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Old October 25th, 2005, 01:36 AM   #1
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Condensors & Achromats?

I've been reading about 35mm adapters for quite a while on here, and there is still a serious point of confusion for me.

Could someone give me a simple explanation as to why condensor and achromat lenses are necessary in the design?

What purpose do they each serve?
I understand the concept of the designs, but I'm definitely getting lost in the details.

Thanks for any clarification.
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Old October 25th, 2005, 02:05 AM   #2
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luis,
most of the 35mm adapters require the on-camera lens to be zoomed in to fill the frame to avoid vignetting. technically, if you zoom in, one cannot focus on the objects near to the lense (in this case will be the ground glass ).so, an achromat is placed between the on-camera lense and the GG which makes it possible to focus on the GG and the image on it.
hope this helps.

krishna
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Old October 25th, 2005, 04:16 AM   #3
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The condenser's (usually a plano convex/PCX lens) job is to even out the light to eliminate or at least reduce hotspot/vignetting. It does this by allowing the camera to view any giving point on the ground glass at the best possible angle.

The achromat is what M. Krishna Babu says, and is to allow the camcorder to focus on the small 36x24mm frame while zoomed in.

Thanks,
Wayne.
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Old October 25th, 2005, 07:42 AM   #4
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Thanks to both of you for the concise responses.
That's what I was guessing from reading the context of the numerous threads...but no one had ever really spelled it out clearly like that.

I appreciate it.
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Old October 25th, 2005, 07:45 AM   #5
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Usually what happens is someone new to the business asks these basic questions, then no one new comes around for a while and the topic gets buried 5 pages back. Since there's no search phrase that would really effectively get these answers quickly, it's easier to just ask for them.

$20 says this topic is shoved into the oblivion of page 12 a month from now when some other newbie to 35mm adapters asks these same questions. :)
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Old October 25th, 2005, 07:46 AM   #6
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Well it won't let me edit my post so I'll post again to say this:

maybe we should make a sticky topic that outlines what, exactly, a 35mm adapter is?
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Old October 25th, 2005, 07:50 AM   #7
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Ben,

That's exactly why I posted this thread.
I searched for quite a while and couldn't find a simple explanation anywhere.

I think a 35mm Adapter 'sticky' is a great idea.

Some of these threads have gotten so long and changed topics so many times that it makes searching very inefficient.
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Old October 25th, 2005, 08:07 AM   #8
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Yes we want a sticky dammit!
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Old October 25th, 2005, 08:11 AM   #9
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Thats a very good idea. I would like to contribute to such a thread.

Wayne.
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Old October 25th, 2005, 10:37 AM   #10
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Hey wayne - i know you...
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Old October 25th, 2005, 12:18 PM   #11
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Yes...sticky this!

Quote:
Originally Posted by Ben Winter
$20 says this topic is shoved into the oblivion of page 12 a month from now when some other newbie to 35mm adapters asks these same questions. :)
Hey Ben

I'll take that bet when this becomes a sticky....expect a PM :)
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Old October 27th, 2005, 12:14 AM   #12
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Quote:
Originally Posted by Ben Winter
Usually what happens is someone new to the business asks these basic questions, then no one new comes around for a while and the topic gets buried 5 pages back. Since there's no search phrase that would really effectively get these answers quickly, it's easier to just ask for them.

$20 says this topic is shoved into the oblivion of page 12 a month from now when some other newbie to 35mm adapters asks these same questions. :)
I've suggested to Chris a number of times, a sticky faq. Last time, a sticky hierarchy faq, so you click through the links to get the information. The users would submit information via form and it would be verified before entry.
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Old November 3rd, 2005, 08:48 AM   #13
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Yes, sticky's a great idea (another mini35 newbie here)...

Another question:

You guys said the acromat goes in front of the on-board lens, but what about on cameras like the XL series? In every picture I've seen, the adapter is mounted directly to the camera. Is there a small lens built into the adapter just for the purpose of focusing onto the CCD block? Is an acromat even used in this case?

Like many of us (I suppose), I decided making my own adapter is the way to go, but without any plans and scattered specifics, coming up with a design has been like reading about a particle accerlerator in a magazine and than trying to make one by "filling in the blanks". Maybe an exaggeration, but by making it even a little easier for people to get into, a higher standard for diy adapters can be established, and we can show companies like Technik that $10,000 (or whatever it is) is too darn much for one of these things!

I was so happy when I found this forum... a place like this is needed for people don't have a money tree to pay for things like DOF converters.
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Old November 3rd, 2005, 09:04 AM   #14
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Quote:
Originally Posted by Justin Haupt
Is there a small lens built into the adapter just for the purpose of focusing onto the CCD block? Is an acromat even used in this case?
The lens you are refering to is called a 'relay lens'. Its job is to replace the stock lens like on the canon XL series or the JVC HD100, to focus on the 35mm frame.

Regards,
Wayne.
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Old November 5th, 2005, 10:37 AM   #15
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I recently gone back to my homemade birdhouse - because my prototype is made out of wood and really looks like a birdhouse (which I lovingly refer to as my Birdhouse35 ;) ) while I am waiting for my upgrade from Quyen to the Letus35a (Thanks Quyen!). With my work-in-progress adapter and with it I have a condenser in place - and I forget what a difference it makes. It really brings up the light level! The condenser I have is quite decent, made of glass instead of plastic and I wish I could find more like it! I only have one, I think two is the right formula. Again, more acknowledgement to Oscar for being right about this nifty piece of glass to brighten up the image consider how much the miniDV loses light with an adapter.
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