what to use as a relay lens? + my 35 adapter concept

Rok Furman · January 27th, 2006, 06:52 AM

hmm, in general what would produce a better picture: a prism mounted in frount of the relay lens (to turn the picture 180°) or a set of surface coated mirrors that would do the same?

i'm begining to abandon the prism idea and thinking about putting the prism in the viewfinder so i can still composite the shot.

or taking the camera apart and physicly turning the CCDs 180° :D
or taking the viewfinder apart and doing the same :D

Bob Hart · January 27th, 2006, 11:00 AM

Surface coated mirrors should lose less light, but may be difficult for some builders to set up accurately and to keep correctly aligned. They are light in weight and tend less to injury from shock loadings if successfully installed without any structural loads placed on them.

Prisms already have their reflective surfaces set up accurately and are easier to mount. If the reflective faces are coated, then light loss can be reduced. They are however heavy and their mass requires much more robust support and insulating structures around them to cope with shock loads.

Don't give up on prisms or mirrors. Life is a lot easier if the image is upright into the camera.

R.P. Cuenco · January 27th, 2006, 05:11 PM

i already tried rotating the ccds 180 (just for kicks, dont ask why), and the cables are just too short to accomodate a half turn since they're customized.

Rok Furman · January 28th, 2006, 04:41 AM

i'm thinking of using this lens as a relay lens:
http://www.cbcamerica.com/cctvprod/c.../mono/125.html
it has an aperture control ring which will come in handy

i'll probably have a 36*24mm frame, such as in a SLR camera - is this lens enough or should i get a lens with a greater focal lenght?

again, what is the flange distance for the XL mount?

btw is there any other way to turn the picture around without prisms or mirrors?
R.P. Cuenco, i could put in longer cables :D

Joel Kreisel · January 28th, 2006, 06:38 AM

Quote:

Originally Posted by Rok Furman

btw is there any other way to turn the picture around without prisms or mirrors?

Check out the thread I just started on that very subject. I have a theory, but no conclusions yet.

Also, there are other kinds of prisms aside from pentaprisms that will do the job. In this case, a dove prism might be more what you're looking for.

Alain Bellon · January 28th, 2006, 11:56 AM

Quote:

Originally Posted by Joel Kreisel

Check out the thread I just started on that very subject. I have a theory, but no conclusions yet.

Also, there are other kinds of prisms aside from pentaprisms that will do the job. In this case, a dove prism might be more what you're looking for.

The other prismatic option aside from a pentaprism plus a mirror is a set of two right-angle prisms (porro prisms are optimized versions with rounded corners and a slit in the middle to minimize internal reflections). The right angle prism coupling is the same you encounter inside binoculars. The penta prism + mirror is the configuration found in SLR cameras.

Both of these configurations can be achieved by mirrors alone placed at the same positions where the prism facets are.

Rok Furman · February 8th, 2006, 01:09 PM

the progress so far:

http://users.volja.net/furmanr/35.avi
http://users.volja.net/potocnikda/35a.avi

it's only a concept build so the quality just isn't there... yet :D
the relay lens is the kit XL lens, but i'll replace it with a CCTV lens when i aquire one. i still have to rotate the GG, it's static for now :)

January 27th, 2006, 06:52 AM	#16
Rok Furman Regular Crew Join Date: Nov 2005 Location: Maribor, Slovenia Posts: 25	hmm, in general what would produce a better picture: a prism mounted in frount of the relay lens (to turn the picture 180°) or a set of surface coated mirrors that would do the same? i'm begining to abandon the prism idea and thinking about putting the prism in the viewfinder so i can still composite the shot. or taking the camera apart and physicly turning the CCDs 180° :D or taking the viewfinder apart and doing the same :D __________________ special people, not special effects. big hearts, not big budgets

January 27th, 2006, 05:11 PM	#18
R.P. Cuenco Regular Crew Join Date: Nov 2005 Location: Concord, CA Posts: 118	i already tried rotating the ccds 180 (just for kicks, dont ask why), and the cables are just too short to accomodate a half turn since they're customized. __________________ Letus35 Flip on HC1 FCP5 w/ Intel Mac Mini and Powerbook Ti G4

January 28th, 2006, 04:41 AM	#19
Rok Furman Regular Crew Join Date: Nov 2005 Location: Maribor, Slovenia Posts: 25	i'm thinking of using this lens as a relay lens: http://www.cbcamerica.com/cctvprod/c.../mono/125.html it has an aperture control ring which will come in handy i'll probably have a 36*24mm frame, such as in a SLR camera - is this lens enough or should i get a lens with a greater focal lenght? again, what is the flange distance for the XL mount? btw is there any other way to turn the picture around without prisms or mirrors? R.P. Cuenco, i could put in longer cables :D __________________ special people, not special effects. big hearts, not big budgets

February 8th, 2006, 01:09 PM	#22
Rok Furman Regular Crew Join Date: Nov 2005 Location: Maribor, Slovenia Posts: 25	the progress so far: http://users.volja.net/furmanr/35.avi http://users.volja.net/potocnikda/35a.avi it's only a concept build so the quality just isn't there... yet :D the relay lens is the kit XL lens, but i'll replace it with a CCTV lens when i aquire one. i still have to rotate the GG, it's static for now :) __________________ special people, not special effects. big hearts, not big budgets

January 27th, 2006, 11:00 AM	#17
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Surface coated mirrors should lose less light, but may be difficult for some builders to set up accurately and to keep correctly aligned. They are light in weight and tend less to injury from shock loadings if successfully installed without any structural loads placed on them. Prisms already have their reflective surfaces set up accurately and are easier to mount. If the reflective faces are coated, then light loss can be reduced. They are however heavy and their mass requires much more robust support and insulating structures around them to cope with shock loads. Don't give up on prisms or mirrors. Life is a lot easier if the image is upright into the camera.