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Old February 11th, 2006, 02:13 PM   #16
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Condensers work on either side of the GG ...
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Old February 11th, 2006, 02:27 PM   #17
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Maybe the gg and SLR lens are too close.
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Old February 11th, 2006, 03:30 PM   #18
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Im thinking from that picture, your probally gonna have to take it all apart, and work with it out of the adapter. just experiment the distance between your SLR lens and your GG. from the screen, it looks almost like there is no GG even inbetween your setup. which is odd. i would have to say take it apart. and then put it together again after you find out whats wrong. Good luck on it.

and for the heck of it, try a complety new prime lens. that might be the problem, but i can't see why.
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Old February 11th, 2006, 04:34 PM   #19
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I've just had a look at the Nikon D -type screen outside of any adapter housing.

Image can be viewed here.
http://www.maths.ox.ac.uk/~smithdm/nikondscreen.html
Certainly the hotspotting isn't as evident here.

Dennis,
A potential reason for having the condenser not on the SLR lens side is that if the slr-gg distance is set for that specific lens, once the lens is changed, the distance might not correspond correctly for focusing.
Whereas, if it is identically set to that as it would be in an slr (no condenser between slr lens and gg), then the setup will still hold for all lenses.
I.e, the adition of a condenser on the slr len side will affect the optical properties that side. (maybe)
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Old February 11th, 2006, 05:04 PM   #20
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Quote:
Originally Posted by David MD Smith
I.e, the adition of a condenser on the slr len side will affect the optical properties that side. (maybe)
This is correct.
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Old February 11th, 2006, 06:32 PM   #21
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Well im back from the store. I painted the pvc interior black, tried a new Nikon lens, threw on different close ups and macros, changed the distances, put on a Minolta prime, and nothing helped.

*sigh* i think iv been beat

tomorrow ill follow Davids advice and try to put something together outside the adapter. If i cant get a better picture ill just wait till i can fork over the $300 for the letus35
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Old February 11th, 2006, 06:55 PM   #22
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dont give up. follows David's setup, and you should get results.
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Old February 12th, 2006, 12:53 AM   #23
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i think iv found the problem.

"Type D: Overall fine-ground matte field. For specialized close-up photography and for use with long lenses."

<Marco Polimeni> I never tested a D screen but, from a Nikon F manual, I know that using lenses shorter then 135mm the edges of the frame starts to became darker and darker so more the lenses are shorter. </Marco Polimeni>
http://www.dvinfo.net/conf/showpost....8&postcount=41

All this time iv been using a 50mm lens.

Turns out this focusing screen is not compatible with my lens.
135mm, thats telephoto isnt it? I was looking forward to using my 28mm and 50mm

I followed Davids instruction. The hot spot did get smaller and i could see a little better on the edges but the camera had to be 12+ inches away from the gg.
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Old February 12th, 2006, 02:06 AM   #24
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I haven't used a D screen either, but that seems pretty odd, because I know quite a few people around here use it, and a 50mm prime is pretty much the standard lens, so I can't imagine it would be so common if it always produced this kind of vignetting on a 50mm.
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Old February 12th, 2006, 02:24 AM   #25
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Yeah i dont understand how. I read about people getting good results with a 1.8 50mm, and a 55mm.

this is directly from the Nikon website:
"Each screen offers unobtructed viewing and easy focusing over the entire matte surface. Type D is especially for telephoto lenses"
http://www.nikon.com.au/productitem....699-7a83f575c6


Im not sure if i measured this right but i think the focal length of the nikon screen+condenser is about ~1000mm, which is way out of range for the 60-125mm recommended condensers focal length

type D apparently should not work with any SLR lens under 135mm

just a shot in the dark.. maybe this nikon screen is working for other people because they are using cameras with large diameter lenses that are able to absorb more light at a greater angle from the ground glass? like the GL2(58mm) and dvx100(72mm)... My camera is a gs150 with a ~24mm lens?

That makes sense right?

i think every working adapter i have seen so far that uses this nikon screen is a pro camera.

Last edited by Daniel Lipats; February 12th, 2006 at 02:59 AM.
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Old February 12th, 2006, 04:38 AM   #26
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Quote:
Originally Posted by Daniel Lipats

just a shot in the dark.. maybe this nikon screen is working for other people because they are using cameras with large diameter lenses that are able to absorb more light at a greater angle from the ground glass? like the GL2(58mm) and dvx100(72mm)... My camera is a gs150 with a ~24mm lens?

I have found that from the same distance from the ground glass, the smaller the cams lens the more the vigneting. For example, 40mm away would produce no vignetting with a dvx100, however, at the same distance an XM2 would start to vignett slightly, my 43mm cam a bit more, and a small 37mm cam much more. I have found that you need to increase the distance between the cam and the ground glass the smaller the cam is, more distance.
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Old February 12th, 2006, 05:27 AM   #27
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i think you have to take back from scratch and understand the theory of the adapter. it seems you are just assembling stuff without really understanding how each parameters influence the adapter.
In the beginning we all spend a lot of trials and errors to understand this, and today, new comers can be happy to find lots of informations to not repeat our mistakes. Unfortunately, taking the best part listed in each project and blindly assemble them will probably not produce the expected results.

if you want some rules here they are:

choose a fast lens (between 1.2 and 1.7) with big aperture at the back (this will help minimize hot spot and vignetting).
Respect exactly the distance between back of lens and GG.
use big diameter tubes, and at first, do not try to make a short adapter.
It will probably look longer than you wish, but you can try to shorten later.
Make a prototype with disposable materials like balsa wood and carton to get
the right dimension.
Start with lens/gg/macro lens setup, it is simple and should give pretty good result. Add a condenser and other additional lenses after you really master your prototype.
do not count on the condenser to solve heavy problems, it only improves general quality.
Good track is to replace the GG by a plano convex lens that act as GG and condenser. you gain light, wheigt and a simpler setup.
use large diameter thin lenses (ideally between 55-60 mm), the thicker, the more you will get artifacts and using a lens on the edge is never good.
yo udo not need a camera to produce a good adapter. just looking at the picture on the GG should give you an indication of the result.
condenser, macro lens are just here to adapt the picture to your camera, depending the ability to zoom and focus, but will not change the quality.
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Old February 12th, 2006, 05:29 AM   #28
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i think you have to take back from scratch and understand the theory of the adapter. it seems you are just assembling stuff without really understanding how each parameters influence the adapter.
In the beginning we all spend a lot of trials and errors to understand this, and today, new comers can be happy to find lots of informations to not repeat our mistakes. Unfortunately, taking the best part listed in each project and blindly assemble them will probably not produce the expected results.

if you want some rules here they are:

choose a fast lens (between 1.2 and 1.7) with big aperture at the back (this will help minimize hot spot and vignetting).
Respect exactly the distance between back of lens and GG.
use big diameter tubes, and at first, do not try to make a short adapter.
It will probably look longer than you wish, but you can try to shorten later.
Make a prototype with disposable materials like balsa wood and carton to get
the right dimension.
Start with lens/gg/macro lens setup, it is simple and should give pretty good result. Add a condenser and other additional lenses after you really master your prototype.
do not count on the condenser to solve heavy problems, it only improves general quality.
Good track is to replace the GG by a plano convex lens that act as GG and condenser. you gain light, wheigth and a simpler setup.
use large diameter thin lenses (ideally between 55-60 mm), the thicker, the more you will get artifacts and using a lens on the edge is never good.
yo do not need a camera to produce a good adapter. just looking at the picture on the GG should give you an indication of the result.
condenser, macro lens are just here to adapt the picture to your camera, depending the ability to zoom and focus, but will not change the quality.
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Old February 12th, 2006, 09:28 AM   #29
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Wayne, that sounds exactly like whats happening. The Vignetting is much less when the gs150 is about 12 inches away from the nikon focus screen. Unfortunately i don't have access to a camera with a larger diameter lens.

I removed the Fresnel focus screen from my Minolta camera and it has a much shorter focal length. I set it all up on the table and it almost works! I think it would just need an enclosure. Unfortunately it has a visible focus aid and i cannot use it.

Giroud, i appreciate you taking the time to help but i dont think your giving me enough credit. First of all This is the third adapter i am building. I took two months to read through 3 forums before i started spending money. You should not have to reinvent the wheel every time someone sets out to build an adapter, the knowledge is all here. For the last 3 weeks "trial and error" is exactly what iv been doing.
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Old February 12th, 2006, 09:35 AM   #30
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OK,
Im thinking the answer to your problem is going to be a mix between a slightly shorter focal length PCX and moving the camera away from the focusing screen,

I think i have read others (Ben Winter?) managing to remove the PCX lens off the Nikon D screen, so that you can use another.
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