so what about medium format bellowsChrisR wrote:Lothar - 52mm bellows? Often bellows + adapters is just too ungainly, or the diameter of the bayonet is too small.
http://www.ebay.de/itm/P-Six-Pentacon-T ... Swax5YrrZg
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so what about medium format bellowsChrisR wrote:Lothar - 52mm bellows? Often bellows + adapters is just too ungainly, or the diameter of the bayonet is too small.
No, not never better. It is better in the cases I explained. In the particular case of a number of sets of the same tubes, only, yes you are correct which is why some series quoted in the original post were irregular. If you're worried about having zero redundancy in multiple sets then yes have a set of primes, or, sets with different lengths in each.Chris, it is never better to make regular series.
Not always, only if you have multiples of the same tubes. 5,10,15 wasn't suggested.Never 5, 10, 15. You'll always have more choices with non-integer multiples.
If I've counted correctly, it takes at least 4 sets to do that well.Lou Jost wrote:Maybe 5, 9, 29 if limited to three. With multiple sets you could then cover 5, 9, 10, 14, 15, 18, 19, 20, 23, 25, 27, 28, 29, 30, 33, 34, 35, 36, 38, 39, 40, etc.
That's a tempting intuition, but I disagree. My tabulation shows a gap of 3 mm between 53 and 56, and between 58 and 61, and repeating regularly after those every 29 mm.Coverage would be virtually complete from this point onward.
I think soelf wrote:Haven't you guys heard of bellows?
It doesn't say 5mm, those are ratios not mm.Look at my example above. The 5mm gaps are big, and unnecessary;
Then you need an adjustable element to get it exact - or state a number you'll accept as close enough, and in what range. The goalposts are moved.The problem I'm trying to solve is not an arbitrary one, Chris. Many of us need to construct tubes that can reach a particular given length (for example, to mount Raynoxes as tube lenses).
So, if Rik was right, that's 4 sets (Edit : or some other multiple ) of tubes plus an unspecified "big tube"?!!For any desired length greater than 40mm, you can use a big tube for most of it and leave the last 40mm to be covered by different combinations of 5, 9, 29mm, exact to within 0.5mm.