I tried searching already, but have still come short of the answer(s) I'm looking for.

First, when I am looking at achromats they are often listed like this: OD is 54mm. Focal Length is 180mm. What does this mean exactly? In other words, how do I know if that is the right one for what I want? Does the focal length=180mm mean that the lens has to be 180mm from the object it is focusing through? Or does it mean something else entirely?

Also, what is the difference between an achromat and a macro lens? Is there a difference? I have a +10 macro filter for my camera, do I need an achromat instead? Do I need both?

Another question, do I need a condenser AND an achromat? Or do I just need one or the other?

One final question, I am working on an image erecting piece for my adapter also. I found a good source of inexpensive prisms, but I'm unclear as to the size I need. Is there an easy way to calculate the physical size of the sides of the prism?

I guess I just need to find a good book on optics :) Thanks in advance for any insight and answers you can provide.

Thanks,
Larry

180fl means infinity focus on your camera will let you focus on 180mm away, so you can focus on anything 180mm or closer to your camera.
Achromat and macro lens does the same function: let your camera focus on the GG. achromat which has 2 pieces cemented together has better chroma correction. You only need 1, not both.
Condenser is used in Letus35 but not all adapters, so you can decide if it needs to be used.
I can only give you advice on prisms if I know your plan. ex: 2,3 or 4 RAs, 1 roof prism and 2 mirrors...
My question for you. Where is the source?
Thanks.

Quyen

Quyen - thanks for the explanation of the focal length, I think I understand now. So if I use an achromat with a focal length of 180mm then I can have it anywhere between 0mm and 180mm from the front of the camera lens and still focus at infinity, right?

I'm still slightly confused on the condenser. I understand that it is not necessary, I can use it or not. However, what exactly is the purpose of the condenser? What functionality does it add to my design?

I was going to use two right angle prisms and simulate a double porro abbe prism (http://en.wikipedia.org/wiki/Porro-Abbe_prism). I purchased two porro abbe prisms, but not understanding size I misread it and got these little tiny (16mm, I think) prisms that are too small to work. So instead I was going to try using two right-angle prisms, like this: http://www.surplusshed.com/pages/item/l2001d.html

My thought was to have one placed horizontal and the other vertical causing the light path to travel the same as in a porro abbe prism (I've seen this done with four front surface mirrors). Unfortunately, I am realizing every day how much I DON'T know about optics...so I don't know if the right angle prism will work or if I should by four front surface mirrors and do it that way.

Anyway, any thoughts on if it will work? And, if so, how do I determine the size prism I need?

The source I found for inexpensive prisms, mirrors, optics, etc, etc is http://www.surplusshed.com I think they get lots of equipment from everywhere, so there is no guarantee that they will always have a particular item. But they have really cheap prices on the stuff they do have, including a lot of prisms, mirrors and lenses.

Thanks again,
Larry

Actually the achromat will be close to your camera lens and your camera now can only focus from ? to 180mm where ? will depend on camera. Some camera has shorter minimum focus range while other has longer range.
Condenser's job is to help eliminate vignetting.
With prisms from surplusshed, I don't think they have enough prisms to do the flipping job, thanks.

Quyen

What achromat would you recommend for the dvx100a? (72mm threads) The macro I bought on ebay is terrible.

Lots of people recommend the +7 from Century Optics , which I'm sure you already knew. But I've also heard that you need 2 +10's for a dvx100a, because it can't focus properly without them (but I can't verify that.... search the forums)

I'm looking at a B+W macro from Schneider Optics, the company that owns Century. I have to imagine they're good, but I haven't heard anyone speak about them before....


Info...
http://www.schneideroptics.com/info/filter_tips_&_tricks/close_up_lenses/

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=77546&is=REG&addedTroughType=search

This one?

Of course, I have a DVX100 so this won't work then I guess...

He's talking about this, although the same company makes both:

http://www.bhphotovideo.com/bnh/controller/home?A=details&kw=BWML58&is=REG&Q=&O=productlist&sku=11209

Looks like it's worth a try for sure.

I just noticed that that one is not front threaded so I'm not sure how you would be able to use 2 together easily...always something I guess. =(

Achromat works or not really depends on the distance of the camera to GG. I use 170mm achromat (about +6) with my newly developed unit (which records image upright) with DVX100 and it works fine. I think what matters the most is using the achromat at the right distance, thanks.

Quyen

Yup, distance is the key.... but are we measuring from the slr lens, or you camera lens to the gg?

Luke, according to Schneider Optics, these are stackable, but they don't suggest using more than two.

If you don't mind me asking, where can I get a 72mm 170mm focal length achromat?

I'll look around for you, but from what I've read, most people are using stepdown rings, and zooming in a little.... Will look though.

Matthew,
I can get you a 50mm 180mm FL achromat sourced here in the UK. Would be happy to send one to you since you sent me that microwax a while back. Email me if interested.

I just bought a couple of 72mm ones on ebay to test them out. They probably won't be the greatest but if my setup works I can then upgrade them to something else.

Now the trick is to find some way to mount Canon FD lenses...

Okay I figured I'd just ask in this thread instead of starting a new one. I know alot depends on the camera but in general if two achromats are the same diameter which would be a better choice a 170mm FL or a 115mm FL? The 115mm FL would be a stronger diopter correct? Would there be any reason to use one over the other?

I would go with the 170mm. I think the other will be overkill and you may end up with soft edges.

Larry.

The 42mm hypotenuse gives you two 21mm half faces, which is all you get when you set them up in 90degree opposition for image erection. This may be too tight.

I'm using 56mm hypotenuse ( = 27mm half face) and I find this only just big eough to pass a 24mm x 18mm 4:3 image without edge fall-off on the side affected by the junction of the prisms. In my arrangment it happens on the left edge in pciture view.

From rear elevation view of the appliance, the physical arrangement of the prisms is up and to right.

These will work for 16:9 with a slightly larger image but only just and pick up a fall-off on one side edge or another depending on how well centred the camera and SLR lenses are with the most aggravated fall-off on the left.

I have tested the following combination into a Panasonic DVX100 in aerial image mode only and it worked :-

Sigma f4 - f6.3 50mm-500mm zoom lens.
Equivalent camcorder framing to 4:3 24mm x 18mm image off groundglass
2 40mm x 40mm x 56mm prisms in 90degree opposition.
Century Optics 7+ Achromatic Dioptre. 58mm thread, mounted via a 72mm to 58mm stepdown ring.

This was not an off-groundglass test. The setup was with an AGUS35 appliance with the disk removed. Success in eliminating the vignette from the aerial image with the Sigma lens suggests that the groundglass image with f1.8 lenses via this arrangement will work with the DVX100.

With the HDR-FX1, prisms with a longer hypotenuse are needed for an aerial image from the Sigma 50mm-500mm via the 7+ acromatic dioptre from a 16:9 image about 18mm high.

With the 56mm hypotenuse prisms, a successful image from the groundglass with f1.8 SLR lenses can be had but centres have to very exact and the prism alignment perfect. Even then, a slight fall-off can occur from the prism junction in certain lighting condtions.