Advance apology #1: I'm sorry if this has come up before.

Advance apology #2: I'm no kind of optics whiz.

The idea:

In a previous thread (www.dvinfo.net/conf/showthread.php?s=&threadid=22416) it was agreed that a larger projected image on the GG would result in a better picture overall, but argued that putting any sort of magnifier between the 35mm lens and the GG would destroy the DOF we're after.

I wanted to toss out the idea of using a medium format lens on the front of the adapter and a magnifier between it and the GG to "correct" the DOF to a more 35mm look but with a bigger image.

Is this based in any sort of reality or is it just fairy dust?

And while I'm here, I was also considering another alternative: bouncing the 35mm image off a two-way mirror onto a piece of that super-reflective material from 3M and then shooting that image with the DV camera through the mirror. The idea was how to get an image off the same side of a surface as the projection, rather than going through the surface and shooting from the back.

If nothing else, a few more ideas for the pot.


-j

1) If your going to go thru the trouble of using a medium format lens then you better not use a magnifier to reduce the target size because it will kill all of the len's characteristic advantages such as less noticeabe grain and even shallower DOF than 35mm.

2)I brought up and made a diagram for this idea awhile back. Its a promising design with only two disadvantages: The heavy light loss due to a two way mirror and the fact that it doesnt correct the image for left to right (just up and down). Its likely however to create a crisper image because its not being difused by GG and will likely be grainless.

-Brett Erskine
www.CinematographerReels.com

Jay,
Keep the ideas coming. Here are my thoughts...

1). A medium format lens would work to increase the image size and hence would reduce the grain (static adapter) I agree with Brett about the magnifyer. I don't know of anyone who has made an adapter based on Medium format lenses though. My guess why is because these lenses are much more expensive and harder to come by than 35mm lenses. If you have one laying around, I'd love to see some images with a medium format rig.

2). Why use a two way mirror at all? Couldn't you use an optic quality surface coated mirror? The mirror would be mounted at an angle that would project the image directly onto the 3M reflective surface mounted just above the opening for the SLR lens. The video camera would be mounted on a higher plane than the SLR lens. The 3M surface could be mounted at a parallel angle with the mirror keeping everything in the same focal plane. The problem I see is the video camera's need to be perpendicular to the reflective surface for proper focus. This would probably require the video camera to be mounted at an angle perpendicular to the 3M surface. This would work with smaller video cameras but would be quite challenging with larger models like an XL1.



.......3M/.......[]Video Lens
SLR[ ]...../mirror

This might be a nice grainless option for the new prosumer HD cams just now hitting the market. Let me know what you think. Joe

Thanks for the responses. I agree that the medium format lens idea isn't very cost-effective but it might not be a total dead-end - I think I didn't explain myself very well in that first post, so here's another go.

Click for a diagram:
Medium Format Idea (http://www.globo-chem.net/~jay/MedFormatIdea.gif)


And in the meantime I've had another thought along the lines of my two-way mirror/3M tape idea.

Another handy diagram:
Idea 3 (http://www.globo-chem.net/~jay/Idea3.gif)


More for the pot.


-j

Hey Jay, or anyone one else interested. I found this Med. Format lens on ebay. It might be ok for adapter making. It's currently at $12 and ends in 2 days. Just in case you wanted a lens for testing your design. Joe

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3807726700&category=3352&sspagename=STRK%3AMEBWA%3AIT&rd=1

Description
This is a Mamiya No. 27972 lens 1:3.5 C series 645mount lens,it is being sold as a parts lens only, the iris is sluggish and is not guauanteed to work. The lens is being sold as is and buyer pays 5.00 shipping in the lower 48, please use paypal if you want the fastest shipment.

I'd thought about this idea too, but don't know anything about medium format cameras other than the film being 6cm x 6cm. A 60mm frame would cover a lot more area (grain) than a 35mm without having to be magnified, therefore preserving the medium format's DOF. That would be pretty neat (granted I don't know the difference between 35mm and medium format DOF... from your description it sounds too shallow?).

Currently, with 35mm, a 4:3 frame requires a 50mm diameter focusing screen (ground glass) and 16:9 requires 42mm diameter. That's just about perfect for these prosumer camcorders. A 6x6 frame would require an 80mm diameter focusing screen at 4:3 and 70mm for 16:9. That would be great as far as overall grain coverage, but the adapter would end up huge. Although it may work out super well with the DVX100's 72mm threads, which would be awesome. Any ideas Brett?

Joe, I also like the prism block idea that you've drawn in your Idea 3 (http://www.globo-chem.net/~jay/Idea3.gif) design. I'm not optical engineering inclined, but it sure looks like a good idea from my standpoint. The only thing I'd be worried about is splitting the colors up... like the "Dark Side of the Moon" album cover. Again, that may or may not apply.

Jay gets credit for the drawings. They're great by the way. Could you do one explaining your two way mirror idea? I'm still a little confused on how the two way mirror works. Thanks, Joe

Oops, sorry about that Jay.

What type of prism as you showing there in your diagram? Let me know and I'll do my best to try and figure out if it will work. Good design by the way. My design is totally different and while it makes sure everything stays perfectly on axis it uses a two way mirror. This one doesnt so potentially it could be a better design. Let me know.

I'll look over the other drawings tomorrow. I'll tell you one thing right now though. Using a magnifing lens to increase the target size will also kill the brightness of the image. For example if you make the image twice as big it will be 1/4 as bright.

-Brett

Here's a drawing of Idea 2 (http://www.globo-chem.net/~jay/Idea2.gif). The more I look at it, the less workable I think it is.

As for the prism idea, I didn't have any particular prism in mind when I drew it and I can see how it could very well be a Dark Side of the Moon result. I went quickly looking through Edmond Optics and was surprised that there's only one sort of prism that bends light to 45° - a Schmidt prism (http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2430). I wasn't surprised that they were really expensive.

Apparently Schmidt prisms show up in eyepieces for telescopes and binoculars so it might be possible to find them in the surplus market, although they probably wouldn't be big enough.

I really like the idea of capturing the image from the positive side of a surface, rather than from the back. It solves those 'transparent yet not transparent' issues. I'll keep thinking about it.


-j

Jay,
I don't think your two way mirror idea would work in the configuration you are showing. I believe that a two way mirror requires one side of the mirror to be in darkness to create the reflective properties on one surface. You show light passing through the mirror from the SLR lens and then being reflected off the opposite surface to the video camera. The light from the SLR lens would reduce the reflective property of your two way mirror. Just like when someone turns on the light in the observation room durring a police lineup and the vicious criminal sees the hapless witness trying to make the ID.

I thought you were putting the video camera behind the two way mirror as in a tele-promtper. The light comes in from the SLR lens, is reflected in the two way mirror onto the 3M surface mounted above the opening for the SLR lens. The video camera, behind the two way, shoots the image reflected on the 3M surface.

I have an idea I'd like to try with the 3M reflective surface material you mentioned earlier. Do you have a link to s supplier of that material? Joe

Like I said, the more I look at it, the less workable I think it is. Maybe there's something to your design, though.

I don't have a supplier link. I picked up a roll of 1" tape at a hardware store. Unfortunately it's got a waterproof coating on it that would probably interfere with the image. I do know it's possible to use this stuff for image applications like front screen projection so maybe it's possible to find it uncoated.


-j

Is this the 3M reflective surface you were refering to?

http://multimedia.mmm.com/mws/mediawebserver.dyn?cccccc4jvorcx2DcQ2DcccsOPOy1yFR6-


Joe

No, but that stuff looks even better.


-j

Joe -

I have one laying around. A medium format camera that is. I've done a few tests using it on the front of my xl1s. The upside is you don't need a macro lens to get a frame-filling image. The downside is that the whole setup is still quite big. The DOF is noticably shallower than 35mm, but that's the effect we're going for here right? I'm going to try to post some stills from my footage but forgive me if this link doesn't work
http://www.savvyproductions.com/newELEMENTS/static/static.htm

Jesse yours resoult hare impressiv ....

Just to know if my way ok tinking is ok ;)

for 6X6 format

you need digonal of 84,85mm

so in as circle of diameter of 84,85mm

you can put one frame of 67mmX50,25mm (4/3 ratio) maximum size...

i think i go for mini 6x6 ....

look at this thechnical sheet i made

READ (http://www.sinedie.org/lickthetoad/paolo_rudelli/mini35/img/dof_compare.jpg)

Images look great Jesse! I can see some minor vignetting in the shots with the truck and the fence. Are you using a condenser lens? There is definately no grain in the shots (none that I can see). Could you give a break down of your rig?
Focal Length and F# of the Medium format lens?
Type of ground glass (how fine grind? WAO 9,5 etc?)
Condenser lens type(PCX or DCX, F.L. and diameter)
Can you post a pic of the rig attached to your video camera? I'm curious how big it really is. Finally, it is also helpful to know what video camera you were using. Great job!

Joe

Joe,

First, let me say that the whole thing was held together with tape. Wanted to see if it would work before building something more permanent. I used it on the front of an xl1s with the standard IS II automatic lens. To get an idea of size, think of an XL1 with another 10 inches sticking off the front.

I ground the flat side of a huge PCX condeser with 1000grit AO. The final grind had quite a few scratches in it, but I was so excited to start shooting with the adapter I couldn't sit and grind anymore. Yes, there is some vignetting. I zoomed in on the image until most of it was gone. I'm afraid my condenser lens was just too big to be effective. I found it in an old overhead projector. It's about the size of a CD. Don't know what the F.L. is on it. But I'm pretty sure I'd get better results from a smaller condenser.

The medium format camera I used was a Kiev 88 with an 80mm 2.8 lens. Do a search for it on ebay and you can find them for relatively cheap. . I took the film back off the camera and taped the shutter down on bulb so the shutter curtains would stay open, then afixed my GroundPCX right where the film would normally be.

BTW this camera is an SLR so you could build a vertical mount system with it. Or maybe there is a big fat prism out there that would flip the whole image?

-jesse

<<<-- Originally posted by Jesse Rosten : Joe,

First, let me say that the whole thing was held together with tape. Wanted to see if it would work before building something more permanent. I used it on the front of an xl1s with the standard IS II automatic lens. To get an idea of size, think of an XL1 with another 10 inches sticking off the front.

I ground the flat side of a huge PCX condeser with 1000grit AO. The final grind had quite a few scratches in it, but I was so excited to start shooting with the adapter I couldn't sit and grind anymore. Yes, there is some vignetting. I zoomed in on the image until most of it was gone. I'm afraid my condenser lens was just too big to be effective. I found it in an old overhead projector. It's about the size of a CD. Don't know what the F.L. is on it. But I'm pretty sure I'd get better results from a smaller condenser.

The medium format camera I used was a Kiev 88 with an 80mm 2.8 lens. Do a search for it on ebay and you can find them for relatively cheap. . I took the film back off the camera and taped the shutter down on bulb so the shutter curtains would stay open, then afixed my GroundPCX right where the film would normally be.

BTW this camera is an SLR so you could build a vertical mount system with it. Or maybe there is a big fat prism out there that would flip the whole image?

-jesse -->>>

Thanks for the info. It gives more meaning to your grabs. Brett Erskine posted in one of these threads (I can't remember where and when or I'd just give you a link) about how to do a crude measurement of the focal length of a lens. I'll try to duplicate it now.
Take your lens outside on a sunny day and hold it perpendicular to the direction the sun's rays are coming from. Project the sun's rays onto a sheet of paper and move your lens up and down until you get the smallest spot possible. Meassure the distance from the spot on the paper to the lens. This will give you a rough estimate of the focal length. It would be most efficient to do this at noon with the sun at its highest in the sky. You can then measure your diameter and then you'll have a baseline standard for making future lens aquirements for testing. Brett also posted that you want to find a condenser with an F1 rating which means the F.L. is equal to the diameter. Based on your images, I'd guess that you either need a shorter focal length condenser (to spread the light out more to the edges) or you need to zoom in until the vignetting is gone.

For grinding, be sure to use white aluminum oxide. Stay away from the grey stuff (they call it blue).

I'm just imagining the size of your rig! I don't think a vertical mount would be very practical for the XL1S. You'd need a step ladder to operate it :>)
Also be sure not to go into war zones with an extra 10 inches sticking out of the end of your camera. You might get shot as a combatant. Keep us posted. As far as I know, you're the first pioneer with medium format lenses. I would think that the HD guys would be very interested in your progress.

Joe

Joe,

When you say the 'white stuff' versus the 'grey stuff', would that be the same as the 'polish' versus the '1000 Grit' on this (http://therockshed.com/grit.html) page (halfway down)?


-j

Jay,
Don't bother with rock shed. They are great but their products no longer serve our needs. We've evolved! Instead check out:
http://www.gotgrit.com/product_info.php/products_id/60


You only need 1/4 lb of each as it goes a long way.
I'd get 9 micron WAO and 5 micron WAO. You'll have better results in your fine grinding with these products. I also ordered Cerium Oxide which is a polishing agent. Some here would advise against the CEO but I've had some luck with it when used sparingly at the end of my grinding process to "finish" the fine grind. If you use the CEO too long, you'll begin to polish your lens again. If you find a source for 3 micron WAO buy it and post it as I'm sure there's a bunch of people who are interested in it. (including me!) As far as how to grind, there are many posts within the Aldu35 thread that give tips and links to step by step instructions. Just do a search for "grinding glass". I hope this helps. Good Luck!

Joe

Hi guys, I'm interested in an medium format adapter for HD, but don't know much about the format, can you help?

I have seen Imax, and it does look impressive. What range of film sizes does medium format cover and what matches Imax? How do I tell what I'm buying? Where can I get them cheap?

As I said, Imax looks impressive, how much better is the depth of feild, converging verticals, and angle of veiw of MF over 35mm film, and how does it compare to human vision?

What is the range of focal length for a standard (feild of veiw) prime lense?

The aperature f ratio of the prime lenses, how low do they go? How does the aperature f ratio work?

I also am interested in getting the brightest image, any suggestions? I was thinking of maybe a wide fast Large format lense image downsized to medium format (same dof as medium format).

I have seen items advertised, called Directors Veiwfinders. Are there any veiwfinders with sufficent resolution to use as an HD adaptor?

Thanks

Wayne.

You are mixing apples and oranges. Imax is a 70mm film. How you would ever adapt that to HD, I don't know. You are kind of trying to compare the Hubble to an amateur telescope.

I'm asking what is the range of film sizes medium format covers, I understand that Imax is a medium motion format. I am asking what I would need to match the image characteristics (convergent verticals, angle of veiw, depth of feild) of the Imax film format (which medium format lense most closely resembles it). I am not looking to get Imax lense or adapt lesne to Imax camera. Just a bit of Imax look (without Imax resolution, or films sensitivity).

A bit of practical info on the glass groundglass.
I found when polishing that I seemed to get less gouging and scratching when the flat glass sheet I was dressing the groundglass upon had been roughened with 120 grade grey emery then cleaned carefully.

I also tried a tip from an amateur telescope article of using some liquid soap to asssit lubrication. It seemed to help a little.

With the roughened base glass sheet, here was less inclination for the groundglass to stick and gouge. It's been a very frustrating learning curve. The first disk has been hopelessly scratched on the clear front face.

I tried using a piece of thick machined aluminium plate to dress the groundglass on but this did not seem to do anything except make me tired. The prescription lens makers use iron as a dressing surface on the machines.

On the other adapter threads I think they have gone to a chemical GG process, also somebody remarked that he saw metal plate being ued to grind the glass professionally.

hello everyon, i have been sitting around waiting for all of the technical folks to come up with a working adapter for the xl1 for quite some time. i've been keeping track of the aldu. have someone come up with an advanced medium format model yet?

how much would something like this cost to put together?

Just wanted to ressurect this thread from the bottom. I'm very interested in seeing where this type of adapter could take us. That it's projecting a bigger image for the cam to record is a major plus in my book and for my situation, negates the 'large' size of the adapter.

have a look at: http://arco.acromedia.de/ than go to projekte and select mini60 - filmlookadapter

Tell me what is your opinion about the system - except of that the last shot was much too dark.
Also watch the focus pulls.

The bosscreen did reduce the light that much, but I think I can reduce this an the vignetting by using a fresnel or a condensor behind it.
The groundglass was a mediumformat gg from Mamyia, the markers on it where removeable with aceton. It isn't as fine as the self grided may be, but at this big size it really doesn't matter. Remember the gg is 6x6cm!
Basis for the project was a Prakti six which is the simple version of the Pentacon six.


dietmar

Unless you're making a big studio budget film, the medium format may not be practical because it is difficult to keep things in focus on things that move. Also the lenses are not as fast (need more light). It would be a nice addition to the 35 mm adapter though. Hacing a 35 and 60 mm adapter.

Wayne, medium format film is 60 mm; IMAX is shot on 65 mm film; very similar image size and DOF.

Mike

HI Guys

What about Medium format Beattie Intense screen, they will take custom orders as well:

www.dvinfo.net/conf/showthread.php?s=&threadid=20408&perpage=40&pagenumber=21

(if it comes out with the wrong page, times the page nuimber by 2 or 4, I'm using 50 or 100 posts per page)

They also found a very fine Nikon type D, unmarked matte screen:

www.dvinfo.net/conf/showthread.php?s=&threadid=20408&perpage=40&pagenumber=23

Thanks Mike.

Wayne.

Depth of feild is dependent of the size of the target. So condensing to CCD size from a MF lense without a projection screen will give you the normal CCD DOF and Convergent Angles. But does this work in reverse?

So can I use a Zoom on a 35mm lense to produce MF DOF? I have also noticed that my present zoom lense produces a projected image much bigger than 35mm film more like MF. So is this a way to get cheap MF lenses.

Thanks

Wayne.

DoF is dependent on the lens and aperture only, not the target. However, coverage changes for different target sizes so the lenses are changed thus changing DoF due to the lens change, not the target itself.

If I were to position the camera (DVX100) directly above a medium format camera and shoot down into a plain focusing screen, would that be adequate? What type of achromat would I need for that and, any additional considerations? The talented guys who filmed Marla with their homemade mini35 kit (marlathemovie.com) did a great job and I was wondering if I could succesfully apply their concept to a DVX100 and a medium format. I'm new in the game here, so please forgive my backwardness. :)
Best and thanks- Frank

Wayne,

You can't do that. Even at the wide edges of the 35 mm film you have noticable light fallout. Further you go, more light you lose, also focus may not be as sharp there.

Mike

Thanks Rob and Mike

this differs from what I have read previously (that the reduction to target size is what reduces the limits of DOF). But still, using the zoom, am I in effect reducing Depth of field?

Thanks

Wayne.

Jesse: Nice looking framegrabs! Thanks for posting them.

I notice some grain on some of the out-of-focus areas in the images. It isn't THAT noticeable, but this is the same thing I'm getting with my adapter, and I have done several tests, so I know exactly what it looks like.

(It is more evident in the motion footage.)

Wayne, yes, it is the same thing.

Hey all,
I realize you guys are busy, and its probably a real pain to deal with my question (since its kind of elementary ), but if you have the time, please help! I have a Bronica Medium Format Camera and a DVX100. I'm going to buy a plain focus screen for it, and get an achromat for my DVX100, but I'm not sure what power I'll need to properly frame the screen. I'm going to do the same concept from the guys from marlathemovie.com (bonus section "just the facts" is where their diagram is located) but I want to use my Bronica rather than an SLR. So the DVX100 will be positioned directly above the medium format and shoot down into the Bronica focus screen. They will form sort of a 90 degree angle cam. Hopefully this makes sense! Will this work and do you have any tips? I'm worried about the light loss and grain if any. Thanks and best regards- Frank

<<<-- Originally posted by Rob Belics : Wayne, yes, it is the same thing. -->>>

Thanks Rob, this opens up a number of cheap lense chioces. I'll check my primes for light drop off, and look out for a suitable multifocal zoom lense.

Hey,
Just wanted to say that I know no one is obligated to answer posts, but it's interesting that if it pertains to the individual's needs, it will get a reply. This thread is just an example of how apathetic people are toward the needs of a beginner. I frequent 2-pop and I wish they were doing an equivalent thread on a medium format mini because I know they'd help. Sorry I posted here. Good luck with things- Frank

Wow... Frank my friend, patience is a virtue. Do you have the dvx100 or the dvx100a? If you have the latter you might not need any achromat. Have you tried focusing on your medium format GG viewer yet? I made one of these for an xl1 and the gg was so big that I didn't need a macro attachment.

I have the patience of Job!!! Just kidding. I understand how it is and patience is certainly a virtue. Thanks for the reply Jesse. I need to get a differnet focusing screen to accurately determine if I can focus. I just bought this used Bronica and the focusing screen is gridded and dim. How'd your footage come out with the XL1?

the footage with the xl1 came out ok. I put my medium format adapter on hold though in favor of a smaller 35mm adapter. I found some of the "useablity" issues raised about this type of adapter to be true. It IS hard to keep stuff in focus, especially if your subject is moving, or if the camera is moving. But don't scrap your project. Perhaps with a little more practice some really nice images could come out of such an adapter. There is very little/no grain with this size of GG.

I posted a link with some pictures a few pages back on this thread.

I'm not sure which focusing screen to get. I'm thinking of the Beattie Intenscreen that posts have referred to earlier. What's your take? Best-Frank

I have no experience with focus screens. I used a GG that I made myself. Worked great.

Jay,
Keep the ideas coming. Here are my thoughts...

1). A medium format lens would work to increase the image size and hence would reduce the grain (static adapter) I agree with Brett about the magnifyer. I don't know of anyone who has made an adapter based on Medium format lenses though. My guess why is because these lenses are much more expensive and harder to come by than 35mm lenses. If you have one laying around, I'd love to see some images with a medium format rig.

2). Why use a two way mirror at all? Couldn't you use an optic quality surface coated mirror? The mirror would be mounted at an angle that would project the image directly onto the 3M reflective surface mounted just above the opening for the SLR lens. The video camera would be mounted on a higher plane than the SLR lens. The 3M surface could be mounted at a parallel angle with the mirror keeping everything in the same focal plane. The problem I see is the video camera's need to be perpendicular to the reflective surface for proper focus. This would probably require the video camera to be mounted at an angle perpendicular to the 3M surface. This would work with smaller video cameras but would be quite challenging with larger models like an XL1.



.......3M/.......[]Video Lens
SLR[ ]...../mirror

This might be a nice grainless option for the new prosumer HD cams just now hitting the market. Let me know what you think. Joe

I have the medium format adapter, if you like to see it check out my website.. www.freewebs.cm/wvargas/ The medium format lenses are a bit more expensive, but not by much any more. Check out the photos of the adapter.

Hey Jay, or anyone one else interested. I found this Med. Format lens on ebay. It might be ok for adapter making. It's currently at $12 and ends in 2 days. Just in case you wanted a lens for testing your design. Joe

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3807726700&category=3352&sspagename=STRK%3AMEBWA%3AIT&rd=1

Description
This is a Mamiya No. 27972 lens 1:3.5 C series 645mount lens,it is being sold as a parts lens only, the iris is sluggish and is not guauanteed to work. The lens is being sold as is and buyer pays 5.00 shipping in the lower 48, please use paypal if you want the fastest shipment.



Check out my medium format adapter and if you have any questions about it please email me.

www.freewebs.com/wvargas

I'd thought about this idea too, but don't know anything about medium format cameras other than the film being 6cm x 6cm. A 60mm frame would cover a lot more area (grain) than a 35mm without having to be magnified, therefore preserving the medium format's DOF. That would be pretty neat (granted I don't know the difference between 35mm and medium format DOF... from your description it sounds too shallow?).

Currently, with 35mm, a 4:3 frame requires a 50mm diameter focusing screen (ground glass) and 16:9 requires 42mm diameter. That's just about perfect for these prosumer camcorders. A 6x6 frame would require an 80mm diameter focusing screen at 4:3 and 70mm for 16:9. That would be great as far as overall grain coverage, but the adapter would end up huge. Although it may work out super well with the DVX100's 72mm threads, which would be awesome. Any ideas Brett?

Joe, I also like the prism block idea that you've drawn in your Idea 3 (http://www.globo-chem.net/~jay/Idea3.gif) design. I'm not optical engineering inclined, but it sure looks like a good idea from my standpoint. The only thing I'd be worried about is splitting the colors up... like the "Dark Side of the Moon" album cover. Again, that may or may not apply.


Check out my medium format adapter using Mamiya 645 lenses. I decided not to use prisms or mirrors because of the increase of surfaces which just collects dust, but more important is the light loss, check out my website www.freewebs.com/wvargas