# Thread: Filters and Large(r) Apertures... Help

1. ## Filters and Large(r) Apertures... Help

Let's preface this by letting you all know (which you'll soon figure out) that I'm terrible with numbers.

I've been loosely trying to figure this out for a while, but thought I would ask on here, as I've had good luck before. Now, let's see if I can explain this properly...

I'm wanting to shoot one of my lenses in the F2.5- F/4 range on bright days (summer is actually here, apparently). Normally, this isn't my bag, but I'd like to give it a shot.

The problem I have (being pretty inexperienced with all the calculations...and math in general... and LF... and...) is figuring out how to compensate with my filters with the limited shutter speeds of my lenses (highest being 1/1000 on my speed graphic , and lowest being 1/400 on my Rodenstock).

I tried to experiment on my digital camera, but reducing the shutter speed according to full stop increments left things under-exposed. I'm sure I'm doing something wrong.

Ok, I guess my question is this (if you've made it this far)...

Example:

-Meter reads at 1/4000 at F/2.5

-I want to keep the aperture at F/2.5 (Don't judge me)

-My highest available shutter speed is 1/1000

-I have a 10stop filter and a 6 stop filter available to me

-What the heck do I do?

Did that even make sense?

2. ## Re: Filters and Large(r) Apertures... Help

6 stop ND filter, your shutter speed is 1/60 @ f2.5
4000-2000 1 stop
2000-1000 2 stops
1000-500 3 stops
500-250 4 stops
250-125 5 stops
125-60 6 stops
And you are good to go.

3. ## Re: Filters and Large(r) Apertures... Help

Originally Posted by seandavid
Example:
-Meter reads at 1/4000 at F/2.5
-I want to keep the aperture at F/2.5 (Don't judge me)
-My highest available shutter speed is 1/1000
-I have a 10stop filter and a 6 stop filter available to me
-What the heck do I do?
One stop equals a change in shutter speed by a factor of 2.
So going from 1/4000 to 1/2000 is 1 stop; from 1/2000 to 1/1000 is another stop for a total of 2 stops.

You need a 2-stop ND filter.

To use your 6-stop ND filter you must drop 4 more stops, thus:
1/1000->1/500, 1/500->1/250, 1/250->1/125, 1/125->1/60

So shooting 1/60 @ f/2.5 should work provided the metered light level is the same.

- Leigh

4. ## Re: Filters and Large(r) Apertures... Help

Thanks, guys.

I did some tests, and I guess my filters are not exactly what they say. The 6 stop is a 7 stop, and the 10 stop is a 10 and 1/3 stop.

Thanks again!

5. ## Re: Filters and Large(r) Apertures... Help

Just a couple of questions:

1. How are your ND filters marked, ex. ND6X, 3.0ND, 0.9, or ?

2. How did you determine their "actual" transmission? Was it with a camera meter or hand-held meter?

6. ## Re: Filters and Large(r) Apertures... Help

Originally Posted by seandavid
I did some tests, and I guess my filters are not exactly what they say. The 6 stop is a 7 stop, and the 10 stop is a 10 and 1/3 stop.
Unless you have some really good optical test equipment, I suggest using the manufacturers' specs.

Very few filters or films are flat across the visible spectrum.
They tried to tailor the density based on the response characteristics of film.

- Leigh

7. ## Re: Filters and Large(r) Apertures... Help

You can adjust your digital camera to work in half stop or third stop increments. perhaps half stop increments would help you understand it. The math is simple but important. Easily conquered with some practice.

I shoot FP4+ on bright summer days because it's a lot slower than my normal film (tmy2).

8. ## Re: Filters and Large(r) Apertures... Help

Originally Posted by xkaes
Just a couple of questions:

1. How are your ND filters marked, ex. ND6X, 3.0ND, 0.9, or ?

2. How did you determine their "actual" transmission? Was it with a camera meter or hand-held meter?
They just say 10 stop and 6 stop on them (respectively). They're from a company called Breakthrough Photography https://breakthrough.photography/pro...nt=30850759697

My test sure wasn't scientific. I used my digital camera. I just metered a scene... meter read 1/1000 at F/4. Took a shot without the filter, Then threw on the 6 stop filter and reduced the exposure by 6 stops. It was dark. I then reduced it until the exposure (here's where it gets real, ummm "scientific") visually looked the same as the shot without the filter (which was a 7 stop reduction).

9. ## Re: Filters and Large(r) Apertures... Help

Given the prices they charge for their ND filters, you deserve an accurate filter, as well as a free night at a luxury hotel.

Your test methods leave a lot to be desired but since I don't know your gear, all I can suggest is to put your camera on a steady support. Then meter a blank, midtone scene, such as a gray card or evenly illuminated wall -- with and without the ND filters. Hopefully your camera gives you some sort of f-stop and shutter speed readout that you can compare. Without that, I'm afraid you are just using your eyeball -- not too accurate.

10. ## Re: Filters and Large(r) Apertures... Help

Originally Posted by seandavid
I used my digital camera. I just metered a scene...
Digital cameras are less than worthless for objective analysis. They're deceptive and manipulative.

They take a meter reading, then manipulate it to achieve the "best" appearance assuming a human subject.

Absolutely invalid for any reliable testing since they don't tell you what the algorithm is.

Get a hand-held exposure meter, preferably of the vintage variety though it really doesn't matter.
Use a sunlit white wall as the subject, standing where your shadow is not in the metered area.
Meter the wall without the filter, then with.

- Leigh

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