Fill Flash compensation - F-Stops question

I've just bought a light/flash meter (Sekonic Flashmate L-308S Digital Light/Flash Meter) to try and eliminate a lot of trial-and-error I'm experiencing, and as such am trying to better understand the f-stop scale.

I read this: A Tedious Explanation of the f/stop which made a lot of sense, although I need to somehow learn and memorise the whole f-stop numbers (1.4 2.0 2.8 4 5.6 8 11 16 22)

I then read this article: Balancing Flash with Ambient Light and again it made sense, except for the bit "I cut down the power on the flash by two f-stops"

Looking at my flash (a Yongnuo 568), the power is adjusted as fractions (1/1, 1/2, 1/4, 1/8, etc). I learnt in the first article that each f-stop is twice (or half) of the previous f-stop, so am I correct in thinking that each flash setting is 1 stop apart. So, in the second article, if the author had their flash at 1/1 power and then needed to drop 2 stops, they'd adjust it to 1/4 power ?

I think I've got it - would appreciate some confirmation.

Cheers
Lawrence

Yes, those numbers are full stops. The progression, 1/1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128 are each either 1/2 of or twice the power level on either side.

You are correct, closing down two stops (from full, or 1/1) would be 1/4 power. Three stops would be 1/8, four stops would be 1/16, etcetera.

You got it!

Thanks John - it's all beginning to make sense.

Lawrence

And remembering whole value f/stops simply is understanding that everything is 2* multiples of 1.0 or 1.4

1.0, 2.0, 4, 8, 16
1.4, 2.8, 5.6, 11, 22

To memorize the aperture full stops start with 1.4 and 2.0, those two are one full stop away from each other.

From there, double each and alternate. 1.4 doubles to 2.8 and 2.0 doubles to 4

Then 2.8 doubles to 5.6, 4 to 8, 5.6 to 11, 8 to 16, 11 to 22


Edit: what he said :P

Remember that each EV is 1.4 times its predecessor. i.e. 1 x 1.4 = 1.4, 1.4 x 1.4 = 2 (rounded up by a few hundreds.) 2 x 1.4 is 2.8 (rounded up) etc.

See if this helps (also contains all aperture settings in full and ⅓ f/stops).

A-ha! There is a 1.6 value. I was squeezing my brain trying to figure out how come from 1.4 to 2.0 there's a full stop (1.4 < 1.8 < 2.0 (!! WTH :confused).

Hm, Phil, isn't it 2.2, 2.5 and 14? At least that's what my cameras report.

Alveric wrote in post #16636209
Hm, Phil, isn't it 2.2, 2.5 and 14? At least that's what my cameras report.

Henry: To be totally, frank, I can't honestly remember other than that these figures were calculated (by me) and pre-date digital reporting by quite some time (as in decades). They also both tally with traditional Continental (ie European) reporting system and commonly marked apertures on mechanically controlled lenses. That the now-dominant English notation we take for granted these days completely supplanted the Continental system is no more than pure happenstance - each is equally valid, just starting from a marginally different base point.

I hadn't honestly looked at how digitally reported apertures sequence. Perhaps I ought to have done, given the paucity of proper cameras and proper lenses this century. Mea culpa

Truth to tell, all the figures we bandy about are more notional than precise because:

1. They are all approximations based on a √2 system. The figures we use are rounded for convenience and errors are self-compounding because of this. We'd end up with apertures like f/1.41421 - f/2 - f/2.82842 - f/4 - f/5.65685 (which would 'tidy' to f/5.7) - f/8 - hence f/11.4 - etc. until f/22 suddenly becomes f/23, with alternate ones wandering further and further from the commonly used figure. Pedantry gone mad - too much for an old man to cope with. I certainly wouldn't want to be remembering
   
2. f/stop notation strictly speaking refers to the diameter of an aperture relative to the focal length rather than light passing ability - that would be a t/stop, which also takes into account the non-100% transmission of lenses. Even here the relationship is to the diameter of a round aperture of equal area to the polygonal aperture we actually use now that Waterhouse stops have, errrm, vanished.
   
3. That we use the term f/stop to describe light passing ability is actually a total misuse of the meaning of the term.
   
4. Because of the mechanical nature of aperture blades physically closing down instantaneously, it's very doubtful if they ever reach other than an approximation of the same area orifice on consecutive activations. Quite some years ago now, I remember the BSI 'within tolerance' standard for mechanical apertures (ie blades opening & closing) was ±33⅓% - not exactly accurate! I've certainly observed visible differences in size between opening to f/5.6 from a smaller aperture and closing to the same setting from a larger aperture.

Makes sense. Too much rounding makes for poor accuracy. I could see that even when filing my taxes: the tax office's online calculator yielded a number that did not match my manual calculator.

At least it's clear to me now that the 'real' stop value is 1.4 and not 1.2, and that there is a full stop 'twixt 1.4 and 2.0 and not only 2/3's of one as I had initially assumed, mostly based on Canon's line of 50mm lenses.

Further to Henry's point about the disparity between my calculated figures (which I have now remembered were also checked against exposure meter dials of the time), it occurs that perhaps the scale would be more useful if it contained figures as reported digitally. Yes, there are changes. Life's like that! Just one of the lumps in the mashed potato of life - as they say.

Anyway, here's the modernised version. I really shall have to stop living in the past so thanks for the kick up the butt. Now, which Century is it??

Alveric wrote in post #16636419
Makes sense. Too much rounding makes for poor accuracy. I could see that even when filing my taxes: the tax office's online calculator yielded a number that did not match my manual calculator.

At least it's clear to me now that the 'real' stop value is 1.4 and not 1.2, and that there is a full stop 'twixt 1.4 and 2.0 and not only 2/3's of one as I had initially assumed, mostly based on Canon's line of 50mm lenses.

You pay TAXES?? Poor soul.

Funnily enough - and it's down to those marketing people again - lenses are round about the worst place to gain accurate information about ........ lenses! In the everlasting search for one-upmanship over competing brands, lens makers historically have just loved to squeak ever last smidgeon out of their labelling. So, for example, while Nikon had a 50mm f/2 standard lens waaaaay back when all cameras came with a 50mm lens, Canon countered with a 50mm f/1.8. Sounds vastly superior and soooo much faster. In effect, a very minor difference to photographers but a massive difference to the Marketing Dept. Minolta's version was a 50mm f/1.7 - again, much faster than the miserly f/1.8 Canon - NOT. And so it continues to the present day; they carry on pushing our buttons.

Similarly, as far back as the 1960s Canon made a 50mm f/0.95 lens - don't get excited, it was in RANGEFINDER fitting for the Canon 7. Mega prestige item to have in your catalogue and it's only in very recent years that anyone else has equalled it (Leitz 50mm f/0.95 Noctilux). Not because we lack the skills any more, just simply not viable except for a company who decided to really make the market sit up and take notice. Worked, didn't it! Definitely a marketing-driven exercise rather than a run-of-the-mill 50mm lens,simply playing on the business of numbers and pandering to those who 'must have it, irrespective'. Yes, I still want one. I've always wanted one almost since I started in photography. To use, not to polish and preen over though - need the Canon 7 rangefinder as well though. Oh well, keep playing the Lottery.

LOL. Yeah, this is the review I was referring to; I was wondering whether the 1.4 version is worth the considerable difference in price. Looking at the picture taken at 1.4 and then at the one taken at 2.0 I hardly see a difference that justifies getting the higher-priced lens. One full stop of light is gained, yes, but then again this is just another thing that has bugged me for a long while: why the obsession with the fastest aperture if you ofttimes have to stop the lens down to f/8 and f/11? Where's the gain really?

Some say, 'fast apertures for low light'... alright, assuming I [I]always[I] want a blurred background, which isn't the case: sometimes I do, sometimes I don't. I acknowledge that greater apertures have their uses, but I also wonder how much marketing psychology is involved.

Henry: I'll happily give you my take on your questions but I think it'd just go too far off topic and ruin the continuity for others - not exactly fill-flash compensation related.

I started with an answer and then thought it'd perhaps be better elsewhere. What I propose is that I PM you with it - hopefully tomorrow but I have a lot going on over the next few days so it may be a bit longer. I will respond though.