DOF
 

Not to get off the focus of this forum but depth of field is dependent on light/shutter speed and aperature.

More light--less softness
Less light--more sharpness

THe B.S. algorithym for depth of field is approx 1/3 soft before focal plane(place of focus) 2/3 soft after focal plane.

This is a rough layman explanation.

<<<-- Originally posted by Stewart McDonald : Depth of field gets shallower the closer you are to the subject, I think. -->>>

That is correct -- distance to subject is a major factor in determining DOF, and the closer you are, the shallower it is.

For shallower DOF, you need to get as close to the subject as you can, use as wide-open an iris as you can, and as telephoto a lens as you can.

"35mm lens>condensor lens>600+ alum. powder ground glass or better>Pechan prism>roof pentaprism>macro lens (+16 power*)>video camera"

will this have to be tweaked with a DVX-100A, due to the different minimum focus length (2' instead of 3' i believe) or does it not matter?

thanks in advance.

-kd

Yes. You wont need a diopter quiet as powerful for the DVX100-a. I'd love to confirm thoughs minimum focus numbers. Find out what they are and its simple math after that.

Frank
 

------I spent about 40 minutes grinding my uv filter on 600 grit aluminum oxide today and the results are excellent. I get a very fine grain glass that is uniform in brightness (no hot spots).------

I am doing another GG today and after a hour I am about alfway to the final result and the last part are longer.

What I have actually is about two time the size of the grain that it as to be ,otherwise I will see the grain.

I was thinking that maybe your gg is made from plastic, there is some uv filter that are made whit plastic and this very easy to grind but also easy to scrath. But easy to repare.


Alain

Hi Alain!

It is a glass uv filter, for sure, but come to find out I quit grinding too soon.

You were right about the grinding time! After comparing your footage to mine, I realize that although my glass appears very fine grain, it needs to be even finer. So, I have taken it back to the ol' grinder for another round since then.
It is looking better and better. I have ground it three separate times and will likely do it some more. Now all I need is a condenser to concentrate the incoming light onto the glass more evenly. Also, I will still likely need that achromat macro adapter.

Thanks for your help!

,Frank

fog filter?
 

did anyone tryed "fog" filter as GG? does it make any sense? is it possible to see anything at all with that filter, i mean is it transparent too much or not?

any thoughts?

filip

I haven't, but I'd be interested in reading what you find.

aluminum oxide
 

I just got off the phone with a place called the rock shed http://www.therockshed.com/grit.html .they have 1000 grit aluminum oxide just placed a order 4.50 a pound
2 dollars shipping said he would ship monday morning first thing ........... my order with sis .it took them one week to tell me it won't ship until march and 15 dollars shipping and handling

Good deal Richard! I think I will place an order with the rock shed too

at what point will it look shiney
 

Rocks are polished with 1000 grit.

You roll and roll and finally they come out mirror smooth. So at some point your fine grain will look like polished glass.

If you look at a polished glass surface under an electron microscope it looks like you are looking at a gravel parking lot. So at some point more is not better.


LCD Screens. Jameco.com sells 4" LCD screens that you can separate the LCD from the light source behind it. Some LCD PC monitors are the same way. Essentially all you need to do is physically flip over the LCD and or invert the panel.

fliping the panel 180 LtoR would of course invert L to R rotating 180 degrees would invert top to bottom.

You don't need to do anything "ELECTRONIC" except perhaps lengthen the conductors

Some LCD panels have an integrated light source that would be difficult to use.

I have to ask why someone would take apart a LCD in HOPES of fliping AND mirroring the image when you can just BUY one that does that at the touch of a button. They are just as inexpensive too. RMPP for multiple links and prices.

Monitor Flips H+V
 

As mentioned prevously...
http://mp3playerstore.com/stuff_you_need/special/headrest-7.htm

I would far rather have this than mirrors etc

it will invert top to bottom at touch
 

it will invert top to bottom at touch of a button right?

a lot of LCD flipout viewfinders do that. My GL1 comes stock with such a viewfinder.

What it won't do is flip L to R. Am I right or does the LCD you found do this as well?

LCD flipping H+V
 

James this is what it say,

color/ brightness/ contrast/ volume/ mute
-video input 1 or 2
-Left-Right Picture Switch
-Up-Down Picture Switch
-16:9 or 4:3 Screen Ratio

I have not see this monitor.

RMPP. Click-on-link. R. L.

Hey Taylor since we are on the same page are you also looking for LCD's that have the addition horizontal vertical squeeze and stretch feature? In case your wondering why I would want that ...think of 2.35 anamorphics. Despite my efforts I havent found one. Would you like to help in the search?

Sure would Brett, but I think chances are slim...I might need to check panavision/arri options? So you are looking for a LCD that will have the ability to stretch and squeeze to 2.35 with R to L and T to B flip?
Let me know how your achromatics work out...cause I'm DVX ready....if we can get this to work, I would be very, very pleased.

Taylor- Thats right. I know Transvideo makes a box that you hookup to your video between the camera and the LCD but its more than $1000. Anything made for the exact purpose of unsqueezing to precisely 2.35 is most likely going to be expensive. Instead we should be looking for a LCD that has the general ability to progessively stretch and squeeze a image and we will just eyeball it unitil it looks right. Doesnt have to be absolutely perfect. Its just for the camera operator to view the picture correctly while operating because at the same time the camera will be recording the full CCD anamorphically squeezed version of the image on tape. Get it? Lets find it.

Check out these small (2.5-4") LCD screen kits with up/down, left/right flip modes.

No idea on pricings, though I have form-mailed them. Will keep you all posted.

- jim

Course you could always just take any old LCD screen and mount it upside down. If it has a 1/4 inch screw threading on it somewhere this shouldn't be a problem.

A lot of these LCD's that offer flip and reverse options are for mounting upside down when the original video comes in correctly (i.e from a DVD player). We're dealing with video that doesn't come in correctly. So any LCD mounted upside down will work for us.

Nope. I wish. This mistake has been made countless times on these threads before and I'll mention it again. You need to ALSO correct the image Left to Right. RMPP.

Brett
 

If you rotate a lcd monitor to put it upside down it is flip left to right also. That's what I did.

Alain

If you rotate a lcd monitor to put it upside down it is flip left to right also. That's what I did.



That is absolutely right! It seems too simple but it works. If it is rotated 180 degrees it will be fine. Think rotating not flipping.

Paul

dvdof.com

Wow I cant believe I looked over something so simple. Your right. I guess I missed that idea because I was working on another problem and thinking in terms of the simple limitations of prisms/mirrors. Great! Thanks.

What's up here ?

Does any body as built something ,any improvement?

Brett , have you already find a good lcd monitor that you have try?

Alain

I just got my 1000 grit Alum Oxide in today from the rockshed, so I should have a working prototype soon. BTW therockshed.com ships FAST and they are cheap, my total w/ S/H was $8.35 for a pound!

Nope. Still looking for that small LCD with vertical and horizontal picture squeeze/expand controls. Would love anybodys or everybodys help in find it. Check out the thread on LCD's for this project for more info.

Damn were close huh guys.

-Brett

aluminum oxide
 

my 1000 grit aluminum oxide came in yesterday. from the rock shed http://www.therockshed.com/grit.html it was the same price 8.35 a pound shipped. i will be getting a lens in a few days.
alain will a uv lens be ok . i think i remember you used a skylight lens

Richard
 

Yes Uv. but be shure to use a glass one ,not plastic.
Tiffen are good and you can unmount it easealy ,it is screw.

Alain

lcd
 

I found a site that seems to be a good place to buy a lcd http://www.azo-store.com/newlcd/index.php3?sesid=C;NO1CM3ZEO8DFLBBHPC you can make an order as small as twenty five dollars . I also had an idea if we were to extend the length of the strap to the lcd maybe we could just turn it around .

Dove Prisms for Image Rotation
 

Provided you didn't mind spending $50-$100 (or slightly more), and provided you could physically find a place to put one of these in the image path, and provided that you didn't mind the inevitable additional loss of light that one of these would create, a Dove Prism as seen here:

http://www.edmundoptics.com/IOD/DisplayProduct.cfm?Productid=2034

Would be very nice for both an image 'rotation' which has the effect of both the top-to-bottom and left-to-right inversions we've been hunting for. This would happen right in the light path, so no LCD-flipping-gymnastics would be required.

The expense is yet another piece of glass to shoot photons through.

(Sure am enjoying these threads, all)

-Jonathon Wilson
Film Composer, camera/photography hobbyist
Austin, TX
jonathon@aqua-web.com

Mounting a diopter...?
 

Perhaps I'm a bit confused, but the way I see that this system has to work is as follows:

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

Camera -> Normal Lens -> Achromatic Diopter ->
Light-proof "Spacer" #1 -> Ground Glass ->
Light-proof "Spacer" #2 -> 35mm Lens Adapter ->
35mm Lens of Choice.

Camera: I am using an XL1s, which has the ability to change the lens and it mounts right next to the CCD.

Normal Lens: For the XL1s, this would be the 16x AF lens that ships with the camera. For other cameras, this would be the built-in or default lens.

Achromatic Diopter: Power needed will vary depending on what camera and/or lens combination you are using. This allows the normal lens (above) to be able to focus on the image being projected on the Ground Glass.

Light-proof Spacer #1: This is simply a tube cut to the correct length for your Achromatic Diopter to be able to focus on the Ground Glass (because they obviously cannot be stacked directly on eachother). This should also be long enough so that the projected image captured by the achromatic diopter and original lens, lets the CCD see the full frame.

Ground Glass: Glass or other material that has been "frosted" on one side so that the light/image coming in from the front of the adapter is projected upon it. The smaller the grains that create the "frosting", the better, and if the grains are smaller than the size of the pixels the CCD picks up, they should be un-noticeable.

Light-proof "Spacer" #2: This is cut to the right length for the 35mm lens in front of the adapter to project its image at the correct size on the Ground Glass, which should be the size of a 35mm piece of film. The length of this spacer can be determined by viewing the chart located at: http://www.gregssandbox.com/gtech/filmfacts/flange.htm

35mm Lens Adapter: A mechanical adapter mounted to the spacer, allowing the use of interchangeable 35mm lenses.

35mm Lens of Choice: self explanatory.

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

1) Can anyone correct me if I am wrong on any of this, or missing anything?

2) For the XL1s, can anyone suggest how we might cut out the need to mount this all to the end of the Normal Lens?

3) If the above was possible, wouldn't we NOT need to worry about flipping/rotating the image?

I ask because I have a business contact that can make small runs of precicely designed metal, and he is local, in the US. If we could come up with a set of specifications for the metal adapters, I can have him create them at a relatively low cost.

If we were able to get the metal parts made at a good price, we might also have the ability to get a pre-produced GG supplement. I also know someone that MIGHT be able to manufacture that as well.

Just thinking we might be able to get this whole thing produced in a professional-strength package, with rails and more for under $1k per unit (perhaps even considerably less, depending on materials and features). Any thoughts or help?

Ignoring of ASpherical Lens
 

One area that deserves more attention before embarking on mass-production efforts would be that mentioned by Brett - the use of a condensor or aspherical lens prior to the ground glass. In virtually all of the test images and film posted, there has been a certain amount (sometimes negligable) of fuzziness and/or darkening in the corners caused by spherical distortion. This is specifically what aspherical lenses are for. (Aspherical or condensor or I've heard them called 'split' fresnels, which is wrong are a lens which is concave on one side and flat on the other. Imagine a standard magnifying glass, but split in half.. and you just take one half). In most of the diagrams I've seen, the aspherical lens is pressed right up against the surface of the ground glass, such that you could even 'grind' the flat side of the condensor for the same effect.

Many times, a second aspherical sits pressed against the other side of the image plane in the other direction. I believe this is basically the function our diopters/macros are performing, and as we're trying to focus through the existing camcorder lens already, I don't think there's any way to include this second reversed condensor. The advantage to including it right on the far side of the ground glass is fewer lens-to-air connections. Each one of these (and we already have a lot) introduces a decrease in contrast, and potential increase in halos and flares. It would be nice to decrease these wherever possible.

The aspherical basically removes spherical distortion (corners should be as clear as the center), while amplifying the existing light level (which we could all benefit from in a system like this).

I'm hoping to press a condenser smack up against my ground glass in my current design attempt (first attempt, so I'm sure there will be many other bugs I have to work out that y'all have already solved) and see if I can remove spherical artifacts while increasing light. We'll see how it works.

I'm no expert, but do some reading on asphericals - they may be the next area of possible improvement for an already sweet DIY adapter.

Jonathon Wilson
Do you know where to get a condenser lens? I've been having trouble finding one on the net.

Also I like the idea of just grinding down the flat side of the condenser to work as the ground glass element. It seems like it would save trying to mount two different elements together. But would there be a downside to this?

aspherical lenses
 

The ever present and 'expensive-but-worth-it' Edmund Optics (no association) carries them (as well as just about anything else you'd ever want for lenses, mounting, focus tubes, etc... as long as you have money to burn).

http://www.edmundoptics.com/IOD/Disp...productid=2454

I've also seen here and there odd little things on ebay that might do... its always hard to tell. Here's an example:

http://cgi.ebay.com/ws/eBayISAPI.dll...category=30059

I could swear that in reading specs for one of the higher-end dv camcorders... that's it: the Sony DCR-VX2100 describes itself as having:
"Aspherical Ground Glass 58mm Lens: Larger diameter allows more light to strike the Advanced HAD™ CCD imagers for greater detail and clarity, while the aspherical lens reduces optical distortion, and provide better corner-to-corner focus." Not sure where the aspherical ground glass lens is positioned in the mechanism. I'd think the condensor would be placed right up against the ccd, but I don't see why they'd need ground glass at that point as the collimated image would just project right onto the imagers. Like I said, I'm new to this, just reading.

Usual disclaimers apply - just throwing out info I thought was interesting. Take it or leave it :)

xl1 version aldu35
 

Eric,
As for what i've discovered with the xl1s. there is some good news and bad news as far as converting this aldu35 version. i'm close to finishing the agus35 rotating gg version and am trying to take my lessons and move forward on a static aldu35 version very soon, as i think it will be more efficent in the long run. the good news is once a version for the xl1 is done it will work well because of it's low light sensitivity, you can also flip the viewfinder to right side the image by just unbolting and flipping to the other side. it's a bit awkward at first but your finally able to see the controls better. and the final reason, because the lens adapter will fit nicely along the xl1 body, as it's made for lens change outs as you know.

on the neg side, it will be a bit more costly because it doesn't have a built in lens to act as a relay lens and you'll want to move from the canon lenses and shift to nikon because they are abundant, cheap and fast. first things first you may want to consider, picking up a canon to nikon adapter. i found a relatively cheap one at www.lesbocher.com, in england, for 180.00 USD (only 100 pounds for them), a nikon/nikkor lens $25-$200(right now i'm using a 55mm f1.2 Nikkor-but there could be better-i don't think the mm make too much of a difference because the ccds shoot straight regardless), a +10 macro close-up lens $30 (this i am not sure about but i'll keep the group posted once i have the magic formula-as i am still having problems), your pipe extension-50¢ worth of 2inch pvc, your gg- another $30 or so, another pipe extension-another 50¢ worth of 2inch pvc, a plain nikon lens connector - $30, attached to the pipe and out to your nikon lens of choice $25-$200. i'm kinda guestimating on the cost, but there is also going to be much effort in there as well...

that's kind of my blueprint i'm aiming for now, as everyone says, it's a lot of testing and perfecting as well as trying to discover new optical tricks and technics. stay tuned....

almost done with my Static35, but I keep getting a hotspot in the center of the gg, I installed a fresnel but it only helped slightly. Im using a 50mm Olympus OM.

How do I get rid of the hotspot? More grinding? or less?

oh yea, im using a glass Skylight filter, ground with 1000 grit alum oxide, and I gotta tell ya it looks great, except for the hotspot!

John RMPP. Dont use fresnels. In Normal SLR viewing system theres a fresnel and a condenser. SLR's need one to solve the hot spot problem and use both for achromatic abberation reasons. Replace fresnel with same power condenser lens.

When you RMPP you will find out what condensers are exactly doing for you and why you cant just grab any old condenser or fresnel (ie cheap ruler with fresnel magnifing glass) and expect it to work. Not only should you not use a fresnel in the first place but my guess is that your not using one from a camera and thus its probably the wrong power. Its not just plug and play. Were are dealing with optics here not legos. Learning the basic of light and lenses will end up saving you alot of money, time and make your adapter better than the rest out there.

Fresnels, Asphericals and Achromatic Distortion
 

So to summarize Brett's previous (it's way back there... somewhere):

Condenser lenses and fresnel lenses do the same thing. They 'collimate' light, which means that light comes in one side from a whole bunch of different angles, but leaves the other side parallel. This helps for our purposes, because we want the image to focus from the 35mm lens onto our hard-earned ground glass in a completely flat and even plane of light.

The difference between a condensor and a fresnel is the shape. A condenser lens (also called an aspherical lens) is like a normal lens which has been cut in half and you throw away one side: it's rounded on one side and flat on the other.

A fresnel isn't much of a 'lens' at all, but a sheet. It's almost like a 'collapsed-telescope' version of a condenser lens - giving you (just like a collapsed telescope) a set of rings inside one another, flattened to a plane.

Unfortunately, where the 'cuts' are, you can see visible affects to the light. This is why a true condenser will give a better result than a fresnel, unless its just a camera viewfinder and not the 'actual image.' Fresnels are often used in the viewfinder of cameras, but never in the actual optics which hit the film.

Both condensors and fresnels, however, reducing or eliminate optical distortion: in which the center of the image is sharp and bright, but the corners are fuzzier and darker. The 'hotspot' is a perfect example of optical distortion.

Achromatic distortion, is less a factor of the shape, and more a factor of the glass quality itself. Achromatic distortion happens when the glass doesn't transmit all color spectrums equally, which puts the focal points for different colors at different locations. This has the troubling effect of causing the image to look slightly colored, because some of the color spectrum is out of focus at your chosen focal point. If you're experiencing this, the shape of the lense won't help, you'll need a higher quality lens. And when I use the word 'lens' I really mean any of the glass through which the light is passing. It could be the 35mm lens (unlikely), the condensor or fresnel, any prisms that may be involved, or (unlikely) your built-in camcorder lens.