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Old February 2nd, 2007, 04:26 PM   #1
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Binocular Achromat for HD?

What is the difference in quality between those USD$200 HD Achromat and those achromats taken from a binocular? I mean will those "cheap" achromat perform much worse than those expensive one? I surely limited in budget. The achromat from my $30 binocular works really well for my DIY adapter using with PD170. But I will have access to a Sony HVR V1P at school soon. I want to know if the binocular achromat will still be usable on HDV?
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Old February 2nd, 2007, 04:41 PM   #2
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I wondered about HD glass as well. Before HD, the glass for C.O. and other companies was 'the best' - but then with HD, suddenly there is 'better glass' for the HD achromats? I don't really get it. Shouldn't they have been using the BEST glass in the first place? How does glass get better?
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Old February 3rd, 2007, 07:27 PM   #3
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I think you will find that the history back hints that before there were the current small crop of achromatic dioptres made specially for adaptors, you could have any 72mm filter width dioptre you liked only if it was up to 4+ and no stronger.

There was a little more choice in the 58mm filter width size. You could get a +7 from Century, some mounted and unmounted from vendors like Surplus Shed and I think a 10+ with a reduced exit pupil diameter from Hoya.

These were an option for 58mm filter mount cameras and some smaller cameras with step-up rings.

For the current pro-sumer HDV cameras with 72mm filter mounts and larger diameter front elements on their in-built lenses, than the older MiniDv cameras, the 58mm achromats, whilst they can be made to work with stepdown rings may not always give an adequate corner to corner sharpness for HDV resolution.

Because the product was not there to be had, builders of alternative adaptors for the marketplace were forced to have their own special achromats made which of course must meet the HD performance standards.

My guess is your binocular lens may work on the V1P if it already works on the PD170 but you may find the corner sharpness may not be what you want.

Back off your PD170 zoom to about 40mm. If you don't get a vignette there, my guess is it should be usable on the V1P.

You may also need to bring the groundglass about 7mm to 12mm closer to the front of the camera than you have for the PD170.
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Old February 3rd, 2007, 07:46 PM   #4
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Surplus Shed achromats

Hi Bob,

Thanks for the info on the Surplus Shed. Had a look at the available achromats on there and found this one.

http://www.surplusshed.com/pages/item/l2160d.html

But not sure what's its magnification power. How can we tell if this one is +7 or +10? The size seems right for a 72mm diameter lens camcorder like the DVX. Thanks.
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Old February 3rd, 2007, 11:25 PM   #5
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Quote:
Originally Posted by Alex Chong
Hi Bob,

Thanks for the info on the Surplus Shed. Had a look at the available achromats on there and found this one.

http://www.surplusshed.com/pages/item/l2160d.html

But not sure what's its magnification power. How can we tell if this one is +7 or +10? The size seems right for a 72mm diameter lens camcorder like the DVX. Thanks.
Diopter power is the inverse of focal length in meters, so 1/.36 = 2.7. It is a +2.7 power diopter.

See how difficult it is to get a large diameter powerful macro for cheap? :) The truth of it is, you're just gonna have to cough up the dough.
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Old February 4th, 2007, 03:09 AM   #6
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Thanks Ben for the theory update. It is now in my useful notes. I never got round to doing that piece of research. I also came up with just under 3+ by doing some comparison trsts with the +7 and +4.

That 68mm would have an adequate exit pupil????(somebody please correct me if I am wrong on the terminology) diameter for the V1P but the focal length is much too long for the available zoom range you have.

The appliance would have to be made way too long to be useful even if you were able to zoom in far enough to get a useable frame on the groundglass.
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Old February 4th, 2007, 06:24 AM   #7
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Achromats from cheap binoculars tend to be inadequate for HD.
Another thing about those is the edge to edge sharpness and massive color cast specially from the "ruby" type of coatings.
There is a reason why good, sharp and powerful binoculars are not cheap.

T
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Old February 4th, 2007, 09:11 AM   #8
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Quote:
Originally posted by Ben Winter

Diopter power is the inverse of focal length in meters, so 1/.36 = 2.7. It is a +2.7 power diopter.

See how difficult it is to get a large diameter powerful macro for cheap? :) The truth of it is, you're just gonna have to cough up the dough.
Hi Ben,

I think I may just do that and order it.

Hi Dennis,

Can you confirm though that your HD achromat is rated at +7? My adaptor is best when mated with a +7 achromat. I have tried +8 from 2 binocular objectives (Compared each objective with my Hoya +4 macro) and I couldn't get a good focus when zoomed in all the way to the focusing screen. Strangely, with a +7 macro (+3 and +4 Hoya macros) I can use my MX500 and zoomed in all the way to 10X and still focus on the screen. +7 it is. I have also tried putting two Hoya +4 macros together to make +8 and still I couldn't get a good focus on the focusing screen. So +8 and above is a no go for me.

I am pretty sure I can work with less power but that would mean I have to have an extension tube to make the light path longer. +7 would be perfect. Sorry if I am repeating myself. I have PM you as well. Thanks.

Last edited by Alex Chong; February 4th, 2007 at 10:14 AM.
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Old February 4th, 2007, 10:16 AM   #9
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Must have been sleeping when typing the above reply. Sorry Ben, I PMed you instead of Dennis. Disregard my PM to you. Thanks.
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Old February 11th, 2007, 09:11 PM   #10
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So what about the achromat in Edmund Optics? Since they have a 50mm achromat with +10 diopter(100mm FL) and they are relatively more affordable than those $200-$300 HD achromat.

http://www.edmundoptics.com/onlineca...productID=1749
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