The Elias Lens System

This page explains a system called ELS (Elias Lens System) which can allow any Digital Single-Lens Reflex (D-SLR) camera to provide both a TTL (Thru-the-lens) view and an external LCD (or similar) display pannel like point-and-shoot cameras, without any image quality degradation whatsoever.

Note that the system is extremelly simple, but will undoubtly increase the cost of a camera that implements it, and thus this system if ever implemented would probably make it first into higher end professional digital cameras.

Note also that this system can be used not just by D-SLR cameras, but also by digital video cameras, and even retrofitted to work with traditional analog film cameras as well (to provide film-based camera operators an electronic view of what the camera sees before taking an exposure, as in for example, remote-control applications).

The objetives of the Elias Lens System are the following:
	To allow the photographer at any time during the composition of a shot to switch between a TTL view and an external LCD view.
	To not compromise on the amount of light being sent to either the TTL viewfinder or the LCD screen (i.e.: allow all possible light to pass through the lens on both scenarios)
	To do so in a simple manner.

How it works
Please reffer to the following 3 images to understand how an ELS system works. note that the yellow components are mirrors, and that the dotted gray line is the path the light takes from the subject (in this case, a flower) to the photographer's eye. Also note that the two black lines connecting the red sensor components and the green LCD component are ment to represent a connection that sends the images captured at the sensors to the screen.

In this image (1) we appreciate that the ELS consists of 3 mirrors (well, two is the minimum, as the top mirror is not needed if the photographer is looking straight "down" the image), 2 photo sensors, and one LCD screen (internal or external). In this configuration, the lens system will behave exactly as a traditional SLR system, where the photographer is looking at the subject thru-the-lens.

Some might ask, do we need two sensors? Can't we do the same with just one? In theory yes, in practice no, because one thing we don't want to do is expose the main sensor to light until the very instant when the photographer pushes the Shutter-release button. This happens for the simple fact that the sensor is an analog device that takes electrical charge (in the form of light photons) and translate them to electrical signals. To make a story short, if the main sensor was capturing light all the time while you were composing the shot, at the time you finally decide to take the shot the sensor might be "loaded" with electrical charges and the exposure you will get will not be the one you intended (or, you might have to wait for the sensor to "discharge" and take take the exposure as intended, as it happens with point-and-shoot cameras). This is why we use a seconday sensor to compose the shot, and a main sensor to capure the image at the desires parameters. Note also that the ideal situation would be to have both sensors to be identical to each other, however a manufacturer might opt to put a less expensive one as the secondary one (maybe with a much smaller pixel count) to reduce manufacturing costs. The only restriction on the seconday sensor should be that the capure area be the same as the main sensor, so that depth-of-field (DOF) and horizontal and vertical lens capture range remains the same.

In this image (2) we see how by a simple rotation of the center lens to a -45-degree angle we can now divert the light to the secondary sensor, thus now allowing the photographer to view the image being composed on an external LCD display. Note that the photographer can switch back and forth between TTL and LCD view as many times as desired by rotating the middle lens with a switch.

In this final image (3), the photographer presses the Shutter-release button, and the bottom mirror flips out of the way to allow light to hit the main sensor and take the exposure.

As you can see, this is a VERY simple mechanism. Let's only hope that D-SLR manufacturers start implementing something similar to this to make our lives easier.

Side note: The reason I went through the trouble of making this "ELS" page, is because although I love my new Nikon D70 (and also like my friend's Canon EOS 300D), that I trully miss my old Sony DSC-F717 LCD display capability. I understand that many professional photographers would never want anything less than a TTL experience with a camera, but I also think there are very real situations where the use of an LCD (specially a large external one) can complement the photographic process. Model and outdoor photography come to mind. Imagine composing a panoramic shot with the aid of a large 12-inch screen. Also, this could help a lot in preventing out-of-focus images as a large LCD display affords you a much better view than a small TTL viewfinder.

Another recomendation I have to camera manufacturers is a creation of a standard to connect laptop LCDs to digital cameras. So that for example I can get a live view of what my digital camera sees on my laptop screen. This would be simply marvelous. Finally I wish to say that if you think this is all rubish, that I completelly respect your decision to do only TTL photography (no sarcasm intended), but that I also sincerelly hope that you understand that there are others like me who would like such basic feature being part of a usually highly-priced digital camera.

José C. Elías
Feel free to email me with your comments or suggestions at josecarloselias@yahoo.com

Disclaimer and Copyright: I came up with this "Elias Lens System" on my own. I do not know if something like this has been implemented before (not to my knowledge), I also don't know of anybody doing research to create something like this, neither do I know if this has been pattented or not. I did this because it seems like a no-brainer common-sense solution to a problem. If you're part of a company that decides to build this thing, you do so at your own risk. If this happens to be a novel way to do something that nobody has done before, then if I have the legal right to do so then I forbid you from trying to patent this, and instead this should be a "free invention" from my part to all who wish to implement it (but see the "thank you for the idea" payment note below...). I also ask that you acknowledge my name and still call it the "ELS - Elias Lens System" *grin*. As for copyright, you may copy this page all you want so long as I'm given credit and a link to this page an my email is provided. Oh yeah, any camera manufacturer who implements this thing is in obligation of providing me with a US$10,000 "thank you for the idea" payment for each product that implements it (we can negociate this for all your products...) *grin* (heck, if I can make some side income off this thing, why not?!!!)