is my next conversion if ever I can get some time. I've been sidetracked for the last 6 months by getting our new house set up. That has included far too many distractions such as roof repairs, gutters and drainage installation, major landscape and garden renewal and endless unpacking.

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