Mmm good point. If the lens is square you should be fine. I can't quite tell from the photo. That said I have this unexplicable feeling that a fully round lens would provide less distortion. Don't take that too seriously though. Just a feeling.

Hrm...you guys are probably right.

Well at those prices I can maybe get two of each type and experiment. :-)

Thanks for the feedback!

If you do let us know which works best.

You might also want to wait and hear others opinions. It might save you some money and frustration.

parts list
 

http://www.thorlabs.com/ProductDetai...roduct_ID=1481

two of thesehttp://www.thorlabs.com/ProductDetai...roduct_ID=1483

http://www.optosigma.com/miva/mercha...+%26+Apertures
you want the 50mm with 70 fl and the 50mm groundglass with 1500 grit
http://www.optosigma.com/miva/mercha...herical+Lenses
you will be able to mount the plcx directly on the ground glass
the threaded retaining rings will allow perfect focal length from the slr lens to the groundglass.

Rich you rock!! What type of camera do you have, and how do you end up mounting it?

Thanks

p.s. Maybe we could start a thread with just parts listed and where to get them? And focus discussion in this thread? It's so hard to wade through all these posts looking for something, and it keeps growing.

Good info, thanks. But how does the lens mount fix to the Thorlabs tube? Does a C mount screw directly on?

parts list
 

I was happy to find when the thorlabs tube came in .that it
is the same as a 52mm camera filter thread so common step up and step down rings will work. the key is the tube. the first one I made was with 52mm filter rings I never was able to get the focal distance from the slr lens to the ground glass perfect or place the plcx directly on the ground glass.I did try the thorlabs groundglass the opto sigma is better. and when you build this dust is your enemy start with the 35mm lens then c mount then tube insert ring at about focal length the ground glass comes dust free
adjust threaded ring untill sharp focus don't let your fingers touch the ground glass. gently place plcx on top and thread the ring down with your finger nail if you didn't trap any dust the glass surface will stay clean. one trick I used is to use a poor ground glass attempt to set the focus . then took the pristine ground glass and set it in.

Thanks again Richard, that's exactly what I'm going to try.

But just to clarify if I may - does the C mount adapter fit directly to the 2" thorlabs tube? Sorry if this is obvious.

I'm using Nikon lenses so I want to attach this:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=77558&is=REG

Best

parts list
 

this is a link to some pictures of step up rings. http://www.cs.mtu.edu/~shene/DigiCam...ead-rings.html the tube is 52mm you would need a ring 52mm to whatever the thread size is in the adapter . and a second one 52mm to whatever your camera thread is

Do you have any footage with this setup rich?

Out of curiousity, if you were to use Loctite 358 UV curing clear adhesive to fasten the pclx lens onto the clear side of the groundglass and face the rough side of the gg towards the objective lens, would this partially solve your dust problem.

You could test by assembling the pclx hard against the gg smooth side then dabbing a dot of water onto the junction. - Just a thought.

parts list
 

It would be nice if we could buy iit as one piece,like a achromatic doublet.

big big news
 

hey everyone this could be big big news. there is a thread
'ground glass grain' chris rubin has a workflow in afteraffects to remove the grain from a static adapter .

Someone a while back also demonstrated a method of using after-effects the eliminate the hotspot with some sort of mask. That process plus the grain eliminator would be a good combination if it could be integrated into one plug-in.

Bob,

you do not need to integrate anything, because that same gg noise mask removes the hotspot at the same time it removes the grain. Remember - your gg test pattern also has a hotspot (if you're shooting it with your lens on). So the inverse of that mask acts as both grain remover and the hotspot remover.

cheers,
Chris

Chris-
I understand what your saying about the hotspot but now we are dealing with part of the image that is under exposed...Yes you will be able to make it appear "brighter" but nothing beats the quality of well exposed footage in the first place. If the hotspot is particular dark near the edges no amount of software can enhance detail that was never captured in the first place. So it sounds like when it comes to a hot spot it can help out only minor problems. Anything more and your trading in image quality for convenience. Chris test my theory out. Give it something really dark v.s. something thats properly exposed. I would be interested in seeing what happens in a real life test.

Re: parts list
 

<<<-- Originally posted by Richard Mellor : http://www.thorlabs.com/ProductDetai...roduct_ID=1481

two of thesehttp://www.thorlabs.com/ProductDetai...roduct_ID=1483

http://www.optosigma.com/miva/mercha...+%26+Apertures
you want the 50mm with 70 fl and the 50mm groundglass with 1500 grit
http://www.optosigma.com/miva/mercha...herical+Lenses
you will be able to mount the plcx directly on the ground glass
the threaded retaining rings will allow perfect focal length from the slr lens to the groundglass. -->>>

How does one go about purchasing from this company? I sent their sales associate an e-mail, but that's the only way i saw.

*edit- NM i had to use that antique thing, i think it's a telephone...

Brett,

you're right - if the light falloff at the edges of the frame is severe, then the hotspot cannot be eliminated without introducing compression artifacts and noise.

Ideally, hotspot should be removed / reduced by reducing brightness in the centre of the image and increasing it at the edges.

This would make the gg noise/hotspot mask look something like this (minus the ring and the text):

http://www.liisikoikson.com/ftp/gg_pattern.jpg

this has not been inverted yet.

Chris

I think we agree here. The hot spot in that example is so minor that I think your system would work great. I'm very impressed with your work and attention to detail. Thanks for all the extra effort and examples. You know this system can even be used for thoughs of us using moving GG because once in a while you might forget to turn on the motor and later on in post you can save the shot. Good stuff.

Does anyone know what the back focal length of 645 medium format lenses is? I need to know so I can place my diffuser in the correct place.

Just wanted to mention to you guys that are using the grain removal technique: DISABLE IMAGE STABILIZATION (Optical and Digital)

I haven't been here for a long time but I thought I would drop in with this screen technology I was going to post about some time ago, it was one of he technogies I was considering. They are called Fiber Optic Face Plates, and Fiber Optic Tapers. Plates are a cut sheet off of a bunch of carefully stacked, modeled and bonded bunch of fiber optic fibres. I think I have found the industries best with around 95% transmission rates, and upto 40 million fibrers, which should deal with any fibre problems. Alltogether probably the best available next to ones that restrict the angle of view down.

http://www.princetoninstruments.com/...beroptic.shtml
http://www.vinci.it/Fibre%20ottiche%20tutorial.htm
http://www.spie.org/app/Publications.../research.html
http://www.photomet.com/library_enc_fiberoptic.shtml
http://www.incomusa.com/products.html
http://www.incomusa.com/technology.html
http://www.incomusa.com/materials.html
http://www.incomusa.com/Faceplates.htm
http://www.incomusa.com/Tapers.htm
http://www.incomusa.com/manprocess.html

http://www.photonicsonline.com/Buyer...&VNETCOOKIE=NO
http://www.photonics.com/directory/b...categories.htm

For those with lenseless cameras (XL1 & cinema camera projects) tapers can be used to reduce a image from 35mm to whatever. Tapers are buindles bigger at one end and more squashed at the other, also a very good way to do 16:9 to 4:3 conversion. I think tapers loss a bit more light than plates dues to here design, but that may not have to be the case. They have to be bonded directly to the CCD, but if your luck your ccd allready has a a face plate on it to protec it and transfer images, so it might be possible to somehow bond it. If your sensor has some non flat version of a face plate on it, then that might cause trouble. All together a expert installation.

Capillary face plates use hollow fibres instead to increase transmsion, but I imagine hollow fibers have downsides for our purposes. While I have seen very poor looking faceplates at Surplus Shed going really cheap, places like Edmunds seem a bit expensive, and I think some of the ones listed above are significantly better.

http://www.collimatedholes.com/examples.html
http://www.collimatedholes.com/capillary_diam.html
http://www.collimatedholes.com/ltd_ratio.html
http://www.collimatedholes.com/interior_sur.html
http://www.collimatedholes.com/products.html


By the way, a note on some of these technologies, like holographic diffusers, I think you still need to use a condensor and to keep your camera's iris on manual, wide open to aviode problems. Whoever tried it before give it a go.

Very interesting idea. I also noted they have inverters for rotating an image 180 degrees...this could be quite useful.

One thing to note though is the transimission spectra...you will drop almost all of your infrareds (probably a good thing except for night vision)...and your reds will be slightly less transmitted than your blues and violets...but I imagine that's not a big deal

one thing i know about fiber optics are they are expensive..wonder how much it would cost?

well if this edmund optics place is any indicator:

http://www.edmundoptics.com/onlineca...productid=1599

assuming we can find the specs we need...which i would assume are 35mm to 1/3" or 1/3.4" ccd size with 4:1 magnification...then probably just under $1000...maybe more if a faceplace for inversion is included.

But the theoretical benefits are quite nice...no grain, higher light transmittance, non-inverted image...possible 4:3 to 16:9 conversion built in for cameras that can't do this already...as well as there is always the interesting fact that you could use those light conduits to build set-ups for some really unique shots.

Wayne: One question though...why do you think a condensor is still necessary? Isn't the device taking the exact light and placing it on the ccd...as the thing says its a "zero depth window"...to me it seems the fused ccd/taper should act almost exactly like a 35mm film plane in terms of light collection...but i'm obviously not an expert to say the least.

to Wayne
 

Wayne,

exellent work!

it looks that this solution may work!
wonderful idea!

filip

p.s.

i will go now thru all your mentioned links very preciselly. i think it deserves our attention.

I meant holographic screens, it was noted the low angle holo screens got a darker image than the high angle ones (when it should have been the opposite). I summise that because the light is so undifused that much of it can go straight ahead and miss the sweet spot on the video cameras lens, which is often smaller than the 35mm frame projecting the light, so the outer portions of the frame will only give the little off axis light that hits the lens. So a conensor is needed to bring the off axis light into tthe lense.Another thing is the iris in the camera could possibly interfere with the low angle light, where as the iris in the still lense (before the light is straightened out) has the normal effect. There is also the possibility that there could be some dependence in the iris/shutter/gain mechanism on normal diffused light sources.

Pricing, quality, transmission:
Next or pricing, surplushed has some funky round 30mm something Fibreoptic plates for around $5-7US. But from the picture they seem dark and not of the quality of some of the specs I've seen. So it is a matter of hunting around to find a place3 thaqt sells good ones cheap (preferably surplus). I have an old Edmund catalogue here, and the ones listed don't seem anywhere near 40Million fibres, and I think max out at 100lines per mm. But apart from resolution there are a couple of other important factors. L:ight transmission is one, with values below 60% still acceptable compared to a GG screen, but better ones have much higher transmission. But also the type of fiber used will also effect this transmission, and also the spectral frequencies transmitted, like Matt said with diiferent colorisation effects so it has to be studied. More below.

There are two values from memory (name will be in those links). One is the transmission of light going through the fibre, another is the amount of light that comes into the fibre, remember there is still clading (some 1:16) around the fibers, and surface reflection etc, that reduces it. I would think that the clading plays a big part in the problem, with poorer face plates using thicker cladding etc.

Angle of light Acceptance:
Another value is what angle of light is accepted, to great of an angle the light starts bouncing off, or hitting the side walls of the fibre and being eliminated (because it can't be internally reflected). From the nice pictures on the princeton link and the income ones. You can see that parts of he face go black, this would be because that paret of it is at too great an angle that light is refected off, or he camera was outside of he transmission angle of the taper.

To get over the angle of light problem certain companies use etchings and patternes on the surface of the plate to increase light acceptance. This is somethign I was wondering why they haven't done until I found recent research into the area.

Image Inversion:
Another problem is that if you use an image inversion, apart from being a luxury feature that might be big money, the fibers will have to cross over somewhere, so unless there is a big buldge in it where the fibres cross over, or some apprartus on the front of the faceplate, I would expect poorer light transmission.


Now, Fibre optic plates have been used for decades, and in cameras for years. In matter of fact I looked at an old videogame system I had the other night, at it's monitor, to see the depth of glass before the phospors, from what I could tell it must have been really thin glass, which I hought was impractically unussual, now it occurs to me it must have been a CRT Fibre Optic Face Plate ;)

<<<-- Originally posted by Wayne Morellini : ...In matter of fact I looked at an old videogame system I had the other night, at it's monitor, to see the depth of glass before the phospors, from what I could tell it must have been really thin glass, which I hought was impractically unussual, now it occurs to me it must have been a CRT Fibre Optic Face Plate ;) -->>>

wayne,

can you explain me quoted part of your previous text in a different way. i do not understand it properly.
if it's not too dificult for you.

thank you,

filip

Last thoughts:
 

BTW don't give up on finding cheap solutions, optically Micro Cystaline wax could do simular things, but maybe not anwhere near as good in resolution and light transmission. I should have posted it over at the HD static thread too.

Just thought of a few more tips, sorry I hope this is the last lot:

Thickness required:
Another thing is that we only need a thin face plate that might further reduce prices, as I think that cutting might be less cost than the material itself (unless it is too thin). Also the thinner you go (and thinner fibers) the plate apparently becomes flexible. But there is a downside to becoming thin, the thickness will cause lightloss from light going out the side of the fibers, that will be greater or smaller depending on type of optic used. The thickness of the plate and the fibers should also much greatly effect the angle of exit of the light becuae of internal reflection, to a certain degree. Go to thin the light will come out at high angles (undesirable), go thinner again and much light should go through it like plain glass, because there will be too little internal reflection to mix the light.

Resolution versus Incidence of error:

It just occured to me again to mention this. If you have one fibre to one pixel you should have sparkly grain and over image stuff, A bit more and you will have softness. The reason why this is, is that the missalignment of pixels to to the entrace of the fibers, cause part of what should go into one pixel to be lost on the clading, or spread inbetween multiple pixels. To reduce this problem I have devised the following scheeme I use for most of my projects, that may or may not be accurate you decide:

Reuce image pixel error by increasing screen resolution:
- You need to reduce the amount of error in the image pixel to less than that of the lowest value possible per pixel. Probably by half. This is 8-bit+1 for most of us, though 8 bit cameras may use upto 12-bits (+1), which is more desirable as the camera does processing on the image in this region, but maybe not really needed (i.e. I don't know). But if you have a high niose level (say 6 or 8 bits worth, around 36db-48db) than that might be acceptable too you. After dertermining how much accuracy you have you have to increase the resolution past the desired image resolution enough to achieve this accuracy. With perfect accuracy, you should get a sharp image as smooth as silk (if your camera can do such a thing).

Problem is I can't remember the formular I use, as I am a bit under the weather at the moment. But I remember, it is actually something like this, you have to calculate the (maybe radom) arrangements of focus screen pixels so that the percentage of area that the outer most pixels (fibres in this case) consume is the same, or less, than the desired accuracy you want. You see, as things come into these outer fibers then to inner fibers, and vice versa, they will cause sudden jumps and falls in brightness as they cross these fibers. Even though the camera pixel will average these out, it will still produce niose (inaccuracy) in the pixel, that sort of flashy grain seen in the spinning and staic GG convertors. The bigger the fibre the worse it will be, the smaller the less nocitable it will be until you reach your signal to niose ratio/max accuracy, then it will contribute a little to the niose and virtually dissapear. For our eyes that is ussually the 8 bit image, but for pro camera, and post, colourisation, effects and editing, this probably should be as much as you can get, or at least 10 bits+1.
There are other ways to do this also, without having to increase the screen res so much, but it gets more complicated.

Has anybody considered doing a static on the new 3chip PV-GS65, I would be interested to see how it goes?

Have fun, tell me how it goes, I spent many hours going through much searching, so keep looking, it takes much time.

Wayne.

Wayne.

I made enquiry some time back with the Electrophysics Corp who make the Astroscope Night-Vision systems.

The NV tubes which erect the image use what was described as a coherent bundle of optical fibres to rotate the image 180 degrees however there was doubt whether these coherent bundles could be had in diameters large enough to erect a 35mm still camera or motion picture camera frame.

I too, am not a fan of going the full hog and turning the image via great expense, I also am dubiouse that it may cost quality/light (see above) , however why not just put a prism in the front of the back of the faceplate/taper, as you may have gotten rid of the need for a condensor/field lense you have more room. For me if I use a digital cinema camera type camera head (no native lense) the image canbe turn electronically for display and editing.

Of interest, One of the uses for faceplates are as interconnects in image intensifiers, to pass the image from one tube to the next.

I have been so involved in the cinema camera project I haven't read six molnths of all the adaptor threads, what advancements have been made? I will have to read it sometime, eventually.

Something has occured to me recently that maybe of some help. You also mentioned a relay lense system for the image intensifier, which I was advocated back in my first thread on dvinfo year before last (for some silly reason stuck in the panasonic group from general, when it was allways about alternative imaging, which led lots of Pana people to descend on it, maybe the moderator would like to move it here or shift it back to general group before I get back to it). It has occured to me recently that when you relay an image down to a smaller sensor through an optical lense image intensifier that you increase the effective aperaure (sending down the f rating) therefore dramatically reduce the DOF. This is simular to what the Drake digital cinema camera project did with using super fast (F0.75) 16mm lense, they were able to obtain simular DOF to 35mm film. So maybe we can get 35MM still camera like DOF by using this sort of shceeme (but now needing a good set of ND filters for mid-day shooting). This however, will not suit all cameras as some cameras may require straigher light for there microlense or sensor cell design, other wise the extra angle of the light will cause it to miss the pixel, or bounce off. Bob, so the question is if we can do the same DOF, and we can do the same FOV, as an 35MM SLR lens through this system, are there any other 35mm image qualities that could be compromised in doing this?


Thanks

Wayne.

Ground Glass
 

Just thought I would drop in to see what is going on as of late.

I am Dave Parker and own Ground Glass Specialties, there have been a few on here that have purchased my ground glass for their projects, both just flat stock as well as a couple that have purchase in filter rings which I have the ability to product now.

I was wondering if anyone that is using our ground glass couldpost some feedback as to how it has worked them or if I need to do a finer grind than I currently am doing, we are currently rated at around 1500, as I specialize in ground glass screens for view cameras, I have not heard if our current glass works correctly for the application you folks are using it for.

Thanks for any feedback that you can provide.

Dave Parker
Ground Glass Specialties
Satin Snow Ground Glass
www.satinsnowglass.com