All glass lenses? x element lenses? x mm lenses? :confused: - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 20 Old 06-02-2020, 10:11 AM - Thread Starter
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All glass lenses? x element lenses? x mm lenses? :confused:

Been watching youtube videos about various projectors.
Selling points include using all glass lenses unlike a lot of our competitors, the large number of lens elements and large size of the lens used.
Which got me wondering about the importance of lenses, which for me raises more questions than answers.
Which if any projectors in the the $3,000+, $6,000+, $9,000+, $18,000+ price ranges have lenses that are not all glass?
Is glass better than optical acrylic? Why?
Is having more lens elements better than having fewer? Why?
Is a larger lens better than a smaller lens? Why?
What effect on image quality does the lens quality have?
What percentage of a projector's cost should be the lens?
Is the lens really a key selling point?
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post #2 of 20 Old 06-02-2020, 10:43 AM
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Aspherical and apochromatic glass is the best you can get. There's a reason Leica uses that type of glass, and their lenses are amongst the most expensive.

In a perfect lens, one perfect element would be best. The more elements, the more reflections, and the lower the MTF.

Larger lenses are better, because they allow a larger aperture for a sharper image and to pass more light.

Lens quality makes a huge difference for sharpness, distortion, and color reproduction.
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post #3 of 20 Old 06-02-2020, 02:20 PM
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Originally Posted by Debonaire View Post
Aspherical and apochromatic glass is the best you can get. There's a reason Leica uses that type of glass, and their lenses are amongst the most expensive.

In a perfect lens, one perfect element would be best. The more elements, the more reflections, and the lower the MTF.

Larger lenses are better, because they allow a larger aperture for a sharper image and to pass more light.

Lens quality makes a huge difference for sharpness, distortion, and color reproduction.
The lower Sony 4K models up to the 760/885 use aspherical lenses with all glass elements except for the final acrylic element.

Also, re the bolded part; Why is it then that when lenses are specifically mentioned it is usually ones with many elements in several groups that are the best ones. Why is that when technically fewer should be better?

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post #4 of 20 Old 06-02-2020, 04:01 PM
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Originally Posted by Archibald1 View Post
The lower Sony 4K models up to the 760/885 use aspherical lenses with all glass elements except for the final acrylic element.

Also, re the bolded part; Why is it then that when lenses are specifically mentioned it is usually ones with many elements in several groups that are the best ones. Why is that when technically fewer should be better?
Cause of the perfect part maybe?
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post #5 of 20 Old 06-03-2020, 03:35 AM
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Originally Posted by Debonaire View Post
Cause of the perfect part maybe?
Que? Don't follow.

You suggested, logically, that fewer elements in lenses are preferable and yet the high end lenses tend to have many elements in many groups.

So why is that, if less is more?

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post #6 of 20 Old 06-03-2020, 03:54 AM
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Originally Posted by dovercat View Post
Been watching youtube videos about various projectors.
Selling points include using all glass lenses unlike a lot of our competitors, the large number of lens elements and large size of the lens used.
Which got me wondering about the importance of lenses, which for me raises more questions than answers.
Which if any projectors in the the $3,000+, $6,000+, $9,000+, $18,000+ price ranges have lenses that are not all glass?
Is glass better than optical acrylic? Why?
Is having more lens elements better than having fewer? Why?
Is a lager lens better than a smaller lens? Why?
What effect on image quality does the lens quality have?
What percentage of a projector's cost should be the lens?
Is the lens really a key selling point?
Sony 4K units 270, 570 and 760 all have lenses with an acrylic aspherical exit element. Don't know of any others but I suspect there are more from other manufacturers

A massive effect. A crap lens will make itself known very quickly with bad chromatic aberration and focus issues.

It can be yes. Whether it is worth the extra of course is down to the individual.

“Remember to look up at the stars and not down at your feet. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up." Stephen Hawking.
"Be water my friend." Bruce Lee.

Last edited by Archibald1; 06-04-2020 at 05:23 AM. Reason: spelling
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post #7 of 20 Old 06-03-2020, 04:01 AM
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Originally Posted by Archibald1 View Post
Que? Don't follow.

You suggested, logically, that fewer elements in lenses are preferable and yet the high end lenses tend to have many elements in many groups.

So why is that, if less is more?
Most high quality lenses use many elements. But it's not the elements which make the lens. Those elements are used for corrections.

Number of elements doesn't tell you anything about the quality of the lens.

Like I said, in a PERFECT lens, the less elements the better. But we don't live in a perfect world now do we?

As you add another element, you lose a bit of the potential for a perfect MTF 1.0, due to reflections. But they add those elements for the advantages they give, to the small amount of MTF lost.

The elements do all sorts of things: correct alignment of colors(chromatic aberration), distortion (ie, barrel or pincushion), light fall off (vignetting), etc.
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post #8 of 20 Old 06-03-2020, 04:22 AM
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Originally Posted by Debonaire View Post
Most high quality lenses use many elements. But it's not the elements which make the lens. Those elements are used for corrections.

Number of elements doesn't tell you anything about the quality of the lens.

Like I said, in a PERFECT lens, the less elements the better. But we don't live in a perfect world now do we?

As you add another element, you lose a bit of the potential for a perfect MTF 1.0, due to reflections. But they add those elements for the advantages they give, to the small amount of MTF lost.

The elements do all sorts of things: correct alignment of colors(chromatic aberration), distortion (ie, barrel or pincushion), light fall off (vignetting), etc.
I see, so talk of element numbers is more marketing waffle than anything else then.

Of course quality of the glass used is more important.

I guess that coatings and treatments have a lot to do with the quality as well.

Interesting subject this!

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post #9 of 20 Old 06-03-2020, 09:10 AM
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Quote:
Originally Posted by Archibald1 View Post
I see, so talk of element numbers is more marketing waffle than anything else then.

Of course quality of the glass used is more important.

I guess that coatings and treatments have a lot to do with the quality as well.

Interesting subject this!
Interesting indeed!

Peace and blessings,

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post #10 of 20 Old 06-03-2020, 09:16 AM
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A quality acrylic lens can be superior to a cheap glass lens so you can't just automatically assume that all projectors with glass lenses are superior to all projectors with acrylic lenses. The overall quality of the lens system is what's important.
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post #11 of 20 Old 06-03-2020, 09:03 PM
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Originally Posted by Dave in Green View Post
A quality acrylic lens can be superior to a cheap glass lens so you can't just automatically assume that all projectors with glass lenses are superior to all projectors with acrylic lenses. The overall quality of the lens system is what's important.
The key word is can be. A good acrylic lens is probably not any cheaper to make than a glass lens. Usually a manufacturer goes to plastic on the largest lens piece to save money.
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post #12 of 20 Old 06-04-2020, 05:31 AM
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The key word is can be. A good acrylic lens is probably not any cheaper to make than a glass lens. Usually a manufacturer goes to plastic on the largest lens piece to save money.
Hmmm, so you are basically saying that an acrylic exit element on 'xx' device is to save money and therefore by your own definition, must be a cheap one or there would be no benefit in going acrylic.

And yet acrylic lenses, if there is no issue in the manufacturing process, can equal or exceed a glass version.

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post #13 of 20 Old 06-04-2020, 06:07 AM
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Originally Posted by Archibald1 View Post
Hmmm, so you are basically saying that an acrylic exit element on 'xx' device is to save money and therefore by your own definition, must be a cheap one or there would be no benefit in going acrylic.

And yet acrylic lenses, if there is no issue in the manufacturing process, can equal or exceed a glass version.
Acrylic can't exceed a high end glass lens. An acrylic lens can only exceed a cheap glass lens, and can approach acceptable quality of a high end glass lens.
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Last edited by Debonaire; 06-04-2020 at 06:10 AM.
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post #14 of 20 Old 06-04-2020, 06:10 AM
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Originally Posted by Debonaire View Post
Acrylic can't exceed a high end glass lens. An acrylic lens can only exceed a cheap glass lens.
Why is that?

“Remember to look up at the stars and not down at your feet. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up." Stephen Hawking.
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post #15 of 20 Old 06-04-2020, 06:12 AM
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Originally Posted by Archibald1 View Post
Hmmm, so you are basically saying that an acrylic exit element on 'xx' device is to save money and therefore by your own definition, must be a cheap one or there would be no benefit in going acrylic.

And yet acrylic lenses, if there is no issue in the manufacturing process, can equal or exceed a glass version.
I am saying they did it as a cost cutting measure. If that lens piece was as good or better than the glass counterparts, then it would be used in the top of the line projector and it is not. You do see it used in all of the 1080P models, including the entry level 1080P model. You also see it used in the entry level 4K models. What does that tell you?

That VW60 you have, has an all glass lens. But all of the much cheaper HW models have an acrylic element in them. Once again, cost saving measure.
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Last edited by Mike Garrett; 06-04-2020 at 06:18 AM.
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post #16 of 20 Old 06-04-2020, 06:25 AM
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Why is that?
Because glass has better optical qualities than of acrylic.

Acrylic has a lower refraction index than glass. Therefore you'd need thicker lens elements.

There's also no such thing as ED acrylic that I'm aware of.

Another factor, acrylic isn't as mature as lenses made of glass.

Abbe and refractive index are how you rate materials, and currently acrylic isn't better than glass, it's only approaching, like I said before.

But it looks like ceramic might overtake glass soon.

http://www.opticiansfriend.com/lenses.html
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post #17 of 20 Old 06-04-2020, 06:39 AM
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I am saying they did it as a cost cutting measure. If that lens piece was as good or better than the glass counterparts, then it would be used in the top of the line projector and it is not. You do see it used in all of the 1080P models, including the entry level 1080P model. You also see it used in the entry level 4K models. What does that tell you?

That VW60 you have, has an all glass lens. But all of the much cheaper HW models have an acrylic element in them. Once again, cost saving measure.
I'm not denying it, it makes sense (business wise), but on the lower 4K models only the outer (aspherical) element is acrylic and the rest are glass.

I haven't much experience of the HW models.

Yes, the lens on my 60 is a great item. Super crisp and sharp.

Edited to add: If I could jemmy it into my 760, I would!
I am sure it would happily resolve 4K no issue.
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“Remember to look up at the stars and not down at your feet. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up." Stephen Hawking.
"Be water my friend." Bruce Lee.

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post #18 of 20 Old 06-04-2020, 06:53 AM
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Originally Posted by Archibald1 View Post
I'm not denying it, it makes sense (business wise), but on the lower 4K models only the outer (aspherical) element is acrylic and the rest are glass.

I haven't much experience of the HW models.

Yes, the lens on my 60 is a great item. Super crisp and sharp.
In the future we might have projectors using diamond lenses with lasers.

https://www.laserfocusworld.com/opti...optics-lighter
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post #19 of 20 Old 06-04-2020, 07:04 AM
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Originally Posted by Debonaire View Post
In the future we might have projectors using diamond lenses with lasers.

https://www.laserfocusworld.com/opti...optics-lighter
"Look honey for our engagment, I bought you a diamond lens."
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post #20 of 20 Old 06-04-2020, 11:56 AM
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glass vs acrylic plasics

Glass is very difficult to make into an asphirical lens ,allthough they can be very good but extremly expensive, asphirical lens elements are frequently made with quality plastics,acrylics
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