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Re: [OM] Plastic Lens question

Subject: Re: [OM] Plastic Lens question
From: Garth Wood <garth@xxxxxxxxxxxxxxx>
Date: Sat, 19 Jul 2003 10:21:10 -0600
At 02:50 PM 7/19/2003 +0800, Albert wrote:
>Sorry, slightly OT, but I was wondering, does anybody know the resolving limit 
>on plastic lenses?
>
>One of my students went on a trip and just got back; well, the pictures were 
>horrible; taken with a P&S camera that had a plastic lens..
>
>She said she was frustrated after seeing my pics as far as clarity and 
>resolution.  I'm just curious if anybody knows just how big of a difference 
>glass vs. plastics is.
>
>I know based on glasses; glass is less than 1/2 as thick..  So I don't know if 
>that's linear or exponential, but that should mean that it at least resolves 
>2x as well vs. plastic??  


Albert:

I'm not aware that there's any resolution limit on plastic lenses that's 
terribly different than glass, and the refraction index of plastic would depend 
on the type of plastic used.  I know that it's much easier to create aspherical 
lenses out of plastic than out of glass (because you can just cast plastic more 
easily), and even some high-priced and high-quality Big Name lenses have 
plastic aspherical elements in them.

My suspicion is that the P&S camera is just cheaply made and of inferior 
quality, possibly with plastic lenses with three or fewer elements.  If it's a 
one- or two-element lens, it's going to have a very difficult time delivering 
quality images, regardless of the configuration of the elements.  More elements 
are typically used to correct more types of image aberrations, which is why a 
relatively stable and simple design like the Zuiko 50/1.8 still has several 
elements (5 or 6, depending on the design -- the 1.8 went through a number of 
formula changes...).  Tell her she needs a better camera, and steer her towards 
the Holy OM series.  ;-)


Garth


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