Out of focus images caused by red LEDs?

[charedan]

<p>I photographed an event last saturday with my 1DMKIII and 5DMKII. The walls of the room were covered in white drapes, and strips of red LEDs were lighting from the ground up, right in front of the drapes.<br>

I noticed a much higher rate of out of focus images. Any one knows if the red LEDs could be responsible?<br>

TIA</p>

[Marcus Ian]

<p>The monochromatic nature of the (presumably) intense red LED certainly<em> could</em> have led to focus shifting due to the saturation of the red channel in the phase detect system, throwing the distance calculation out of whack - since the phase detect makes it's calculation based on intensity of the peaks, and their position of the different wavelength peaks. If this is what was happening, I would anticipate that the problems primarily occurred when the LEDs were in the frame (reflected light wouldn't have the same intensity, nor complete uniform wavelength). </p>

<p>Not being there, I certainly couldn't say if this was the certain cause, but it seems the most likely explanation. I assume the problem occurred with both cameras.</p>

[robin_sibson1]

<p>Since Canon use a red/nearIR beam as the AF assist beam from several of the Speedlite flashguns, with entirely satisfactory results, it seems very unlikely that the redness of the light is the source of a problem with AF.</p>

[charedan]

<p>@Marcus, Thanks for that explanation. And yes, both cameras showed the same problem and it was in fact more obvious when more red light was in the frame.<br>

@Robin, I had a similar thought but in the opposite direction. Since the AF Assist beam is red, if everything the AF system sees is bathed in red light, doesn't that would cause difficulty?<br>

The pictures done in a area where there was more white light are all OK!</p>

[jaydesi]

<p>Daniel, I just took some pictures of my daughter this weekend, and noticed the red AF stripes from my flash were on constantly and showing up in my pictures. I ended up having to cover them up because I couldn't figure out how to shut them off. I suspect you had the same problem. My flash was a Sigma EF610 off camera, triggered by a PW TT5. What were you using?</p>

 

[charedan]

Hi Jay, I. was using a 580 II on each camera. There is no AF assist light on any of the images, this is not the problem.