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.

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

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.

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.

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. :)

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?

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.

Yes we want a sticky dammit!

Thats a very good idea. I would like to contribute to such a thread.

Wayne.

Hey wayne - i know you...

Yes...sticky this!

Hey Ben

I'll take that bet when this becomes a sticky....expect a PM :)

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.

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.

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.

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.

Shot with static Optosigma adapter. My Nikon D screen broke, and my Letus wasn't working (not Quyen's fault, it was mine, I didn't test my modifications enough).

http://www.frozenphoenixproductions.com/misc/still1.bmp
http://www.frozenphoenixproductions.com/misc/still2.bmp
http://www.frozenphoenixproductions.com/misc/still3.bmp
http://www.frozenphoenixproductions.com/misc/still4.bmp
http://www.frozenphoenixproductions.com/misc/still5.bmp

All I can say is that I love the sun. I was able to shoot at 1.8, 1/8000 shutter even with this baby on. That much light = zero grain.

Ben,

The images look good, but I think your focal length is off - the focused images are a bit soft
BTW, what is the Optosigma adpater you speak of?

The focal length is indeed off, I changed it mid-shoot since it had been too close and I didn't have enough time to fine-tune it. The adapter I speak of is one suggested very early on by Richard Mellor, found here:

http://www.dvinfo.net/conf/showthrea...threadid=37296

I had originally intended to build only this adapter but my Nikon D Screen arrived first in the mail, and, impatient as I am, I found ways to use that instead of the Optosigma glass and liked the results too much to try other options. Of course, once my Nikon D got scratches...

My adapter is built on the optisgma-glass and it works really good! I have some sample pictures at www.kokokaka.com/35mm. The adapter costs me about $250. It was not that hard to build it!

I get this: "You need Flash 8 to visit this site, download it for free. Best regards Kokokaka.com "

Yet I have Flash 8.

Also your giant and lengthy Flash intro is cute but my GAWD please put a "Skip" on there.

You may want to put a list or back/forward arrows on your list of More News. I had to scroll through the whole collection to get back to the 35mm link!

Wow, I found that too. I couldn't get to the link!

It's fixed now. Very nicely designed page, Jimmy!

Ok, fixed the flashcheck now I think. No one likes my my site, I know. But you can skip the intro if you click on "read the koko kaka news" in the footer.

I use Flash 8 becasue it's really good on videocompression and you don't need any codecs, only flash 8.

People asks me if I will sell the adapter but I don't have the time to build it and sell it. It costs about $200 to build so if I want to sell it it would be quite expensive. When I have some time I will create a "build your own adapter tutorial" with links where to buy all stuff and more but first I have to build my next version of the adapter, I'm going to use two condensorlenses, +10 diopter, a better nikon f-mount and a lens holder.

I still can't get the link to work. It is just a blank black page with the koko type on the bottom. Nothing happens.

Jimmy I like your site! It's just that the intro is so long and you can't interrupt it once it starts, hehe

Just want to mention that ebay is a great place to get achromats.

Don't murder me, but I picked up the $200 Century Optics 7+ achromat on ebay yesterday for 73 bucks. Doesn't get much better than that, does it?

someone can post some photos of the condenser lens and of the proper GG.

in some threads I have read that someone use Aspheric Lens.
which is the difference?

I have chosen to use a GG of the Mamyia RZ.
what do you think of it?


thanks Manu

an other small question.

and....
...the lenses of Fresnel?

who has as condenser used it?

__________________________
thanks Manu

i vote for a sticky. the knowledge in these forums will really drive the development better and better 35 adapters.


...and for newbies that are DIYers or cannot afford them