Silly Sekonic Question

semi-ambivalent · Jul 7, 2011

My Luna Pro SBC recently died and I picked up a Sekonic 308s. I've set it up and it certainly works but how do I read the aperture readout? E.g. it says "5.6 7". Is that some kind of logarithmic thing, or does it mean 3/4 of a stop past 5.6 ([5.6].75) towards f/8? I'm trying be be digital saavy here and all, and the 308s is a nice little device, but I really miss the Gossen's semi-piechart view of the world.

thanks,
s-a

tkamiya · Jul 7, 2011

That means at f/5.6 and the indicated shutter speed, you have SEVEN-TENTH of a stop too much light. (over-exposure) In other words, you are almost there to the next stop.

I was confused about this and called Sekonic tech support. The rep was very good at explaining this.

John Koehrer · Jul 7, 2011

IOW, Exactly......... 5.6+.7 at a given shutter speed.
But it is confusing when you first see them.

polyglot · Jul 7, 2011

As above, 0.7 of a stop more than f/5.6. Which makes it f/ (5.6 * 2^(0.7/2)) = f/7.2.

2F/2F · Jul 8, 2011

I don't think it is logarithmic in the way that you meant it. I think it simply uses commonly-used language to make the meter more readable to most people. Most people would know what you meant if you were to say "f/5.6 and two-thirds," but most people would not know exactly what you meant if you said "f/7.1."

Personally, I wish the meters would simply read out in 1/3 stops or 1/2 stops, and possibly 1/6 stops, each selectable by the user.

But for practical intents and purposes, there are only a few you need to know. If your f numbers are precisel to the 1/2 stop, you need to know .0 and .5, and how to decide which way to round for the given application. If your f numbers are precise to the 1/3 stop, you need to know .0, .3, .6, and how to round.

The decimal system on such meters is terrible for cameras with 1/3 stops IMHO.

polyglot · Jul 8, 2011

2F/2F said:
Most people would know what you meant if you were to say "f/5.6 and two-thirds," but most people would not know exactly what you meant if you said "f/7.1."

Really? f/7.1 is a standard 1/3-stop point. I'd be surprised if someone buying a meter didn't know what that** meant. It's not like incident or flash meters are handed out with P&Ses, they're aimed at a pretty technical audience.

** fully agree that the 10/ths stop extra digit the OP ran up against is confusing though.

Chan Tran · Jul 10, 2011

It's difficult to display and read aperture in 1/10 stop increments with a direct aperture readout. My KM Flashmeter VI has that option but when you set to direct aperture readout and with only 2 digits between f/1.0 and f/1.4 is only 4 steps. Larger aperture numbers are ok but still it will display values that we are not sure where to set on the camera. I believe new Sekonic meter has options to display in 1/2 or 1/3 stop along with option of displaying in 1/10 stop.

Diapositivo · Jul 11, 2011

Most probably any lens with an aperture ring can be set to any value, the aperture ring must not necessarily be set at a "click-stop", so you have all the positions between say f/8 and f/11 in any case.

The reason why light metres give 1/10th of a stop is not because you would need to set the aperture ring at exactly 7/10th of the distance between two values, but because you can use your lightmeter to check evenness of lighting which is important in certain cases such as reproduction work. The meter with a high "granularity" will allow you to set the lights just right so that you have a uniform appearance.

I use "thirds" of stops at most and don't bother with smaller subdivisions. If the meter says 5.6 + .8, that's 2/3 stop for me (doesn't coincide with a click-stop).

8 .1 = 8
8 .2 = 8 + 1/3
8 .3 = 8 + 1/3
8 .4 = 8 + 1/3
8 .5 = 9.5 (half stop between 8 and 11)
8 .6 = 8 + 2/3
8 .7 = 8 + 2/3
8 .8 = 8 + 2/3
8 .9 = 11

Fabrizio

PS If you are interested in typical numerical values for half-stop scale and third-stop scale:
http://en.wikipedia.org/wiki/F-number

benjiboy · Jul 11, 2011

These digital meters are also flash meters of course, and modern studio strobes output and modelling light output can be adjusted in 1/10th of a stop increments.

2F/2F · Jul 11, 2011

benjiboy said:
These digital meters are also flash meters of course, and modern studio strobes output and modelling light output can be adjusted in 1/10th of a stop increments.

Some can, and some cannot. Mine cannot. I have only 1/3 stop settings on the power pack of my Dynalites.

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