f/3.5

EASmithV · Mar 15, 2012

It's time for me to stop whoring the small details of exposure using negative film, or rounding it up to f4 for shooting slides... What exactly should F3.5 read on a Sekonic L-508 or similar as? f/2.5 + 5/10?

removed account4 · Mar 15, 2012

hi there

this might help!

http://en.wikipedia.org/wiki/F-number

it is confusing ... 3.5 is 1 full stop beyond 2.5

have fun !
john

EASmithV · Mar 15, 2012

Oh god, I got lost in the numbers...

at least for f2.5 it's close enough that I can meter at f2.8 and probably not worry about it, besides my only f2.5 lens has an f2.8 click... haha.

I always thought that f3.5 was ha half stop slower than f2.8... so wouldnt it be f2.8 plus half a stop, reading as f2.8 and five tenths on the meter?

Or am i missing something.

holmburgers · Mar 15, 2012

f/2.8 + 2/3rds, or f/4.0 - 1/3rd.

You could probably get away with calling it halfway between f/2.8 & f/4.0

removed account4 · Mar 15, 2012

EASmithV said:
Oh god, I got lost in the numbers...

at least for f2.5 it's close enough that I can meter at f2.8 and probably not worry about it, besides my only f2.5 lens has an f2.8 click... haha.

I always thought that f3.5 was ha half stop slower than f2.8... so wouldnt it be f2.8 plus half a stop, reading as f2.8 and five tenths on the meter?

Or am i missing something.

on the page i linked to there are 3 tables one is labled "1/3 stop"
it has both 2.5 AND 3.8 and there are 3 third stops between them ... 3 third stops is 1 stop

they go like this ...

.07 .8 .9 1 1.1 1.2 1.4 1.6 1.8 2 2.4 2.5 2.8 3.2 3.5 4 4.5 5 5.6 ...

bold are full stops the others are 1/3 stops ... 2.5 is 1/3 less than 2.8 and 3.5 is 1/3 less than 4
they are 1 full stop relative to eachther

i have never used your meter before
but you should set it up as 2.5 + 1 ... pretty easy

you are lucky you don't have any lenses that use the stoltz or other oddball systems
yours is pretty easy as long as you don't overthink it

EASmithV · Mar 15, 2012

Argh. I swear they make f3.5 lenses to annoy me.

BrianL · Mar 15, 2012

My Weston has 3.5 on the dial; maybe they courted Rolleiflex users.

Ole · Mar 15, 2012

There are historical reasons for this, of course...

In Germany, "base 100" was common. 2.2, 3.2, 4.5, 6.3, 9, 13, 18, 25, 36, 50, 72, 100 ...

In France they tended to use "base 10": 2.5, 3.5, 5, 7, 10, 14, 20, 28, 40, 56, 80 ...

And the "modern" system is "base 1": 2, 2.8, 4, 5.6, 8, 11, 16, 22 (which is really closer to 23), 32, 45, 64 ...

The US (Unified System or something like that, not USA) was 1, 2, 4, 8, 16, 32 and so on - where US16 =f/16.

And of course the "reverse systems", which are proportional to either the diameter or the area. Stolze is one, another was called "French System".

Some lenses, especially casket sets and convertibles, have markings corresponding to the diameter of the aperture. Or the area. In whatever units seemed reasonable at the time.

Worst of all are what I call "AU", or "Arbitrary Units" - where the aperture settings are marked with 1, 2, 3, 4, 5, 6. Or 1, 2, 3, 4, 8, 10...

Poisson Du Jour · Mar 15, 2012

Your Sekonic should show f3.5. It's measures go much further below that, and much higher. If you have set the custom functions to 1 stop, it will not show you the smaller increments. Likewise, half-stop is better, third stop better again for reversal metering.

keithwms · Mar 15, 2012

For negs I usually treat 3.5 as 4, so as to err on the side of slight overexposure. For slide, I treat 3.5 as 2.8, so as to err on the side of slight underexposure. You can of course also change the EI just a bit to compensate, as needed.

Don't sweat the petty details, and don't pet the sweaty details.

EASmithV · Mar 15, 2012

keithwms said:
For negs I usually treat 3.5 as 4, so as to err on the side of slight overexposure. For slide, I treat 3.5 as 2.8, so as to err on the side of slight underexposure. You can of course also change the EI just a bit to compensate, as needed.

Don't sweat the petty details, and don't pet the sweaty details.

Got a present for you now

Taken somewhere in London

Poisson Du Jour · Mar 15, 2012

Keith's vacation dig, obviously.

keithwms · Mar 15, 2012

Haha. Only the very finest accommodations for me.

What is that, provia in non-5000 K light, Eric?

Vaughn · Mar 15, 2012

BrianL said:
My Weston has 3.5 on the dial; maybe they courted Rolleiflex users.

I have a Graflex 22 -- a TLR with a Graftar 85mm/f3.5 taking lens. Made after Graflex bought out Ciroflex, I believe. So its f/stops go f3.5, 4, 5.6, etc...while an old Rolleiflex of mine goes straight from 3.5 to 5.6. No f4 marked.

Vaughn

Doremus Scudder · Mar 16, 2012

I like to use the one-third stop scale. I also often don't bother with the numbers, but just think of intermediate stops as "+" or "-" one-third of a stop from one of the whole-stops (e.g., f/5.6 +1/3).

Question: do you really shoot at f/3.5? If so, then just think of it as f/4 + 1/3-stop (remember, smaller f-numbers = more exposure) Most meters are laid out in one-third stop increments so this should line right up with a mark on the meter somewhere. (Shutter speeds are not so easy though... if you're shooting wide open at f/3.5 then you'll have to pick a shutter speed that can be up to 2/3-stop off. You get to decide whether to over-or underexpose).

@keith: I think you've got your exposure backwards -- f/4 is 1/3 stop underexposure from f/3.5 and f/2.8 is 2/3-stop over (assuming that f/3.5 is the "correct" stop).

Best

Doremus

www.DoremusScudder.com

ath · Mar 16, 2012

And then there are manufacturers which call the half stop between f/4 and f/2.8 simply f/3.5.

removed account4 · Mar 16, 2012

ath said:
And then there are manufacturers which call the half stop between f/4 and f/2.8 simply f/3.5.

you make it so simple

Roger Cole · Mar 16, 2012

keithwms said:
For negs I usually treat 3.5 as 4, so as to err on the side of slight overexposure. For slide, I treat 3.5 as 2.8, so as to err on the side of slight underexposure. You can of course also change the EI just a bit to compensate, as needed.

Don't sweat the petty details, and don't pet the sweaty details.

But then you're overexposing neg film by 1/3 stop, which you will never notice, and underexposing slide film by 2/3s stop, which you WILL notice.

For neg film I too pretty much just treat it as f/4. If I'm shooting slide film hand held, I'm doing it in 35mm and have TTL metering anyway. If I'm shooting slide film in medium format I am probably working off a tripod or in decent light and won't be shooting my one medium format 3.5 lens (on my Yashicamat) wide open anyway. And in 4x5 I don't have any lenses that fast anyway. So for practical purposes it's a non-issue.

Even slide film can generally handle 1/3 stop overexposure though it will change the look, but if you treat it as half way between 2.8 and 4 you will be only 1/6th stop off and even in slide film you won't notice that.

EASmithV · Mar 18, 2012

keithwms said:
Haha. Only the very finest accommodations for me.

What is that, provia in non-5000 K light, Eric?

E200 pushed 1 stop, shot in twilight with a Nikon F and a 50 f1.4 pre ai

John Austin · Mar 18, 2012

It's just a aperture, between f2.8 and f4

f/3.5

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