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Posted: 11/21/2012 1:38:32 PM EST
There are a multitude of setups on the market utilizing "doublers" or zoom optics.

Can anyone put the reason into laymen's terms why a doubler would actually improve the image of the base lense system.

Here is a video that shows what I am asking, this is not my video:

Watch the difference starting at 1 min mark

Now as enticing as it may be to respond "Because the base lense is crap" That theory to me doesn't hold water because adding a lense still includes the base lenses in the optical equation.

I am thinking that the answer has to do with distance of the target and magnification and perhaps even shapes of the lenses BUT someone has to be able to turn my assumption into an educated guess.

Thx guys and Happy Thanksgiving

BB
Link Posted: 11/21/2012 2:03:16 PM EST

Originally Posted By Bennybone:
There are a multitude of setups on the market utilizing "doublers" or zoom optics.

Can anyone put the reason into laymen's terms why a doubler would actually improve the image of the base lense system.

Here is a video that shows what I am asking, this is not my video:

Watch the difference starting at 1 min mark

Now as enticing as it may be to respond "Because the base lense is crap" That theory to me doesn't hold water because adding a lense still includes the base lenses in the optical equation.

I am thinking that the answer has to do with distance of the target and magnification and perhaps even shapes of the lenses BUT someone has to be able to turn my assumption into an educated guess.

Thx guys and Happy Thanksgiving

BB

Well, the answer, as you guessed, was "Because the base lens is crap"

So why did the doubler improve performance?

Cheap lenses often have greater aberation around the periphery of the lens - and this leads to image problems overall. However the doubler also has an effective aperture mask that reduces the light entering the periphery of the cheap base lens and so performance is improved. ( lens performance of cheap lenses is always better towards the centre )

At least that's a common reason I've observed. You can test the theory by making a fake aperture the same size as the one the doubler causes and fixing it to the front of the cheap base lens and see if it improves picture image any :)

Regards
David

Link Posted: 11/21/2012 7:08:45 PM EST
Hawk -

Makes sense, I will test the theory.

Oh and I figured the base lens quality would be a heavy factor in the equation

Too bad there isn't a company that specializes in quality replacement lenses for CCTV cameras, or doublers, etc etc etc.

BB
Link Posted: 11/21/2012 8:33:12 PM EST

Originally Posted By Bennybone:
Hawk -

Makes sense, I will test the theory.

Oh and I figured the base lens quality would be a heavy factor in the equation

Too bad there isn't a company that specializes in quality replacement lenses for CCTV cameras, or doublers, etc etc etc.

BB

There are several companies that specialize in exactly that - check out people making "machine vision" systems - This is very high quality and specialised lenses for all kinds of purposes - many with very fast lenses.

Let us know how the test goes :)

Regards
David

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