"Elliott, Rolland" wrote: > > BELOW ARE SEVERAL RESPONSES IN ALL CAPS TO SEVERAL QUESTIONS: > > My 1n manual says nothing about metering > problems with IR, only focus problems. And if a meter has a problem > with IR, wouldn't a 25 or 29 filter cause problems with metering normal > film? After all, a blue green filter would block most of the > transmission of red light in general, wouldn't it? > > SINCE CAMERA MANUFACTURERS DON'T PUBLISH THE LIGHT SENSITIVITY CURVES OF > THEIR METERS IT IS NOT POSSIBLE TO KNOW EXACTLY WHAT THE EFFECTS THE VISIBLE > RED FILTERS WILL HAVE ON THE METER SYSTEM. I WOULD ASSUME THE IR BLOCK > FILTER IS A VERY SHARP CUTTING FILTER THAT BLOCKS LIGHT MAINLY OUTSIDE THE > VISIBLE SPECTRUM, AND STILL LETS IN ENOUGH RED LIGHT. I'LL LET YOU KNOW WHEN > I GET MY FILTER TESTED. > > Well it [THE DIAGRAM SHOWING IR LED'S IN IS LENSES] isn't in the "L EF > Lenses" literature, there are half schematics > with no reference to "IRLED." I don't remember such from the 1v lit, > either, but could be mistaken. I'm not sure what an IRLED would do for > IS. But wouldn't it emit outward, rather than inward towards the film. > What possible function would it have involving TTL or distance to film > plane? > > IT IS IN THE EOS1V TECHNICAL BROCHURE. I DON'T KNOW IF CANON REGULARLY MAILS > OUT THIS PUBLICATION. I'VE ONLY SEEN IT AT TRADE SHOWS. YES IT WOULD > PROBABLY EMIT OUTWARD, NOT DIRECTLY TOWARDS THE FILM, BUT THIS OUTWARD LIGHT > COULD EASILY BOUNCE AROUND AND CAUSE POSSIBLE FLARE IF THE LENS IS NOT WELL > BAFFLED. > > So what you're saying is that the red filter > will prevent the camera from focusing on blue and green wavelengths and > shift its focus more toward the red end of the spectrum, correct? And then > the DOF at 5.6 is deep enough to accomodate the IR wavelength focus? > > YEP, PRETTY MUCH. ALL LENSES ARE A LITTLE BIT DIFFERENT, BUT AS A GENERAL > RULE THIS IS RIGHT. > > One other question -- why is it so important to camera manufacturers to > prevent their AE cameras from metering IR light? If the amount of IR light > in a typical nature scene is approximately proportional to the amount of > visible light, why is it such an issue? Are there special conditions that > have IR light in wildly varying proportions? Do these internal AE filters > block UV light too? > > IT IS IMPORTANT BECAUSE THERE ARE MANY SPECIAL CONDIDTIONS. FOR EXAMPLE > SHOOTING INSIDE UNDER TUNGSTEN LIGHT, SHOOTING UNDER FLUORESCENT LIGHTS, > SHOOTING EARLY OR LATE IN THE DAY (SUNRISE, SUNSET PICTURES). > > I've just looked through the EOS-1V and the EOS-3 pamphlets, neither has the > exploded IS mechanism diagram, I would be interested to hear from anyone who > has found the reference of IR LED. > > LIKE I MENTIONED ABOVE IT IS IN THE 1V TECH BROCHURE. > > However, I did notice while the -1V literature does say the film transport > is "compatiable with IR film", the -3 literature doesn't, and we have all > heard of (slight) fogging of the edge of IR films in -3. Off hand I do not > know what difference the film sprocket hole counting mechanism between the > two bodies are, I had thought they were the same...... > > THE 1V HAS AN OPTICAL ELEMENT ABOVE THE IR LED WHICH FOCUSES THE LIGHT AND > ALSO HAS A MASK TO PREVENT THE LIGHT FROM BOUNCING AROUND. > > PEACE, ROLLAND Well, that settles that, then. I'll be shooting some (false)color IR this weekend with my 28-135. If I have any problems, I'll post them here first! Skip -- Shadowcatcher Imagery http://www.shadowcatcherimagery.com * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
