Static 35mm Adapter Solution at DVinfo.net

Louis Feng · December 22nd, 2003, 03:09 PM

For those of you interested in a static 35mm adapter that produce upright image, see the following design (not meant to be pretty other than functional).

http://f2.pg.photos.yahoo.com/ph/lou...=/35mm+Adapter

You can see full size image (look for the button above/blow the image).

You are authorized to use this design for personal use.

Helen Bach · December 22nd, 2003, 03:29 PM

Hi Vendible.
Shouldn't that be a roof pentaprism? I think that if you use a plain pentaprism (as you appear to show) the image will be laterally inverted.
Best,
Helen

Louis Feng · December 22nd, 2003, 03:46 PM

"Shouldn't that be a roof pentaprism? I think that if you use a plain pentaprism (as you appear to show) the image will be laterally inverted."

I have carefully check and rechecked (see the ray trace). The design is very similar to the viewfinder on a SLR camera, except the order is reversed.

The penta prism does not invert the image, it only redirects the image 90 degree. Then the mirror does the inversion. A roof prism by itself will invert the image, but you will have to shoot at a right angle.

I'll just mention the dove prism. To get a 24x36 or 36x36mm dove prism will require a length of at least 150mm, just by itself. Mirror and penta prism is still the best combination.

Helen Bach · December 22nd, 2003, 05:02 PM

Vendible,

I am referring to a roof pentaprism, not a roof prism. Nearly all SLR cameras use a roof pentaprism - a plain pentaprism (as you have shown, which is not like the ones in most SLR cameras) leaves the image laterally inverted. That's why SLRs use roof pentaprisms. If you don't believe me, look at the shape of the top of an SLR.

Best,
Helen

Louis Feng · December 22nd, 2003, 05:21 PM

Helen,

http://f2.pg.photos.yahoo.com/ph/lou...m=DSC00140.jpg

Thanks for pointing that out. I'll recheck and make sure what exactly it is.

If you could draw or refer me to a picture, that would help.

Louis Feng · December 22nd, 2003, 06:34 PM

Helen,
After some reading I think you are right, roof pentaprism. Thanks again.

Don Berube · December 22nd, 2003, 06:40 PM

Yes, Helen is correct.

Thank you Helen!

- don

Filip Kovcin · December 22nd, 2003, 06:44 PM

i have two roof pentaprism, one from SLR 35mm camera and one from 6x6 camera. i'm not expert on physics, but i think that ROOF makes the difference here. in BOTH cases (35 and 6x6) the ROOF exist, not just ordinary penta prism.
if you look closer inside the prism - you will see almost invisible thin line which is the uppermost part of that roof, but when you look through eyepiece it looks flat. no splited image, no visible left and right half, but whole image.

in my opinion, just in that ROOF part the image changes the position - left goes to right, right to left, and then after that transition goes to your eyepiece.

and before that (in SLR cameras - or - in your project) finally the miror makes it upside down, so we see it normally.

again - i'm not physics guru, but in my opinion WITHOUT that ROOF image will be still wrong.

i can send to certain e-mail my photos of this roof pentaprism, to show in more visible way what i'm talking about. so anyone can see it. (or if someone has possibility to put it on his server... and make a link in this thread?)

filip

p.s.
i know that this sounds like almost a coinsidence, but i bought the pentaprism (roofprism) just because of that - to use it in agus35 modyfied project and have proper position of the image.

Taylor Moore · December 22nd, 2003, 06:49 PM

Hi Filip,

Send the file to me taylor@moorefilms and I will post for you.

Taylor

Louis Feng · December 22nd, 2003, 06:54 PM

Clarification:

Pentaprism will deflect image 90 degrees without any inverting(up/down) or reverting (left/right) to the image.

Roof Pentaprism will deflect image 90 degrees and revert (left/right) the image, but does not invert (up/down) the image.

Using a pentaprism with a mirror will invert the image but not revert.

Using a roof pentaprism with a mirror will invert and revert the image.

Problem solved.

http://f2.pg.photos.yahoo.com/ph/lou....dnm=img13.jpg

Filip Kovcin · December 22nd, 2003, 07:35 PM

yes, that's it!

penta roof+mirror=success!

Filip Kovcin · December 22nd, 2003, 07:49 PM

taylor,

i just sent the pictures of my pentaprism to you.

thanks

Louis Feng · December 22nd, 2003, 08:32 PM

This roof pentaprism introduces some more design problems because the outgoing surface is smaller than the incoming surface. That's OK for a camera view finder, but in this case, the bigger projected area, the better (more detail is preserved).

Dove doesn't work because it only inverts the image, doesn't revert it.

I'm looking for another solution.

Don Berube · December 22nd, 2003, 09:48 PM

For what it is worth, you may find the following Optics FAQ handy:
http://www.edmundoptics.com/TechSupport/optics.cfm

Optics:
http://www.edmundoptics.com/IOD/Browse.cfm?catid=10

Fresnel Lenses:
http://www.edmundoptics.com/IOD/Disp...Productid=2039

Ohhhhh! (this looks very familiar)
http://www.edmundoptics.com/IOD/Disp...productid=1966

T-Mount Adaptors (hmmmm...):
http://www.edmundoptics.com/IOD/Disp...productid=1460

More Lens Adaptors:
http://www.edmundoptics.com/IOD/Disp...productid=1459

Video Lenses?:
http://www.edmundoptics.com/Catalog/Custom/218.cfm

Cool!!!:
http://www.nightowloptics.com/addfra...product=NOCA42

- don

Louis Feng · December 22nd, 2003, 11:28 PM

Ok, I have verified that with a normal penta prism and a roof prism, you can create a correct inverted and reverted image.

December 22nd, 2003, 03:09 PM	#1
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	Static 35mm Adapter Solution For those of you interested in a static 35mm adapter that produce upright image, see the following design (not meant to be pretty other than functional). http://f2.pg.photos.yahoo.com/ph/lou...=/35mm+Adapter You can see full size image (look for the button above/blow the image). You are authorized to use this design for personal use.

December 22nd, 2003, 06:40 PM	#7
Don Berube Moderator Join Date: Mar 2002 Location: Boston, MA (travel frequently) Posts: 837	Yes, Helen is correct. Thank you Helen! - don __________________ DONALD BERUBE - noisybrain. Productions, LLC Director Of Photography/ Producer/ Consultant http://noisybrain.com/donbio.html CREATE and NETWORK with http://www.bosfcpug.org and also http://fcpugnetwork.org

December 22nd, 2003, 06:44 PM	#8
Filip Kovcin Major Player Join Date: Dec 2003 Location: warsaw, poland Posts: 440	roof pentaprism i have two roof pentaprism, one from SLR 35mm camera and one from 6x6 camera. i'm not expert on physics, but i think that ROOF makes the difference here. in BOTH cases (35 and 6x6) the ROOF exist, not just ordinary penta prism. if you look closer inside the prism - you will see almost invisible thin line which is the uppermost part of that roof, but when you look through eyepiece it looks flat. no splited image, no visible left and right half, but whole image. in my opinion, just in that ROOF part the image changes the position - left goes to right, right to left, and then after that transition goes to your eyepiece. and before that (in SLR cameras - or - in your project) finally the miror makes it upside down, so we see it normally. again - i'm not physics guru, but in my opinion WITHOUT that ROOF image will be still wrong. i can send to certain e-mail my photos of this roof pentaprism, to show in more visible way what i'm talking about. so anyone can see it. (or if someone has possibility to put it on his server... and make a link in this thread?) filip p.s. i know that this sounds like almost a coinsidence, but i bought the pentaprism (roofprism) just because of that - to use it in agus35 modyfied project and have proper position of the image.

December 22nd, 2003, 07:35 PM	#11
Filip Kovcin Major Player Join Date: Dec 2003 Location: warsaw, poland Posts: 440	problem solved yes, that's it! penta roof+mirror=success!

December 22nd, 2003, 07:49 PM	#12
Filip Kovcin Major Player Join Date: Dec 2003 Location: warsaw, poland Posts: 440	to taylor taylor, i just sent the pictures of my pentaprism to you. thanks

December 22nd, 2003, 03:29 PM	#2
Helen Bach Regular Crew Join Date: Nov 2003 Location: New York, NY Posts: 120	Hi Vendible. Shouldn't that be a roof pentaprism? I think that if you use a plain pentaprism (as you appear to show) the image will be laterally inverted. Best, Helen

December 22nd, 2003, 03:46 PM	#3
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	"Shouldn't that be a roof pentaprism? I think that if you use a plain pentaprism (as you appear to show) the image will be laterally inverted." I have carefully check and rechecked (see the ray trace). The design is very similar to the viewfinder on a SLR camera, except the order is reversed. The penta prism does not invert the image, it only redirects the image 90 degree. Then the mirror does the inversion. A roof prism by itself will invert the image, but you will have to shoot at a right angle. I'll just mention the dove prism. To get a 24x36 or 36x36mm dove prism will require a length of at least 150mm, just by itself. Mirror and penta prism is still the best combination.

December 22nd, 2003, 05:02 PM	#4
Helen Bach Regular Crew Join Date: Nov 2003 Location: New York, NY Posts: 120	Vendible, I am referring to a roof pentaprism, not a roof prism. Nearly all SLR cameras use a roof pentaprism - a plain pentaprism (as you have shown, which is not like the ones in most SLR cameras) leaves the image laterally inverted. That's why SLRs use roof pentaprisms. If you don't believe me, look at the shape of the top of an SLR. Best, Helen

December 22nd, 2003, 05:21 PM	#5
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	Helen, http://f2.pg.photos.yahoo.com/ph/lou...m=DSC00140.jpg Thanks for pointing that out. I'll recheck and make sure what exactly it is. If you could draw or refer me to a picture, that would help.

December 22nd, 2003, 06:34 PM	#6
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	Helen, After some reading I think you are right, roof pentaprism. Thanks again.

December 22nd, 2003, 06:49 PM	#9
Taylor Moore Regular Crew Join Date: Dec 2003 Location: Canada Posts: 94	Hi Filip, Send the file to me taylor@moorefilms and I will post for you. Taylor

December 22nd, 2003, 06:54 PM	#10
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	Clarification: Pentaprism will deflect image 90 degrees without any inverting(up/down) or reverting (left/right) to the image. Roof Pentaprism will deflect image 90 degrees and revert (left/right) the image, but does not invert (up/down) the image. Using a pentaprism with a mirror will invert the image but not revert. Using a roof pentaprism with a mirror will invert and revert the image. Problem solved. http://f2.pg.photos.yahoo.com/ph/lou....dnm=img13.jpg

December 22nd, 2003, 08:32 PM	#13
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	This roof pentaprism introduces some more design problems because the outgoing surface is smaller than the incoming surface. That's OK for a camera view finder, but in this case, the bigger projected area, the better (more detail is preserved). Dove doesn't work because it only inverts the image, doesn't revert it. I'm looking for another solution.

December 22nd, 2003, 09:48 PM	#14
Don Berube Moderator Join Date: Mar 2002 Location: Boston, MA (travel frequently) Posts: 837	For what it is worth, you may find the following Optics FAQ handy: http://www.edmundoptics.com/TechSupport/optics.cfm Optics: http://www.edmundoptics.com/IOD/Browse.cfm?catid=10 Fresnel Lenses: http://www.edmundoptics.com/IOD/Disp...Productid=2039 Ohhhhh! (this looks very familiar) http://www.edmundoptics.com/IOD/Disp...productid=1966 T-Mount Adaptors (hmmmm...): http://www.edmundoptics.com/IOD/Disp...productid=1460 More Lens Adaptors: http://www.edmundoptics.com/IOD/Disp...productid=1459 Video Lenses?: http://www.edmundoptics.com/Catalog/Custom/218.cfm Cool!!!: http://www.nightowloptics.com/addfra...product=NOCA42 - don __________________ DONALD BERUBE - noisybrain. Productions, LLC Director Of Photography/ Producer/ Consultant http://noisybrain.com/donbio.html CREATE and NETWORK with http://www.bosfcpug.org and also http://fcpugnetwork.org

December 22nd, 2003, 11:28 PM	#15
Louis Feng Vendible Book Join Date: Dec 2003 Posts: 59	Ok, I have verified that with a normal penta prism and a roof prism, you can create a correct inverted and reverted image.