Solar filters for cameras and phones: on the front of the lens, the right size and safe for viewing

A real solar filter over the front of the lens, covering it completely: for a camera, a screw-in one or one in a holder sized to your lens; for a phone, one with a clip, Velcro or a similar fastener over the lens. It stays on throughout the partial phases and only comes off during totality: in Cádiz, from 09:40:48 to 11:59:33 (Spanish time, CEST, UTC+2), with 2 min 54 s of totality in the middle. If your camera has an optical viewfinder, the filter has to be one that is safe for viewing, because your eye is behind the lens. And a photographic ND filter, even a variable one, is not a solar filter.

For a camera: screw-in, magnetic or film in a holder

According to the AAS (American Astronomical Society), “Filters should fit snugly over the front of all camera lenses and telescopes”. There are three ways of fitting one:

• Screw-in, matching the thread diameter of your lens. It sits firmly, but the AAS warns that it’s hard to take off and put back on quickly at the start and end of totality. That’s why it considers them “ideal if you’re outside the path of totality”.
• Magnetic. According to the AAS, these come off and go back on faster than screw-in ones.
• Film in a holder that grips the lens or the lens hood. Baader describes its density 5 film as being “for construction of high-quality objective-filters for observing the sun with telescopes, binoculars or cameras”. You choose the holder by the outer diameter where it attaches, and it mustn’t leave any gaps.

Densities, materials and securing the filter against the wind are covered in solar filters for telescopes and binoculars, and they apply just the same to a telephoto lens.

An optical viewfinder looks through the lens

On an SLR, what you see in the viewfinder comes through the lens: what the AAS calls “through-the-lens viewing”. If you look through that viewfinder with the filter on, the filter is the only thing between your eye and the Sun.

That’s why density matters: for taking photos, the film’s maker accepts density 5 and also a lighter 3.8, but of the 3.8 it writes “Not suitable for visual observation”. If you’re going to put your eye to an SLR’s viewfinder, the filter has to be one that is safe for viewing. That conclusion is ours, from putting together what the AAS and the maker say.

Cameras that don’t see through the lens, the ones with a separate optical viewfinder, need a second filter on that viewfinder. The AAS asks for one “over the viewfinder if the camera lacks through-the-lens viewing”, and Baader, in the instructions for its film, asks you to cover “the viewfinders front lens” on cameras.

And a tip from the AAS that isn’t about safety: “Don’t spend all your time gazing through your camera’s viewfinder”.

For a phone: a filter that doesn’t move

For the partial phases, the AAS asks you to “place a solar filter over your phone’s camera lens”. In its list of suppliers it describes products for phones that “include safe solar filters and Velcro or other fasteners” to hold them over the phone’s lens or lenses. One of them combines a dark filter for viewing and a lighter one for the camera.

What to check on a clip-on filter:

1. That it’s a solar filter, not an effects filter or an ND.
2. That it covers the lens or lenses you’re going to shoot with.
3. That the fastener can take a knock and leaves no gaps.
4. That it comes off with one hand when totality begins and goes back on just as fast.

The settings, and why the sensor can suffer without any warning, are in eclipse photos with your phone (in Spanish); video and timelapse are in film the eclipse with your phone.

What isn’t a solar filter

B. Ralph Chou’s eye-safety text on NASA’s eclipse website has a list of filters that are not safe: colour photographic film, black-and-white film with no silver, negatives, smoked glass, sunglasses (alone or several together) and “photographic neutral density filters and polarizing filters”. A variable ND is a photographic ND filter, so that’s out too. And nothing homemade: Chou asks you not to put any filter on a camera that isn’t made for the purpose and fitted on the front.

In totality, off, and back on in time

For a total eclipse, the AAS asks you to take the filter off at second contact and put it back on at third: as soon as the diamond ring lights up and the corona starts to fade, “reattach the solar filter to your camera”. In Cádiz, off at 10:45:24 and back on before 10:48:10, which is the end time given by the IGN (Spain’s National Geographic Institute): use the earlier of the two end times. The times for each town are in when to take off eclipse glasses in totality, and the shooting sequence in photographing totality with a camera (in Spanish).

Outside the path there’s no such moment: the camera’s filter and the phone’s stay on all morning.

On Order your glasses you can ask for ours: cardboard, with the EN ISO 12312-2 certificate, along with the phone filter and packs for groups. We reply with the price and the delivery time.

Sources: AAS — How to Shoot Solar-Eclipse Images & Videos (filter fitted snugly over the front of the lens; filter over the phone lens; filter on the viewfinder of cameras without through-the-lens viewing; off at second contact and on at third; don’t spend the eclipse at the viewfinder); AAS — Solar Filters for Optics (screw-in and magnetic filters); AAS — Suppliers of Safe Solar Viewers & Filters (phone filters with Velcro or other fasteners); B. Ralph Chou — Eye Safety During Solar Eclipses, on NASA’s eclipse website (unsafe filters; nothing that isn’t made for the instrument and fitted on the front); Baader — AstroSolar Photo Film OD 3.8 (not suitable for viewing); Baader — AstroSolar Safety Film 5.0 instructions (PDF) (objective filters for cameras; cover the viewfinder’s front lens); Baader — Instruction Manual: Baader Solar Filters (PDF) (photography with density 5 or 3.8); times for Cádiz: eclipseando data (skyfield engine + DE440s) checked against the IGN; totality duration: IGN.