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Thinking about the LA7200, oh god diopters


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I am very confused here because the statements being made are conflicting with my own personal experiences using a century 16:9 adaptor (pd150) and a tokina +0.4 achromatic diopter.  When using the combo on an aps-c sensor and 28mm taking lens, I was getting way better sharpness and less CA over the entire focus range (which was around 500mm-infinity).  The benefits were not just in improving close focus.

 

Am I right in assuming that you (John) are saying that if I were to fit a +0.4 (non achromat) instead of the tokina +0.4 (achromat), I will still obtain the optical improvements in the more distant focus range?  

 

I had my century and tokina continually used together and never needed to separate them.  I got sharper infinity focus at f2.8 with the tokina achromat that without.  Are using saying a non achromat will have sharpened up my infinity focus and overall CA issues in the same way as the tokina?

 

 

Conversely, I do not get any noticeable sharpness improvements when I use a tokina achromatic diopter +0.4 on an iscorama 36.  All I gain is a shorter minimum focus distance.  Sharpness and CA on the more distant subjects which wouldnt need any closer focus ability is not affected by the tokina when used on the isco which introduces next to no noticeable CA and very little dulling of sharpness even when the taking lens is wide open.   

 

I honestly believe that in respect to the century and panasonic 16:9 converters there is a noticeable improvement over the entire focus range when using the tokina.  And I struggle to see how adding a non achromat (even of the highest quality) would go any way towards doing anythign other than applying magnification.   

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i sold 40 of the tokina single element +0.5 and
70 tokina +0.4 achromatic doublet.
it took 2 mins of flipping in and out to see the power of the achromatic design.
clearly the doublet advantage is in the f1.4-f4 range
by far the biggest improvements was with century/optex design and other slightly rough or off anamorphics.
what you want with the best anamorphics is the min introduction of error from a poor additional quality optic.
most single element stuff is shit and will degrade the image.
schneider are using single element for price point they shift more at 250 dollars than a doublet at 700-1000.
i have had many optics ex nasa and they loved doublets.
over 100 anamorphic nutters have the tokina.
the original price was quite good selling today would get some people a nice profit but i see people keeping the achromat and selling the anamorphic.
clearly they cannot all be mind controlled idiots.
it would be a lot easier if we knew exactly what gear mr barlow has and if he has done these tests himself.

i have always offered a full refund on the tokina doublet never had even one returned even when the buyer had a single element tokina at the same time.
as i stated before economics are behind this cemented doublets are more complex and you cannot cut corners with them so they should always be an improvement.
iscorama is one of the few lens that does not degrade the image hitting the taking lens.
the tokina doublets do not degrade the image either.
making statements and hinting that low power doublets are pointless is futile.
if you have one john why have you still got it ?

i have a lovely 5cm nikkor 1.1 lens from the 1950s i also have an f1 leica noctilux.
do i really need them when i can sell them for thousands and buy a cheap noctor 0.95.
do i need the doublet or these other lens yes simply because the quality is fantastic and superior to other stuff i have tried.
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It is well known that achromats are specific to the correction of CA. See this reference http://en.wikipedia.org/wiki/Lens_(optics)#Chromatic_aberration

 

Basically the flint glass corrects the dispersion caused by the preceding optic, tightens up the rays and causes them to land on the focal plane together. So the blue-yellow and magenta-green CA is diminished. For weak dioptr < 1.0 there is little dispersion and no significant CA to correct so no need for achromat. It is not wrong to use an achromat but it is not essential. Alternatives are high Abbe glass

 

So why does  a 0.4 close up improve a Century/Optex/Pana over a 0.5? The fact that it is 0.4 power is the answer, it just happens to hit the sweet spot

 

The Century/Optex/Pana is different from conventional anamorphics  - it is designed to give best results at about 3m hyperfocal distance, which is a compromise based on the average hyperfocal distance for a range of f-stops and focal lengths of a 1/3 inch chip camera. Move out of this range and the image falls apart, I seem to remember with the PD150 - don't zoom more than 5x

 

Adding a 0.4 D just makes it afocal and better performance at longer distance. It is equivalent to slightly increasing the distance between the front and rear elements

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Further to my post above, it appears that the Pana was designed for 2.5m distance which is of course -0.4D

 

So when you add a +0.4D close up, it cancels out 

 

0.4D -0.4D = 0D

 

If you were the one to discover this then Kudos to you, nothing to do with achromat BTW :)

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<p>do the tests use your eyes come back when you have.<br />
i have my eyes are getting old but they do not lie.<br />
<br />
<br />
i have single element angenieux +0.25<br />
and angenieux +0.4<br />
the tokina doublet is better.<br />
<br />
you still have not told me what optics you have for your visual tests?<br />
<br />
your gonna make a million john with all your booky wook info.<br />
the power of words over real image testing : )<br />
<br />
<br />
for your info i have been working on a various new close up's myself.<br />
<br />
all the tests done so far show double element design being the way to go on +0.3 or +0.4<br />
the lab tests showed the angenieux single element + 0.4 to be inferior to the tokina double element +0.4 meniscus design.<br />
angenieux made some mighty fine quality optics so a good single element lens to test.<br />
all the recipes where put into zemax the tokina design won out.<br />
i suggest you start doing some buying testing or making maybe help vidatlantic out he has a quality control issue with his tin and glass : )<br />
figure out what the money split is and you will be laughing especially if you buy the junk from china.</p>
<p> </p>
<p>a perfect optic for the panasonic would not be the 72mm tokina +0.4</p>
<p>it would be a large double element +0.25 or +0.3.</p>
<p>but that is from real world testing.</p>
<p> </p>
<p>thank god you have destroyed the myth and seen through my lies just in time before the christmas rush.</p>
<p>hail the single element.</p>
<p>hail the barlow wangchung close up image sharpener</p>
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Hey Tony - I have one of your Tokina Achro's - it is the only diopter that makes my little Soligor Ana adapter usable - it goes from being a nightmare to a wet dream the difference is astonishing!

 

For the record do you know of any 112mm or larger low powered Achro's - just a brand name and filter dimension will be a huge help in my endless Google quest.    : )

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Hey Tony - I have one of your Tokina Achro's - it is the only diopter that makes my little Soligor Ana adapter usable - it goes from being a nightmare to a wet dream the difference is astonishing!

 

For the record do you know of any 112mm or larger low powered Achro's - just a brand name and filter dimension will be a huge help in my endless Google quest.    : )

 

not in double element..

i am making some after christmas they will be +0.3 and +1 in double element not sure of the size exactly.

 

the stuff that is sometimes around now is the kenko and the schneider but as you know they are single element.

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watch this space mr barlow i did a variable focus diopter last year.big deal
nothing is new here.
all been done and sorted by 1960.
isco patented applied for in 1957
just tweakin and fiddling that is all.
unless you have designed a variable compression anamorphic with the ease of use of an iscorama with the sexy imaging of a bolex moller 1.5.
priced below an optex.
now that would be worth watchin and waitin for.
damn maybe that is it those pesky mollers don't need silly close up screw on optics.
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watch this space mr barlow i did a variable focus diopter last year.big deal.

 

 

 

So, where is it? 
If its such a big deal why is it not for purchase? 
Why have you not brought it to market?
What focus range does it support? 
Which scopes does it support? 
Do you have some photos we could see?
 

nothing is new here.

 

Sounds like you are out of ideas...
 

all been done and sorted by 1960.
isco patented applied for in 1957
just tweakin and fiddling that is all.

 

I am glad you brought up the patent. The most current US patent that I can find for that ISCO is http://www.freepatentsonline.com/3002427.pdf
which cites the 57 patent - ISCO basically puts a shifting diopter system in front of a custom afocal 2x scope design. I cant find the 1.5x design in the short time I looked, but its probably generic or lapsed.
 
This is what I see - the focus is done through racking the front element, everything else including the prime taking lens is set at infinity. The lens scheme is shown in Fig3 and the lens prescription is at Table II. The spec says it can focus from 2m to Infinity, so that shifting dioptr goes from 0.5D to 0D. 
 
I can't see any achromats among the shifting dioptr can you? The index of those two front elements look like crown glass. They probably thought, as I do, that achromats are unnecessary for this dioptr range.
 

 

unless you have designed a variable compression anamorphic with the ease of use of an iscorama with the sexy imaging of a bolex moller 1.5.
priced below an optex.
now that would be worth watchin and waitin for.
damn maybe that is it those pesky mollers don't need silly close up screw on optics.

 

Seems to me like you are fishing or clutching at straws.
I wish I could show you something sooner, but I have to wait for the paperwork to come through, you know how it is. 
 
 
Are we done?
 
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i have nothing for you barlow.
who are you?
why do i need to prove anything to you
you think you know best
why the fuck would i tell or show some shitter i do not know my projects.
you are a bore.
fishing are you serious from you fuck off : )
i was shooting super 8 scope when you where still jerking off to jilly johnston and sam fox
i have had 40 more iscoramas than you have ever had
destroyed my first one in the 1980s.
i do not need to here pointless theory from you if it is true or not is not important.
it has all been done by germans americans and french men decades ago.
bottom feeding that is all.

how many iscorama have you had 1 or none?
why do you think i do not know about iscorama design
for your info the 2 double element cylindricals where so superb that the 2 front single element focus groups could be used.
but you understand all of this cos yer gonna bring down slr magic with the power of the barlow brain.<br />
out of ideas?
go fuck yourself : )
did i say i had any fucking ideas am i messing people about in any way.
i am not in a race i tinker and fiddle with lens
i have got plenty of projects but may not bother because of cost.
i may do stuff i may not it is not a big deal.
feel free to blow the moving picture market wide open orson einstein.
just because i don't show my stuff or sell stuff does not mean it does not exist.
anyway let us agree that you know better than everyone and leave it at that.
good luck with the china paper work means nothing from a legal position though..
please be gentle on us john.
what has vidatlantic and slr magic and redstan ever done to you apart from ignore you.

 

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