NikonGear'23
Gear Talk => Lens Talk => Topic started by: Kuri on September 13, 2017, 18:59:15
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I often photograph using infrared (and ultraviolet), so I am interested in the filters and possibility of replacing some of the filters in the 8mm filter carousel.
The Nikon 8mm f/2.8 AI Fisheye lens has a built in rear filter carousel containing 5 filters.
L1A - Clear Skylight
Y48 - Medium Yellow
Y42 - Deep Yellow
O56 - Orange
R60 - Red
These tests were shot using a full spectrum DX conversion, so the full circle of this fisheye is cropped by the DX sensor.
These shots are white balanced from RAW in NX-D.
From looking at the 8mm f/2.8 repair manual it doesn't appear that the filter carousel can be removed without taking apart most of the rest of the lens.
Here is what I learned from removing the 'filter cover' (part 40-1):
1) The filters can't be removed by removing the 'filter cover', because there is not enough clearance to lift them out, and also
2) The filters seem to be glued into the 'filter revolver' plate (part 41). Note: The line of residual glue on the 'filter revolver' plate.
To remove and/or replace these filters you would need to dismantle the front end of the lens, focus ring, etc., to get the filter revolver plate removed.
It is unknown to me how easily the filter glass could be removed given the glue used to hold them in place.
The filters are 20mm in diameter, and they look like about 2mm thick.
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thanks for posting this.
I'd love to see larger versions of your photos!
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I have the repair manual, and yes it's a total disassembly as far as I can see,,,
also you would need more or less exactly the right thickness filter or you will loose infinity or focus range.
Filters in front of the camera sensor is preferred with these fishy lenses ;)
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Erik, Thank you. Both Andrea and Bob recommended you as 'the person to ask' about this. I am glad you have the repair manual also.
It looks fairly involved to get access to the filters...
Brent, here is a larger version of the red filter shot. I didn't even focus those shots, so...?
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Sorry not much help.
Focus is quite critical for the 8mm, even the 6mm demands it!
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unfortunate that it is not easier... would be quite nice to change those filters..
interesting shot.. you need a full frame cam! :)
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Erik, You are quite helpful actually. Thanks again.
Yes, those I shot just to see how even filter would white balance. I 'may' have focused it to infinity? But I doubt I focused it.
I don't have a full frame full spectrum converted camera yet, so that is why I used the converted DX, just to see how the existing filters worked in full spectrum.
I will make sure I focus next time. ;-)
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The 8mm f/2.8 lens filter revolver removed.
Filter glass is all 20mm diameter x 1.8mm thick.
Glue holding filters in revolver is relentless. I don't know yet how to remove the filters or loosen the glue. ???
The revolver is NOT easy to access. I advise getting the service manual and digesting it a few days first.
This lens transmits UV very poorly. The front elements are very dark blue in UV, add to that the lesser dark blue of the rear elements and L1A clear filter.
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you did it!... disassembled the lens!?
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Wow, this is a formidable project!!!
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Wow, this is a formidable project!!!
Following with increasing interest ::)
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To the OP: you may try 20mm filters for Microscope collections. I did find there 20mm Pola filters, as well as many more, 30 years(about!) ago, for the same needs. Only the problem there, most of them are 2.5 and more mm thick. You have to spend time try to find ones of 1.6 - 1.8mm thick. If not, you may find square ones, they are about 1.4 mm thick, and cut it out, not a big deal. Good luck, it really worth it! LZ
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Thomas, I make filters, any size, any thickness, so that is no problem, but I am not sure how to remove the glue, without also removing the paint, etc..
One possible idea would be to mount gel filters over some of the colored longpass filters.
For example, mount a Wratten 89B (720nm) or Wratten 87C (850nm) over one of the colored filters. There is enough clearance to do that (I think).
Those glass revolver filters are all just longpass filters and transmit IR, so stacking IR gel filters will cut out the visual and still transmit the IR that the gel filter transmits.
Not sure how that would work optically compared to the visual results using this lens, but a test of this idea would be interesting.
This idea can also leave the clear filter available for visual stock camera shots, and any of the other filters that one might want to use.
I would still like to find a way to remove the glue, but... for now... ?
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Kuri, if you are not particular about this Fisheye Nikkor, there are possible alternatives. Sigma makes circular and rectangular fisheye lenses both for FX and DX, and all have holders on their rear ends for the gelatine filter.
I'm not sure if they offer the image quality in IR to suit your need, though...
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Kuri, somehow I believe you are answering to my post. I do not think to use the gel filter is such a good idea. The gel can't be perfectly flat, to some degree. So it may contact the glass, and those contact points will produce a Fresnel effect, less or more. Yes, glue. It is a problem. I removed it with the knife, with the paint, simultaneously, but did paint the new filters sides to the black deep matte. Never had any reflections! LZ
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You can't add much to the thickness of the filter I think,,, you will loose focus range.
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Thanks Akira, good idea. I will try that sometime too.
Longzoom, Yes, I meant you, not Thomas.
Those are all go points, thank you for your ideas on this.
This is an excellent point about the gel contacting the glass, I will keep an eye on that. It looks like the Wratten gel filters I have lay very flat, and given the 20mm diameters, I am estimating they will stay separated.
I don't see any way to remove these glass filters with a knife, it would most likely result in breaking the filters. The glass is so tightly inserted into the hole that there is no room for even a very thin exacto knife blade.
You have removed these filters from this lens before?
Erik, Good point. I will give it a try and compare focus range. Thank you.
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Kuri, I removed 3 of them thru small hydraulic press, using middle pushers, made of wood, about 19mm and 24mm, from the opposite side. It is very ease, if you know how, (be careful not to deformed the main ring!), or ask experienced personnel. Knife I used after all, to clean the saddle from remains of glue and paint. LZ (BTW, the gel filters will stay flat and firm at the winter, what about +40?)
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Wow !:-) You have removed filters from this lens? In your case, why did you remove them?
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One of them was pola - clear mistake, it covered about 1/3 of the circle, center only. Was usable to some degree, in very rare cases. Second one was 5x gray dark B/W filter, I needed way long exposure, for some color project. The last one was +2 or 3 extra thin diopter lens. With this one I moved closer, with significant loss of border circle, coze I was able to use the center only, about 12mm in diameter, due to its thickness to the borders. But it was not important - I got my art effect, by enlarging the central part of the full circle, B/W film of ISO 16 let me do it. In this last case I should use another fish, 15-16mm with the same effect from the full frame, without heavy cropping, but I had nothing else with me, unfortunately! LZ
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Oh, forgot to mention: if someone, anyway, wants to try the polarizing filter, do not even open any pola unit - there will be only 1-ring piece, turning by gears. You need a regular 2-rings filter from a Microscope collection, extremely delicate, thin and fragile one. I used to turn it by the teeth stick, a lot of try without any visible stable result, as I have already said. But if one is driven by curiosity, why not, really! Good luck! LZ
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i wouldn't even use a polarizer with lens less than 20mm focal length.... even 20mm is uneven.. why would you ever think a polarizer was the way to go with an 8mm fish??
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Thank you, I knew that, believe me, but for reason of curiosity! And hope - the filters are very close to very curveted inner elements - the effect could be drastically differentiated from my own experience. Did not happen, unfortunately. Very interesting to repeat it today, with a new generation of pola filters. I used very old linear ones, who knows... THX! LZ
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i wouldn't even use a polarizer with lens less than 20mm focal length.... even 20mm is uneven.. why would you ever think a polarizer was the way to go with an 8mm fish??
If a PL filter is used within the optical system, the angle of incident of the light can be much more perpendicular to the filter. So, the effect may be more even.
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Exactly, Akira! More than 25 years ago I've parted with this lens, so, can't try a new CPL on it, behavior of such could be completely opposite to the old one I've already tried. Nobody knows, so far. THX! LZ
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Exactly, Akira! More than 25 years ago I've parted with this lens, so, can't try a new CPL on it, behavior of such could be completely opposite to the old one I've already tried. Nobody knows, so far. THX! LZ
LZ, now that there are full frame mirrorless cameras, one could use a PL filter behind the lens using a mount adapter such as this (I purchased one accoding to Klaus' advice). This is a m4/3 version but there is a Sony FE mount version, too:
https://www.bhphotovideo.com/bnh/controller/home?O=email&A=details&Q=&sku=1190856&is=REG
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If a PL filter is used within the optical system, the angle of incident of the light can be much more perpendicular to the filter. So, the effect may be more even.
good point, i failed to take that into consideration... thx.
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Some progress here. Forget about the gel filter idea now. A picture is worth a thousand words:
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you did it!
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LZ, now that there are full frame mirrorless cameras, one could use a PL filter behind the lens using a mount adapter such as this (I purchased one accoding to Klaus' advice). This is a m4/3 version but there is a Sony FE mount version, too:
https://www.bhphotovideo.com/bnh/controller/home?O=email&A=details&Q=&sku=1190856&is=REG
Thank you, very interesting! Slowly-slowly, this way or that, we are moving to unification of all kinds of mounts, I somehow believe. LZ
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Some progress here. Forget about the gel filter idea now. A picture is worth a thousand words:
Hah! Congs! You made my day! How you did it and what you gonna put inside? THX! LZ
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Longzoom, Thanks for your idea about the 'hydroponic press'. I have a pneumatic press, which would not work exactly the same, but decided to use a lower tech method. A rubber mallet.
After spending a lot of time testing the filter adhesive with various solvents, I found nothing that softened the adhesive, which I was surprised about given the list of solvents I tried:
Toluene, Acetone, Methylene Chloride (DMC), Methanol, Lacquer Thinner, etc....
I would really like to know the exact adhesive used for those filters, if anyone knows.
Teflon sheet, with 7/8" hole (slightly larger than filters).
1/2" socket set socket (this fit inside the filter hole, has a flat large surface contact area, almost fills up the hole, but leaves enough edge room for the PEC padding).
Wooden dowel inserted into front of socket (flat back of socket was facing filter).
PEC pad (double folded for cushion, was placed between flat back of socket and filter glass)
Rubber mallet.
The idea of the rubber mallet is a softened strike with a positive drive. PEC pad protects the glass surface from scratching.
Filter was aligned over Teflon hole, and 'WHAM', filter falls right out.
Not guaranteed to work, or to work without breaking your filters, but none of mine broke, cracked, or chipped at all.
At least two of my filters were not subjected to any solvent tests, and they all came out just as easy.
Setup:
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Well done! It is your choice now, what to insert! Keep us informed, please! LZ
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I have an 8mm f/2.8 non-AI that I used on film cameras years ago. I can't use it on FX Nikons unless I have it AI-converted which would likely harm its resale value. (It could be mounted with an adapter on a Canon full-frame digital camera, but I already have a Canon 8-15mm fisheye which is native on that mount and much easier to use.)
Earlier this year, I was considering trying to replace one or more filters on this Nikkor lens (and another), but set that idea aside for the time being after running into mechanical difficulties. Since then Nikon has come out with their own 8-15mm fisheye with half the weight and far less bulk, so I expect to go that route. I should have a copy in my hands shortly. The 8/2.8 is just too heavy and bulky for general use, in contrast to the Canon which I have used while hiking. The new Nikon should be similar to the Canon in usability. If the new lens is suitable then I expect I'll sell the others.
I appreciate the filter information in this thread which completes the answers to questions I had raised in a previous thread (http://nikongear.net/revival/index.php/topic,5267.msg83366.html#msg83366).
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Thanks Longzoom. :-)
In order to use it on a stock camera and to keep the original L1A - Clear Skylight filter for that, I am left with 4 filter holes.
I would definitely populate one with Schott RG850, that leaves me 3 more.
I could put in a BG38 for visual shots, this way giving myself the option of doing Visual/IR composites in Photoshop.
This leaves me 2 more.
RG715 comes to mind, and maybe RG665 or RG695.
Of course one might want to leave the Red or Orange or Yellow in the revolver for doing stronger false color IR, as well as EIR/Aerochrome post processed shot from a yellow minus blue filter.
Ideal, I suppose, one could build an insert contraption, that would allow a single filter to be slid in/out of the space that the revolver was once housed in. That would make it much more versatile,
but perhaps not as quick and convenient.
If someone never needed to use it on a stock camera, but only on a full spectrum conversion, then the L1A - Clear Skylight filter position could be used for another filter.
Oh!! I almost forgot, I would definitely include a U-360 (or UG1) for IR with blue skies. So this drops the number down.
Hard to decide. ::)
Anyone contemplating all of this, just take a look at this diagram first. ;)
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Bill, The diagram makes it look quite complicated, but the filter revolver is removed by unscrewing its pivot screw, which is accessed from the rear of the lens after removing 3 or 4 composite parts.
It is not terribly hard to do, but does require the repair manual if you have never done it.
The rear elements are all removed as one composite part.
The front elements are also removed as one large composite part, only in order to remove 4 screws holding the revolver cover on, which can actually be removed without removing the front if you have a very short screw driver, but is arguably a lot easier if the front is removed, but that is very easy to do, one set screw and then the whole front section screws off.
I put everything in small covered containers, zip lock bags, and plastic film cans (for the screws).
One more important thing to point out about diving into this:
When you take the revolver pivot screw out, there is a ball bearing under the revolver plate, and also 2 small plastic washers stacked under the pivot screw,
these are small, and will be lost if you are not being aware of them. They need to be replaced and aligned in place when reassembling the revolver plate.
One needs to pay attention to those two parts, or they will be lost or not resembled correctly.
Yes, I have seen the new 8-15mm Nikon Fisheye-Zoom.
I don't know yet if it has any hot spot in IR or not. Does anyone know?
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Thanks for the information, Kuri. That's quite a project you're undertaking.
In my case, infrared use of the fisheye is not as important as overall usability. The new fisheye is just another lens when placed in the camera bag, while the 8mm is a monster to carry around and to mount, limiting its practical range of uses.
I actually have a number of fisheyes in several formats, some of which are circular fisheyes, though I haven't tested the circular fisheyes in infrared yet. I also pretty much stick with ~850 or ~1000nm infrared cutoffs rather than all the other variations you've mentioned, so it works well to just mount the lens I'm using on a modified camera that can also be used with other lenses in the same spectral band. We're pursuing somewhat different combinations of spectral ranges, so it makes sense for us to pursue somewhat different equipment choices.
BTW, the Panasonic 8mm full-frame fisheye for Micro Four Thirds does well in ~850nm+ infrared (https://www.photo.net/photo/18138335/1000049rev).
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Thank you Bill. :-)
Longzoom, What adhesive did you use when reinstalling filters in your 8mm revolver plate?
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Very nice work guys! Looking forward to the results ;)
Comforting the rear cell came out in one piece ;)
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Thanks again Erik for your input about all this. Very much appreciated.
Also thanks to Bob Friedman, who has demonstrated so superbly the ability of this lens to do IR. I would not own this lens if not for his artistic examples.
Thank you Longzoom for your hydroponic press idea. Let me know what adhesive you used for remounting these filters.
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I would suggest to use one of the glues that stay somewhat flexible, like the ones for mixed materials, for rubber soles on shoes, since you might want to take it apart again,,, ;)
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Thank you Bill. :-)
Longzoom, What adhesive did you use when reinstalling filters in your 8mm revolver plate?
First off all, I covered the sides of the filters with deep black matte paint - successfully, to prevent possible reflections. Fortunately, filters came back to its cleaned saddles ease, without any efforts. Sorry, I do not remember what was the name of the composite glue I used, it contains of 2 parts, I should mix it together in some certain proportions, wait about 12-15 min before usage. It was completely unnecessary to put it thru the diameter, 3-4 points of that glue was enough to keep the filter deadly cemented to its place where it belongs. BTW, good idea to make the insert contraption! Good luck! LZ
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I would suggest to use one of the glues that stay somewhat flexible, like the ones for mixed materials, for rubber soles on shoes, since you might want to take it apart again,,, ;)
Nice idea, really, for future use! LZ
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How about the UV-cure adhesive (actually kind of plastic) like this (Bondic)?
https://notaglue.com/
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As long as it is not too easy flowing, fluid,,,
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Longzoom, Sounds like some kind of epoxy, given the 2 part mix, which would not need the full circumference, like you said, especially if you painted the filter edges black.
Probably a few points of superglue gel would work, just enough to keep them from falling out.
Sure would be interesting to know the glue they originally used.
Akira, UV cure is what I generally use for laminating (gluing) glass together, like say U-360 glued to S8612.
However the adhesives I use for that are extremely tough, and need to be soaked in solvent for a day to weeks to remove them, depending on the solvent.
With all the solvents I tried, I never 'soaked' the revolver, because I didn't want to remove the painted colored filter labels from the edges of the revolver plate.
I am pretty sure many glues will work for cementing new filters in the hole, but it would be nice to use something that is not so hard to remove.
So far anyway, I am not a glue expert. :-)
But this make me wonder what kind of glue would be good for holding the glass in the holes, but still be easy to remove, even maybe with water, or some solvent that will not damage the paint or labels if soaked for days...
Erik, The repair manual mentions 'binding agents', page 4.
See the section where is says, "...or glass with metal", but it lists, 4 different #'s only... #616, #621, #631, and #634. None of which I have any idea what they are.
Maybe one of those is what was used... but I don't know what those #'s are.
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FWIW, Kuri:
#616: Cemedine Super and Cemedine #1500
#621: Cemedine #1565
#631: Araldite AT-1
#634: Base resin: Araldite AY101, Hardener: Araldite HY951
All adhesive are 2-part mix epoxy. Cemedine is one of the leading adhesive company in Japan. At least Cemedine Super and #1500 seems to be readily available.
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"Superglue"(cyanoacrylate, methacrylate) has outgassing issues. It is not recommended for parts in lenses that will be placed into an air-sealed environment. I have seen the outgassing leave deposits on lens elements.
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The "superglue" is only indicated "For the temporary adhesion in the process" rows. #921 and 922 are the adhesive of such type. "Aron Alpha" is their product name, is very popular here in Japn and, according to wiki, sold as "Krazy Glue" in foreign countries. Other temporary adhesives indicated are shellac (#201), screw lock (#350: kind of locktite) and locktite (#410, yellow, red, purple, blue and orange).
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Akira, Thank you for translating that! That really sheds a lot of light. Sounds like the adhesive is epoxy.
In my understanding, super glue and Krazy Glue are essentially the same thing, just different names.
Pluton, Thanks for the heads up about out-gassing of Supper Glue.
I will stay away from that then.
I wonder if silicon would be OK, easy to separate.
Thank you very much for your input and ideas about this.
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The shape of things to come. Work in progress.
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Looks nice, Kuri!
One coaution: Schott BG38 as well as BG40 glasses are fairly easily deteriorated (supposedly by the moisture). Both of my samples shared the same destiny. :'(
It would be advisable to see to it that BG 38 is glued only lightly so that it can be replaced easily.
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Looks like a very good job! Looking forward to the images ;)
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Thanks Akira, and Erik.
I don't have those glued in yet. I think it was some kind of epoxy, as you translated, but I have not decided what to use.
The glass is cut to be tight, same as the original size, and they pretty much 'snap' into place and stay there, but they might need a bit of a light seal between the glass and the footing.
As far as BG38, I have used BG38 and BG40 forever, and never found any surface problems with those two types of glass myself, in my location.
S8612 (and similarly BG39) are the more prone to surface deterioration.
I recommend polishing those with Cerium Oxide slurry, whenever possible to keep them free of surface problems.
But that needs to be done before deterioration becomes too advanced, otherwise the Cerium Oxide will not work.
Here are the pertinent warnings for those 4 glass types::
BG38 (no warnings)
BG40 [!] Long-term changes in the polished surface are possible under some circumstances.
BG39 [!!] Long-term changes in the polished surface are possible.
S8612 [!!] Protective coatings recommended. Long-term changes in the polished surface are possible.
BG38 is my preferred glass for visual on a full spectrum camera. Baader UV/IR-Cut looks too red to me. BG440 also works well, but S8612 looks too blue to me, and this is after white balancing out of camera.
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Kuri, the environment in which I stored BG 38 and 40 wasn't that humid, but the surfaces of both glasses became "sticky". Apparently the surface was melt with moisture.
FWIW, my Hoya U330 was deteriorated in the same envionment as well. Its surfaces are fogged. My U360, again, stored in the same environment hasn't been deteriorated at all.
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Akira, Yes, U-330 and UG5 are prone to that also, as well as UG11 and U-340. UG1 and U-360 are more stable, and I have not seen issues with those two U-glass types, and those don't have warnings as the others do.
BG38 is the most stable, I have never seen any problems with that type of glass, which I work with on a regular basis, so not sure what is going on with your BG38.
I have seen the 'sticky' thing before, usually with S8612, which should clean off.
My general advice for any surface problem on non coated class is:
1) clean with hydrogen peroxide and/or other cleaner (first), even soak it for however long.
2) then polish with cerium oxide.
That should remove any surface problems that are not eroded into the surface of the glass.
If there is erosion into/below the surface, then that can't be removed, it would need to be resurfaced, which can be almost as expensive as a new filter.
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Kuri, I hadn't used my BG filters for months when I found their surface sticky. And the sticky layers were already too thick to remove. I don't think they could be cleaned anymore. :'(
U330 became foggy just on the surface. It is unusable as optical part, but should be able to use as UV-pass filter for a flash.
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i want one! ;D
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Bob, I know. :-)
Akira, I would try cerium oxide on both, worth a try, if the surface of the glass is not etched/eroded, then the cerium should remove the problem, but it is hard to know until you try it.
Cerium oxide is available on eBay, etc., in powder form, just mix with water like mud. Also available already mixed in bottles.
Get the good stuff, not from China, often they mix zinc with cerium to make it less expensive.
Either pink or white will work the same.
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Bob, I know. :-)
i spend any amount of money that it takes to have one.. well perhaps not.
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Akira, I would try cerium oxide on both, worth a try, if the surface of the glass is not etched/eroded, then the cerium should remove the problem, but it is hard to know until you try it.
Cerium oxide is available on eBay, etc., in powder form, just mix with water like mud. Also available already mixed in bottles.
Get the good stuff, not from China, often they mix zinc with cerium to make it less expensive.
Either pink or white will work the same.
I've had celium oxide (pink powder) to remove the yellow coating from the flash xenon tube. The GB was so deteriorated that I could scratch the sticky thingie off using my fingernail! Oh, well.
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Akira, don't be afraid to try cerium on your 'sticky' filter. :-) It can't make it worse.
Bob, here is what I made:
BG38
RG665
RG715
RG850
U-360
But so far I have no decided how/what exactly to glue them with.
I am still not an expert at dismantling and reassembling that lens. So that is actually the tricky part for me still.
It remains to be seen just how well these filters will work still, infinity focus, etc..
I have you in mind, my interest in this lens originated with your fine IR photos using that lens. You have helped me learn how to use it and process the photos.
From that list of filters, I think I know how you would populate the carousel, all of them except the BG38 which you would probably forgo for the original L1A clear filter instead.
I would not expect you would be interested in the yellow filter.
So:
L1A
RG665
RG715
RG850
U-360
So here are my current ideas on gluing. Let me know any thoughts, ideas, anyone.
Since the glass circles fit so tightly into the carousel holes, instead of gluing the glass onto the metal footing below the glass,
as the original filters we glued, I am instead thinking of only putting some kind of glue around the top, in the crack between the glass and the metal.
This could just be a few drops to hold it in place, or full circumference to also block off any possible light leak that might make it's way through the footing and around the edge of the glass.
Preferably the glue should be non out-gassing, and something that could be removed somewhat easily if the filters needed to be change.
It would be best if the glue is black or non light transmitting.
Something like black silicon, very finely applied around/into the circle crack, comes to mind, perhaps, but I don't know the specifications of that type of glue.
I am sure there is some kind of glue that might work well for all these criteria. Any ideas...let me know.
Am I thinking correctly here?
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In theory, the light-fastness of the edges of the filters in their holes could be tested before returning the wheel back into the lens.
Obviously, the less glue used, the easier an eventual filter removal would be. Two or three spots in the circumference might suffice.
I would look to a very thick paint-like material, like fingernail polish. It dries completely and without subsequent outgassing, is easily dissolved later by common solvents.
I'd stay away from RTV "silicone rubber', as there is no known 'safe to use' material that dissolves or removes it.
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Pluton, Thanks for your ideas and advice.
I was thinking of the silicon because it can usually be removed fairly easily without any solvents.
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Pluton, Thanks for your ideas and advice.
I was thinking of the silicon because it can usually be removed fairly easily without any solvents.
Yes, IF you can physically peel/scrape it off of the work, then you are correct. If it happens to attach with good adhesion to a clean surface, it can be a lot of work to scrape off.
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Bob, here is what I made:
So:
L1A
RG665
RG715
RG850
U-360
- why not U-330 or a 1mm thick UG-1 instead of the U-360
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- why not U-330 or a 1mm thick UG-1 instead of the U-360
Here: http://www.ultravioletphotography.com/content/index.php/topic/2459-the-shape-of-things-to-come/ (http://www.ultravioletphotography.com/content/index.php/topic/2459-the-shape-of-things-to-come/), much nicer blue sky for dual band IR
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Here: http://www.ultravioletphotography.com/content/index.php/topic/2459-the-shape-of-things-to-come/ (http://www.ultravioletphotography.com/content/index.php/topic/2459-the-shape-of-things-to-come/), much nicer blue sky for dual band IR
the U-330 looks like it would be better based on the spectrum, greater sensitivity, etc.... and i have used UG-1 extensively.
(http://www.hoyaoptics.com/img/color_filter/u330_lg.gif)
(http://www.pbase.com/bobfriedman/image/141132783/original.jpg)
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Guess it is less the graphs, but the visible outcome which triggered the decision...
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Guess it is less the graphs, but the visible outcome which triggered the decision...
i guess the U-330 is a UG-5
(http://www.pbase.com/bobfriedman/image/141132929/original.jpg)