Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2

Started 4 months ago | Discussions thread
Anders W
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Re: Crop Factor, Low Light and Aperture with m4/3 lenses? Part 2
In reply to bobn2, 4 months ago

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

bobn2 wrote:

Anders W wrote:

If you can scale down manufacturing tolerances by a factor 2

Why wouldn't manufacturing tolerances scale?

That is such a ridiculous question, if just you stop to think about it. Every manufacturing process has an associated set of tolerances. So, if you use the same process to produce a smaller product, you are not scaling the tolerances. If on the other hand you develop the tolerances so as to be able to scale them for the smaller product, then that finer tolerance process is available also for the larger product. The exception is only if the smaller size itself allows some change in the process which provides for smaller tolerances.

See my reply to noirdesir here, penultimate section:

http://www.dpreview.com/forums/post/53893177

No connection with the question of scalability of tolerances at all. Linking irrelevant posts, implying that you had made some response to the point already is a most dishonest mode of argumentation.

I pasted the wrong link by mistake. Try this instead:

http://www.dpreview.com/forums/post/53896543

OK, what you said was

The tolerances at issue in this case are those for producing and fitting glass elements. Suppose we were to fit a lens with a diameter of one centimeter and another with a diameter of one meter to the same precision in absolute terms, say one micrometer difference between the edges. Do you think that could be done with the same ease for the one meter lens as for the one centimeter lens?

That in no way answers the question. It is a 'thought experiment' situated in a fantasy. You have chosen an absurd example to 'prove' your case.

I just chose an example that makes the general point that the ability to reach a certain tolerance target as expressed in absolute terms (e.g., micrometers) rather than relative terms (proportions) depends on the size of the objects we are dealing with.

There are no 1m elements in commodity photographic elements, and those optical instruments which use them certainly do not use the same production processes either for grinding nor for mounting the lenses - but then they don't have to be produced to the same market costs. Is the technology used to grind, coat and mount mFT lenses, for example, any different to that for FF lenses, so a 2cm vs a 1cm element? Are the mFT lenses half the size of FF lenses? If we're talking about scalability of tolerance (if it actually existed) then you'd have to assume that they are, else the tolerances wouldn't scale.

As I said, the truth is that the tolerance goes with the production process, not the size of thing being produced. If the size allows another production process, then tolerances will change, otherwise they won't.

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