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Aspherical glass and plastic
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PostPosted: Thu Jun 21, 2007 10:36 pm    Post subject: Aspherical glass and plastic Reply with quote
I have read somewhere (I have the bad habit of not bookmarking sites) that in order to make an aspherical glass, they have to layer plastic elements over the glass and press it so that the plastic elements will keep it in shape.

So whenever you see "aspherical" in the description of a lens, it means there is plastic in the optical elements.

This is true even for the huge names like Leica.

What to say... I am happy to have an older, glass-only Summicron, rather than the APO version (which has an aspherical element inside) - not just because it costs a fortune, but also because I like to have no plastic in the way of my images - no matter how good they are reported to be.

Call me a short-minded traditionalist.... I don't mind, I want my glasses to be glass, not polymers.


PostPosted: Thu Jun 21, 2007 10:41 pm    Post subject: Reply with quote
Plastic lens has plastic taste! Smile I don't like them at all, perhaps if I could buy the top expensive ones my opinion would be different (I am not sure at all).I am happy with my old glasses.


PostPosted: Fri Jun 22, 2007 5:43 am    Post subject: Reply with quote
A glass is a glass. All the new lenses are plastic. They are made from Polycarbonate. Just the level of precision is high in the top line of produced lenses. Its funny. In the lenses we use there are barely a 10 elements in the new age in some lenses there are double to that with all that funky LD and Aspherical glasses.

But anyway its proven that in most cases and old MF produces better color and contrast than its plasticized brother.


PostPosted: Fri Jun 22, 2007 5:50 am    Post subject: Reply with quote
sqwall wrote:
A glass is a glass. All the new lenses are plastic. They are made from Polycarbonate. Just the level of precision is high in the top line of produced lenses. Its funny. In the lenses we use there are barely a 10 elements in the new age in some lenses there are double to that with all that funky LD and Aspherical glasses.
But anyway its proven that in most cases and old MF produces better color and contrast than its plasticized brother.


Yes, definitely. I am not technically trained to be able to tell exactly why they are different, but my eyes don't lie to me, they are different.


PostPosted: Fri Jun 22, 2007 8:48 am    Post subject: Reply with quote
well, I don't really mind 'em. I can have as much fun with my AF lenses as with my MF...from an optical point of view then.

However, I do like the feel of metal lenses. They're heavier, and for some reason I like that.

Tom


PostPosted: Fri Jun 22, 2007 8:53 am    Post subject: Reply with quote
TDN wrote:
well, I don't really mind 'em. I can have as much fun with my AF lenses as with my MF...from an optical point of view then.
Tom


I don't know, maybe I am paranoid, but the plastic glass feels different. Optically it's probably better than the best glasses of the past.
But there's something in the result that don't cut it for me.
I have one of the sharpest Canon EF lenses (at least amongst the non-L ones), which is the 100mm f/2
It makes razor sharp pictures but the output looks sterilyzed and cold and washed-out and FLAT.
Then if you work hard on it in postproduction you can fix most of these aspects.
But yet... they don't make it for me.


PostPosted: Fri Jun 22, 2007 11:30 am    Post subject: Reply with quote
Normally, only very fast lenses use aspheric surfaces, but the uses are becoming less because new design. years ago use only moulding plastic aspheric elements onto glass to overcome some problems with less cost.


PostPosted: Fri Jun 22, 2007 12:02 pm    Post subject: Reply with quote
Hurryup wrote:
Normally, only very fast lenses use aspheric surfaces


I have a Tamron zoom 18-200, for crop cameras, quite slow, a model of a couple of years ago, and it has aspheric elements.


PostPosted: Fri Jun 22, 2007 12:05 pm    Post subject: Reply with quote
Someone clever told: Keep the things simple. And he is always right.
Think of the todays lens they have tons of parts LD ASP glasses and other stuff and produce near or worst quality compared to old ones.
I have read all kings of comparisons between modern and old lenses in most cases vintage overcomes modern. I found an article testing Zuiko 14-54 (which is a great lens) against Zuiko OM 50mm 1:1.4. The sharpness at 5.6 of the both lenses were near to identical. At F16 the Zuiko Digital has started to dim but the OM was there to perform. In contrast and color rendition the much better one was the OM lens. Before to buy my Takumar 50mm 1.4 I scorched the net for material regarding it. And I found a test comparison between Taku and Canon EF 50mm f/1.8 lens. The overcome was that Taku beats the new canon lens in all aspects. Even in corner details.
I am sure that the technology is pushing things further and further but it does not get simpler it gets really complex. And one very complex thing is much easy to be broken than something simply made and covered in metal.


PostPosted: Fri Jun 22, 2007 4:14 pm    Post subject: Reply with quote
sqwall wrote:
Someone clever told: Keep the things simple. And he is always right.
............
...........
And I found a test comparison between Taku and Canon EF 50mm f/1.8 lens. The overcome was that Taku beats the new canon lens in all aspects. Even in corner details.
I am sure that the technology is pushing things further and further but it does not get simpler it gets really complex. And one very complex thing is much easy to be broken than something simply made and covered in metal.

You raised really good point... I cant imagine why these companies with "uber-modern" tools and facilities are not good in keeping things simple and best.
Canon 50mm f1,8 is sharp lens, and as Orio said for other lenses, the results are flat and more like colored movie posters. No life...
Takumar is unbelievable lens, and I cant think of life with that...
I think its more about business. If EF is made sharper like Takumar, very few people will buy EF 50/1.4 (only who needs that speed).
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