Lenses getting sharper! every few years! is there a downside?

Started Jun 3, 2013 | Discussions
Cytokine
Contributing MemberPosts: 626
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Lenses getting sharper! every few years! is there a downside?
Jun 3, 2013

I came across this publication from Schott Glass. (Zeiss is part of thi Schott group). Entitled:

Optical glass and glass ceramic historical aspects and recent developments: a Schott view

And it seems that lenses are becoming better and lighter because they are using higher refractive glass, but the downside is that Blue violet transmission could get worse, CMOS technology is already pretty bad at registering Blue violet. Here are a few quotes:

"Therefore high index glasses
(n > 1:8) ensure a high refractive power of the lens
and reduce the monochromatic aberrations. In addition
the high refractive power reduces the curvature
of the lens which in turn reduces the monochromatic
aberration as well as the weight of the lens. Unfortunately
the increased refractive index reduces the
transmission of the glass at about 400 nm (“blueviolet
transmission”) and below. This is a fundamental
relation since the refractive index rises only in the
vicinity of absorption lines, which also leads to higher
slopes, i.e., higher dispersion. There is no way
around this. High purity raw material and optimal
melting process can only avoid additional losses
and thus make the UV-edge steeper. However, for
thin lenses the blue-violet absorption may be low enough
to be acceptable"

"Camera software nowadays can compensate for
some color imperfections. However, current image
chips still have one major drawback: their weak sensitivity
in the blue range of the visible spectrum. This
requires that red and green channels have to be reduced
in intensity to fit to the weaker signal of the
blue channel."

Grevture
Veteran MemberPosts: 4,129Gear list
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Links and a minor (?) point of contention ...
In reply to Cytokine, Jun 3, 2013

Cytokine wrote:

I came across this publication from Schott Glass. (Zeiss is part of thi Schott group). Entitled:

Optical glass and glass ceramic historical aspects and recent developments: a Schott view

Here is the full article:

http://www.opticsinfobase.org/ao/fulltext.cfm?uri=ao-49-16-D157&id=202488

And here a short summary:

http://www.opticsinfobase.org/spotlight/summary.cfm?URI=ao-49-16-D157

And it seems that lenses are becoming better and lighter because they are using higher refractive glass, but the downside is that Blue violet transmission could get worse, CMOS technology is already pretty bad at registering Blue violet.

Now this is something you claim, and which I find a bit off target: What is your source of that statement of CMOS sensors specifically having problem with blue violet? It certainly is not mentioned in the article you quote. Actually, CMOS technology is not mentioned at all there. Which is not surprising, since CMOS technology has almost nothing to do with color reproduction and color response anyway since CMOS technology - just like CCD technology - is effectively color blind ... They are talking about image chips, meaning the complete package, including the color filter arrays which are very likely the culprits here - not the CMOS technology.

Other from that lapse, thank you for bringing up some interesting info on where optics are going.

Here are a few quotes:

"Therefore high index glasses
(n > 1:8) ensure a high refractive power of the lens
and reduce the monochromatic aberrations. In addition
the high refractive power reduces the curvature
of the lens which in turn reduces the monochromatic
aberration as well as the weight of the lens. Unfortunately
the increased refractive index reduces the
transmission of the glass at about 400 nm (“blueviolet
transmission”) and below. This is a fundamental
relation since the refractive index rises only in the
vicinity of absorption lines, which also leads to higher
slopes, i.e., higher dispersion. There is no way
around this. High purity raw material and optimal
melting process can only avoid additional losses
and thus make the UV-edge steeper. However, for
thin lenses the blue-violet absorption may be low enough
to be acceptable"

"Camera software nowadays can compensate for
some color imperfections. However, current image
chips still have one major drawback: their weak sensitivity
in the blue range of the visible spectrum. This
requires that red and green channels have to be reduced
in intensity to fit to the weaker signal of the
blue channel."

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I don't suffer from insanity, I enjoy every moment of it!
By the way, film is not dead.
It just smell funny

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Cytokine
Contributing MemberPosts: 626
Like?
Re: Links and a minor (?) point of contention ...
In reply to Grevture, Jun 3, 2013

Grevture wrote:

Cytokine wrote:

I came across this publication from Schott Glass. (Zeiss is part of thi Schott group). Entitled:

Optical glass and glass ceramic historical aspects and recent developments: a Schott view

Here is the full article:

http://www.opticsinfobase.org/ao/fulltext.cfm?uri=ao-49-16-D157&id=202488

And here a short summary:

http://www.opticsinfobase.org/spotlight/summary.cfm?URI=ao-49-16-D157

And it seems that lenses are becoming better and lighter because they are using higher refractive glass, but the downside is that Blue violet transmission could get worse, CMOS technology is already pretty bad at registering Blue violet.

Now this is something you claim, and which I find a bit off target: What is your source of that statement of CMOS sensors specifically having problem with blue violet? It certainly is not mentioned in the article you quote. Actually, CMOS technology is not mentioned at all there. Which is not surprising, since CMOS technology has almost nothing to do with color reproduction and color response anyway since CMOS technology - just like CCD technology - is effectively color blind ... They are talking about image chips, meaning the complete package, including the color filter arrays which are very likely the culprits here - not the CMOS technology.

Grevture, fair comment, I mentioned CMOS as I don't think CCD DSLR's are still being made. (Unfortunately) and they may have a different spectral response. However while sensors only record a signal for a given photon that is collected, not all colours (wave-lengths) give the same signal response.

It is unlikely that the filters will block the desired wave lengths, as filter technology is very advanced, with broad band glasses having been available for some time.

Other from that lapse, thank you for bringing up some interesting info on where optics are going.

Thank you. Also for providing the links.

John

Here are a few quotes:

"Therefore high index glasses
(n > 1:8) ensure a high refractive power of the lens
and reduce the monochromatic aberrations. In addition
the high refractive power reduces the curvature
of the lens which in turn reduces the monochromatic
aberration as well as the weight of the lens. Unfortunately
the increased refractive index reduces the
transmission of the glass at about 400 nm (“blueviolet
transmission”) and below. This is a fundamental
relation since the refractive index rises only in the
vicinity of absorption lines, which also leads to higher
slopes, i.e., higher dispersion. There is no way
around this. High purity raw material and optimal
melting process can only avoid additional losses
and thus make the UV-edge steeper. However, for
thin lenses the blue-violet absorption may be low enough
to be acceptable"

"Camera software nowadays can compensate for
some color imperfections. However, current image
chips still have one major drawback: their weak sensitivity
in the blue range of the visible spectrum. This
requires that red and green channels have to be reduced
in intensity to fit to the weaker signal of the
blue channel."

-- hide signature --

I don't suffer from insanity, I enjoy every moment of it!
By the way, film is not dead.
It just smell funny

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