Is this an acceptable filter for eclipse?

Discussion in 'Beginner Questions' started by frank_thomas|3, Aug 15, 2017.

  1. I recently purchased an EOS 80D and have bought a Polaroid
    HD Multi-Coated Variable Range Neutral Density filter. If I set it at 16 stops, is this filter suitable to protect the camera? I will only use the LCD viewer.

    The more I read about this the more nervous I get about damaging the camera.

    Thanks for any input.
     
  2. No! The ONLY safe filter will be to use one made for solar viewing, either home-made from proper materials, or store-bought. I just finished fabricating six filters for various camera lenses, binoculars, spotting scope, and a telescope. I used "black polymer filter sheet" as sold by Thousand Oaks Optical and other vendors. Transmission is rated at 1/1,000 of 1%, or 0.00001 of unfiltered, and acts across the entire spectrum, rather than falling off in the UV or IR ranges. You might still be able to get some,either from a local vendor or via rush delivery. You can also make do with one side of a set of cheap viewing goggles. Cut-out an opaque cardboard circle the same diameter as your lens hood, then cut out a circle in that smaller than the ocular filter. Tape the filter over the cardboard, and then tape the whole assembly to your lens hood. Make sure there are NO light leaks. By using your lens hood as the filter mount you'll be able to remove it easily for totality (if applicable in your location), and replace it when totality ends. This approach is accessible and cheap, but does give a somewhat smaller objective aperture than you can otherwise achieve. It does work. Here is an example of an image I made testing one of my home-made filters on a Tamron 150-600mm/5-6.3 mounted on a D7100:
    Sol-8957a-sml.jpg
    Note the small sunspot in the lower-right quadrant. Please be careful and take good care of both your camera and your eyes. Good luck!
     
  3. Here is the filter for the Tamron 150-600mm, mounted on the front of the lens hood. This rig captured the image above, and is safe for digital cameras. The same approach is safe to use on binoculars, telescopes, spotting scopes, etc, and is endorsed by my wife, the physicist and university astronomy instructor.
    solar filter-170816.jpg
     
  4. Absolutely not.
     
  5. FYI: The mylar filter material used in viewing goggles/glasses and sold commercially provides something in the neighborhood of 13-14 full stops. There is no good way to duplicate this with standard photographic kit, at least that I know of. Standard mylar, such as used in balloons or space blankets, is not an acceptable substitute. There's no way to know what level of filtration they are providing, or if it covers the full spectrum from IR to UV. You can also use shade 14 welding goggles/glass, if this is the only thing you can get. You can buy the replacement, loose glass pieces for hoods. You can also stack multiple pieces of lower value to obtain the shade 14 value. These will work for fabricating photo filters, but they have a higher probability of distortion than the mylar. (The glass is thicker, so any variations in the parallel surfaces results in significantly larger lens effect.) Here is an excellent article on filters for solar viewing and photography: <LINK>
     
  6. I just bought some of the Thousand Oaks solar material also-it's not terribly expensive on Amazon. I think it was $30 for a 6x6 sheet. That's enough both for me to make a filter or two(and glasses in case the local TV stations run out before I can go to get some).

    I'm "making do" since I don't have a lot in the way of long lenses. My plan is to tape a piece of filter material to the BACK of my Nikkor 500mm mirror lens. I know the lens is far from optimum, but that's what I have to work with.

    The lens is designed to take rear-mounted filters, which is why I'm planning to do it at the back(unless letting direct sun into the lens is a bad idea).
     
  7. The ONLY safe place to position the filter material is in FRONT of the lens objective end. It is essential that you first filter the light before it enters any portion of the lens. Your reflector has a lot of light gathering capacity, so it will be OK to reduce the size of the objective opening to some small degree, if needed to fit the material you have. See my example, above.
     
  8. Thanks-noted.

    I've decided to forgo the terrible traffic of totality and instead will just enjoy the 96% here in Louisville(and wait for 2024, which I think will pass right over).

    I'll throw a filter on the mirror lens, then, and get it positioned on a tripod at work a little before. I might get brave and try a TC, although mirror lenses are crummy enough optically that I don't know if I want to brave that.
     
  9. Here at ground zero in Carbondale (link), the current forecast is for cloudy. :(
     
  10. I'm closely tracking the weather for Rexburg, Idaho. There appears to be increasing potential for clouds, but the more detailed forecast suggests these will develop in the afternoon, hopefully after totality, at least, and perhaps even later. Morning looks clear.

    On another note, the locals and early visitors have already cleaned out the local supermarkets in anticipation of enormous crowds. <LINK> I'm glad we'll be fully self-contained and independent of local resources.
     
  11. Unfortunately, false information seems rampant especially as glasses get scarce in this area.

    A co-worker today came and asked me for a piece of 35mm film. She had been told that it would be "safe" for viewing the eclipse if you hold it over your eyes.

    Of course, I can provide a piece(I'd just cut some off a bulk roll) but I'm not about to as that doesn't strike me as a safe viewing medium. Certified glasses-with a bit of hunting-can be had from $5 on down to free around here, and it's not something I want to cheap out on.

    The local media pounced on this and has been giving away glasses by the thousands. Unfortunately, one of the four TV stations realized that theirs were in fact counterfeit and had to issue a recall on them as well as stop giving them out.
     
  12. We bought a pack of 100 glasses months ago. We had about forty left over, so our daughter sold them to the gas station where she works. The station sold out at $5/each before my daughter could even make a sign announcing them to customers.:)

    Well, we're off for eastern Idaho in a few hours and expect to be out of touch until at least Tuesday. Happy trails, safe travels, and have fun with the eclipse!
     
  13. Welding mask filter inserts are a good substitute for viewing goggles. They may even do as a lens filter.
     
  14. Comments on filters ... for my first eclipse in 1963, the solar films designed to cover the full aperture of telescopes (or telephotos) had not been developed. Solutions we used - A) fully exposed and over-developed B&W film for eye shades. Only B&W film blocks IR and anyone assuming exposed color film is OK is asking for trouble. B) eyepiece projection from a telescope onto screen - commercial screen holders were available or DIY. C) Welding shades (OK for a binocular but disappointing quality for a telephoto). And finally, D) Herschel wedge + eyepeice filter - this was the equipment available for an antique 8" Alvin-Clark telescope. The concentrated light+heat of sun the telescope lands on a 2" piece of wedge-shaped glass where only a small fraction is diverted to the eyepiece to be further filtered. A scary solution as we were always concerned of heat-induced failure of the wedge or the eyepiece filter - the device had open ports and looked like a solar furnace in operation.

    The corollary of mounting filters inside a telephoto applies here ,,, concentrated sunlight is inside the telephoto tube building up heat. The solar film filters available today are designed to be mounted in front of the optics and I would not trust the polymer material in a hot environment inside a lens.

    At this stage, if you can't obtain a sheet of solar film, your options for photographing the partial phases are using a projection method or mounting an eyeglass filter film in front of the telephoto (may cause vignetting but the sun in the center of the frame should be OK).
     
  15. Sandy Vongries

    Sandy Vongries Administrator Staff Member

    Checked welding gear, since I have it around - some sources say helmet or goggle with grade 13 or 14 lens will work for viewing. Supposed to be cloudy here, and I'm sure not going to drive anywhere with possibility of the same within reasonable range. Good luck to all both for travel & photographic outcome!
     
  16. Used shade 12 (highest available at my welding supply) for the last eclipse. Worked fine for naked eye but was not aberration free for telephoto use.
     
  17. Sandy Vongries

    Sandy Vongries Administrator Staff Member

    Read that elsewhere -- just excess caution on my part -- one site said, not that it was harmful, but it was too bright for some. You have the experience, so better!
     
  18. I have heard that well exposed and developed black and white film is good. That is, dense silver grains.

    Anything that isn't metallic likely lets through IR, bad for both eyes and cameras.

    I suspect that cameras can take a little more light (heat) then an eye, and also that the repair cost is lower.
     
  19. As reported in another thread, the Lensrentals blog has an article detailing heat damage to lenses, shutters, and sensors. Keep the heat out of the lens by using the inexpensive filter films.

    The good news is you can buy new gear to replace the stuff you burned up. But you can't buy replacement retinas for your eyes. Solar filters and welding shades are readily available so use the gear made for filtering the IR and UV.
     

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