That's the site I was thinking of Stefan, just never bookmarked it. Exposing to the right rarely works out correctly when there isn't a lot of white in the picture. The mid tones come out too light but I suppose they can be taken down abit in PP. The digital preview is about the safest.

If you photograph say a swan you have to adjust the exposure so that large areas of white aren't clipped, but if the next shot is of say a female Mallard using the same exposure will be too dark (assuming it's sunny). So you have to use a bit of common sense even with the Sunny 16 rule

It's still valid using an 18% grey card, I should have mentioned I use it also for colour balance. In a correctly exposed shot (mid-toned) the grey card should read around RGB 118

Unfortunately sensors won't cover the full range of tones, but 35mm B&W film won't either it loses a full Zone of the Zone System compared to 6x6 or 5x4 from the highlights.

Just as a warning in case anyone ever considers using any type of oil on a lens don't!! It will eventually get on the aperture blades and make them stick. Even good quality lens grease has in the past caused problems when it separates back into oil and soap.

Special expensive greases are used nowdays, mostly lithium based.

Pentax are one of only a few lens manufacturers that have used greases that rarely cause problems. CZ Jena and the Russians have used greases that become very stiff over the years, probably waxes rather than grease.

That lens probably isn't that rare and unless some of the SN figures are missing it's a fake. CZ started using mm's in the description in 1952 instead of the previous cm's. The SN would have been over 3.47M. If it has a 6M+ SN it would be from 1961-64. I can't see the name Biotar on it and it has CZ rather than Carl Zeiss? Does have 12 aperture blades though? Carl Zeiss will have a record of what lens was made with that SN.

For anyone interested this is a good write up about the CZ history. There's also a bit on the official CZ site

The Zenith Helios 58mm was a copy of the Biotar, but with 6-8 blades.

Nice sharp shots. I've never seen ducks running like that
Really cute

Meercat for me (colour version).

I'm not usually a fan of digital B&W but these are really
sharp and close to the quality of film B&W. I particularly
like the 2nd one.

Very Nice.....Reminds me of Salford

There was a famous American wedding photographer in the 70's who had fixed exposure settings for everything on a wedding from bright sunlight right down to candlelight which was "wide open at 1/8th sec. handheld" (if I remember correctly.

When I was at school (in the 60's)one of out teachers had a Johnsons Diary with an exposure calculator that was made of stiff card that rotated around a rivet. You had to dial in location (long, lat from a table). Time of day. Type of lighting, sunny, cloudy bright etc. and then read off the exposure.

Luckily this US seller of a stiff "very rare carl zeiss Jena 58mm 2.0 aperture lens" hasn't link

He's advising buyers "a dab of gun oil on the sides of the focus ring will make it like new again, ran out of lens or gun oil so Ive only been able to work on it with twisting methods."

I don't have any links handy, but it's more or less covered in the theory about exposing to the right of the histogram. More bits are available to store RGB information in the lighter areas.

For exposure as long as you know how many stops higher the reading is it's easy enough to compensate for it. You could take a reading off a white sheet of paper and expose for 3 stops less or 2.5 stops if you want detail recording in the white paper. Similar to taking a reading off snow.