Flash ND calculator?

Is there a calculator out there that allows you to input your cameras sync speed as well as the aperture and iso that will then output how many stop ND filter you need to get down to your sync speed in broad daylight?

Sunny 16. Go from there.

Your sync speed is fixed, so just add as many ND filter densities as stops of aperture you open up. Sunny 16 = 1/200, ISO 100 @ f/11. Thus:

@ f/8 — ND 0.3 (1 stop)
@ f/5.6 — ND 0.6 (2 stop)
@ f/4 — ND 0.9 (3 stop)
.
.
.

Alveric wrote in post #18011391
Sunny 16. Go from there.

Your sync speed is fixed, so just add as many ND filter densities as stops of aperture you open up. Sunny 16 = 1/200, ISO 100 @ f/11. Thus:

@ f/8 — ND 0.3 (1 stop)
@ f/5.6 — ND 0.6 (2 stop)
@ f/4 — ND 0.9 (3 stop)
.
.
.

There are also apps for the iPhone and I presume Android that will do the calculating.

Some Ambient and studio flash meters will also do this... The Sekonic L-478DR-EL

Better yet, take time to figure this out yourself too. It's fast and easy once you do it a few times. Nothing beats the mind of a good photographer to work problems! If your batteries run out, you'll have to do it anyway. It's really a very minor calculation. Just know and understand your f-stops.

Angmo wrote in post #18011492
Some Ambient and studio flash meters will also do this... The Sekonic L-478DR-EL

Better yet, take time to figure this out yourself too. It's fast and easy once you do it a few times. Nothing beats the mind of a good photographer to work problems! If your batteries run out, you'll have to do it anyway. It's really a very minor calculation. Just know and understand your f-stops.

The key is knowing how many EV each of your ND filters block.

Stregone wrote in post #18011383
Is there a calculator out there that allows you to input your cameras sync speed as well as the aperture and iso that will then output how many stop ND filter you need to get down to your sync speed in broad daylight?

Heya,

I do it manually with Sunny 16 in mind. I was shooting the other day with a 90mm F2.8 out in the evening sun. It was a little darker than the brightest time of day, so I had even more room to play around. But, I knew that 1/100s, F16, ISO 100 meant that 1/200 (-1 stop), F2.8 (+5 stops from F16) and ISO 100 meant I had to make up for +4 stops of light. It was a bit darker than the brightest part of the day, so I really probably only needed a 3 stop ND filter to make up for the light I added with my targeted settings. I then measured my flash output to be a bit lower than my exposure value (F2.8 + 3 stops of ND is the same as metering at F8). I wanted it just under that, enough to fill, but to blend in more, so I metered at F6.3. Then took my photos.

I'm sure there are android/iphone calculators for this. But I just do it in my head. It's not hard to count 4~5 stops. It only gets nuts when you're dealing with 12~16 stops of ND filter (obviously not with flash, and meant to be in minutes or even hours depending on context). In general, I know I can get away with 1/200s, F2.8, ISO 100 and a 3 stop or 4 stop ND filter in most daylight situations. I know I need 6 stops to do it at F1.4. I just stick to those.

I do use a lightmeter though, the Sekonic 478D. When I meter, I just use my aperture + any stops of ND for a total stopping value to meter at. Again, F2.8 + 3 stops of ND is F8 light, so I just meter the flash to F8 and I'm good to go (then purposefully under expose or even over expose depending on goals, etc).

Very best,

Why not a chart like this one. http://f128.info/p/lat​ex/ev_table.png

To use it, ignore the true EV values at your desired ISO, but simply assume ISO 100 (the brightness difference, in #3, is always the same!)

1. look up the EV value of your desired sync speed and f/stop combination
   
2. then look up the actual ambient shutter and f/stop combination
   
3. Subtract #2-#1, and the resulting difference is how many EV you need in the ND filter reduction
   

1. 1/250 f/8 is EV14
   
2. 1/400 f/16 is (about) EV17
   
3. difference is 3EV...so you want an ND8
   

Wilt wrote in post #18012719
[..]
The world is so darn reliant on automation that nobody knows how to THINK any more!

Sometimes not even the coders of the apps and software we rely on!

Alveric wrote in post #18012721
Sometimes not even the coders of the apps and software we rely on!

They are the exceptions!

Like Wilt, I must be old.

I don't even consider it a calculation, it's just counting stops rather than metric digits.

yup, practice plus experience and then you will just be able to figure it out. Reliance on letting someone else do it for you will keep you from experiencing the critical thinking that will help you become a better, more efficient photographer.

... you old people aren't making me feel any better about my fast approaching 46th.

Alveric wrote in post #18011391
Your sync speed is fixed, ...

True, but your recommended sync speed might be fudged a little. Depending on your camera & the situation, you might be able to use a higher sync speed: Strobe sync @ 1/400: Pushing the limits.