Solar Filter

[The Conservative]

You are multiplying the wrong things.

95% filtered from 100% leaves you with 5%.

95% of 5% is: .05 * .95 = 0.0475%

95% of 0.0475% is: 0.0475 * .95 = 0.045125%.

If you stacked three filters that filter out 95%, you'd filter out all but 0.045125% of the light, which may be okay depending upon your aperture and shutter speed settings (I don't really know about that). I am just straightening out your calculations.

Times three?

No.

Each subsequent filter receives a smaller amount of light since they are serially arranged with a single input transmitted in sequence.

If X is the initial amount of light:

((.95 * X) * .95) * .95)

Isn't x 100 in this case or 1.0?

[Speaker to Animals]

Times three?

No.

Each subsequent filter receives a smaller amount of light since they are serially arranged with a single input transmitted in sequence.

If X is the initial amount of light:

((.95 * X) * .95) * .95)

Isn't x 100 in this case or 1.0?

In this case, it would be 1.0 since we are dealing with percents, and 100% is 1.0.

There might be some other factors that limit it further that have to do with refraction and opacity and whatnot. I am just talking about the idea of stacking filters and how to mathematically represent that. You can't just multiple the filter's percentage by the number of filters, since they are stacked and each filter is filtering out an ever decreasing amount of light.

[The Conservative]

By your own equation using 1.0 as x, I get .857375

[Speaker to Animals]

By your own equation using 1.0 as x, I get .857375

Oh, sorry. I fucked up and forgot the subtraction since we are calculating the amount of light left after the filter rather than the total filter amount.

Base equation: L - L*P, where L is the amount of input light to the filter and P is the percent of light filtered out. So if you have one 95% filter, then you get 1.0 - 1.0 * 0.95 = 0.05, which is 5% light getting through the first filter. To stack the filters, you have to nest them inside of parens.

But just step-by-step, you can see how it works for each filter..

Filter 1

L0 = 1.0
P = .95

1.0 - 1.0 * 0.95 = 0.05


Filter 2

L1 = .05
P = .95

0.05 - 0.05 * 0.95 = 0.05 - 0.0475 = 0.00225

Filter 3

No point going further. Stacking that many 95% filters is a bad idea. It filters out most of the light.



Conceptually you should see the problem. If the first filter transmits only 5% of the light to the second filter, then the second filter is going to take 95% of that light away and transmit the rest to the third filter. 95% of 5% is 4.75%. So the second filter is only transmitting 0.25% of the light to the third filter. The third filter is taking another 95% off of that, which is 0.2375%. Thus you get only 0.01215% of the light coming out of filter number three.

[The Conservative]

By your own equation using 1.0 as x, I get .857375

Oh, sorry. I fucked up and forgot the subtraction since we are calculating the amount of light left after the filter rather than the total filter amount.

Base equation: L - L*P, where L is the amount of input light to the filter and P is the percent of light filtered out. So if you have one 95% filter, then you get 1.0 - 1.0 * 0.95 = 0.05, which is 5% light. To stack the filters, you have to nest them inside of parens.

But just step-by-step, you can see how it works for each filter..

Filter 1

L0 = 1.0
P = .95

1.0 - 1.0 * 0.95 = 0.05


Filter 2

L1 = .05
P = .95

0.05 - 0.05 * 0.95 = 0.05 - 0.0475 = 0.00225

Filter 3

No point going further. Stacking that many 95% filters is a bad idea. It filters out most of the light.

Except that solar filters block 99% of all light.

[Speaker to Animals]

By your own equation using 1.0 as x, I get .857375

Oh, sorry. I fucked up and forgot the subtraction since we are calculating the amount of light left after the filter rather than the total filter amount.

Base equation: L - L*P, where L is the amount of input light to the filter and P is the percent of light filtered out. So if you have one 95% filter, then you get 1.0 - 1.0 * 0.95 = 0.05, which is 5% light. To stack the filters, you have to nest them inside of parens.

But just step-by-step, you can see how it works for each filter..

Filter 1

L0 = 1.0
P = .95

1.0 - 1.0 * 0.95 = 0.05


Filter 2

L1 = .05
P = .95

0.05 - 0.05 * 0.95 = 0.05 - 0.0475 = 0.00225

Filter 3

No point going further. Stacking that many 95% filters is a bad idea. It filters out most of the light.

Except that solar filters block 99% of all light.

Like I edited it before you replied, you are getting far less than even 1% out of the three filters:

Conceptually you should see the problem. If the first filter transmits only 5% of the light to the second filter, then the second filter is going to take 95% of that light away and transmit the rest to the third filter. 95% of 5% is 4.75%. So the second filter is only transmitting 0.25% of the light to the third filter. The third filter is taking another 95% off of that, which is 0.2375%. Thus you get only 0.01215% of the light coming out of filter number three.

Instead of getting only that 1% of the light, you are getting 1% of that 1%, which is probably far too much. That's an order of magnitude more.

[Speaker to Animals]

Try going with a 95% filter on top of an 80% filter.

That gives you 1% of the light coming through.

So if you are trying to mimic 99% filtering, and you have access to a 95% filter and an 80% filter, it probably would be roughly the same as a single 99% filter.

Though I suspect it could be a little bit more filtering than if you had a single 99% filter because of some optics math that's too complicated to bother with.

[The Conservative]

Try going with a 95% filter on top of an 80% filter.

That gives you 1% of the light coming through.

So if you are trying to mimic 99% filtering, and you have access to a 95% filter and an 80% filter, it probably would be roughly the same as a single 99% filter.

Though I suspect it could be a little bit more filtering than if you had a single 99% filter because of some optics math that's too complicated to bother with.

Thanks. I'll see what I can get my hands on. Right now this stuff is a hell of a lot cheaper than actual solar eclipse film.

[Ex-California]

If you want to view it you can use a welding mask

I'm fucked off because i'm never in full shadow either.

[The Conservative]

If you want to view it you can use a welding mask

I'm fucked off because i'm never in full shadow either.

Actually, that isn't a bad idea, just make sure you put it in front of the telescope and not the back end.

My idea is still cheaper. I spent 6 dollars for 100 feet of this stuff.