I must admit Les, that flick does nothing but injustice to the footage. I will recompress it again ..... (edited) thanks.

Hello - New On Board
 

Hi all,
I'm new to the discussion and I've been reading these two threads all week long to catch up and I'm finally at the end. :o) .....all 45 pages or so.

Every since I saw the mini35 first come out I've been wanting to do something similar. I've read thru all your design ideas, what's worked and what's not worked, so in a way I've used all of you as my design iterations. I've sketched out a little design of my own that I'm going to be doing shortly. Maybe next weekend I'll start iterating further on it.

I'll be machining mine by hand at a friends shop. Pretty cool deal, actually. I get to use his shop whenever I want for my projects in exchange to do a video on DVD for him that shows all his tools and machines for insurance purposes. I've actually got a steadicam version nearly finished that's been put away for about a year and a half now. Going to finish that one up and got some more too.

At any rate, I wanted to ask the group a question that I haven't seen worked out yet...at least from the two threads that I've read. Just recently in this thread I've read that the so far premier design is Dan's and that the image is upside down and reverse. I'm sure people have tried, but perhaps you've given up on it.....has anyone tried to get the image right side up and corrected left to right before going into the camcorder lens?

I'm a mechanical engineer with a decent background in optic-physics. To get the image correct, what you need is a convex lens. I've chosen one for my project that has a short focal length. If you place a convex lens at twice its focal length distance after the ground glass and the camcorder on other side of the convex lens - again at twice its focal length distance - then you will have the correct image; right side up and correct left to right.

The problem that some might see is that focal length distance...and for some of you that have already built your device might find that adding this extra distance makes your adapter way too long. If you choose a lens with a short focal length and make up some of that distance by bouncing the image off of some mirrors or prisms - as in a 35mm camera - your overall adapter can still be somewhat compact. This is what I've choosen to do with an oscillating ground glass.

So again, has anyone tried to reverse the image using optics or has everyone just given up on it because it yielded unacceptable results?

By the way, when I start I'm going to use balsa wood to go thru some iterations to get the distances and math worked out - and also for the real-life/sanity check - and then I'll machine it out of aluminum. What I'll do after I'm finished and if it yields decent results, I'll offer the designs to anyone that wants them including the circuit diagrams.

Some details:
adapter will mount medium format and 35mm lenses.
oscillating ground glass (several different glasses with different grain sizes for different looks)
oscillation will be variable controlled
battery powered circuit to help keep a constant power to motor until batteries are dead
LED battery power read out
two mirrors to bounce image
convex lens to reverse & invert image


Courtney

I think people have decided to wait on inverting the image until they get the rest perfected. You will probably see some light loss and perhaps some image quality loss too. Ultimately image quality is what we need and it's easier to do a 180 in post than it is to add image quality back in later... so you should try tests with and without your image orientation solution. Some people around here might trade image quality for a flipped image though... guess it comes down to personal preference.

If you get yours to work I'm sure people around here would want to buy one from you, so keep in mind what you and your machinist might charge to reproduce your efforts. I really love the medium format idea, the image to grain size ratio is much better.

Good luck and post footage when you get it!

Hi Joel,
Thanks for the response. I wasn't expecting one so soon.

Yea, I realize they'll be some light loss. The more glass you go thru the more f-stops you lose, but the mini35 does it as well as the pro version....at least I would guess. I haven't seen on in person yet so I don't really know other than the pics that I've seen on their website. I certainly would hope that $8k includes an upright correct image.

Anyways, I'll deal with the light loss, which is why I'll be using the medium lenses mostly. The negative for MF 645 lenses is nearly twice as large as a 35mm negative. I figure if I can bump the light input some - by using MF lenses - then I should be able to deal with the light loss on the other end. What I'll do is light meter the input and output. Has anyone done that yet?

As for selling, I won't be doing that. I'll draw up the plans and put them out on a PDF file, JPG's or something, but no selling. I'll be doing the machining myself. I've got about 8 years experience in the shop so it's all going to be me. I plan on making note of the hours I spent machining though so other people can take the plans to a machinist with a rough idea of how many hours it's going to take. Machinist's hourly rates vary, but I think $60 an hour won't be out of the question....maybe even on the low end. I don't know.

Once finished I'll do some pics, footage and what-not and post it up for everyone.

Thanks again for the response.

Courtney

Yeah - the mini35 has an upright image. It's more like $10k than $8k when functional though. Plus lenses.

I know Dan has tested different Ground Glasses for brightness. The beattie and maxwell optics GG's seem to be the brightest from what I've read, but they'll run in the $200-$400 range each. It might be worth considering basing the size of your GG on the size if your 645's GG so you could buy a higher end replacement after all the testing is done with a cheaper GG.

Good luck and don't give up!

Twice as large is right, but that does not mean twice as bright! Most medium lenses have 2.8 (if you have deep pockets) as a start vs 1.4 in 35mm SLR.
http://www.ephotozine.com/manuals/Ha...ls_t21m44.html
That alone means 4 times less light.
The image from a 50mm SLR on a 24/36mm (normal) is the equivalent of an 80mm on a 6/6. The look, perspective, etc is the same. They are both "normal" for their image size. The DOF would be shallower on the 80mm if you were to set the 50 at the same 2.8 aperture (as the 80 has, but I bet you would use the 1.4 (if avail). Less grain (which you may not see since you want to shake the GG) and less light.
(as near as I can figure..;-)<
As for the image flip, my first contraption (July 2004) used the parts and configuration of an SLR lens (one mirror and one pentaprism) Same Minolta that I used in 2003 to videotape the "film-like" image TTL using a CMOS on the viewfinder.
>>>>>>two mirrors to bounce image
convex lens to reverse & invert image<<<<<<<

How would (two mirrors) and (a convex lens) work?
One at a time I can understand, but both at the same time?

That's a really good point Dan. I forgot about that. The 35mm format is plenty shallow at wide apertures and medium focal lengths. Keeping in focus using medium format may be a real pain.

Leave aside a larger dia of the lens housing (the lens themselves are not much larger) if one would want gears on them (for FF use).

Imagine having the ground glass, then 3 inches behind that is the convex lens and 3 inches behind that is the camcorder. That's 6 inches and you haven't even put the camera lens on yet. So if you were to use mirrors to bounce the image, like a still-picture film camera does then you could make up some of that 3 inches and the entire adapter wouldn't be quite as long any more.

With mirrors, imagine the ground blass then 1.5 inches behind that is the mirror at 45 degress, 1.5 inches above that is another mirror at 45 degrees, then the convex lens, 3 inches behind that is the camcorder. You've made up 1.5 inches. You could do that again - if you wanted - for the remaining 3 inches between the convex lens and camcorder. That's if the focal point for that particular convex lens was 1.5 inches. Placing that lens at twice it's focal distance from the ground glass and the camcorder lens will invert and reverse the image.

Yea, that's another project I plan to do.

Courtney

I did something like that once (one mirror between the adapter lens and the GG.) and I have one mirror in my new setup. But you have to consider you loose quite a bit of light. One mirror is acceptable, but two almost unusable, so with one mirror you'll have to place the camcorder vertically or in 90 deg.
Also, you have to find a photographic type of mirror with the chrome side on top of the glass.

Putting the camera in 90 deg. will correct the flipped image, right? If your camcorder has a LCD that can be closed but with the LCD on the outside (I mean: open the lcd screen, turn it 180 deg. and close it) you can look at it with the camcorder put in 90 deg. (if I'm not too clear, I'll post a drawing)

Why use MF lenses
 

Everything that has been mentioned before about the positives and negatives of using MF lenses is true but I can add two more positives that led me to make my adapter use both MF and 35mm lenses. By far the weakest point in the optical system of a DOF adapter is the ground glass. Thankfully MF ground glass is much larger so the clarity you can achieve from it will be greater than that of 35mm. Also the moving "grain" from the ground glass becomes even more subtle (almost like using 100 speed film instead of 800 speed). I would say run a test and see if you are losing any resolution after shooting thru your ground glass at a resolution chart. Dont forget that a HDV or HD camera might be in your near future so make sure your GG isnt robing your new HD camera's resolution. If you dont see ANY resolution loss between shooting with your adapter or without your adapter when using 35mm lenses and 35mm GG then your fine. Just use 35mm GG. BUT I personally haven't found that to be true. HD shooters have even complained about the P+S Pro35 and its inability to resolve FULL HD clarity. Now some people like the softness (as I do) but how much is the question. Does i My thoughts are why not make it with MF ground glass and you can always use 35mm lenses with it too.

A second reason why I went with MF is that for MY particular video camera I wasnt able to zoom in and focus on a 35mm sized piece of GG without the aid of some type of close up lens. I found that unless I paid big bucks for top quality glass, like the Century close up diopter, I was losing a lot of quality in my image. Now you my have a camera that CAN zoom in and focus full frame on a piece of 35mm GG (a lot of smaller/non-professional cameras can do this) so in this case you can go without a diopter and thus MF gg is not as important.

Anyways run tests.

The way I see it is the a 35mini/micro device is good for medium/close-up talking head shots. This way the shallow DOF isolates the subject from the background. plus the resolution loss on HD is welcome when you have medium/close-ups on people. Last thing I want to see is blackhead blemishes.

For the wider establishing shot the more detail the better. So no GG for those. Plus I for one want a deep depth of field for those shots because in normal eyesight in long 'shots' (or views) aren't as focus dependent. So seeing the whole scene in focus is cool by me...generally...of course there's moments in the story where you will need to think about controlling your depth of focus field.

Brett, my camera is like that too - I cannot zoom in close enough to the GG withou some sort of Macro or Dioptre to fix this problem. What did you do to fix this?

You can read the details above. Of coarse if you want to do 35mm lenses we have no choice but to use a high quality diopter

I went through the post Brett, but I guess I am missing something. What does the MF stand for? Manual focus? I am not sure I am following you on this one. I have a panasonic dv-pv852 and I cannot get near the GG without it going out of focus (at least while maintaining the 18X24 ration. Kind of sucks because I am still waiting around for an achromatic dioptre that I can find that is cheap enough for me to test. So if you have a work around, I would love to hear about it!!

zoom out Leo (till you can focus) and get closer to GG till you fill the frame.
what gg do you have?

I am using a spinning CD with mylar. It is really nice as far as the picture without any spinning striations. Problem is light loss which is a bit heavier than I would want, but that is the trade off.

If I get really close to the GG, I will see the black vignetting as well as the image in the GG. That is why I wanted to get a proper and strong Achromatic Dioptre (which seems to be out of my price range).

I did not mean that close to get vigneting, just a touch closer. If it does not work, $219 to Century and it will work.
How is it possible for GS200 to play back 24P footage from DVX100A?

Yes the problem is that I cannot find that middle ground. I cannot get close enough without vignetting or far enough that it does not focus. It is a crappy deal even though the camera is great. The dioptre sounds great, but again too much money - I already spent $85.00 on a macro lens that I problaby will never use, so I am trying to tone down my spending on anything else - if possible. Any surplus places sell Achromatic dioptres?

Mandy-
Been down that road...many times. Trust me. I've been fine tuning this project for a long time, even longer than Dan, and I can tell you that your going to save yourself a lot of headached, time and perhaps even money in the end if you just get yourself a Century Optics. I never have been able to find a proper surplus lens that will be nearly the quality of the Century. Or you can use MF lenses and MF ground glass only and you wont need to buy any diopter.

MF= Medium Format

Dan-
"How is it possible for GS200 to play back 24P footage from DVX100A?"

Pulldown. The same thing happens when you professionally telecine 24fps film to tape. You can read about it in detail on Panasonics site (Google 2:3 pulldown).

Thanks for the info. I have never heard of Medium Format lens, so I will have to do some research. Yeah, I am still going to try and find a surplus one for cheap, just to make sure it works, then I probably will go with a Century or something along those lines.

Brett,
I have heard of pulldown. My question was how come a few $ hundred camera has the feature built in.
You mean to say also that original 30P or 60i footage could be converted and played back as 24P right (from whatever NLE)?

Leo, make a test with your camera and see if it gets a 6 x 6 cm image (so about 2,4 ") in focus. There are professional camera's that use such big negatives (is this MF?), with expensive lenses. But you could find second hand Rolleiflex or Rolleicord camera with a non detachable lens a lot cheaper.
Those are camera's with two lenses like this:
http://www.classiccamera.org/rolleif...d%20v%20rt.jpg

A good thing about this is you probably have even more DOF that 35mm and some have a nice sort of rack focus. It would also be easy to put a GG on it because it's just a box. Disadvantage is you have just one lens.

(I bought an old one called Lubitel2 for about $5, but a Rollei could be more than $ 40.)

EDIT:
It is probably best suited (because of it's size) to use with either a static GG or a oscillated one, hum...which brings back the subject of this thread.)

Dan,

The challenge with pulldown is that it doesn't exactly look like film, but it doesn't look like video either - it is a beast all its own.

Dan-
Send me your email and I can send you detailed info about the pulldown issue. I dont want to talk of subject in your thread.
berskine@mail.com

I have just sent you another one. Did so a while ago when you said "let's chat"

Just did a test on POC GG two days ago and here is what I have found:
the GG has the best diffusion of all GG I have tested (finest grain structure)
almost perfect for static. (grain is visible on soft areas but the grain is much finer than Beattie focusing screens)
light loss is above 3 stops (good enough for exterior day time) but almost unusable indoors (without proper lights)
soft focus is nicer than the way it looks on Beatty (subjective)
vigneting big time, (no surprise) just as any other GG.
Confusion: (I mean conclusion) : nice softs, razor sharp sharps, light loss, vigneting (you could avoid some of it zooming-in more and using FASTER lens)
very thin (bends easy) potential planarity issues. Best (I know)for static and worth a try but proceed at your own risk.

and added some stills from last weeks of footage:

http://dandiaconu.com/gallery/Work-samples

Dan , what does the POC stand for?

Physical optics corp.
http://www.poc.com/lsd/default.asp
it has been mentioned a while ago...here or on another thread.

Dan, which GG from POC did you try? Their Light Shaping Diffusers offer a very wide range of diffusion angles, which (I'd guess) would have a significant effect on the amount of vignetting and light loss.

50 deg. Very nice image but the cost is light.

I owe it to myself. I took some stills of POC vs. Beatty. I am too old to fall in love, but the image is gorgeous (well,...except the light loss) and also the vigneting is ok (not that bad that is) (and the fine grain allows a zoom in to get rid of it).

http://dandiaconu.com/gallery/album15

Is this shot static? Looks very good.
I had the same with tracing paper (on rotating GG), it had beautiful DOF and mid-tones, but too much light loss.

Anyway, nice of them to allow you to play around with camera equipment in prison.

THAT was a hell of a good one!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
took me some 5 seconds (like five years) to figure it out!!!!!!!!!!!!!!!!!!!!!!!!!!!
oh man........ that was good........... give us some more............rotf

I wanted to post a contented smile, but Smilies are Off.



EDIT:
Great images really, (that part was no joke.)

which ones? outside the prison?

No, your actual black chapter: album15
I like the POC, for exterior shots, it'll be great, because the light loss is more of a gray filter, right? So I'm looking forward to outdoor tests when you are on parole.

The actual structure of the grain is different from Beatty. Most rewarding would be outdoor portraits .......
Found a 1.2/50. BEAUTIFULL lens but Pentax mount.
still dreaming of this lens:
http://www.alaska.net/~rowlett/image...ilux/mimi4.htm
but at 3k..... it will have to wait.... a bit

Never really seen anything like this (I mean the organic DOF effect, not the girl)
It would be terrific on DV. Incredible, especially on B/W I think, now I reconsider to shoot B/W (not with such a lens though >3K)