optical viewfinder extension.. DIY? at DVinfo.net
DV Info Net

Go Back   DV Info Net > Special Interest Areas > Alternative Imaging Methods > Apertus: Open Source Cinema Project

Reply
 
Thread Tools Search this Thread
Old January 2nd, 2009, 10:32 AM   #1
Major Player
 
Join Date: Jan 2005
Location: (The Netherlands - Belgium)
Posts: 735
optical viewfinder extension.. DIY?

Hi everybody,

Some time ago I built this optical viewfinder on my Elphel Cmos camera (see Elphel 333 thread)
One thing I'd like to improve, if possible, is to make some sort of extension. (similar to this, but a lot smaller of course (the viewfinder I use is adapted from a 8mm camera. It would be very nice to enlarge the image too, because it's quite small now.
All ideas are welcome!

Here is an image of the Elphel with viewfinder.
Attached Thumbnails
optical viewfinder extension.. DIY?-viewfinderelphel.jpg  
Oscar Spierenburg is offline   Reply With Quote
Old January 10th, 2009, 05:36 AM   #2
Regular Crew
 
Join Date: Jan 2007
Location: Vienna, Austria
Posts: 112
Great idea!

Could these be of any use: Prism mirror, precision grade
Sebastian Pichelhofer is offline   Reply With Quote
Old January 11th, 2009, 05:28 AM   #3
Major Player
 
Join Date: Jan 2005
Location: (The Netherlands - Belgium)
Posts: 735
Sebastian, I have used such a mirror prism in the viewfinder. First, the beamsplitter in front of the sensor mirrors the image into the tube that sticks out of the camera. Then the image is mirrored again through the mirror prism into an eyepiece. See the original drawing attached.
From that eyepiece I need the extension tube. Here is a quick drawing of what I mean.
Now if I make the same kind of tube that comes from the beamsplitter, I'd flip the image 180 deg. Is there another setup possible?
Attached Thumbnails
optical viewfinder extension.. DIY?-original-drawing.jpg   optical viewfinder extension.. DIY?-elphel-opt-viewfinder-extension.jpg  

Oscar Spierenburg is offline   Reply With Quote
Old January 18th, 2009, 08:08 PM   #4
Major Player
 
Join Date: Jan 2003
Location: Portland, OR
Posts: 220
Oscar, are you using a longer focal length lens and diopter to extend the optical path?
If I remember correctly (and I may be way off, so don't go by my figures) wouldn't a longer FL lens be of value? If so, I found a really long PCX here: PRECISION PCX 21MM CLEAR DIA X 300MM FL MTD - Surplus Shed. It's 21mm diameter mounted by 300mm FL. A hair under $16 plus shipping.

You can then use a diopter to bring your eye closer to the focal plane, which should effectively perceptually enlarge the image.
Brandt Wilson is offline   Reply With Quote
Old January 20th, 2009, 07:26 AM   #5
Major Player
 
Join Date: Jan 2005
Location: (The Netherlands - Belgium)
Posts: 735
I'm not sure. I hope it would work like you describe it. The first tube is actually creating the distance to the focal plane. So what is left is the eyepiece, I don't know if you can extend it..


Right now I've done a huge compromise, but I need to have this working: I've put a tiny cmos pinhole camera (without the lens of course) in place of the eyepiece. The output of the camera is displayed on a separate B/W viewfinder from an old TV camera.
The advantage is that I can flip the whole thing when I'm using a 35mm adapter.

This is just temporarily a quick solution, because of the quality loss, so I'll continue to make it totally optical.
Oscar Spierenburg is offline   Reply With Quote
Old January 20th, 2009, 11:02 PM   #6
Major Player
 
Join Date: Jan 2003
Location: Portland, OR
Posts: 220
I think a diopter at the eyepiece end would bring the eye closer to the imaging plane. Perhaps someone more knowledgable about optics can time in here, but I think that's right.
Brandt Wilson is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

B&H Photo Video
(866) 521-7381
New York, NY USA

Scan Computers Int. Ltd.
+44 0871-472-4747
Bolton, Lancashire UK


DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Special Interest Areas > Alternative Imaging Methods > Apertus: Open Source Cinema Project

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



All times are GMT -6. The time now is 12:46 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2021 The Digital Video Information Network