Using B&W film as eclipse filter

[Cholentpot]

+1000!I'm starting to buy stock in blind-dog breeding. Hey guys, this is not too difficult; build a pinhole projector to enjoy the eclipse without blinding yourself or others, But,now, that the eclipse is over,plese report on actual experiences if you still have your vision and are able to see the keyboard.

For some reason no-one has a nose anymore.

Don't worry, we got till 2024 to keep researching. I must say, I did pinhole and used the paper glasses. Paper glasses were far far far far more awesome than the pinhole. Pinhole was 'Cool, alright...' Glasses were 'Woaaaaaaaaaaaah!!! You gotta see this!'

 

[Sal Santamaura]

...now, that the eclipse is over,plese report on actual experiences if you still have your vision and are able to see the keyboard.

I already did that in post #19. Perhaps you missed it:

Now that the eclipse is over, here's a follow up. I still have an 8x10-inch sheet of the Delta 100 negative mentioned above that hadn't been cut down. My densitometer's 1.0mm aperture limits what it can measure to 3.5 maximum, and it hit top of scale with this negative. That's why I estimated the density at 4.0.

My first attempt to look at the sun through two layers (I folded it in half) revealed no image at all. It was as opaque as being inside the house and looking up through the ceiling, attic and roof. Unfolding it and looking through one layer was just right. I suspect that typical black and white film/developer combinations, which might top out at densities lower than 4.0, would be more appropriate for doubling.

For those who argue that a metal foil is necessary, recognize that density of the film described here is a result of metallic silver. There's no question it absorbs the full solar spectrum and is safe. But only if prepared and used properly.

 

[Wallendo]

I used eclipse glasses from a NASA-recommended supplier, and shot images with a solar filter using a digital camera which came out OK. I went with the darkside camera as I could frame the image using the LCD screen without having to look towards the sun. The images came out OK, but, as is was early afternoon, the sun was almost directly overhead and I couldn't place anything of additional interest in the photos. I had my film camera ready to go for totality, but a dark cloud moved in a few minutes too early.

 

[Jon Shiu]

I used a sheet of FP4+ film mounted in a cardboard frame and it came out just right. I tried with 2 layers, but couldn't see anything. One layer worked well, and shooting my pocket digital camera through the single layer film, good exposure of the eclipse was equivalent to 1/125, f8, ISO 100

 

[Sirius Glass]

A bad idea waiting to damage someone's eyes.

 

[paul ron]

we used the media of a 5.25" floppy disc doubled over. I've used this for many eclipses.

 

[Sal Santamaura]

A bad idea waiting to damage someone's eyes.

What is? Please be specific.

 

[Cholentpot]

I used a sheet of FP4+ film mounted in a cardboard frame and it came out just right. I tried with 2 layers, but couldn't see anything. One layer worked well, and shooting my pocket digital camera through the single layer film, good exposure of the eclipse was equivalent to 1/125, f8, ISO 100View attachment 185442 View attachment 185443 View attachment 185444

Those are some unique looking shots.

we used the media of a 5.25" floppy disc doubled over. I've used this for many eclipses.

What's a floppy disk? Some sort of hat?

 

[paul ron]

What's a floppy disk? Some sort of hat?

hahahaha kids!

 

[Rick A]

 

[Sirius Glass]

A bad idea waiting to damage someone's eyes.

What is? Please be specific.

Duh!!!!
No testing for passed wavelengths and attenuation.
No safety testing.
No quality control.
This list goes on.


I am surprised your posts are usually technically accurate.

 

[Sal Santamaura]

...No testing for passed wavelengths and attenuation...

Posts #9 and #19 detail a viewing mechanism that was tested for passed wavelengths and attenuation many decades ago by none other than NASA. See the next-to-last sentence in the third paragraph of this:

https://eclipse.gsfc.nasa.gov/SEhelp/safety.html​

...No safety testing...

It's been tested for safe viewing numerous times by numerous people making previous solar observations.

...No quality control...

I'll trust my own quality control more than any manufacturer's. Especially one peddling 'viewing glasses' off the Internet.

...This list goes on...

It goes on only as long as decisions are influenced by lawyers. In my opinion, teaching people the science behind things, as well as how to think for themselves, shortens that list dramatically. To zero items.

...I am surprised your posts are usually technically accurate.

Why would the technical accuracy of my posts surprise you, Steve? We're both engineers. This subject is like all others I post about. Either I write with conviction or, when such a response is appropriate, say "I don't know." This time the first condition prevails.

 

[Cholentpot]

hahahaha kids!

The sounds of the FDD spinning up lulled me to bed on many a nights.

Posts #9 and #19 detail a viewing mechanism that was tested for passed wavelengths and attenuation many decades ago by none other than NASA. See the next-to-last sentence in the third paragraph of this:

https://eclipse.gsfc.nasa.gov/SEhelp/safety.html​

It's been tested for safe viewing numerous times by numerous people making previous solar observations.I'll trust my own quality control more than any manufacturer's. Especially one peddling 'viewing glasses' off the Internet.It goes on only as long as decisions are influenced by lawyers. In my opinion, teaching people the science behind things, as well as how to think for themselves, shortens that list dramatically. To zero items.Why would the technical accuracy of my posts surprise you, Steve? We're both engineers. This subject is like all others I post about. Either I write with conviction or, when such a response is appropriate, say "I don't know." This time the first condition prevails.

Thanks for that link! I knew my DIY glasses were good for something! NASA approved will get penned in on the side.

 

[Rick A]

Couple of my neighbors were out with welding helmets, I asked if they had a #14 lens in the hood, their reply, "don't need it these are auto darkening".

 

[Cholentpot]

Couple of my neighbors were out with welding helmets, I asked if they had a #14 lens in the hood, their reply, "don't need it these are auto darkening".

So I shouldn't put sunscreen on my auto-darkening sunglasses?

 

[titrisol]

YES, this has been done for ages and ages
The premise, of course is that you will look up only for a few seconds (unless you are stupid) and shoot a picture
I made a filter this time using the dark portion of XRay plates, sandwiched in cardboard to make a Cokin-A filter. That went in front of my 135mm lens and the results are not bad
in the original size you can even see sunspots.
Eclipse-1327

I even found I still had my solar glasses, that I made fro the 1991 eclipse from X-ray plates.... LoL
I, however bought new eclipse glasses from Thousand Oaks and found them to be "yellower" thus more UV shielding but the transmittance was in the same range
(equivalent to a 14 welding glass shield) as measured using a bright LED flashlight and a lightmeter on the other side there was about 1/2 - 2/3 stop difference

I wasn't sure where to ask this as it's about film but maybe not taking photos.

I've been out of curiosity putting together some solar filters for the eclipse and sun viewing in general. I remember being told as a kid that negatives work. My research has turned up that you need to use exposed and developed B&W film double stacked. However I've seen also that modern B&W films don't have enough silver to filter anything.

I just so happen to have a bulk roll of ancient Tri-X from somewhere in the 70's or 80's. This is 'silver rich' and should work. Now, I have the regular glasses that are ISO rated and will be using those, I'm just wondering if using film would work.

Thanks.

 

[Cholentpot]

YES, this has been done for ages and ages
The premise, of course is that you will look up only for a few seconds (unless you are stupid) and shoot a picture
I made a filter this time using the dark portion of XRay plates, sandwiched in cardboard to make a Cokin-A filter. That went in front of my 135mm lens and the results are not bad
in the original size you can even see sunspots.
Eclipse-1327

I even found I still had my solar glasses, that I made fro the 1991 eclipse from X-ray plates.... LoL
I, however bought new eclipse glasses from Thousand Oaks and found them to be "yellower" thus more UV shielding but the transmittance was in the same range
(equivalent to a 14 welding glass shield) as measured using a bright LED flashlight and a lightmeter on the other side there was about 1/2 - 2/3 stop difference

Nice shot.

The plates were exposed and developed?

 

[titrisol]

Yes, of course....
I took the dark portion of the X-ray plates to make a ~55x55 square filter which sandwiched between cardboard would fit a Cokin holder
In the 90s, I used to get the "bad ones" from a local clinic (which meant they were dark)
Unfortunately now, most XRay are digital, and it is becoming harder and harder to find them
However, I still use 120 film, so next time I develop some I will have a "white" frame to test that one too.

 

[Wallendo]

When I was in elementary school, sometime between 1966 and 1972, there was a partial eclipse in my hometown. We were given information by our school that one of the best ways to view the eclipse was by looking through unexposed 35mm film. We were cheap and just used a pinhole, however.

This is apparently no longer recommended, although I am not sure if this is because of problems with the film, or the general sense that film is not widely available.

 

[Cholentpot]

Yes, of course....
I took the dark portion of the X-ray plates
In the 90s, I used to get the "bad ones" from a local clinic (which meant they were dark)
Unfortunately now, most XRay are digital, and it is becoming harder and harder to find them
However, I still use 120 film, so next time I develop some I will have a "white" frame to test that one too.

I made glasses out of 35mm. 120 would work great as a filter for the lens though...

 

[NB23]

So, what y’all be saying for this new upcoming one?

 

[Cholentpot]

So, what y’all be saying for this new upcoming one?

I already have glasses. I think I'm going to make a filter for my camera from some film though. I can't find my welders glass I used last time.

 

[Chuck1]

Smoked trout

 

[reddesert]

TLDR: Just get the darn eclipse glasses, from a reliable source.

In the Bad Old Days we sometimes used totally fogged and developed silver black and white film to observe solar eclipses. Like a throughly exposed and developed 35mm leader. Official sources will not recommend this now. Ideally, you should use eclipse glasses purchased from a reliable source (not a random anonymous seller on amazon or ebay), or solar filter film purchased from a reliable source (like Baader or Astro-Physics). These are tested to be effective. If you do take it upon yourself to use a fogged developed film leader, just look for a few seconds, don't stare at the sun for minutes like an idiot.

Under no circumstances should you use something like an R72 filter. The whole point of the fogged film or official solar filter is that the metallic film blocks infrared.

Reasons that official sources endorse eclipse glasses and not fogged developed B&W film include that:
- eclipse glasses are easier to get now, if you order ahead,
- people confuse color and B&W film (undeveloped color film does not have enough silver, and developed color film doesn't have any),
- people confuse silver B&W film and chromogenic B&W like XP2, which has no silver when developed,
- no official source knows your film type or developing practices or whatever and can test or guarantee the opacity of your film leader, even if you are actually using a real B&W film.

Before the 2012 (annular) and 2017 solar eclipses, I tried out a few undeveloped and developed pieces of silver B&W film, observing bright lights and scanning across the sun, and my memory is that the opacity varied a lot, which is not reassuring. In particular, I think undeveloped B&W film (silver halide, not metallic silver) was not opaque enough visually, which suggests worse in the infrared. I got the official solar filter material from Baader and made a filter to go over binoculars.

I've made pinhole cameras to view solar eclipses. It's not trivial because the angular diameter of the sun is small. I used a cardboard box for skis, about 6 feet long. This still makes only about a 15mm diameter solar image. With a maybe 0.5mm pinhole, you have a camera of about f/3600. The sun is bright, but you still need to shade the viewing screen from ambient light (less so during totality).

 

[ic-racer]

What ever you do be careful. I was out testing one of my proposed setups. I had a proper slip-on solar filter on a zoom lens. Essentially the same filter material for the glasses, so safe for optical viewfinder viewing. All was fine until I zoomed and the sliding zoom ring bumped the filter off the front of the lens. For just the fraction of a second until I could close my eye the light was literallhy blinding. Even though the sun only coverd a portion of the focus screen, the entire screen was blindingly bright. Much worse than when a strobe or speedlight goes off and leaves a lasting image.

Also, heed warnings on lenses, some of which warn against internal fires if un-filtered sunlight enters the front element.

It is a little bit of a paradox as a SHORT focal length lens is used to start a fire when camping. But a LONG focal length lens on your camera will burn out your eye quicker.
For example you can't start a fire with a +1 diopter close up lens (1,000mm FL) but looking at the sun through a 1,000mm lens on your camera will damage your eye quickly.