Publish Date: April 9, 2012
Last updated May 29, 2017.
If you’re just now trying to get a solar filter for the upcoming total solar eclipse, hurry! Try a telescope store if there is one near you. Trust me, most of them are sold out. PLEASE DO NOT attempt to photograph or observe the sun if you are not properly prepared. PERMANENT BLINDNESS or DAMAGE TO EQUIPMENT may result.
I have been asked a lot about solar filters and why I was strongly encouraging people to get them. First let me explain how you might use them, then I’ll talk about the different kinds of solar filters and their costs.
Here are several shots of the sun rising behind Lick Observatory on Mount Hamilton, San Jose, CA. All shots are without any filter.
The upper exposures are pretty conventional. The exposures at the bottom, however, are clearly MUCH shorter and exhibit excessive flaring mostly due to IR light. Indeed, here are the settings from upper left to lower right:
- ISO 200, f/11, 1/80
- ISO 200, f/11, 1/640
- ISO 200, f/11, 1/8000
- ISO 100, f/36, 1/2000
What is probably immediately obvious is the glare / flare and color fringing. Compare the above shots to this one:
This is NOT a single shot, it’s a blend of two shots. The thing to notice is how much better tamed the violently bright sun is. Another important consideration is that a solar filter provides a boatload of protection to both the eyes and the camera equipment more on that in a moment. The bottom line is that the flare is well controlled and the sun exposure is sufficient that if there were a large sunspot on it, you’d be able to see it.
What Can I Do With A Solar Filter?
So glad you asked. Consider these:
- Safely capture a Solar Eclipse prior totality.
Why: Because it’s cool and solar eclipses visible from any given area are relatively rare.
- Safely capture the Transit of Venus on Tuesday, June 5, 2012.
Why: Because this event won’t repeat for another 105 years! It’s rarer than Halley’s comet and it’s visible from everywhere in the continental United States. [Sorry your missed it!]
- Capture sunspot activity.
Why: We are approaching the solar maximum where sunspots and coronal mass ejections are at their most active.
- Composite a nicely formed sun into your shots. You can use my “Easy HDR” method described in a prior column.
- Seek solar alignments where the sun forms the back light to silhouette a foreground object.
- Catch the International Space Station (or other spacecraft) as it hurtles across the face of the sun.
- Use the solar filter as an “ultra stopper” to make extremely long daytime exposures of e.g. waterfalls or surf.
For some good background on how to observe an eclipse, see here.
Do I Need Protection?
For your eyes, absolutely. For your camera, HIGHLY recommended. People often go “over the top” in their worry that a big lens will burn an instant hole in the sensor or camera body should they aim it at the sun. The image projected is onto a broad area at least as big as your sensor. In a short period of time i.e. a 1/4,000 of a second exposure nothing horrible is likely to happen to the sensor at least. The combination of a mirror and shutter in a DSLR provides SOME protection to your camera and sensor from “certain doom” however if you were to ask my advice, I’d say DON’T use your camera to photograph the sun unless you have a SOLAR FILTER. Most especially do not use live view (or a point and shoot camera) pointed at the sun. That tactic is very likely to damage your camera.
When I zoom in on the sun, isn’t that concentrating the light even more?
Well actually, just the opposite. Instead of focusing all the energy on one spot, you’re spreading it over the sensor surface. So in fact, the sunlight is more concentrated when you don’t use a telephoto lens.
DO NOT look through the viewfinder to compose your shot unless you have a proper solar filter! Permanent eye damage may result. Even then be careful. And we just figured out that it’s not a good idea to use Live View to compose a shot.
What Kinds of Filters Are There? What Do They Cost?
Protection For Your Eyes
There are filters that you can wear or hold over your eyes. I highly recommend you get a pair. These are rated “ND 5”** and allow only 1/100,000 of the energy to pass through – they are effectively 16.6 f-stops of light reduction. Alternatively you can use a welders mask (though I bet not many of you have one!) #13 or greater. Cost of wearable / simple filters ranges from $1 or so to $20 and more depending on the type. Wearable filters are usually made of black polymer which blocks all wavelengths of light (important to prevent eye damage from non-visible light) and renders the sun a yellow-orange color. Most locations only sell the personal filters in bulk (10 or 25 are the usual minimums). I purchased a stock of 60, for example and have sold them all.
**IMPORTANT NOTE: There are at least FIVE different standards for measuring the transmissiveness of filters: “Neutral Density: ND, Optical Density – also often called OD, Shade Number – for welders glass, transmissiveness, and stops). For a photographer who is familiar with the ND scale used to rate Neutral Density filters this is NOT the same scale as the “Optical Density” scale used to rate solar filters! An ND3.8 (photo solar filter) in the optical density scale is equivalent to the ND8192 neutral density filter! An ND8 filter for your camera is 3-stops of light. For safe visual viewing you need about 14 stops! So an ND8 is woefully short of light snuffing capabilities. Moreover neutral density filters used with cameras may or may not extinguish harmful Infra-red and Ultraviolet radiation.
- What about using an 8-stop Vari-ND (ND2-400 Filter)?
At the maximum 8-stop setting (ND400) the filter is passing 0.4% of the sun’s energy. That’s more than 40 times the recommended energy for PHOTOGRAPHIC use. A photo filter should transmit less than 0.01% (1/10,000). Even a 12-stop reduction in light (ND4096, Optical Density 3.6) may pass too much energy for safe and effective photographic use. 13-stops which is the same as Density 3.8 or ND8192 is preferable.
- What about the “Big Stopper” by Lee or Hitech?
10-stops sounds like an impressive reduction in light but the resin filter (Hitech) passes quite a lot of IR and UV light. And 10-stops still really isn’t enough. I haven’t see the response curve for the Big Stopper. It would be UNWISE to assume the Big Stopper or any filter is safe if it isn’t solar specific – especially if you plan to try to take more than a few shots. These filters certainly aren’t visually safe.
In addition to not reducing the light to safe levels, having an insufficient energy reduction means that you’ll have problems with flare / glare.
Photographic and Visual Filters
There are several varieties of solar filters that can be used for photography.
- Black polymer screw-in solar filters – pre-made you order them to screw in on the end of your lens(es). There would be little point in getting such a filter for any lens that is less than about 200 mm effective focal length. It might be worth making your own from an existing UV filter.
- Black polymer “covers” or black polymer solar sheets from which you can make filters.
- Silver solar mylar sheets (make your own) which render the sun a more natural white to a blueish cast. Mylar is less durable than polymer.
- Glass solar Filters in a housing to fit over a lens hood or dew shield (ND 5.0)
- ND 3.8 (Photographic) solar filters which are NOT suitable for visual observing. This type generally only comes in sheet form and you must make your own filter. Not suitable for visual use because it allows too much of the suns energy to pass through to your eyes.
- Tuned solar filters (also called Hydrogen Alpha) – like those found in the Coronado solar telescope. I don’t have a background in these, but normally you will need a set of filters and they are primarily designed for use with telescopes. The cost is upward of $600.
Normally when you buy a solar filter, you select a size that will cover your lens hood (or for a telescope the “dew shield”). Fit on filters should be snug so that they cannot come off if bumped or buffeted by wind. You really do NOT want your eyesight destroyed by a gust of wind! The filter should also seal out light leaks since most solar filters are reflective.
Since the upcoming event(s) all require solar filters, they are in short supply. It may take literally MONTHS to get a filter from some suppliers.
Costs depend on the size and quality of the filter. For the average telephoto lens expect to pay from $60 to $100 for the glass type filters. For very large lenses or for telescopes that cost could reach up to $200 and more.
Black polymer or silver mylar sheets will run you about $35 not including shipping. The ND 3.8 Baader photo filter is about $90 for a 19 x 39″ sheet. I also ordered a “natural color” Mylar polymer sheet (12″ x 12″) for about $30 from RainbowSymphony. RainbowSymphony also has the solar glasses at minimums of 25 pieces. Finding things on the RainbowSymphony site is a bit tedious. (NOTE These prices were as of May, 2012)
There are many references on the web for building your own solar filter if you choose not to buy a glass filter.
As with all things, quality varies quite a bit. I do not have the resources to exhaustively test all filters, but so far my best photographic results have come using the Baader Astrosolar Film (PHOTO) and hand made filters. This filter passes enough light to keep the exposures fast at low ISOs and is optically superior to any other mylar or polymer material I’ve tried. The glass (visually safe) filter I have darkens the image to make it visually safe and renders the sun an orange color (which it isn’t by the way). Somewhat longer exposures are needed for this.
I’ve placed these in order according to my experience surfing and buying from the company.
- OPT Really fast to ship. Also has smaller sheets of ND 5 and ND 3.5 films available. Shipping is about $10, however.
- Thousand-Oaks Optical A little slow to ship (due to demand) and you have to know what you want exactly to use their website.
- RainbowSymphony Difficult to navigate website, but efficient and inexpensive otherwise.
- Orion Slowest to ship, least communication. Note this link is to a specific filter, you may need to find a different size – which is, unfortunately, not as easy to do as it should be.
- Astro-physics.com – Large sheets of Photo density filters (ND 3.5) – placed an order but Astro-physics lost my payment information. They have an excellent reputation for high quality scopes, but I am worried about a process that “loses” payment data. There are also some significant flaws with their website / ordering process.
If your goal is photos, get a Baader Astrosolar filter. It is not eye safe, but it does allow higher shutter speeds and versatility. Practically this means you’ll have to make your own filter from sheets as there are few resources with pre-made photo transmissiveness filters. Making your own filter is not that hard.
Second choice based on quality is a glass filter that seals well over your lens hood (you do have one, right?). The “outside diameter” of your lens hood must be about the same as or slightly smaller than the inside diameter of the glass filter you’ll put over it. Since most glass filters are designed for visual use, you’re shutter speeds will be a bit slower but good quality glass will keep your photo sharp.
Get a pair of solar glasses for your eyes regardless of what else you do.
Depending on what solar filter and for what equipment you need the filter, it is maybe already too late to get one in time for the Annular Solar eclipse this year.
For the Thousand Oaks and some other glass filter for telescope you have to wait more than a month.
The film filter which is the cheapest and usually not the best filter you can still get in time.
The solar/ND filter for camera lenses (screw on), no idea what the availability is there.
I don’t think this is a fair / accurate statement as the statement assumes that all suppliers are backlogged and unable to make a timely shipment. For example my purchase of solar film from one supplier (about 2 weeks ago) was received in 5 days. I even doubt that this is true of Thousand Oaks who lists lead times on their site. As I write this sheets and camera filters are listed as up to 2 weeks, and even the glass filters are up to 4 weeks maximum.
So as I noted, I recommend anyone thinking of purchasing call the supplier to inquire about delivery times. Finally, I placed an order yesterday (April 10th) with OPT. I just received a notice of shipment today. We’ll see when it arrives.
Sorry didn’t say it clearly. I was refering mainly to the glass filter. I don’t know about the polymer srew-on for camera lenses. The film filter you can almost awlays get and if not as ready to use filter available you can build one with solar film sheets.
I don’t know if someone here reading this has a telescope and need a filter for that, I recommend using a glass filter instead of film. If you have a refractor telescope the Lunt Herschel wedge shows more details than any of the glass filters.
Btw. I ordered on March 4th the glass filter from ThousandOaks for my 8″ telescope and still not have it. Hopefully I get it in time.
You should ask before you order about delivery time so that you can get your filter before the May 20th eclipse or June 5th Venus transit. There was a large backlog for a while for these items due to demand.
Another great resource for building your own filters is by Joseph A Cali.
Thanks for such a detailed article, Steven. I looked at the websites you listed for purchasing a solar filter. Can you let me know the name of the solar filter you used on your camera at Dennys? I couldn’t find this in the links you sent. May be I am missing something.
Ravi: The part number (name) of the filter I used will not be helpful to you because you must buy based on the size of your lens hood (for an external enclosure) or lens filter diameter for a screw-in filter. I showed both a black polymer screw-in filter and a glass filter in an enclosure that fits over the dew shield of my 80mm refractor. You can see the screw-in filters in the Thousand Oaks list. Search for “THREAD SIZE” (though of course they are free to change their page around).
I was asked “what filter do I need for my Canon 70-200 mm lens”.
If you want a “screw on” filter which will be just exactly like you are used to for most filters, you just need to order the right sized filter. Often a search on Google will help you figure out your filter size – as will looking at the lens.
For a 70-200 mm f/4 L the size is 67mm
For a 70-200 mm f/2.8 L that’s 77 mm
Note that there are IS and non-IS versions of each lens, but I do not believe those options affect the filter size.
Pretty much the only option for screw on filters is the black polymer kind.
Another way to go is to measure the outside diameter of the lens hood. It’s ALWAYS a good idea to have and use a hood. Buy a glass filter, or make your own filter to fit over the hood.
FWIW- I bought this Solar filter http://www.telescope.com/410-ID-Orion-Full-Aperture-Solar-Filter/p/7733.uts?keyword=solar%20filter
from Orion. It fits over my Nikon 80-200mm AF-D front element and/or the hood.
I found the staff ( Vanessa) very friendly and helpful when I called to order mine, and when I went in to pick it up.
I ordered it back in late Feb. and it took 2 weeks to arrive at the store. I don’t know how long the lead time is now.
Thanks, Deborah. I ordered some solar film from OPT on April 10th. I received it TODAY, April 13th as well as as a CLS (light pollution clip-in filter) for my Canon.
OPT shows what is backordered (much of it from Thousand Oaks) and what is in stock.
So not everyone is “slow”.
Here is a shot using the “white” Baader Astrosolar filter that I received on April 13th:
The sun is a bit yellow because it is very low on the horizon so atmospheric extinction and refraction keeps it yellow.
The Baader Astrosolar Photo filter is not suitable for use for visual observing. Looking through it you can see even a relatively dim light.
Here is how I made a Solar filter from film:
The easiest way to build a filter is to get 3/16″ to ¼” foam board. Cut 4 squares several inches wider than your lens hood. E.g. if your lens hood is 3″ In diameter, cut the boards 6″ square. Glue two squares together. Trace the lens hood with a pencil on one side of the doubledboard. Use a sharp knife (Xacto) and cut out the inside of the square as neatly as you can. Sand or trim for a snug fit over your lens hood. If it’s slightly loose, a large flat rubber band around the hood may make it snug.
On one of the remaining boards, trace a circle that is smaller (by about ½ inch in diameter) than the lens hood on each of the boards and cut out each of those circles. Using a small amount of tape, tack down the corners of the solar film – don’t stretch and don’t wrinkle. You can then tape or glue the foam boards with the film sandwiched between. Don’t glue the film, however. Secure the filter to the base using rubber bands and/or binder clips.
Takes about 20 minutes to do it well. The most important part is to get a good fit over your lens hood. If you don’t have a lens hood, or if it is irregularly shaped (e.g. Tulip Style) You may need to use method “B” which may comes as an instruction sheet with your film For example these: http://www.baader-planetarium.com/sofifolie/bauanleitung_e.htm
Rather than using the method they describe, I made the outside edge of the tube 1″ longer than the others, then by cutting a series of slits and bending the edges out I was able to easily attach the square foam board with the proper sized inner diameter and built the “cell” using the square method I mentioned earlier.
If you search, you’ll find yet more methods: http://www.cosmoscopio.com/solarfilter.html
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Hi Steven , thanks as always for the informative article. There seems to be a discrepancy between the info you provide and my experience shooting the eclipse yesterday. I have a Fader Filters Variable Neutral Density filter that I use for video. It is rated as “8 stops.” On their site, they say that it is ND400. You said in your blog post that this is not effective for “safe photographic use.” I was shooting my sequence in 10 minute intervals, f/22, 1/8000th down to 1/200th, and the sun was not overexposed. In fact, if you blow the sun up to >300% in shots I made with a 200mm lens on a 50D 1.6x crop body between sequences, you can discern sunspots. I’m not really clear on how this isn’t safe – when you take a picture of someone playing soccer and you get the sun in your frame, even if you are shooting with no filter and at say 1/500th af f/2.8, you don’t damage you sensor. Now, I knew better than to stare at the sun through the viewfinder for long periods of time, and I didn’t have live view on for three hours either. How is a ND400 variable ND filter “not safe?” Is it the UV light that is damaging?
Thanks for your question, Grant.
There are several points here. First the primary goal of the article is for people to safely approach both viewing and photography. Perhaps the article wasn’t completely clear on the point but I wanted to make people thoroughly aware that using “non solar specific” filters puts eyesight at risk.
With that in mind “safe photographic use” in context here includes safe for your eyes e.g. while viewing or composing the shot through the viewfinder.
Camera safe is another thing. I’ll try not to be alarmist. That one is able to get a successful image does not mean the camera was not endangered. Heaven knows my camera is in constant peril by merely being near my person. The camera has many components that can be damaged by excessive radiation: the external body, the cement that binds lens elements together, the shutter curtain, the interior camera box, and, of course, the sensor. Strong unfiltered sunlight has been observed to melt the black housing in and around the shutter – logically incomplete filtering would have a similar effect. Strong enough radiation (IR or UV in particular) for long enough will certainly degrade the colored micro lenses on the sensor. Camera manufactures (e.g. Canon) warn specifically of the danger – especially when using live view.
An eclipse is quite a different animal than the incidental sun in a soccer shot. I spent over 2 hours with my equipment constantly pointed directly at the sun (with solar filters, of course). And I wrote the article assuming others would be doing the same. To use a human analogy, not many people feel the need to wear sunscreen when they walk to the curb to grab their mail. But sitting outdoors in the sun all day… that’s an exposure of another sort.
Getting back to your specific statement, however, you’ve actually protected your camera quite a lot: by taking short exposures, by not leaving he sensor continuously exposed and by filtering the light by *about* 7 stops and by using a telephoto lens that spreads the collected light over the sensor. And your camera has some internal protection beyond all that… e.g. an IR rejection filter (hot mirror) in front of the sensor. The hot mirror is NOT as good at handling UV, however so a filter that fails to attenuate that energy is asking for trouble. Saying with certainty that you HAVEN’T damaged something in some way (great or small) is not a conclusion that can be reached without before and after measurements. Am I saying that I’d never point my camera at the sun and take a picture… not at all. The camera is a tool and if it degrades when I abuse it a little to “get the shot” I think I can live with that. Not everyone will share my view with respect to their equipment, however.
Thank you for this very informative article! You saved me from damaging my beloved 7D today! 🙂
This stuff you wrote here is still very useful as eclipses occur every now and then and thank God I decided to do a little research before trying to shoot timelapse 😉
Great interest generated in reading your posts.
I wish to ask you about long exposure photography like getting dreamy waterscape with the Baader astrofilm. If used in such a way, will the natural colors of the surrounding be lost or washed out with such a film? I used ND filters but I was looking at Baader Astrosolar films to fit specific lenses.
Also, if colour rendition is good – for a 10-stop photographic stop-down, which Baader film is suitable?
Hey, Jack. We didn’t know off the top of our head, so we looked up the two available films: one is “photo” at 3.8 OD, the other “eye-safe” at 5.0 OD. These correspond to a 12.6 stop and a 16.6 stop reduction in light. They claim to be white, and I didn’t notice a color shift in my photos with the 3.8 film … but then I only used them for solar photography.
I’ve got a 300 mm Sigma telephoto lens with a internal filter ” drawer” between the front and rear elements. I have a glass solar filter in there now, It’s 46 mm have already snapped a few photos of the recent sunspot. Works great. The reason I ask is everything I’m reading says put a filter over the lens hood which is 5.25 inches across. This filter gives the sun a yellow cast.. Will a prolonged look at the sun harm the lens using this internal filter? Thanks.
I don’t think we can say yes or no. Depends on the quality of the filter, whether it is designed for prolonged exposure and how well heat is dissipated. Lenses are generally “light neutral” meaning they let the light energy through with very little effect on the lens. The point of putting filters in front of the light path is to prevent excess energy from entering your lens/camera. Your filter (if appropriately dense) should protect your sensor, but I would be concerned about heating and possible catastrophic failure*. I recommend an experiment: point the apparatus at the sun for a minute or two, then point away from the sun and remove the filter. If the filter is too hot to touch, I’d recommend NOT using it since it could heat the surrounding area enough to damage the holder, lens body or the cement that binds lens elements together. If after a few minutes the filter has not grown too hot, try more minutes up to the amount of time you plan to point the camera at the sun.
You can try the filter heating experiment without attaching a camera.
*I have seen where adding a filter at the eyepiece of a telescope quickly destroyed the filter and the eyepiece… and potentially the eye of an observer.
Steve, thanks so much for your answer. I’ve decided to not chance it and have purchased a Meade Glass White-Light Solar Filter. They’re becoming scarce. It fits over the front of the lens perfectly, 3 thumb screws holds it securely. The internal filter blocks visible light but wasn’t sure about UV and IR. Now nothing will get into the lens. It’s for telescopes and after lugging the 300mm around for a few hours it feels like it is a telescope. 🙂 Thanks again for taking the time to answer. my question.