Is this a good rule to know when I can shoot the sun? "if the sun is not too bright to look at with naked eye, then it's not too bright for a DSLR" [duplicate]

Question

Most of what I have read about this, say that whether or not the sun is bright enough to harm the DSLR, depends on a lot of factors e.g. time of day, cloud cover etc.
What setting aperture, shutter speed, telephoto lens etc. is being used is also a factor. So, for this purpose I am sticking with smallest aperture and highest shutter speed of a 18-55m lens.

For example, I am quite sure taking a photo of the midday sun would be quite harmful for a DSLR. But shooting a sunset probably is okay.
So, exactly how harmful is the sun for DSLRs? Is it more of a "it's okay once in a while, but do not do it all the time" kind of thing? What if I shoot a person with the sun in the background? Will that damage the DSLR?

Also, I understand that the human eye's safety threshold is lower than that of a DSLR.
If that is true, then is "The sun is not too bright to look at with naked eye" a sufficient condition to determine when it is okay to shoot it with a DSLR?
What about cellphone cameras?

Is there a good rule of thumb/guideline to figure out when it is safe to shoot the sun?

Answer 1

Typical damage is heat damage. To estimate heat damage, you'll need to look at the amount of light going into the camera. Light reaching the sensor comes in approximately through a circle of diameter f/a where f is the focal length and a is the aperture number. As you stop down, the light reaching the sensor comes through increasingly smaller circles. But the only thing stopping it is the aperture blades which are as light-absorbing as the manufacturer can make them. And the shutter which is uniformly warmed for a leaf shutter and warmed where the image is bright for a focal plane shutter.

When the camera is reacting/metering with open aperture, you'll boil the shutter, when it is doing so with stopped down aperture, you'll boil the aperture blades.

Note that this does not require you to take a photograph: it is enough to aim the camera. For a DSLR, that's the main damage mode when not using live view. In live view, you might also damage the sensor, while in optical viewfinder mode you might also damage your eye.

The reason few people damage their cameras taking shots not explicitly aiming for the sun is that the sun will very rarely be accidentally in the frame of a tele shot while in wide angle shots the actual amount of light making it to shutter/aperture is much less because in f/a (with a being the aperture number of the widest possible aperture), the value of f is small.

The only reliable way of avoiding damage is to use solar filters which prevent light from even getting into the lens.

Answer 2

I think it only depends on the level of light energy that strikes the sensor. To damage the sensor, it has to be focused on a larger amount of energy that the one it is initially designed to deal with.

You can shoot the sun using ND filters to minimize this energy and keep having exploitable information. But sun rays are not laser, it is a diffused energy, so your sensor is not going to melt if you integrate sun in your compositions. Just avoid using lenses that focus sun rays, like macro and telephoto lenses.