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UltravioletPhotography

Getting a filter on a fisheye


ehunt123

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Hi,

 

New here but from the threads that I have read, there's some great discussions and exploration with filters here.

 

I've got a modified 6D that I'd like to shoot with a fisheye lens. My current setup is with a 60D, modified for 720nm, and an 8mm that is great. I'm planning on purchasing either the Canon 8-15mm or Rokinon 12mm.

 

I know Fotoidox makes a kit to fit the 8-15mm, but it uses 145mm squares. That lens also has a tiny slot, like my 17-40mm lens, for gelatins. The Rokinon has no holder. I'm aware of someone cutting out a 39mm lens and sandwiching it in-between the lens and body, but this is a little bothersome.

 

So, I eventually found the clip sensors via Astronomik. In researching around, I also found that there's clones from Optolong and IDAS. A few folks here seem to have the Astronomik filters but have reported that its smaller than the sensor and can wobble around. Is this true?

 

I was also wondering if with the IDAS system or Optolong, has anyone been able to have a piece of optical glass cut to size as a custom filter? IDAS has an innovative system for crops where it puts a similar clip ahead of the mirror and can offer 37mm filters, but only if they're very thin.

 

Astronomik says they can do a custom filter but I've never heard back from my numerous requests. I've also contacted the IDAS distributor and Optolong asking if they'd do a custom one, but have heard nothing back.

 

I've got an Optolong OWB on order (backordered as of today) that I planned to experiment with. The IDAS filters solutions start at $289USD for full-frame and this is a bit pricey to experiment around with, but from looking at multiple shots of their product, it looks to be nothing more than a piece of glass inside an aluminum holder.

 

GIven the lack of success here, I started to wonder if there was anyone else in this situation who had come up with a solution. Each seems to be nothing more than either an injection molded piece of plastic or a CNC'd piece of aluminum that sandwiches itself inside the frame, holding the optical glass in it. I've got access a number of tools, including 3d printers and a nice Tormach CNC mill, and am tempted to replicate the filter and then have a filter cut down to size and grinded/polished to the proper thickness.

 

Any thoughts? Thanks

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Rear-mounting filters is the usual approach for fisheye lenses. My Nikkors come with handy filters designated for a filter slot in the rear. I'm sure one can replace with almost anything there. No idea of what options exist amongst other brands, though.

 

Welcome to UVP, by the way.

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Rear-mounting filters is the usual approach for fisheye lenses. My Nikkors come with handy filters designated for a filter slot in the rear. I'm sure one can replace with almost anything there. No idea of what options exist amongst other brands, though.

 

Welcome to UVP, by the way.

 

Thanks.

 

When investigating, I did notice that Nikon did include that with specific lenses. What an awesome feature. I wish Canon did that and am surprised they didn't copy it.

 

The closest Canon itself does is the "rear gelatin" slot that you'll see on specific lenses, like the 8-15, 11-24:

 

http://petapixel.com/2015/03/01/did-you-know-about-the-rear-gelatin-filter-slot-on-some-wide-angle-lenses/

 

I have one on my 17-40. It's a piece of plastic, or similar material, but it would not work with anything much thicker than a mm.

 

In that fashion, the other idea I had for this would be having a filter cut into a diameter that would fit into the recessed cavity. It'd still need to be secured or require you to always take a lens off with the camera pointed down, so you would not have it drop into the sensor/shutter area. That would mean that you could use the finder window and not have to mess with the mirror-up mode. On my 17-40mm, that "clip" for the gelatins is secured with some really small screws but only to another plastic cover that protects the internals to the lens. It's an option but trying to swap filters by having to remove two tiny screws and deal with trying to not smudge up or damage the lens would not be fun in the field.

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I've mounted Fisheye on my modified Sony NEX-6 with rear filters. I have a noname Chinese copy of the Samyang 8mm (sounds crazy I know) and I love it for IR photos.

Now there is one issue that I had to face when I first did this and namely that any glass element behind the lens is seriously affecting the path of light, which means the flange distance won't be the same. The setup I am using is a mix of a NEX-Canon EF helicoid adapter (I've choosen Canon because of the wide mount) a set of filters that fit inside the Helicoid held in place with a Step Up ring. I have not tried it for UV as a, my fisheye is terrible with UV transition (so far I could try) and I don't have such small UV filters.

 

Finsbury IR Park

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...having a filter cut into a diameter that would fit into the recessed cavity

...trying to swap filters by having to remove two tiny screws and deal with trying to not smudge up or damage the lens would not be fun in the field.

 

No, this would be very messy in the field. You'd probably just have to dedicate the day to using the lens with that filter and do the insertion/removal at home before/after the shoot.

 

It might be possible to......secure the filter with some kind of velcro shenanigans. I have done some crazy things meself with velcro and filters. You would have to get a velcro which is not the strongest kind. And cut very very thin strips to make fittings for the filter and inside the recessed area. I don't see making an entire ring of velcro inside the recessed area as a good idea because it would be difficult to remove the filter from that. Maybe just 3 or 4 tiny velcro dots? However you would probably have to put an entire ring around the filter in order to block non-UV light leaks. Removal might still be a problem. If the velcro is too strong then too much pressure would be put on the filter during removal.

 

Well, it was just a thought. I might try this later myself because I have that shiny mirror 340/10 which I want to set as a rear mount filter to see if that helps cure the reflection problem. I'm not sure it will, but I gotta try.

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...having a filter cut into a diameter that would fit into the recessed cavity

...trying to swap filters by having to remove two tiny screws and deal with trying to not smudge up or damage the lens would not be fun in the field.

 

No, this would be very messy in the field. You'd probably just have to dedicate the day to using the lens with that filter and do the insertion/removal at home before/after the shoot.

 

It might be possible to......secure the filter with some kind of velcro shenanigans. I have done some crazy things meself with velcro and filters. You would have to get a velcro which is not the strongest kind. And cut very very thin strips to make fittings for the filter and inside the recessed area. I don't see making an entire ring of velcro inside the recessed area as a good idea because it would be difficult to remove the filter from that. Maybe just 3 or 4 tiny velcro dots? However you would probably have to put an entire ring around the filter in order to block non-UV light leaks. Removal might still be a problem. If the velcro is too strong then too much pressure would be put on the filter during removal.

 

Well, it was just a thought. I might try this later myself because I have that shiny mirror 340/10 which I want to set as a rear mount filter to see if that helps cure the reflection problem. I'm not sure it will, but I gotta try.

 

I discussed the same with a local friend, who shoots IR, that would like to come up with a solution. I'm paranoid about the same things. Putting something on with a non-mechanical link (adhesive), then going into an entirely different environment (temperature, humidity, etc), you're asking for that lens to pop out at the worst time and possibly do some damage.

 

 

As a more "ready-made" solution, the Nikon lens - F to EOS adapter - camera was suggested. Are there downsides to using a setup like this? My intention was a fisheye, or an entirely manual lens, anyways, so not having the EF chip isn't an issue.

 

What is the 340/10 mirror?

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340/10 = Edmund Optics 340FWHM10 UV-Bandpass Filter.

 

I was looking at that Canon rear filter holder which is quite nifty. Couldn't you replace the existing screws with longer screws and a spacer which would permit insertion/removal of a thicker filter? Would another 2 - 3 mm of filter thickness intrude too far into the mirror box?

 

Any adapter like an F-to-EOS would interfere with the flange focal distance and you would lose infinity focus. How exactly that would play out in a fisheye lens, I'm not entirely sure.

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ehunt123,

 

A filter over the fisheye objective glass could be affixed to the lens hood of the 8-15. You would want to trim off the tabs of the hood, as they cannot be used at 8mm. Just for a trial, you could use a piece of black plastic garbage bag stretched over the lens and secured under the hood ring. :)

 

There are some excellent, I'm told, plastic filters for NIR, starting at 680nm, that will heat deform at 110C. You could create an inexpensive bowl-shaped filter to cover the lens with only the filter stock, a heat gun, an appropriate template, and patience. Then you could affix the filter to the hood ring for easy attachment and removal.

 

Just a thought.

 

Regards,

Reed

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I was looking at that Canon rear filter holder which is quite nifty. Couldn't you replace the existing screws with longer screws and a spacer which would permit insertion/removal of a thicker filter? Would another 2 - 3 mm of filter thickness intrude too far into the mirror box?

 

If it is the same on my 17-40, I took a cut part of a razor blade (0.5mm on my calipers) and that's pushing the fit. Sure, I could 3d print some type of 'replacement' as a prototype and have something better either machined or made, but you're absolutely right on how far it can get into the lens before you might have problems with the mirror, upon going up for a photo, hitting it. I do not know. You also have the issue if the rear element, upon a specific focusing direction, might run into it.

 

From reading about some of the clip filter stuff, there's very little room. I think folks who fit M42-style lenses on to a Canon, it's the same problem.

 

I'd need to get a mirror body/front setup to see if it works. For my 'clip' project, this is probably going to happen, as it'd be the only way (without taking my 6d apart) to test fitment.

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A filter over the fisheye objective glass could be affixed to the lens hood of the 8-15. You would want to trim off the tabs of the hood, as they cannot be used at 8mm. Just for a trial, you could use a piece of black plastic garbage bag stretched over the lens and secured under the hood ring. :)

 

To get it "evenly" so you wouldn't have creases would require some type of professional setup, I'd think. I've done a few thermoforming runs and getting "even heat" is critical. I can't imagine this with something thinner like a gelatin film working without a professional machine that would vacuum to firm so you wouldn't have creases, no?

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Just some updates:

 

My current plan, at the moment, is to experiment using Optolong's clip that's on order (backordered). They're clones of Astronomik's setup, just much cheaper. The vendor, who deals both, said to me that customers like both but Optolong's prices are definitely a selling point. He also indicated that both are nothing but fixtures that hold glass (removable fairly easily) in place. Much of the price for both of them is the optical glass used.

 

Once I get it, I plan to remove the clear filter and have an identical piece of BG3 cut and lapped to swap into there. I've sourced two optical shops that are open to doing square-sized filters and lapping down to 1-2mm, but it might run into the hundreds per filter. If all goes well, which it should, I was going to replicate the size and dimensions of the filter in Fusion 360, and have it 3d printed in nylon by a friend who has a good 3d printer. That way, I'd be able to have multiple filters like ones for the outside of the lens, available.

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ehunt123,

 

Have you looked at matte boxes for 15mm rail systems. The matte boxes often have at least two filter holders. For example 410GE5pEwhL._SX425_.jpg

I have started using the 15mm rail (rod) components for large lenses. Your camera and lens would be supported by the rails and the matte box would be supported independently. Just a thought. The box above is at https://www.amazon.com/FOTGA-holders-Camcorder-Cameras-DSR-PD198p/dp/B00EPDN8F2

 

Regards,

Reed

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enricosavazzi

I don't know if this has been discussed elsewhere, but the Rokinon/Samyang 7.5 mm fisheye for Micro 4/3 is potentially usable for UV imaging. I tested it a couple of years ago by holding a Baader U in front of the lens (which of course causes a bad vignetting), and the images suggested that this lens transmits sufficiently in the 380-400 nm range. I would not know where to look to find these old test images, and likely I discarded them.

 

Also in this case it would be necessary to use a rear-mounted filter, and I don't know how feasible this would be (unless of course the UV-pass filter replaces the built-in UV- and IR-cut camera filter). The 7.5 mm has a small rear element, which means that it illuminates the peripheral areas of the sensor quite obliquely (at least 45 deg, probably more oblique in the corners). Therefore, an interference-coated filter like the Baader U may perform oddly when rear-mounted with this lens, just like it performs oddly when front-mounted on a super-wideangle lens.

 

Unlike many fisheye lenses, the Samyang 7.5 mm is small, lightweight and has a relatively flat front element, which means the glass is not very thick in the center. My tests here, although nothing in UV:

http://savazzi.net/photography/samyang75.html

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In your original post you said;

My current setup is with a 60D, modified for 720nm ...

Does that mean your stock internal filter was replaced with a 720nm longpass filter?

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Enrico, that's a nice review of the Samyang 7.5. I enjoy shooting my converted Lumix GH1 in unfiltered mode for interesting effects which I hope sometimes might fall into the "artistic" category. So that Samyang fisheye is very appealing to me for such work.
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  • 2 weeks later...

ehunt123,

 

Have you looked at matte boxes for 15mm rail systems. The matte boxes often have at least two filter holders.

Regards,

Reed

 

Would that work for a Fisheye w/a 165-180 deg FOV? I've not seen one that does

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In your original post you said;

Does that mean your stock internal filter was replaced with a 720nm longpass filter?

 

Correct. That's been sold now, so I'm left with my 6D that's a full-spectrum.

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This took a bit but I was able to find the mirror-box assembly for a 6D that didn't cost close to retail due to "saltwater damage".

 

I put on a Rokinon fisheye to it, just to see how much distance is between the rear of a lens and everything inside, but without a feeler gauge we're under 2mm by eyeballing it. I've read somewhere that the 6D (now 5d IV) have more room than the previous 5D, but not much to work with.

 

I'm still waiting on my clip-filter so I can prototype but having the ability to play and prototype is quite handy.

 

http://i.imgur.com/VNcRaR3.jpg

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  • 2 weeks later...

Nice find!

 

Saltwater damage? The camera must have fallen overboard? :) Yikes! :blink:

 

I didn't ask when I paid under $40 for the unit, instead of having to pay 2-4x that for a working one. But, yeah, gotta not be a good day for the owner of the equipment. Their loss is my gain.

 

I finally got the filter in today, finally. The Optolong housing is definitely metal. We grabbed a magnet and it stuck, so it is most likely steel. There's no reason (cost, too) to use a 400-series stainless here. The glass is blue, identical to my CW500 glass for regular shots, and 1.0-1.2mm thick. It looks like they've got a jig that, after cutting (EDM or precision laser) or stamping with a die, presses the metal into the shape you see. They have an outside "frame" that sits over the filter, but when inspected under a microscope, you can clearly see adhesives used to keep the piece of glass on the filter.

 

http://i.imgur.com/PjfLy36.png

 

(Can't embed on this forum for some reason)

 

[[Admin Edit: Here is a conversion to JPG.]]

post-4-0-10489900-1477757302.jpg

 

Next step is 3d printing a prototype. I've got a friend with a descent one (50um layers) who suggested Nylon would be good to print with 100% in-fill. Once I can verify a test fits, it'll go forward. There are rumors of vignetting with wide-angles when using Astronomik or Optolong's, but I saw none on a 14mm

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This will be an excellent engineering effort. And very cool that some 3D printing will be involved!

 

Yes, there can be vignetting on "full frame" cameras with some of these filters. But that depends on various factors, of course. The 6D has a smaller sensor doesn't it??

 


Your diagram probably would not load because it is a PNG which are often very large for photo forums to deal with. So the software probably rejected it?

Nope, that was not the reason.

I converted it to a JPG for you and uploaded.

Now I'm thinking maybe you did not click the Image icon on the editor toolbar?

Next time, copy your http string, click the image icon and paste string into the popup box.

Nope that was not it either. What gives?

 

Update: Sorry about all that. It took me a minute to figure out the problem.

As it turns out, this forum software will NOT take PNG images. So they must be converted to JPG for either embedding or uploads.

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  • 2 weeks later...

This will be an excellent engineering effort. And very cool that some 3D printing will be involved!

 

Yes, there can be vignetting on "full frame" cameras with some of these filters. But that depends on various factors, of course. The 6D has a smaller sensor doesn't it??

 

Update: Sorry about all that. It took me a minute to figure out the problem.

As it turns out, this forum software will NOT take PNG images. So they must be converted to JPG for either embedding or uploads.

 

No problem. I'll convert to JPG next time.

 

6D is full frame. I think it borrowed the 5kII housing (5kI is a different size) and the 5kIII also uses this. No word on the brand new 5kIV and I just saw rumors that Canon is gonna produce a 6d vII next year.

 

I had read reports of the early Astronomik filters having some but could never fully confirm. When I started researching this, as of 2015, there were none. I also confirmed this with the vendor who sells both theirs and Optolong. I used a fisheye and 14mm on mine and there is none.

 

As far as my copy, I won't be able to say the same until a good working prototype is made. The other half of the process is the actual glass, which requires specialized tools to cut. There's a local optical vendor who recently quoted me $85-$120 a piece for a 38mm x 24.4mm @ 1.2mm thick (asked about BG3/RG830).

 

My friend with a nice 3D printer and lots of experience did a run w/ABS and Nylon. The walls are so thin (0.6mm), so we're playing around. We're also now experimenting with using tiny tabs to hold the glass in instead of a separate surrogate that would require a tiny amount (syringe) of adhesive like epoxy to hold. Picture is below.

 

I'm now at the stage where I need to decide what to do with it. Is there interest for anyone with a 6D in something like this? I started this to solve a personal problem and as I talked with others, I have a few who would like them. I do not intend to produce a 'product' nor is this a money maker. You'd still need to have an optics shop to lap and cut a piece of glass for it.

 

From the first batches, ABS was fine. It's flexible enough to take a little bend to insert the glass (see below). It would break if given a bit of stress. You don't need anywhere near this to put in or remove, but there's a reason why things this small are produced out of metal.

 

Optolong's filter is steel. I suspect its too thin to be done reliably in Ai (also cost of materials). I'd think a part like this has a custom die that it initially stamps out to shape and later presses using this die or a metal brake. This is pretty specialized machinery that I don't have access to and making small runs would not be cheap ($250+ was a quote I got).

 

3d printing them, well the model you see below uses 15g of filament. Spools are usually sold by the KG and can be $20-$30. Not factoring time/power, that's well under $1 per part. I uploaded the model to Shapeways and, depending on material, it's anywhere from $5+ (basic PLA) to $10 in high-def Acrylate.

 

I'm still a bit away from having something I will produce for my own uses, but doing a small run using a 3d printer isn't impossible.

 

http://i.imgur.com/SvQaPj1.jpg

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We bumped the thickness up to 1mm from 0.6mm and did a test print on a calibrated, mid-tier 3d printer with 1.75mm black abs (heated build chamber). After some filing to clean up where the supports are on the side flanges, it fits into the housing and two lenses went on. It's a little snugger, I suspect due to the 0.4mm increased thickness on the side flanges that "hold" it in. No vignetting, though.

 

I'm still waiting on my local optics shop for a final quote on a piece of glass.

 

http://i.imgur.com/K4OGDr8.jpg

http://i.imgur.com/qtBq4L4.jpg

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