Flipping image by lens at DVinfo.net

Martin Diruf · January 31st, 2005, 10:39 PM

A main problem handling the homebuilt 35mm-adapter is the flipped image, upside down as well as right to left. I'd like to discuss a simple idea that seems to be a possible solution.

www.bodyhey.com/big_screen.gif

I would avoid a hotspot by using a glasscreen:

www.glasscreen.com

By blowing up the picture from 35mm diameter to about 60mm you maybe don't even need a diopter and have increased resolution.

cheers,
martin

Cody Dulock · January 31st, 2005, 11:30 PM

one thing i have been wondering is if theres an element in the 35mm lens that flips the image... i havent got an old broken lens to take it apart and find out... but im guessing its mirrors? but maybe glass? if so is there a way to adapt to a mini35 of anykind?

Martin Diruf · February 1st, 2005, 01:54 AM

Well, there is no mirror inside a 35mm objective, it's the lens itself. With a convex, magnifying lens parallel rays of light are focused in one point (until then the picture is upright) After that point, the picture you'll get is upside down.

This linke explains it by the method, a telescope works.

http://members.shaw.ca/quadibloc/science/opt01.htm

Martin Hesse · March 5th, 2005, 12:36 PM

Martin D-
I've considered this option as well. The problem with this scherme (http://www.bodyhey.com/big_screen.gif) is that the DOF will be affected. More DOF, less DOF... I don't know. Secondly, this will probobly make the lens adaptor quite long and not very efficient in terms of light loss.

Aaron Shaw · March 5th, 2005, 01:00 PM

I don't see any reason the DOF would have to be affected. If you placed the lens inbetween the GG and the 35mm lens you would inevitably affect the focal length. However, if you placed it behind the ground glass you would get the same affect without the problems associated with the other method.

Adding a single element shouldn't affect light loss much at all - assuming you use a decent coated element.

Martin Hesse · March 5th, 2005, 02:14 PM

"I don't see any reason the DOF would have to be affected. If you placed the lens in between the GG and the 35mm lens you would inevitably affect the focal length."
Yes, I agree. Martin D's drawing shows the "field" lens between the 35mm format lens and the GG. Placing the field lens after the GG would be a better option.
I doubt that you can use just one single element. Multiple elements would have to be used to achieve this task. In this process you're bound to loose at least a stop and a half at least.

Aaron Shaw · March 5th, 2005, 03:50 PM

One should be enough if you get the right focal length and distance from the GG and the video cameras lens. It would take some intentional design though. It wouldn't be as simple as most stuff.

Steve Brady · March 6th, 2005, 11:55 AM

Wouldn't it need to be at least a doublet, to reduce chromatic abberation?

Aaron Shaw · March 7th, 2005, 12:25 AM

Oh absolutely. I mean, just one lens should be enough (a muli-element lens but only one of them). I hope that made sense.

January 31st, 2005, 10:39 PM	#1
Martin Diruf New Boot Join Date: Jan 2005 Location: Germany Posts: 9	Flipping image by lens A main problem handling the homebuilt 35mm-adapter is the flipped image, upside down as well as right to left. I'd like to discuss a simple idea that seems to be a possible solution. www.bodyhey.com/big_screen.gif I would avoid a hotspot by using a glasscreen: www.glasscreen.com By blowing up the picture from 35mm diameter to about 60mm you maybe don't even need a diopter and have increased resolution. cheers, martin

January 31st, 2005, 11:30 PM	#2
Cody Dulock Major Player Join Date: Sep 2004 Location: arlington, texas Posts: 420	one thing i have been wondering is if theres an element in the 35mm lens that flips the image... i havent got an old broken lens to take it apart and find out... but im guessing its mirrors? but maybe glass? if so is there a way to adapt to a mini35 of anykind?

February 1st, 2005, 01:54 AM	#3
Martin Diruf New Boot Join Date: Jan 2005 Location: Germany Posts: 9	Well, there is no mirror inside a 35mm objective, it's the lens itself. With a convex, magnifying lens parallel rays of light are focused in one point (until then the picture is upright) After that point, the picture you'll get is upside down. This linke explains it by the method, a telescope works. http://members.shaw.ca/quadibloc/science/opt01.htm

March 5th, 2005, 12:36 PM	#4
Martin Hesse New Boot Join Date: Dec 2004 Location: San Francisco CA. USA Posts: 15	Martin D- I've considered this option as well. The problem with this scherme (http://www.bodyhey.com/big_screen.gif) is that the DOF will be affected. More DOF, less DOF... I don't know. Secondly, this will probobly make the lens adaptor quite long and not very efficient in terms of light loss.

March 5th, 2005, 01:00 PM	#5
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	I don't see any reason the DOF would have to be affected. If you placed the lens inbetween the GG and the 35mm lens you would inevitably affect the focal length. However, if you placed it behind the ground glass you would get the same affect without the problems associated with the other method. Adding a single element shouldn't affect light loss much at all - assuming you use a decent coated element.

March 5th, 2005, 02:14 PM	#6
Martin Hesse New Boot Join Date: Dec 2004 Location: San Francisco CA. USA Posts: 15	"I don't see any reason the DOF would have to be affected. If you placed the lens in between the GG and the 35mm lens you would inevitably affect the focal length." Yes, I agree. Martin D's drawing shows the "field" lens between the 35mm format lens and the GG. Placing the field lens after the GG would be a better option. I doubt that you can use just one single element. Multiple elements would have to be used to achieve this task. In this process you're bound to loose at least a stop and a half at least.

March 5th, 2005, 03:50 PM	#7
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	One should be enough if you get the right focal length and distance from the GG and the video cameras lens. It would take some intentional design though. It wouldn't be as simple as most stuff.

March 6th, 2005, 11:55 AM	#8
Steve Brady Regular Crew Join Date: Feb 2005 Location: Rainham, Kent, UK Posts: 69	Wouldn't it need to be at least a doublet, to reduce chromatic abberation?

March 7th, 2005, 12:25 AM	#9
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Oh absolutely. I mean, just one lens should be enough (a muli-element lens but only one of them). I hope that made sense.