I have the 380EX and the ElanIIe.

I was told when I bought the flash that the preflash was infrared, emanating from the AF assist beam "projector" on the front of the flash.

However, when the flash exposure lock (FEL) button is pressed a visible preflash is fired. I have read on our forum that the 430EZ has both infrared and white light preflashes depending on the tilt of the bouce head. No matter what position the 380EX flash head is in, straight on or tilted, the preflash is visible.

Is there an infrared component to the light? If so, what is its function?

Thanks

-- Roy Kekewich (roykekewich@yahoo.com), October 31, 2000

Answers

The EZ series uses IR preflash for A-TTL metering. It can also use a small regular flash if the head is tipped up. The EX series uses E- TTL and always uses a small dose of regular flash. No IR used.

The 550EX and 420EX use near IR to communicate with remote slaves, I believe.

-- Jim Strutz (jimstrutz@juno.com), October 31, 2000.

The near IR emitter on EX series flashes if for AF assist only. Preflash is always visible.

-- Brad Hutcheson (bhutcheson@iname.com), October 31, 2000.

Thanks guys.

Regarding the AF emitter. When I use either the Elan's AF beam or the one projected from the 380EX, a visible red beam with a "striped pattern" is cast on the subject. If that is the near IR light you refer to does that mean that near IR is within the visible light spectrum, or is the IR just a component of the projected light beam?

By the way, both work really well. I did test shots with both of them in blind darkness and the shots were in perfect focus and well exposed as well, using full auto and Program modes.

-- Roy Kekewich (roykekewich@yahoo.com), November 01, 2000.

The red light you see is the "near IR". All that means is it's close to being true IR.

I believe they use the red because it's less intrusive than colder colors and doesn't tend to dialate the eyes, which might cause you reduced night vision.

-- Jim Strutz (j.strutz@gci.net), November 01, 2000.

All EX speedlites use "white light" for the E-TTL pre-flash and the MR-14EX and 550EX masters use "white light" for controlling slaves. The ST-E2 Transmitter uses near-IR for controlling slaves, but itself emits no "pre-flash". See my web page: http://mate.kjsl.com/~ dave/wireless.html.

EX speedlites use near-IR for AF-assist only.

-- Dave Herzstein (dherzstein@juno.com), November 02, 2000.

Okay, so does that mean that the red beams emitted by my camera and flash are near infra-red? Is there another part of the spectrum in those beams? If not, then near infrared light is visible, while far infrared is the stuff picked up by infrared film and made visible by thermal cameras, though invisible to the eye. Is this right?

I've tried a lot of book and web sources to answer these ancillary questions to no avail.

Any of our resident scientists out there to come to the rescue?

Thanks,

Roy

-- Roy Kekewich (roykekewich@yahoo.com), November 03, 2000.

"...does that mean that the red beams emitted by my camera and flash are near infra-red?" - Yes that's why it's NEAR infra-red

"Is there another part of the spectrum in those beams?" - Like most light sources, this one has a spread of the spectrum, some of which you can see and some that you cannot. But regular tungsten light bulbs do this as well. That's why they're warm. Most likely the AF sensor in your camera is not all that sensitive to true IR, if at all. But the red works well with it and still doesn't seem too bright to our eyes.

"...then near infrared light is visible, while far infrared is the stuff picked up by infrared film and made visible by thermal cameras, though invisible to the eye. Is this right?" - Yep.

-- Jim Strutz (jimstrutz@juno.com), November 07, 2000.

Ah, the whole picture! Thank you.

-- Roy Kekewich (roykekewich@yahoo.com), November 08, 2000.