WARNING:

All care and no responsibility !!!
This is YOUR EYES at stake - exercise due care.
If smoke curls gently from the camera, odds are you have got it wrong.
Be very aware that a camera optical system MAY focus the sun's rays into a viewfinder - even if the main image is defocused.

Don't be scared away by the potential risks - just be certain that you have adequately allowed for them.

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Main methods are

• A suitable neutral density filter.
  Use when absolute certainty of performance is needed.
  Beware of pinholes in the filter!!!! People have had their eyesight damaged (not surprisingly).

Avoid allowing direct sunlight from "pinhole lenses" reach your eyes unless you are a world expert on likely performance.

• Photograph a projected image.
  This is safer.

I have seen articles in the past suggesting heavily exposed film as a good filter. X-Ray film is said to be good - a vanishing resource in this digital age. YMMV. Pinholing is a risk, and density is not well controlled.

It is highly likely that a suitably sensible person could make a safe and suitable filter from a range of materials.

It is also likely that some people could end up with eye damage because they were less careful or competent than they needed to be :-(.

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There is much useful material available on the web.

Baader astrosolar ND material - make your own - excellent page with information and warnings. They say -

• ND 5 ( 0.00001 transmission) (1/100,000) for direct visual use, and

• ND 3.8 (0.00016 transmission) (16/100,000) for photography only.

Instructions on DIY filters using their material

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Solar eclipse photography links:

{1} Solar eclipse photography

However, unless you're a complete die hard, don't bother. Photos of the sun before totality are considerably less interesting that photos of the moon. The best you'll get are a few sunspots.

Instead, I recommend indirect photos, which can include interesting background and human subjects. For example, you can photograph the image of the crescent sun being projected onto a piece of cardboard through a pinhole. You will probably be with a lot of other excited people, with lots of fancier equipment than you. Use them as your subjects. My best before eclipse photos are of a crowd of people surrounding a large telescope, projecting the solar image onto an 8x10 ground glass.

{2} NASA - ECLIPSE PHOTOGRAPHY

Some excellent suggestions:

A mylar or glass solar filter must be used on the lens at all times for both photography and safe viewing. Such filters are most easily obtained through manufacturers and dealers listed in Sky & Telescope and Astronomy magazines. These filters typically attenuate the Sun's visible and infrared energy by a factor of 100,000. However, the actual filter attenuation and choice of ISO film speed will play critical roles in determining the correct photographic exposure. A low to medium speed film is recommended (ISO 50 to 100) since the Sun gives off abundant light. The easiest method for determining the correct exposure is accomplished by running a calibration test on the uneclipsed Sun. Shoot a roll of film of the mid-day Sun at a fixed aperture [f/8 to f/16] using every shutter speed between 1/1000 and 1/4 second. After the film is developed, the best exposures are noted and may be used to photograph all the partial phases since the Sun's surface brightness remains constant throughout the eclipse.

They also contradict the advice above regarding photographing at totality :-)

Certainly the most spectacular and awe inspiring phase of the eclipse is totality.

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This simple search will give lots of useful material

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NB - the following are my personal observations only - treat with due care:

In my personal opinion, the stated necessary degree of attenuation for eye safety is excessive. Full solar flux is about 100,000 lux, so a 100,000:1 filter will reduce the light level to 1 lux which is far lower than necessary for safety. A bright LCD screen is about 300 lux - brighter than what you want to stare at for any time (he said, staring deeply into his monitor at close range 'just to see'). 10,000:1 attenuation to give 10 lux seems OK and 1000:1 to give 100 lux is getting somewhat bright.

The results from the Hoya NdX 400 at 500:1 seem to support this.