Why does sekonic 308S have a f3.6 vs my Canon 30Ds f3.5?

[buurin]

I noticed my Sekonic L308S light meter, when setup for 1/3rd stops, calculates an f-stop of f3.6

My canon 30D (and every 1/3rd f-stop chart I've seen) shows f3.5.

Just curious.

[FlashZebra]

Possibly due to leap year rounding.

Enjoy! Lon

[Curtis N]

One-third of a stop less than f/4 would be 2 to the power of (11/6), or roughly 3.563594873 .

So technically, if you're going to round it, you should express it as 3.6 .

Improper rounding of f/ stops is a long-standing tradition among camera makers. One stop less than f/8 is roughly 5.656854249 which should round to 5.7 but it's generally expressed as 5.6 .

Go figure.

[cccc]

It's called truncating, not improper rounding.

[buurin]

Thanks guys.

[TMR Design]

It's called truncating, not improper rounding.

You are correct Sir!

[Curtis N]

I know what it's called. And every math or science teacher I've ever had will say it's improper.

[PacAce]

It's called truncating, not improper rounding.

I think Curtis expressed it correctly in his sentence because it's not always the case that the number is being truncated.