It's not hard at all once you learn to "think in f-stops." The first thing to learn is the film speeds, which progress in 1/3 stop increments, as follows, and starting from 25:
25 32 40 50 64 80 100 125 160 200 250 320 400 500 650 800 1000 1250 1600 etc.
The numbers are easy to remember once you notice that each third number is doubled: 25 50 100 200; 32 64 125 250; 40 80 160 320
And of course, each third film speed is a full stop faster or slower, depending on the direction you move.
Full f-stops are also a numerical progression; every other one is doubled:
f1.4 2.0 2.8 4 5.6 8 11 16 22 45 etc.
To apply compensation, all you have to know is whether you are opening up or stopping down, and how many stops.
This post is exactly what I've been looking for since I started photography again. I pretty much forgot the basics. I'd been able to piece nearly everything back together except for the above.
This is a very helpful thread and Eddy makes it very clear on the relationship of film speed and f-stops. I do however want to make sure that I am clear on this - is the original poster and the responses dealing only with a hand held meter and a non-metered camera? What I have never been clear on is if you use a filter on a TTL metered camera does the TTL metering system fully take care of the reduction in light getting to the film or are there circumstances where you would have to make additional compensation to the TTL meter reading.
Yes, The meter compensates, sort of.
But. The meter doesn't have the same response to color that film does. So in theory it's not 100% accurate. The question is can the differences be seen.
Try exposing the same scene with and without the filter & process the film.
The exposures should be very close. If not you need to provide a bit of a fudge factor.
Thank you for this response. It's good to know and I guess that I will try this over the coming days. I should however have been more specific in my question and it relates to very dark filters in b+w photography for example a dark red (Nikon R60) to give really dark skies. I have never had much success with this filter and I don't have the filter factor for the R60 however I have seen 4-6 stated on the internet (which I assume equates to 2-3 stops). Is it best to use a handheld meter and adjust manually, or use a TTL meter and bracket when using dark filters?
I've never been one to do things the easy way.
Personally I'd be inclined to the test exposure/process with each of the darker filters rather than ttl. You could use the in-camera meter and adjust for a tested compensation or use a dial in +X compensation.
Or, bracket. I would think to the side of overexposure rather than under.