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I know it's usually said you need a 16-20 stop reduction 'solar' filter to safely take pictures of the sun. Any modern camera is going to usually meter and compose fully open for the sake of easier focus among other factors. So the required filter must be strong enough to be safe at bulb shutter and maximum aperture.

Most people use zooms these days, or longer telephotos for this purpose. These are often not very fast, especially for newbies. Is the usual advice given in relation to an f/4 zoom? Is the 16 stop figure only safe at that level?

So, if you're composing pictures of a solar eclipse and all you have is a fast normal or portrait prime at f/1.4 or f/1.8, do you need a 18-20 stop filter instead of a 16 stop to prevent damage to the camera or your eyes?

And how does a mirrorless camera effect this? Does composing with a screen instead of a pentaprism increase the safe zone far enough that 16 stops is safe again if it wasn't before?

davolfman
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    IMHO You shouldn't be using an ND filter for taking photos of the sun, you should be using a solar filter. You should read up on many of the other questions on here about eclipses – Peter M Mar 07 '24 at 21:46
  • I was under the impression that was essentially an ND filter in the 15-20 stop range give or take extra bit like a narrow-band if you want to capture prominences and sunspots and stuff. – davolfman Mar 07 '24 at 23:46
  • I'm sure that the bigger the ND you go, you'll arrive at a value that is not damaging to your camera, but I have yet to see a professional recommend anything other than a solar filter for an eclipse. Also see this question – Peter M Mar 07 '24 at 23:56
  • @PeterM the only real difference i can see with an ND filter vs a solar designed filter, is that solar filters are normally reflective rather than absorptive. Which doesnt really have much of a difference, other than i guess heat could be a problem if you use it for like a timelapse – Topcode Mar 07 '24 at 23:58
  • I just don't plan on buying mylar as a matter of self respect. – davolfman Mar 08 '24 at 00:04
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    @Topcode The link I suggested also says that there are different IR and UV responses between an ND and solar filter. And while there are the Lens rentals horror stories (which also incudes some damage when using an ND filter), I consider a solar filter cheap insurance compared to the cost of my equipment. – Peter M Mar 08 '24 at 00:05
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    "the only real difference i can see with an ND filter vs a solar designed filter, is that solar filters are normally reflective rather than absorptive." Please search this site for "solar filter" questions. Several of them state that the reason for the difference, and the need for a solar filter vs. just an ND, is that solar filters block farther into the IR and UV spectrum than ND filters do. – scottbb Mar 08 '24 at 20:45
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    "I just don't plan on buying mylar as a matter of self respect." This is a weird hill to plant a flag on. If a mylar solar filter does the job, what's the problem with using it? – scottbb Mar 08 '24 at 20:46
  • Permanence mostly. I can guarantee I will not find a way to store a mylar filter that doesn't damage it. – davolfman Mar 08 '24 at 21:15
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    @davolfman The solar filters I bought for last year were just like any other screw on filter, and came with their own individual plastic filter cases. That's about as best you can get for safe storage. – Peter M Mar 09 '24 at 16:53
  • What kind of filter do I need for safe sun photography? and Can the sun damage the camera sensor? Under what conditions? and Do you need a solar filter for a wide-angle camera? and most importantly Can it be dangerous to look at the sun through the viewfinder? – Michael C Mar 09 '24 at 20:42
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    @davolfman I store some of my mylar filters in Ziploc sandwich containers. My homemade foamboard slip-on filters (using Baader mylar) use extra squares of foamboard as protective "caps" to protect them. I made them 10 years ago, they're still in great shape. – scottbb Mar 12 '24 at 00:03
  • "is that solar filters block farther into the IR and UV spectrum than ND filters do." I see, that is definitely something to look into when buying a specific filter. However, there are from what I can tell, some solar designed ND filters, such as the dwarf II solar filter. – Topcode Mar 14 '24 at 01:36
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    @Topcode All solar filters are also ND filters, but far from all ND filters are solar filters. – Michael C Mar 14 '24 at 10:00
  • @MichaelC And almost any filter with more than density 3.0 is some variety of solar filter, and usually mostly neutral. – davolfman Mar 14 '24 at 18:07
  • Anyway, does anybody have an answer to the actual question? If I were to hook up a 200mm f/2.8 to my camera with no stop-down controls, and then sensibly not look through the lens with my own eye, would a density 5.0 / 1000000x / 15.y stop solar filter be enough? Or do I want a density 6 filter instead? – davolfman Mar 14 '24 at 21:29
  • @MichaelC well, not exactly. Neutral density requires no uneven wavelength attenuation(basically, color has to stay the same), a solar filter isnt required to have that, though I would assume most do, there is likely more tolerance for color bias in a cheap solar filter, than in a professional ND filter. Thats probably part of why most solar filters use OD rather than ND – Topcode Mar 15 '24 at 03:28
  • @davolfman Any filter designated as a solar filter should have documentation with it that describes what is and is not safe usage of the filter. Some are safe for visual viewing using the camera's viewfinder. Some are not. The ones that are not are usually clearly documented as such with the materials accompanying the filter. – Michael C Mar 26 '24 at 11:33
  • @Topcode Some ND filters are concerned with preserving color. Many (such as those made for use with orthochromatic film) are not. – Michael C Mar 26 '24 at 11:36

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