Is there a need for F1.4 lenses....

Started 4 months ago | Discussions thread
JimKasson Forum Pro • Posts: 27,806
Re: Is there a need for F1.4 lenses....

Philnw2 wrote:

JimKasson wrote:

AiryDiscus wrote:

fferreres wrote:

Philnw2 wrote:

I won't mention any brands, but there have been chronic reports of decentered f1.4 lenses for some. Perhaps specific facilities are not all equipped to deal with accurate mfr of these kinds of lenses.

HEre are some examples of sample variation. You buy a lens, and itmight be trash or diamond. It it a lottery? Apparently, yes,

The longer the FL and the faster, the worst this is.

This ones give an idea over 2D surfaces. It's not just less sharp...

In all honesty, I don't think the principal and unavoidable cause is a faster aperture. A faster aperture, with good glass, may not necessarily be harder to align.

It takes an optical designer of extraordinary skill to produce a design of a larger aperture that is easier to align than one of a smaller aperture.

And, given the same designer, doesn't a smaller aperture always make the job easier? At the very least, not harder, since you can produce an f/2 lens by not allowing the diaphragm of an f/1.4 lens to open up all the way.

Larger apertures almost by necessity have larger ray angles, which are more sensitive to small perturbations than small angles.

The difficulty is that producing small nm layers and layers (3? 5? per side) perfectly even

Antireflective coatings can be anywhere from a few angstroms (airsphere or whatever Canon calls, it nano or whatever nikon calls it, and so on) to 10s of nanometers thick. As a race, we figured out how to deposit atomically thin layers of these compounds decades ago. It is challenging, but very much a solved problem. Coating [uniformity, layer thickness, ...] are a nonissue in modern optics.

at that scale and also aligning what, 20 elements, grows in complexity exponentially. Anyone that ever played Yenga can have an intuitive way to visualize it.

More elements does not mean harder to align. Often, the number of elements is increased to trade production cost in terms of grinding, polishing, etc, for production cost in alignment tolerances.

Jim, i know you understand the theory, but have you actually made a lens yourself??

Only telescope mirrors.

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