hi new here, but I have been followng the theads about 35mm adapters for some time , I have made a pretty decent prototype static adapter for my dv cam using a homemade wax screen and a fast minolta lens some pvc pipe and lots of duct tape also a couple of condensers from some old focusing screen (possibly the cheapest and most easily available source for made ti fit plano convex lenses there is) , but having alot of touble trying to figure out how to erect the image ( looked into prisms and mirrors ,porro abbe or double porro seems the easiest or setting up mirrors in such a configuration alternatively a very large and expensive roof-pentaprism and mirror set up)
Anyway i checked out some info on optic fiber face plate ( which have a high resolution and low light loss potential) they come in taper (for image resizing) and inverter styles , I was thinking a combination of which could invert ,enlarge the image and make the adapter more compact , does anyone know anything about this stuff , some of the fiber optics companies claim that these face plates are used for "ccd coupling" also as a cost effective alternative to conventional optics in nightvision equipmet.
I havent found any prices yet so I dont know how feasable this all is but it struck me as a simple solution if you could just stick a couple of these face plates up against your GG say sandwiched inbetween the GG and the PCX

anyway thats my thought
rob

some links

http://www.adphotonics.com/products/fiber_optic_faceplate.html

http://www.emagin.com/html/fiber_optic_taper.htm

http://www.fairchildimaging.com/main/ccd_custom_485fiberoptic.htm

better links
http://www.hioptic.com/night-vision-equipment/accessories/fiber_optic_faceplate.htm

http://www.incomusa.com/products.html

found one for sale

http://www.alibaba.com/catalog/10939123/Fiber_Optic_Image_Inverters.html?chkProductIds=10939123&ad84kt=y

Just a note -- it needs to be about 43.5mm round to get a full frame image from a 35mm SLR lens.

I investigated coherent fire bundles some time back. These are used to erect "flip" the image from a night vision intensifier for viewing by the eye or a camera. The info I had then was that the resolution was not up to scratch but things could well have changed since.

you right looks like the largest at the moment that I can find is about 30mm diameter not big enough but I think some of these places can make to specification and I thought that I saw somewhere somethimg about 70% light transmission I wonder how that stands up against two prisms as far as light loss is concerned though as far as resolution is concerned seems ok for DV anyway I`ll keep looking, still havent got a price on one of these things yet.

rob

by the way , a quick question ,if using two prisms do they have to be aluminized on the appropriate sides for refraction or just polished ?
rob

70% is terrible. Most flip options utilize front-surface mirrors -- something like three pairs of such mirrors, each suffer something like .5% light loss. When calculated, you're losing something like 5-10% light loss from the flip module, IIRC. 30% is way off the mark, especially when added to other factors (light loss of the 35mm lens, which goes up as DOF and FL goes up; and of course light loss of the diffuser in use).

Actually in real-world applications light loss tends to go down as FL goes up. Fast shorter FL lenses aren't plentiful, so most short lenses lose more light than most long lenses. Even a 20mm F2.0, which sounds like a fast lens if you're fixated on the aperture, only transmits about as much light as a 50mm at F5.0.

Also keep in mind not all lenses are equal... cheap lenses usually aren't as bright as nice (and usually therefore expensive) ones.

How much are these? I'd really like to be able to use the viewfinder in my dvx to compose shots rather than the LCD, so even if only for that purpose (inverted in the viewfinder) this might be useful..

Actually in real-world applications light loss tends to go down as FL goes up. Fast shorter FL lenses aren't plentiful, so most short lenses lose more light than most long lenses. Even a 20mm F2.0, which sounds like a fast lens if you're fixated on the aperture, only transmits about as much light as a 50mm at F5.0.

That's all fine and well, but try finding an f/1.4 80-200mm lens around. They don't exist. 50mm on the other hand, they're abundant. That was my point, so as FL of the lens "goes up," so, loosely speaking, does the total minimal lightloss of the system. Most wide to tele lenses with good range between extremes (17-105; 18-80; etc.) I've seen start with a base of f/3.5 or f/4, so your base starts with needing a lot more light suddenly.

Also, I was mistaken -- it's a total of four FS mirrors (http://wannabemini35.blogspot.com/).

That's all fine and well, but try finding an f/1.4 80-200mm lens around. They don't exist. 50mm on the other hand, they're abundant. That was my point, so as FL of the lens "goes up," so, loosely speaking, does the total minimal lightloss of the system. Most wide to tele lenses with good range between extremes (17-105; 18-80; etc.) I've seen start with a base of f/3.5 or f/4, so your base starts with needing a lot more light suddenly.

No, not all f-stops are equal. Just because two lenses are F1.4 for example, doesn't mean they pass the same amount of light. If you use decent lenses, a 50mm F1.4 probably doesn't pass more light than a 200mm F4.0.

Furthermore, a 20mm lens with a given f-stop, for example, won't pass as much light as a 50mm lens with that same max aperture.

Robert.

A reflective coating on the reflecting surfaces would be better but in practical terms is not worth the expense for me because I am still experimenting and sooner or later would injure the reflective coating pulling things apart and reconstructing them.

I'm working at the Fedcourt in Vic Ave Perth tomorrow, probably finishing up at 5pm and also Friday, so could bring the thing in for you to examine if you want to make your way into the city.

I have two built, one set up for a Sony HDR-FX1, the other for a JVC HD100. Most weeks I am in for two or three days a week. Give me an email if you want to set up an inspection time.

No, not all f-stops are equal. Just because two lenses are F1.4 for example, doesn't mean they pass the same amount of light. If you use decent lenses, a 50mm F1.4 probably doesn't pass more light than a 200mm F4.0.

Furthermore, a 20mm lens with a given f-stop, for example, won't pass as much light as a 50mm lens with that same max aperture.

I see your point about different lenses at the same f-stop, and it's a good distinction to make, but I disagree that any SLR lens at f/4 could possibly provide as much light as another SLR lens at f/1.4 or even 2.8. That's been my experience with Nikon's glass -- the 1:1.4 50mm fully open provides a dramatically brighter image than either of the 1:2.8 28-70mm or 1:2.8 80-200mm I have. I'm under the impression that Nikon makes good lenses.

Otherwise, while subtle differences of similar lenses across manufacturers are a factor, my bet is that they will never approach the exponential light loss that full stops exhibit. The leap from f/1.4 to f/4 (3 stops) requires 8 times an increase in lighting to get approximately the same exposure. There's plenty of good shooting to be had at f/2 and f/2.8 -- but many of the wide/tele lenses start at f/3.5 or f/4 and rob you of the chance to work that way.

Dennis Wood did a great write-up about this on DVXUser (http://www.dvxuser.com/V6/showpost.php?p=580543&postcount=1).

I see your point about different lenses at the same f-stop, and it's a good distinction to make, but I disagree that any SLR lens at f/4 could possibly provide as much light as another SLR lens at f/1.4 or even 2.8. That's been my experience with Nikon's glass -- the 1:1.4 50mm fully open provides a dramatically brighter image than either of the 1:2.8 28-70mm or 1:2.8 80-200mm I have. I'm under the impression that Nikon makes good lenses.

Otherwise, while subtle differences of similar lenses across manufacturers are a factor, my bet is that they will never approach the exponential light loss that full stops exhibit. The leap from f/1.4 to f/4 (3 stops) requires 8 times an increase in lighting to get approximately the same exposure. There's plenty of good shooting to be had at f/2 and f/2.8 -- but many of the wide/tele lenses start at f/3.5 or f/4 and rob you of the chance to work that way.

Dennis Wood did a great write-up about this on DVXUser (http://www.dvxuser.com/V6/showpost.php?p=580543&postcount=1).

I can't say as that's a valid example since wouldn't expect an F2.8 lens even at 70mm to be brighter than an F1.4 50mm.

Furthermore there's a heck of a lot more than "subtle differences" between similar lenses across manufacturers. Nick Bartleet illustrated just how dramatic that difference can be; check out some of his previous posts about his Nikons.

I can't say as that's a valid example since wouldn't expect an F2.8 lens even at 70mm to be brighter than an F1.4 50mm.

It's certainly a valid example of the argument I'm making. I can only assume you meant to say "I wouldn't expect an F2.8 lens even at 70mm to be brighter than an F1.4 50mm." In which case, we're in agreement completely.

Otherwise, I was using the term "subtle" in reference to relative exposures at the same f number. Even within the Nikon family of lenses, there are differences in exposure for different models of the same lens -- but the difference is subtle when compared to any lens at f/1.4 or 2.8 versus any other lens at f/4.

To belabor my original point in case it's not clear, many zoom lenses have a starting point of f/4 versus others which start at f/2.8. This means the minimum illumination required for a proper exposure on the GG with these lenses is a factor of 2x (or, one stop). Granted, choosing a lens is a question that involves more factors than simply minimum exposure, but sometimes available light makes it impossible to shoot with anything over 2.8.

70% is terrible. Most flip options utilize front-surface mirrors -- something like three pairs of such mirrors, each suffer something like .5% light loss. When calculated, you're losing something like 5-10% light loss from the flip module, IIRC. 30% is way off the mark, especially when added to other factors (light loss of the 35mm lens, which goes up as DOF and FL goes up; and of course light loss of the diffuser in use).

It's the right place to talk about diffusers lightloss in percents which is more realistic than in F-Stops. Did anyone measure lightloss of different GG(optosigma, nikon, wax, zenith,... etc.)? It seems that major avarage is about 1 T-Stop or little less. 1 T-Stop makes 50% lightloss!

F-stops are relative to focal length, so (theoretically) 200mm @ f5.6 should let in as much light as 50mm @f5.6 EVEN IF the aperture size at 200mm is the same as 50mm would be at f1.4. The aperture size is the same at 50mm f1.4 and 200mm f5.6 but the f-stop is NOT.

This is part of the reason why fast telephoto lenses are expensive; the glass must be huge. But fast wide angle lenses are also very expensive. 50mm, for some reason, seems to be the sweetspot.

Yes, there is some disparity between t-stops and f-stops, but it is NOT this significant. Half a stop or so at most for a decent lens I'd expect... Assuming decent lens quality, f1.4 should be roughly equivalent to f1.4 on all lenses. (Although vignetting, etc. may cause some to fall off a stop or two near the edges.)