Condensor, fresnel?
 

Hi, I've been following and reading all threads (even the agus35 ones)

Just need to know...
What does a condensor and a fresnel lens do?

-----------------
Eric Öhman
www.de-interlaced.net

Rather than re-write the whole book try the search feature on this web site and plug in "condenser", "fresnel". Also www.Google.com is a good source for techincal info. You should find everything you need.

blur focus looks distorted!
 

i've done a few tests with different magnifiers... this is what i'm using:

Cam(vx1000)->magnifier->frosted rotating cd->50mm f/2.0 minolta lens


when i change the focus on the minolta lens, like when i blur the picture.. everything gets distorted, especially in corners. why is this? please help. i'm pretty close an 35mm adapter now :)

and by the way, would it be better to use medium format lenses? do you think i would be able to skip the magnifier lens then?

THANKS IN ADVANCE
ERIC
www.de-interlaced.net

Still no response on the acid-etching? Is everyone distracted by all these Build Your Own HD threads?! Is it the XL2?

:)

- jim

Eric-
Thats real odd that you would get distortion from simply changing focus. Describe what kind of "distortion" your seeing and maybe I can help. The only thing that MIGHT be going on is that your not framing up the right size on the GG. Your video camera should be looking at roughly 36mm wide by 24mm tall section of the GG. Perhaps your looking at a much wider section of the GG and the outer edges are revealing some type of distortion that wouldnt normally be seen. Check it and let me know.

As far as using a medium format lens question - the answer is no you generally wont need any type of magnifier. I say generally because every model of video camera is different. Draw a 2 1/4 inch square (basically the smallest medium format size) and find out if you can focus sharply from the center all the way out to the edge and without any barrel distortion. Generally a good distance to try is about 2 inches. Read all of the other pros and cons of using medium format lenses in some of my recent post in the "oscillating ground glass" thread.

-Brett Erskine
www.CinematographerReels.com

-> Brett

I just found the reason for the distortion. It was simply my ground glass wich had some mm convex bending...

Yeah, I frame about 36x24 but I haven't find any good magnifier lenses to use yet. Do those HOYA(for example) close up filters work? This will surely be different because of what camcorder you use and the vx1000 is pretty big (52mm thread so pretty big front lens) so the I really need some magnifier lens that will take away the hot spotting (I'm at f/2.0 on my 50mm minolta md lens.)

Any help is appreciated.
ERIC
www.de-interlaced.net

Eric.

Some of my early Agus35 experimental images were with a PD150 and a stack of 1+,2+,4+,Hoya lenses to get up to 7+.

This meant my GG had to be about 4 inches from the front of the close-up lens.

Some of these are at www.dvinfo.net/media/hart and will be among the earlier files by date which is on the right side of the list.

I subsequently used a SW5042 lens set which is the optics out of an unbranded 50mm 2" telescope eyepiece sold in Australia for for Tasco telescopes.

This enabled me to close couple to about 18mm from the groundglass but introduced difficulties with edge softness. The arrangment works adequately but not brilliantly with the 4:3 motion picture frame of 24mm x 18mm ( see Brett Erskine's test chart ) but fails miserably on the larger still-camera frame.

Whilst the PD150 has a 58mm front filter mount, the front element is 52mm.

You may find that if you build to precision along the centerline of your lens, cropping/vignetting, may first occur on the left side of your image as viewed. This happens with the PD150. It may or may not be the case with the VX1000.

I don't know about the VX1000 but with the VX2000/PD150, the lens center axis does not fall in the center of the 3xCCD array, but partly to the right as viewed on the LCD screen.

I have not gone with condensers or fresnels as yet as I am still trying to get the raw resolution on the groundglass up to scratch beforehand. Look for Brett's posts through the Agus and Aldu threads or run a search as he suggests above.

The latest images on www.dvinfo.net/media/hart were shot off a spinning wax composite disk (home made boss-screen). The image is subjectively about the same resolution as a spinning 5 micron groundglass but it is very difficult for a home-builder to achieve a consistant grading of the crystal texture in the wax layer around the disk.

On my specimen, the variable density amounted to over 2 f-stops which introduces unacceptable flicker.

The wax composite disk image seems marginally better but the two glass disks require more precision on the wax faces than I can achieve on my home figuring/polishing setup.

So far, on a test pattern, the glass disk with 5 micron dressing and the SW5042 lens set achieves the 530 lines horizontal resolution which is the spec of the PD150.

Eric-
Yeah that explains it.

The +1,+2,+4 close up kits you see out there are pretty much all single element diopter. You dont want to use these because of color "abberation" problems. You need to get a two or three element diopter. These are called achromatic diopters. More expensive but well worth it. Basically the best deal out there is the Hoya +10. Its the strongest power to diameter ratio diopter out there in photography. The largest they make them is 55mm. Anything larger and its a single element diopter. Its real hard to tell which one your buying any other way than by price. A single element will go for about $25 and a double element will be around $70. I found though that while the two element Hoyas much better than any other diopter in its price range - it still has a slight amount of chroma abberation. Century Optics pride themselves on great optics but are pricey and their achromats arent as powerful as the Hoyas.

-Brett Erskine

-Brett and Bob
Thanks for your comments.

-Bob, is there any place to buy that SW5042 pretty cheap? I did a search but couldn't find too much

-----------------------------------------------------------

I dismounted a reversal projector and find this lens wich is flat on one side and curved on the other. The focal length is around 9-10mm but I'm curious if there is any way to check what the x-factor is?

I think I will go for that HOYA x10 filter and test it even if this lens from the reversal projector seems to be working fine.... I always find it better to work with filters cause then I can just order the 52mm one that will fit directly to my vx1000.

I'm going to post some pictures soon. Too bad I've short circuit'ed my vx1000 firewire port (this happens when you accidentically put the 6-pin plug upside down in the computer's firewire port).

-All the best.
ERIC

www.de-interlaced.net/mini35/mini35.mpg

i was having my vx1000 on a tripod but i held the cd and the 135mm lens (@ f/2.8) that's why it is so shaky and often out of focus... but what do you think except that?

XL1 Static Adapter
 

This adapter consists of a canon 1.2 50mm FD mount lens and adapter on a Radioshack 4.5x6.5inch project box. the GG is a Linhof 4x6inch micrograin obtained from B&H. Next step is to make a platform for the whole setup to rest on. Perhaps a mattebox & support rod setup. I used the stock 16x auto lens and the Macro is a 5x single element. when money and time permit I'll replace it with an Achromat, perhaps more powerful although with a little more tweaking I think 5x should be enough to fully eliminate the vinetting.

the clip is about 1mb and is a fairly low bitrate so pardon the compression artifacts. It doesnt like to stream so download before viewing.

www.quicktel.com/users/archamian/candletest.wmv

The +10 may be the best way for you to go. It should be more controllable than the SW5042 set because you would have to have access to a lathe and some flo-cast bronze stock and the skills to to turn up the adaptor and cut an internal 0.70mm thread. The assembly order of the SW5042 glass elements also has to be reversed for best resolution.

The SW5042 seems to be a generic product out of mainland China. Retailers who carry telescope parts should be able to track them down.

My attempt
 

Hi everyone. I have posted here once before about my ALDU35 type adapter. Anyway, I just made a little movie for my kids, starring my kids, and tested my adapter on it. Here are some of the results.

http://www.kidventures.net/mydownloads/other/scene1.jpg

http://www.kidventures.net/mydownloads/other/scene4.jpg

http://www.kidventures.net/mydownloads/other/scene7.jpg

Thanks,
Josh

Nice images! What cam are you using?

- jim

Hi,

I am using a Panasonic PV-GS70. I bought the camera at a circuit city for like $650 or so...

Oh and you can watch the actual movie if you like. It is at http://www.jayfor.com/jnjosh/ and click on the image for the movie, 'Not Fair'. It was the first movie I have ever made... So I was happy with my new adapter...


Thanks,
Josh

Cool -- thanks for the response.

One more question -- where'd you get your grit? Is AO5 the same as 1500 grit?

Incidentally, I think today's my acid etching day...

- jim

Jim
Could you post a full res. pic from your Aldu35 (static adapter), I'ven seen the pics from it at ideaspora.net but it would be great if I could see some in full screen (I'd prefer that street w/ computer scene..)

Just want to have a closer look at the grain as I just ordered that Aluminium Oxide 1000 grit to make one of my own.

I've been working with a cd-mini35-adapter (agus35)? but I want to have 2 adapters, one static and one cd.

THANKS in advance
/ Eric

Eric,

I'd be happy to -- just give me a day or two.

Incidentally, the reason I ask about 1500 grit is that I know that, as my adapter is currently, the grain is evident, particularly under certain conditions -- low light, especially.

So, I'm interested in seeking out finer grit, or moving to acid etching -- I've got the acid cream here and plan to endeavor the etching tonight -- and this might be especially relevant if you've got a higher res cam than my lowly GL-1.

Not that I need to have the grain disappear completely, but I would like to achieve finer results than those gotten with 1000 grit.

- jim

Ok. Just thought I'd post something to make myself known. I just stumbled on this stuff a couple of days ago so it's a bit of a learning curve. I've only managed to get through about half of the material here so I'm probably jumping the gun somewhat.

I thought I'd share my experiments so far anyway. Describing them as rough would be an understatement but I just wanted as quickly as possible to get an idea of how this all worked. I'd experimented a bit previously with just a lens and obviously ran into troubles. So, here I am. This is my short journey so far.

After some examination I put together a baking paper and toilet roll screen and spacer. As far as the flange focus length goes, I wasn't suer becacue I had an old lens lying around and I wasn't sure what camera it came from. Some trial and error and I had an image.

I then stepped the technology up a notch and cut up a plastic vitamin bottle and pulled a plastic freezer bag across the opening and pressed the lid on top. I found that the plastic was too transparent so I could see the light directly through rather than just the image on the screen. I tried it with a couple of layers and found that this was better but I could still see the light from the apeture opening behind the screen.

I've got an old Sharp MiniDV camera which has macro abilities but only at fully wide. It focuses on the screen fine when the camera is pressed right up against the screen.

Unfortunately, as you might expect, it didn't really work. Basically I have a very faint image in the centre of the screen but nothing else. The image projects perfectly on the whole screen which is approximately 40mm diameter. Not sure reading the thread if 'hotspot' and 'vignetting' is the same thing in this context but I have some thoughts.

Firstly, I think one problem is that the light from the apeture opening can be seen through the screen so the camera is adjusting based on the brightest point of light. I don't think this bit is related directly to the physics of light per se.

The next problem is the physics of light. The light from the back of the lens comes out in a cone like this

35mm lens ()><|<()< CCD

|=screen
()=video lens

where light would normally come into the camera like this

\
..()>CCD
/

So when the light from the lens goes into the video camera the light on the outside misses the CCD entirely. This is where the fresnel/condenser comes in, yes???

In the current versions, you use the fresnel to make the light go like this -

35mm lens ()><|=()> CCD

Basically, without the fresnel, only the light that is going straight or an angle cloese to straight that allows it to reach the CCD gets picked up.

Does that sound about right?

I'm going to read more. I know this stuff is all pretty obvious but I thought I'd share anyway.

On a side note. About the flipping in post, for PC users, it might be worth looking at some software called avisynth. It's a frame serving program which is mainly used in DVD ripping but basically you write basic scripts which can be used instead of avi files and add some fairly sophisticated effects. Flipping, deinterlacing and the like are easy and it allows you to use the original file, virtually filtered so you don't need to render the flipped file first. If this sounds interesting to anyone I'll give you some other info to get it working for you.

Cheers for reading. This wo'nt be the last you'll hear from me.

Raavin (AKA Jason Keenan)

acid etching can kiss my grit
 

I followed his instructions METICULOUSLY this evening and found acid etching to produce terrible results. What a shame -- or is it sham?

-- James "The Chemist"

Macro of my acid-etched filter:

http://ideaspora.net/acid.jpg

I'd love to be proven wrong...

- jim

I also just downloaded the freeware OSLO from http://www.sinopt.com/

It's supposed to be lens design software. I haven't had much of a chance to play but it might be useful for illustrations and hopefully useful for testing lenses virtually before you purchase.

Raavin :)

whooo... that acid etching didn't look any goot at all. It looks just like my pre-frosted cd look, terrible.

- Jim
(100% res frame with the static adapter footage..)
Yeah please do that. Take your time

Eric,

I hope you're on broadband and like over-achieving:

Here's a link to a zipped 12.2mb NTSC DV .avi from the source footage -- it's the computer shot in question, a simple rack focus from the computer to passers-by.

And, for the truly adventurous, a link to a 50mb zipped bit of shallow DOF business that I like quite a bit. I'll keep this second clip up for a day or two and then take it down.

Now, I've got some apologies for the footage:

1) There's plenty of dust on one of the three glass elements in my setup in this footage -- the macro lens, the GG and the Nikon -- or all three, in fact. I didn't have proper cleaning stuff on me at the time, so it is what it is.

2) Scratches -- I reground this glass last night and they persist -- my worry now is that others have been right about the quality of Rockshed grit -- every time I grind away old scratches, new ones appear. I've ordered WAO 5 from Got Grit hoping to eventually solve this problem

3) Shakiness/Color -- none of this has been deshaked or color corrected.

edit: wow, I'm getting 77k upstream -- most I'd ever get in Philly was 20.

- jim

How to evaluate GG DOF grain troubles
 

Nice clips!

For those looking to have usable footage without the 'stuck grain' look that less than perfect GG gives, please review the excerpt below from my post on the "Mini35 Oscillating Ground Glass Idea " thread.
It appears that many people have been disappointed by the video they get because they were a little mislead by some samples they saw.


---- Tips and Info on GG grain evaluations below : --------

1) Posting still images of a GG video is WORTHLESS for evaluating the grain. Period. You need to see a slow panning shot of the GG in use, preferably with some of the scene out of focus a bit and shadows and highlights. Only then do you have a chance to see the grain pattern because it remains in the same place on your monitor while the image moves past it.
So you shouldn't ask for frame grabs of the GG for evaluating it for grain.

2) Posting TINY video,or some highly compressed format is also worthless for seeing grain effects. The first thing that a compression codec throws away is the grain pattern! The poster should use a 7 megabit/sec mpeg4 or Media9 video to show the details. Then you can see possible fixed pattern grain effects.

-Les

Stuck Grain -
 

I agree with Les re 'stuck grain'. Has anyone really removed the stuck grain in the static approach? Like Les says, static frames don't cut it for evaluation. The second a slow pan happens, and that grain, regardless of how fine, doesn't move - it's immediately apparent and obvious... yuck! Frankly, I'm not convinced that it can be removed without moving the ground glass using traditional grinding. I think the only way would be to have a truly grainless diffusion surface (which catches enough image to be fixable with a condensor AND doesn't kill you with so much light loss that you have to bake the talent with 18k's). Seems like the bossscreen or something like opal glass are the only things that even get close to this.

It just seems (to me) like the second you can buy into moving the ground glass, everything gets easier... don't worry quite so much about the 'coarseness' of the grain - giving you better diffusion and light transferrance, and there is no problem with any dust on the ground glass because its moving.

For what its worth, I've completely dismantled my static adapter (which worked fairly well) and used the parts to build a 'spinner' - it's good enough for me that I've actually _stopped_ working on it, which is saying something in our little group of addicts.

Would anyone kindly point me in the direction of the proper PCX lens setup I should be using? Any relevant info like where I could buy two cheap close to 58mm would be great, as well.

Thanks!

- jim

- jim

thanks for uploading the clip and very nice shooting on "bottle.avi"

i also need some kind of pcx or fresnel lens cause i get vignetting. please take the time and download this file and tell me what you think.

the zip-file contains a videoclip and a picture of my temporary rig that i use now for testing.... =)

this is the +10 macro lens i use:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=30045&item=3826338236

when i zoom in i get blurry corners... but hopefully a fresnel lens or pcx lens will help me so that i don't need to zoom that much with my vx1k...

btw, what is the difference between the pcx and fresnel, do you always need both?

THANKS
Eric

Microcrystalline wax beats using AO ground glass, no doubt about it. I have posted stills of my progression through different ground glasses and eventually microcrystalline (even shots with the iris near closed, with no sign of grain).

http://www.frankladner.com/m_001.jpg
http://www.frankladner.com/m_002.jpg
http://www.frankladner.com/m_003.jpg

Yeah, I know you can't tell as much with just stills, but after you've looked at so much footage shot with these adapters, it becomes easier to spot, even in stills (esp. on out of focus parts). With me being on a dialup connection at home, it takes a while to upload big video files. However, i'd be willing to upload an uncompressed 720x480 clip of a quick pan or something that you guys can look at in an NLE. That way you have some frames to scrub through and see if you can spot any grain.

It has been mentioned in the microcrystalline wax thread that it may not be fine enough for HD. I don't have an HD camera to test it on, so I don't know if that's true, but I will say that I haven't found a better static solution for SD.

,Frank

DVX100
 

I first read about the agus35 last night and I have been reading about all the variations and trying to catch up for hours now.

I'm starting a short film Saturday night. I have access to a GL1 and a DVX100. I'd love to use the DVX100 but am having trouble figuring out exactly what I need.

In a short thread on here someone gave this diagram:

(SLR) - (PCX condenser) - (gg) - (+10 macro) - (+10 macro) - (DVX)

Is that still the best way to do it? If so, which PCX condenser do I need exactly? I have various camera lenses I'd like to be able to use if possible, if I can only use one then probably a Nikon 50mm f1.4.

Also, is there any possible way to get the macro filters I need by Saturday night? I willing to get the poorer single-element right now. Would it be possible to use 2 +1+2+4 kits? A local store has those.

If I were to use it on a GL1, what's the cheapest macro filter I could get away with?

-----

I realize that having this done by Saturday night is pretty unrealistic, but I'd love to try, and that's just the first night of shooting so maybe we could use it for the other days, though I would worry about continuity.

Any help would be appreciated, thanks.

Frank,

Can you post some shots that are actual full, well-lit frames from your adapter? Where'd you get ahold of the micro-crystalline wax/glass?

- jim

I'd just like to say that I've been working on this project since the begining and despite my daily post Im still hearing the same questions and still giving the same answers OVER AND OVER again... You would think most people would start using the search engine on this site to answer some of their questions or perhaps do some research to find the answers for themselves. Oh well. Cant fight human nature. Trust me I've tried. I've put too much of my own personal time helping people that arent willing to take the simplest first steps in helping themselves. I hope you understand my frustration and decision to no longer answer questions that have been answer dozens of times before.
Im not saying I dont want to post any more. I just think at this point I want to use my time to make progress with the project and have a open discusion with people with the same mind set.
Anyways I hope I was some help over the last year or so.

Now its time to finish the project.

-Brett Erskine

Frank, Even a very short clip of 10 frames from a slow pan would show everything. It may be beneficial to have fully lit frames, rather than just the middle. It does not need to be the DV compression, but for 10 frames even that would not make that big of a file!
-Les


<<<-- Originally posted by Frank Ladner : Microcrystalline wax beats using AO ground glass, no doubt about it. I have posted stills of my progression through different ground glasses and eventually microcrystalline (even shots with the iris near closed, with no sign of grain).

http://www.frankladner.com/m_001.jpg
http://www.frankladner.com/m_002.jpg
http://www.frankladner.com/m_003.jpg

Yeah, I know you can't tell as much with just stills, but after you've looked at so much footage shot with these adapters, it becomes easier to spot, even in stills (esp. on out of focus parts). With me being on a dialup connection at home, it takes a while to upload big video files. However, i'd be willing to upload an uncompressed 720x480 clip of a quick pan or something that you guys can look at in an NLE. That way you have some frames to scrub through and see if you can spot any grain.

It has been mentioned in the microcrystalline wax thread that it may not be fine enough for HD. I don't have an HD camera to test it on, so I don't know if that's true, but I will say that I haven't found a better static solution for SD.

,Frank -->>>

I'm sorry for your frusturation, but all the information is so incredibly scattered that its extremely difficult to understand it and know all that has been discussed without having been here from the start.

It would help a lot to have a definitive FAQ. The tutorial here http://ideaspora.net/aldu35/index.html is extremely beneficial. But in it he says to just go here and look at your posts and figure out how to use it with a DVX. I tried that, couldn't find anything definitive, so I asked. Sorry.

in fact part of the goal is the path/time you spend to reach it, that is why most of references to build this device are not referring to the definitive how-to procedure.
it depends the camera you get, the ressource you can find and so on...
there is almost a different solution for every project.
if you plan to build an industrial solution there will be a recipee for it, but it will be probably a different product than the ones we are talking about in this forum.
to build mine a spend several night to read several forum (probably about several hundred of post) and still surfing the web for info. that is the price to pay for a cheap miniDV

Ok, i understand that. But then why doesn't everyone post exactly what they did to build theirs, with pictures and everything. I have seen a few, but like I said, I'm trying to find out how to do it with the DVX.

when you build your project, you do not know where you go and when you reach the target, you probably do not really how you get there, so making a clear recap. seems easy but has no meaning since the chain of move you do has been generated by pure chance.
My project start by reading a french forum, challenging to build an equivalent to P+S for 10$.
At this time i do not even knew what was this device and how it works. the first step was to collect info, to know what it is and acquire the knowledge required to build one.
then i start to build MY strategy, consisting to purchase cheap lens and body camera from ebay. That was an expensive step i would not consider or advise now.
By chance i got old SHARP tube camera with very nice lens that i dismount for other reason. Inside the zoom lens i found some glass and aluminium stuff that i reuse. in parallel my first purchase start to de delivered. Now i got tons of mirror, prism and lens that are uselesse for the miniDV but at the time, i was sure that i would need them.
In parallel, there was too the problem of building the gg and finding the AO. I got the chance on a forum to find a guy who purchased too much and was willing to share.
The same for the lense, all my effort to define/find a good one gave no result until i found one but i was really lucky.
Finally a got my miniDV build and performance seems very good.
But now we are on the vibrating GG... another story.
As you can see there was many line crossing at different times and i doubt this will happens the same way for you.
If you want to go the fast way (and expensive) there are some website that are selling already made component (like gg or lens) that could you help to go faster.

Les: Ok. I will try to get something put together. Thanks!

Jim: Check here:
http://www.dvinfo.net/conf/showthrea...threadid=27433

I believe I posted some outside shots there. The wax I'm using is from a free sample. However, the guy I talked to quoted a price of around $1.50 / lb for the wax, so it's not that expensive. However, I believe he mentioned a minimum order of 50 lbs. This may be negotiable, however. See the above referenced thread for contact information.

Thanks!

That's a huge shame Brett. Seems like I got on board at the wrong time. I've only known about this for a few days but I understand your frustration. Unfortunately it is difficult to find info on a particular question when people aren't sure what questions to ask. A FAQ is good in this respect because it gives you the questions too. It takes someone who knows which are the right answers though to do this eg. someone who has a working model

Generally, when I join boards for research I try to offer stuff before, or as, I ask questions. I must admit, I tend to use them to store my own info too which is probably a waste of memory, but I do it in the hope that someone might find it interesting or answer a question they are asking, dumbass to dumbass.

I hope that you will still be checking in from time to time to add good content even if you aren't answering questions per se.

Perhaps the Topic could be split into different topics like "Aldu35 Screen tech", "Aldu35 Lens tech", "Aldu35 test footage"... etc. Even a thread only for people who have completed projects to discuss how to improve them rather than basics.

Both the "Homemade 35mm Adapter" and this topic are around the '1000 posts' mark so for single threads they are a bit unwieldy. If they were separated, for example, if someone went through the footage thread and liked the look of it, they could search for that person on the other threads and see what method they used.

Just a thought.

Anyway, take care everyone and, to use a much overused cliche...I'll be back

Raavin ;)

Brett,

I know where you're coming from. However, despite your tireless hours on the forums and the generosity you're inclined to with all your knowledge of optics, I think your frustrations are a little misguided.

What I see when I search for words like "PCX," "condensor" and "plano convex" is a list of posts a mile long, with you answering questions that are highly specific. If I were building an adapter exactly like someone else, this would be a lot of help, but many of us here are building with different materials and cams. So, specifics -- and believe me, I've got a 2,000 word document of PCX related posts lifted from this thread -- are all but useless -without a proper understanding of how they're interrelated.

May I suggest you write up a 'Condensed Tutorial on Condensors?' This would save you a LOT of hastle. For someone like myself, a good overview of the relation of focal length to condensor diameter and, relatedly, their relation to the GG would be enormously helpful.

To put it in context of my specific situation:

I've, at the moment, only got about 2 inches of space alotted in my setup between the rear of my Nikon lens and my ground glass. At the other end, where my macro is inserted into the adapter, I've got probably a half inch between the macro's outer surface and the rear of the GG. This doesn't exactly leave me with a lot of wiggle room to be placing a double PCX setup inside.

From what I understand of your posts, I should be placing two condensors together, convex sides facing AWAY from eachother, with the plano side of the rear-most PCX ground.

In ASCII, a cut-away side view would look like:

<-- action ||nikon|> (][) |macro|[]=[dv camera]

1. I'd be grinding the plano side of the right lens ( ---> [) ) ?

2. How do I determine the distance between the ground plano side and the rear of the Nikon lens? This is flange focal length, in other words, and I'm unsure if it changes with the condensors in place -- and how would I ascertain the change in FFL -- if any -- by other factors of the condensors (diameter, power, F1, ???)

3. I've got a setup based around a 58mm filter for my GG at the moment. Given that I've already built a housing to accomodate 58mm, I'd clearly like to get a PCX closest to that diameter. If, however, I have to settle with a smaller pair of PCX's (say, 50mm in diameter), how will this affect their optics (and FFL)?

4. How is diameter related to focal length (if at all)?


I don't have all the time in the world, but over the course of the next month or so I'd like to help you write the tutorial up -- if you're interested, that is. We could host it -- you'd get the lion's share of credit -- on my site along side my building tutorial (which is due for a facelift and writing updates...)

Drop me an email off board and we'll get it rolling -- jim@ideaspora.net.

- jim

edit: nevermind