EDIT: Previously known as "Get Cinematic Depth of Field, Focusing, and True 35mm On your DV!"

This was in another thread, but I'm sure only some people were looking at it so I figured others would be interested.

There is a big hooplah over at dvinfo.net (click on Community --> alternative imaging) about building lens adapters so you can use a 35mm SLR lens on your DV camera.





I know how we all want panavision-like depth of field on our DV camcorders. Until I found that dvinfo community I thought it wasn't possible. Apparently it is.

I know this was definately confusing the first time I read what they were doing, so I'm offering to lay it out for you all and explain the whole "situation" in the 35mm DV Adapters world. Believe me, it is a large community.

The adapter they discuss building involves the concept of using a 35mm SLR still camera lens to project an image onto a translucent piece of glass. This projected image is then literally focused on by the DV camcorder and recorded. All this takes place in a tube.

These are main concerns:
- The projected image has to appear on the translucent glass for the DV camera to "see it". The most difficult aspect they've been having is using a piece of glass that is ground so finely that you cannot see the individual gravel-like texture that appears as a "film-like" grain. You might think this is fine since we all like a small amount of grain, but it does not move. Picture thousands of specks of dust on your lens that you cannot wipe off.

So, they have come up with two options: Use a more finely-ground glass, such as what they call 1500 grit (it is ground with rated aluminum oxide), OR, shake or rotate the translucent "projection screen" so the grain cannot be seen. Some people have even ripped out the motor from a CD player to accomplish this.

Ground glass is referred to as GG.

If the GG in this system is not moving, the whole assembly is called a "static adapter."
I assume a moving assembly would be called a dynamic adapter, but I haven't heard that term used yet.

All of these designs are attempting to emulate the more expensive, prosumer marketed "micro35" which follows the same principle I'm explaining here. http://www.redrockmicro.com/

Since the "projection screen" is very close to your camera's lens, you have to use a macro diopter if your camera cannot focus on it because of its proximity.

Building one, materialistically, involves:

A 35mm lens of your choice. the fstop ratio is important here. Lenses will list their f-stops as a ratio, such as 1:2.8, which is common. You want the lowest number possible. 1:1 is ideal, but not practical. Most good lenses should be 1:1.8, but the lower this number, the more expensive the lens.

A Ground Glass Projection Screen. There are ones available from optics stores, but some people discuss actually grinding your own glass with aluminum oxide found at rock/stone hobby stores. You should buy them at the size of a camera filter since that's probably what's going to work (duh.) 50mm, I believe.

A Plano Convex Lens (Optional) When the light hits the GG diffuser, light goes in all directions. The plano convex lens helps to keep the light going where it should.

A Macro Achromatic Diopter(Optional) If your camcorder can't focus on the screen, you need one. The one that is recommended is from Century Optics for $200, but you can find non-achromatic diopters for 30 bucks on ebay.

A Way to House It All From Light and Dust. If light filters in, it washes out your image. If dust collects, prepare to dissassemble the whole thing to clean it out, or else suffer dust in your image.

A Way to Connect it All Together. Step rings that convert from different diameter lenses are available at any photo shop.

If it's too heavy, a Way To Support It. Somewhere there's a store that offers a rail system that bolts to the underside of your camera and sticks out to support the lens, which can end up being pretty hefty.

What Tutorials I've Found:
--------------------------------
I recommend this one. It all screws together, is relatively inexpensive and simple, and works by all accounts I've found. About $170. Props to Richard Mellor.

A Tutorial to Build an Adaptor for the Canon GL1 and GL2. Personally I think it's a bit hard to follow, and it requires you get the $200 Century Optics Diopter and grind your own glass (although it would probably work with pre-ground glass too). But for the do-it-yourselfers, it produces an excellent picture.

Well, I hope this summed up the whole situation. I'll be constructing mine soon, so hopefully in the next few months I'll post results.

Best of luck!

-Ben

This message has been edited. Last edited by: funkbomb,

Wow! Thanks for putting all of that together. It's such an amazing and bizarre idea, but it looks like it really does work!

What I keep wondering is, how come you need to focus on the glass up close, and not just let the camera focus through the whole lens assembly?

Because if you were to do that, you'd have to have a camera that doesn't have a built-in lens, and has a CCD chip thats many times bigger than what DV cameras have.

The whole reason DV cameras can't have good depth of field is because the CCD chip(s) are too small. So, we let the image focus itself on the diffused glass, and then use the built-in lens to take it from there.

Taking out the diffused glass would give you an image of the inside of a long barrel with a small distorted, blurred image at the end that is completely unusable.

The whole idea of this is to use a "screen" to act as a sort of "CCD chip" that will display the image for the camera to focus on.

I'm not going to pretend to be an optics expert, so I can't give you good scientific details, but that's just how I understand it to work.

Ahhh... It's amazingly clever actually. I really, really want to try this some time.

A couple of important factors about devices such as these....

1. They suck up a lot of light. On the professional versions of this product (Made by P+S Techniks) you have to make about a 2 stop compensation.

2. There is image degradation involved. You may have heard people complain about the halation like artifact in the highlights (Like a promist filter), but when I've worked with these things they've always felt a bit soft across the board.

3. The low resolution of Mini-DV cameras actually help the sellability. In other wordds, HD cameras are less happy shooting through such devices.

4. They can be cumbersome. One of the advantages of DV is that the little cameras fit anywhere, but with one of these gadgets on it you might have a camera twice as long as you expected, and they can be heavy to boot with all the support etc...

These gadgets have been around a couple of years now. I'd definitely only use one if I needed the thin DOF for some reason.

Nota "What's uncinematic about deep focus?" Mono

quote:

What's uncinematic about deep focus?

Shallow DOF is considered cinematic because it's what we've been trained, as life-long moviegoers, to expect in a professional product. And the reason they've been in movies is because isloating the subject by making everything else out of focus is a very powerful tool for telling a story and getting details across.

quote:

They can be cumbersome.

As shallow as this may seem (pun not intended) I don't know of a single student filmmaker here who wouldn't want to make thier cameras look more serious. A huge lens on the front of my camera will add a big statement towards "I'm here to film something, and I mean business. This isn't a vacation video. These are actors, not dumb kids...etc...".

quote:

There is image degradation involved.

Apparently it's not noticable if you build it with the right materials, although I've yet to spot one that's flawless. Personally, I sort of like the softer diffused look the well-made ones still give.
Check this out. If that is image degredation, I'll take it. I think this kind of image problem is what you're referring to. Personally I would hate to have those kinds of artifacts in my picture. You can clearly see vignetting and grain problems in each of those pictures. Granted, those who make the rotating screens out of a cd player motor and one of those translucent cd dummies they package with blank CD-R spindles (which is a popular cheap method, believe it or not) you're not going to see a great picture. Plastic of the insanely cheap variety is not an optimal light carrier. Which brings me to...

quote:

The low resolution of Mini-DV cameras actually helps the sellability.

It's true. But keep in mind this is for a reason: if we miniDV owners had the money to buy a higher resolution camera, we'd probably have the money to buy one of these gadgets with more accurate optics, like the mini35. Lower-quality gadgets come with the lower-budget territory. There's plans in the works to make an adapter like these for HD cameras.

quote:

They suck up a lot of light.

Bullets...my only weakness...how did you know?

Sniff...I guess some things are too good to be perfect...I think if it ended up being a seriously problematic factor I'd end up only using it outside.

This message has been edited. Last edited by: funkbomb,

Even with 2 stops less light, the sensitivity of modern CCDs even at +0 gain is enough that you will be fine. On a normal day outside I usually have to set the shutter to at least 1/250 sec. and close the aperture to f4.0 or so. Just leaving the shutter at 1/60 sec. would probably give enough exposure to compensate for less light.

quote:

Originally posted by funkbomb:
Shallow DOF is considered cinematic because it's what we've been trained, as life-long moviegoers, to expect in a professional product. And the reason they've been in movies is because isloating the subject by making everything else out of focus is a very powerful tool for telling a story and getting details across.

Well, you don't get much more cinematic than Citizen Kane, which went way out of it's way to get deep focus. The thin DOF being more 'cinematic' always felt like an over-intelectualized filmmaker concept to me. There are many other ways to give things graphic weight.

quote:

Originally posted by funkbomb:
Apparently it's not noticable if you build it with the right materials, although I've yet to spot one that's flawless.

quote:

Originally posted by funkbomb:
keep in mind this is for a reason: if we miniDV owners had the money to buy a higher resolution camera, we'd probably have the money to buy one of these gadgets with more accurate optics, like the mini35.

My experiences are entirely with the Pro35 adapter, which is the highest quality one available, and works on all B4 mount cameras (Both SD and HD). These are artifacts that are just inherent in this type of process.

quote:

Originally posted by funkbomb:

quote:

They suck up a lot of light.

Bullets...my only weakness...how did you know?

Sniff...I guess some things are too good to be perfect...I think if it ended up being a seriously problematic factor I'd end up only using it outside.

No need to be snippy. It is an important factor that people need to know about if they're gonna put the time into trying to use one of these things. 2 stops of light is significant even in video world.

quote:

Originally posted by Evan Kubuta:
Even with 2 stops less light, the sensitivity of modern CCDs even at +0 gain is enough that you will be fine. On a normal day outside I usually have to set the shutter to at least 1/250 sec. and close the aperture to f4.0 or so. Just leaving the shutter at 1/60 sec. would probably give enough exposure to compensate for less light.

Outside isn't the problem (We use 50 IE film stocks outside, and get a deep stop). But for those that are used to shooting in low-light conditions inside (Which many students/indies are), this will create a pretty major problem.

Nota "Time to crack out the big guns!" Mono

This message has been edited. Last edited by: NotaMono,

Didn't mean to come across as snippy! Sorry about that, I was just watching Harold and Kumar when I was writing that. I honestly meant that if the light factor was a serious issue it would have to be an "outside-only" thing to use.

quote:

But for those that are used to shooting in low-light conditions inside (Which many students/indies are), this will create a pretty major problem.

Argh, I do agree! If I had a dollar every time a fellow student filmmaker thought it was ok to film inside with a few incandescent lamps on...I'd buy a Pro35, and be ashamed at how wrong I was about them. Sorry again about that.

I think the shallow DOF is like underage drinking; you don't get to have it until you're old enough in the business, so you want it more.

Again, sorry if I came across as snippy. I wasn't trying to challange anything you said. Although I will just mention that users on the dvinfo.net forums report losing about 1 stop of light with the micro35, which I'm sure is still a hefty amount. Perhaps shorter optics mean less places to lose light? Of course, I guess it's all also based on the lens used, etc. I suppose the bottom line is that it's not a perfect world when you have a fixed lens in front of the CCD.

Cheers.

"Outside isn't the problem (We use 50 IE film stocks outside, and get a deep stop). But for those that are used to shooting in low-light conditions inside (Which many students/indies are), this will create a pretty major problem."

Hm, I somehow don't feel sorry for them at all. They'll just have to learn to do proper lighting (or shoot outside more ). I shoot with a 25ASA stock most of the time.

and once more, all I can say is listen to NotaMano

I'd go with the pro adapter and rent lenses...it might be even cheaper than building everything and getting the35 lenses (less quality)

i think a large reason why movies look so boring nowadays (batman was one of them, such a waste in that movie) is because DPs rely on that D.O.F. to focus the audiences' eyes.

and while it DOES draw the eye one way or the other, you still have elements in terms of color and in terms of graphic composition that are in the image, and no amount of shallow depth of field is going to fix any of that.

a lot of the time the background isn't all that interesting, and throwing it out of focus is supposed to make it less uninteresting. that's lazy, i think.

i think having a good graphic sense in terms of color and placement, and having an eye for detail within the frame will go farthe in showing what a professional visual artist you are than in shooting something at f/1.4

its funny you mention this RFranco. I faced a problem concerning exactly what you mentioned. In my next film, we shoot a big night scene and I want to have a big D.O.F. Yet, we are shooting 35mm film and we barely have the money to get the lights up to a f 4.0. Pushing the film might be the only solution (which is not a problem with 35...batman was shot on ASA 1000, pushed a fulll stop and it looked great in terms of grain).

I believe there are reasons for a d.o.f to infinity. Yet, many times it makes a lot of sense to narrow the field. It all comes back to the story in the end.

I received my optics tube and spacers from ThorLabs today (really fast shipping, that is) and placed my order with Optosigma for the GG diffuser and PCXL (plano convex lens). 50mm Canon lens and spacer/step ring are in the mail. I should have this all assembled in about a week or so.

Well I promised I would post results, so here they are. It's not a great landscape to video (my computer desk at a low angle) but it's just to demonstrate what's goin on with this thing.

http://www.astronautradiomusic.com/dofpracsmall.wmv

Some photos taken with the GL2's photo mode of my backyard. Yes, the PVC piping is a track for my homemade dolly.



I still have to install the plano convex lens which gets rid of the lens distortion and slight vignetting, which may or may not be in these photos but is definately prevalent when not zoomed in as much.

I will be selling this adapter in about a month or so for $270 in preparation to build another one. Despite what you may think, I'm not making a lot of profit off of that. If you're interested in buying it, please contact me.

P.S. That includes the 50mm SLR lens--basically everything you need. It will be up to you to get a step ring($10-15), however - it's a 52mm barrel.

The top one looks nice, but is the focus always so soft on wider DOFs like the bottom one? Or is that distortion from the glass?

It's because of a few problems:
1. I'm using a lot of macro lenses because I had to zoom in a lot to get rid of the vignetting.
2. You can see chromatic abberation (the colors spreading out, most noticable on the right side of the PVC pipe) because of using so many macros. This will definately be improved when I get the PCXL.

But mostly,

It's because I was using a broken SLR lens that won't turn past the 3 meter point. I can't get it to focus on infinity. lol. So I suppose you could ignore the fact it's so soft and definately expect better focusing in the future when I use non-impaired lenses.

I wish I hadn't seen that 'cause I want one now! I just had to order that microphone...

I just got the Nikon D Screen from B&H today. After installing it like this, so it could be mounted in the barrel, I got these results:


That's a lower-sized one.

Check out the rest:
http://www.astronautradiomusic.com/AUT_0074.JPG
http://www.astronautradiomusic.com/AUT_0075.JPG
http://www.astronautradiomusic.com/AUT_0076.JPG
http://www.astronautradiomusic.com/AUT_0077.JPG
http://www.astronautradiomusic.com/AUT_0078.JPG
http://www.astronautradiomusic.com/AUT_0079.JPG

At this point, ignore the dark corners (vignetting) and distortion I'm getting because I've discovered it's because of the lens I'm using. A few higher-quality ones are in the mail.

Essentially that picture you see at the beginning of this post is the results I'm getting for video, minus the smudges of course.
That's because that one is 640x480, the same general resolution of MiniDV video. The higher quality, bigger pictures show the grain, yes, but they're not the same size as what video would be like.

This message has been edited. Last edited by: funkbomb,

OK, I took video with it, and here's what resulted:

http://www.astronautradiomusic.com/jukedofprac.mov

Here's some framegrabs:






And without the adapter:

This message has been edited. Last edited by: funkbomb,