New moving ground glass mechanism

[Dan Diaconu]

Although only 3Mb (for 80 seconds) this one looks better:
http://rapidshare.de/files/1176958/Premiere.rm.html
one-a-diz-daiz I'll find the 27Mb one I was looking for ....s-got-a-be here somwhere....

[Dan Diaconu]

http://rapidshare.de/files/1228767/beauty_shoot.avi.html


http://rapidshare.de/files/1230175/BSHOOT4.avi.html


http://rapidshare.de/files/1230020/bshoot2.avi.html

[Dan Diaconu]

http://rapidshare.de/files/1230281/bshoot3.avi.html
.

[Dan Diaconu]

http://dandiaconu.com/gallery/ALL-CLIP-TESTS/IMGA0516
http://dandiaconu.com/gallery/ALL-CLIP-TESTS/IMGA0517
How is this Obin? OK? Left side is bit soft (I think camera was not squared to the chart, not much but enugh to show)

[Les Dit]

Dan,
I looked at "beauty_shoot.avi " and saw a lot of block-grid artifacts. I'm sure this is due to your render and not the adapter. You really should look into compressing with a modern codec, like media9 , at say 9 megabits/sec . You will get a bit more than 7 seconds out of 30 megabytes as a bonus too !

-Les

[Dan Diaconu]

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

[Courtney Lana]

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

[Joel Aaron]

Originally Posted by Courtney Lana

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

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!

[Courtney Lana]

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

[Joel Aaron]

Originally Posted by Courtney Lana

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

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!

[Dan Diaconu]

Originally Posted by Courtney Lana

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.

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?

[Joel Aaron]

Originally Posted by Dan Diaconu

The DOF would be shallower on the 80mm if you were to set the 50 at the same 2.8 aperture

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.

[Dan Diaconu]

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).

[Courtney Lana]

Originally Posted by Dan Diaconu

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

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.

Originally Posted by Dan Diaconu

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).

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

Courtney

[Oscar Spierenburg]

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)