Optical viewfinder discussion at DVinfo.net

Oscar Spier · February 2nd, 2008, 06:53 PM

I'd like this to be a general discussion, but to quickly sum up my project:
I've made an optical viewfinder on the Elphel 353 cmos camera. Because of the small size of the sensor, I was able to use most parts from a super8 camera.
So far, it all seems to work really well. I still have to fine adjust everything though.
I posted some pictures of my first sketch and the result. here

I think this could be useful for any DIY HD camera projects.

One thing I'd like to improve, or have as an option, is a viewfinder-extension. It would be much more comfortable to position your head behind the camera :)
Does anyone know how such an extension tube works?

Another option I'd like to add, is an inverted(rotated) image when using the 35mm adapter. (Maybe by skipping the flipping tube in my setup?)

Any thoughts?

Brandt Wilson · February 4th, 2008, 11:39 AM

Hi Oscar,

I have a few thoughts on this.

If the viewfinder is working as you would like it to, there may be no need to extend the tube. The camera itself isn't much larger than video taps that are installed in other viewfinder systems on larger 16mm and 35mm cameras. This being the case, couldn't your solution be treated as being the viewfinder component of a larger system (mini-itx pc, battery, audio mixer, etc)? If so, you can mount it on your rails and adjust it to meet your eye comfortably, while the rest of the system is farther back on the rails to provide balance.

Just my $.02.

What is your viewfinder built from? You mentioned the other day that you are using a super-8 VF to match the sensor size. Did you pull these components out of a S8 camera, or is it all fabricated from scratch?

-Brandt

Oscar Spier · November 13th, 2009, 06:57 PM

This is a very old thread, but still... I'd like to reopen the topic.

I recently took up my hobby again: wrecking and taking apart an old camera :-)

This time it was a nice Olympus Camedia C-1400L
This camera had a fairly large CCD and a real optical viewfinder. It was not using a flipping mirror like a SLR camera though, but a beamsplitter.
This beamsplitter was a 45 deg prism (roof prism??) that directs the image straight to a simple eyepiece, and also 45 deg downwards to the CCD that is placed directly to the prism. Can't be simpler. A little bit like this image. The CCD would be on the bottom plane.

So the idea came to mind about the Elphel camera 45 deg front end . Although using the 45 deg front end, the sensor would remain in it's normal place with a roof prism type beamsplitter between the sensor and the lens and an eyepiece in 45 deg on top of the camera.

Just an idea to think about.

BTW, I remember there used to be a SLR camera that used a 35mm sized beamsplitter in stead of a mirror for high speed continuous shooting. Does anyone remember the camera type and brand?

February 2nd, 2008, 06:53 PM	#1
Oscar Spier Major Player Join Date: Jan 2005 Location: (The Netherlands - PAL) Posts: 717	Optical viewfinder discussion I'd like this to be a general discussion, but to quickly sum up my project: I've made an optical viewfinder on the Elphel 353 cmos camera. Because of the small size of the sensor, I was able to use most parts from a super8 camera. So far, it all seems to work really well. I still have to fine adjust everything though. I posted some pictures of my first sketch and the result. here I think this could be useful for any DIY HD camera projects. One thing I'd like to improve, or have as an option, is a viewfinder-extension. It would be much more comfortable to position your head behind the camera :) Does anyone know how such an extension tube works? Another option I'd like to add, is an inverted(rotated) image when using the 35mm adapter. (Maybe by skipping the flipping tube in my setup?) Any thoughts? Attached Thumbnails __________________ Oscar APERTUS - open source cinema -

November 13th, 2009, 06:57 PM	#3
Oscar Spier Major Player Join Date: Jan 2005 Location: (The Netherlands - PAL) Posts: 717	This is a very old thread, but still... I'd like to reopen the topic. I recently took up my hobby again: wrecking and taking apart an old camera :-) This time it was a nice Olympus Camedia C-1400L This camera had a fairly large CCD and a real optical viewfinder. It was not using a flipping mirror like a SLR camera though, but a beamsplitter. This beamsplitter was a 45 deg prism (roof prism??) that directs the image straight to a simple eyepiece, and also 45 deg downwards to the CCD that is placed directly to the prism. Can't be simpler. A little bit like this image. The CCD would be on the bottom plane. So the idea came to mind about the Elphel camera 45 deg front end . Although using the 45 deg front end, the sensor would remain in it's normal place with a roof prism type beamsplitter between the sensor and the lens and an eyepiece in 45 deg on top of the camera. Just an idea to think about. BTW, I remember there used to be a SLR camera that used a 35mm sized beamsplitter in stead of a mirror for high speed continuous shooting. Does anyone remember the camera type and brand? __________________ Oscar APERTUS - open source cinema -

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February 4th, 2008, 11:39 AM	#2
Brandt Wilson Major Player Join Date: Jan 2003 Location: Portland, OR Posts: 211	Hi Oscar, I have a few thoughts on this. If the viewfinder is working as you would like it to, there may be no need to extend the tube. The camera itself isn't much larger than video taps that are installed in other viewfinder systems on larger 16mm and 35mm cameras. This being the case, couldn't your solution be treated as being the viewfinder component of a larger system (mini-itx pc, battery, audio mixer, etc)? If so, you can mount it on your rails and adjust it to meet your eye comfortably, while the rest of the system is farther back on the rails to provide balance. Just my $.02. What is your viewfinder built from? You mentioned the other day that you are using a super-8 VF to match the sensor size. Did you pull these components out of a S8 camera, or is it all fabricated from scratch? -Brandt