TTL Flash

Discussion in 'Beyond the Basics' started by Actor, Apr 1, 2010.

  1. Actor

    Actor TPF Noob!

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    TTL view-finding, focusing and metering are standard. I have been working on taking the TTL concept to the next level with through the lens flash. As a proof of concept I am working to modify an SLR for TTL flash. My approach is to mount a flash to project its light through the viewing system, bouncing the light off the mirror and through the lens. Conceptually one envisions the output of the flash progressing in reverse through the view-finding system and out the lens to the subject, then returning to the camera with the mirror up and thus onto the film/sensor. Unfortunately, due to the great speed of light, this system is unworkable.

    Modifying this approach I plan to replace the mirror with a 45 degree prism. This means that the prism's glass has to be selected so that the reflection is not total but acts as a beam splitter. This has an unwanted side effect. Since the reflector is a beam splitter part of the outward bound light can return to bounce off the underside of the splitter and onto the film. Obviously all of the light that is transmitted through the splitter (i.e., not reflected toward the subject) on its outward journey must be absorbed. Thankfully, physics provides the answer in the form of a cavity, also known as a black body. The physicists among you will immediately realize that cavities absorbs all light.

    In my prototype I will lose TTL view-finding, focusing and metering, but this is only a proof of concept model. Once I have the basics down I'll build another camera which retains these features.
     
  2. Garbz

    Garbz No longer a newbie, moving up!

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    May I ask why?

    Aside from the technical hurdles there's the conceptual image issues. You will lose all shadow projection, making the image incredibly boring, and not to mention every subject you attempt to photograph will without fail exhibit red-eye.

    The goal has always been to remove the flash as far away from the angle of incidence of the lens, within reason of course. Why go to all the effort to create the opposite? I understand for creative reasons is a likely solution, however the technical problems to overcome would border on those of the guy with the stereoscopic in-flight bug photographer.
     
  3. Derrel

    Derrel Mr. Rain Cloud

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  4. Actor

    Actor TPF Noob!

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    One eye on the screen, the other on the clock. Thanx for the link. :lol:

    See you next year. ;)
     
  5. Garbz

    Garbz No longer a newbie, moving up!

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    I'm still waiting for the year where the Onion decides to post actual news for april fools day.
     

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