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F-stop split


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#1 Aaron Solomon

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Posted 30 March 2010 - 12:31 PM

Hi all,

What does it mean when you have, say a f/2.8-5.6 split? I came across it in another forum and I'd never heard of it.

Thanks,
Aaron
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#2 Brian Drysdale

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Posted 30 March 2010 - 12:42 PM

Any times I've heard the term used it's setting the aperture half way between two f stop markings on the iris ring. E.G. split between f2.8 & f4, you set the aperture at the mid point between these stops.
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#3 Aaron Solomon

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Posted 30 March 2010 - 12:45 PM

Any times I've heard the term used it's setting the aperture half way between two f stop markings on the iris ring. E.G. split between f2.8 & f4, you set the aperture at the mid point between these stops.


Thanks!
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#4 Adrian Sierkowski

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Posted 30 March 2010 - 01:30 PM

I don't think I've ever heard of a 2.8/5.6 split, but for the record that'd be an F4 ;) Generally it has to do with increments between 2 stops which are next to each other.
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#5 Aaron Solomon

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Posted 30 March 2010 - 01:41 PM

I don't think I've ever heard of a 2.8/5.6 split, but for the record that'd be an F4 ;) Generally it has to do with increments between 2 stops which are next to each other.


Sorry yeah I just made up two F numbers because I was was just trying to find out what the split meant. How do you calculate that to be an F4? So it refers to increments between stops?

Thanks

Edited by Aaron Solomon, 30 March 2010 - 01:42 PM.

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#6 Adrian Sierkowski

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Posted 30 March 2010 - 01:46 PM

F4 is between F2.8 and F5.6, so if you "split it" meaning down the middle that's where you'd wind up. There's no calculation really. Generally when you're calling a "split' you mean between, something like a reading of 2.8 and 1/2. You could say 2.8 and 1/2, but most people call out a 2.8/4, or a 2.8/4 split. I also often call out "bumps," which would be 1/3 or a stop. something like a Bump over 2.8 (2.8 and 1/3) or a bump under 4 (2.8 and 2/3).

The other time you might use a split is when you have 2 different luminance which you want to keep exposure on; let's say you meter a scene and you see that person A by the window is at an 8 and person b in the room is at a 2. You could bring in more light, but for this example you'll just call out a 8/2 split and split the difference in exposure. letting person A over expose a bit and person B under expose a bit. Again, this would be an F4 as its directly between 2 and 8 on the F stop scale (2/2.8/*4*/5.6/8).

Hope that helps.
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#7 Rob Vogt

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Posted 30 March 2010 - 01:51 PM

Between stops are usually done in thirds or halves a 2.8/4 split would be directly between the two, or 2.8 and a third or 4 minus a third. In Europe people usually just say 2.8 plus to mean 2.8 and a third.
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#8 Aaron Solomon

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Posted 30 March 2010 - 03:43 PM

Thanks guys. Adrian I understand your second example. For the first example, are you saying that it's sort of a way of breaking down a stop into smaller pieces? So its half way between 2.8 and 4? Remind me to go memorize the f stop scale. My mom would never want me to say this but im a minor (out of respect for her I'm not gonna say my actual age, though I trust you guys) who does event camera work but I love doing fiction stuff and my goal is to be DP so let's see how this turns out. Thanks again guys.
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#9 Aaron Solomon

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Posted 30 March 2010 - 03:50 PM

I think I get your first statement now too.
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#10 Adrian Sierkowski

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Posted 30 March 2010 - 04:10 PM

That's it. Just a way of breaking things down. Nothing wrong with being a minor, I was a minor once. it's good to start young and get your feet wet.
The thing with F stops that helped my was looking at their pattern of doubling and halving every other number so:

0.5 0.7 1 (see double the .5) then 1.4 (double the .7) 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45 64 . . .

For the most part you'll be working with 1.4--->22 on lenses ;)
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