50D - Camera won't consistently take the shot with Polarizing or ND filter on the lens

[IBaSchmuck]

If I have a polarizing or ND filter attached to a lens, any lens (Canon, Tamron, offbrand)(EF or EF-S)(zoom, fixed or macro), camera set to "Full Auto" (manual modes also), any image stabilization turned off, or on, the lenses will always autofocus, but some times the camera won't take the shot. Some times it will. The camera acts like it would if it were too close to a subject for the installed lens. However, moving further away, or closer, to the subject has no affect on the issue. I can AF the camera, switch the lens to "manual" focus and it will take the shot.

Changing the ISO makes no difference. Changing the AF point/s makes no difference.

At first I thought one of my lenses was the problem, then I tried another one and got the same result.

Is there a setting I may have changed that would cause this? Easy fix? Or am I going to have to send it in to Canon for diagnosis?

[jrhoffman75]

OK. Reason I am suggesting that is it uses a different focusing method - it focuses using the actual image sensor rather than an AF sensor.

I have never experienced a situation where camea wouldn't fire when focus confirmation was green.

[IBaSchmuck]

I'm pretty sure my Hoya PL-C is a circular polarizer. I've only been taking photos since 1965 though, so I could be wrong.

My bad on the Tiffen ND filter. It's a "variable".

[IBaSchmuck]

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@jrhoffman75 wrote:

OK. Reason I am suggesting that is it uses a different focusing method - it focuses using the actual image sensor rather than an AF sensor.

I have never experienced a situation where camea wouldn't fire when focus confirmation was green.

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Understood. This only started last month, that's why I'm confused also. Up until then I had had no issues with the camera. (Well, there was that sticking switch under the flash spring.)

Another problem is that it doesn't happen all of the time. Twice, it was at car shows. Lots of chrome/glare. Another time it was at a desertPetroglyph site. Bright sun but dark rocks.

[RobertTheFat]

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@jrhoffman75 wrote:

OK. Reason I am suggesting that is it uses a different focusing method - it focuses using the actual image sensor rather than an AF sensor.

I have never experienced a situation where camea wouldn't fire when focus confirmation was green.

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Does the confirmation light blink or stay on? In one-shot AF mode on a 50D, the light blinks if focus cannot be achieved.

[jrhoffman75]

I have the Tiffen 10X Cariabke ND and confirmed that it does not affect focusing as long as there is enough light. Solid green dot and beep.

[IBaSchmuck]

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@jrhoffman75 wrote:
I have the Tiffen 10X Cariabke ND and confirmed that it does not affect focusing as long as there is enough light. Solid green dot and beep.

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I just spent the last hour, or so, outside (bright sun, 86°, 30% humidity) trying to MAKE it not work. And nothing. Took the shot every time. Two different lenses (1-EF, 1-EF-S), both ND and Polarizing filters tried. Shooting my Fiat Cherokee station wagon, lots of glare, shooting some Sunflowers, Lilacs, dog, concrete, trees, leaves, chickens. With and without Live View, every "creative" mode, every "basic" mode. And nothing. Not a single failure to fire. Focused every time, but then that was never the problem. It would focus, just not activate the shutter. That does sound like the subject would NOT be in focus. But the light was on all those times it wouldn't work.

No problems when I want it to not work and then doesn't work when I really want it to.

It's rather frustrating, to say the least.

Heading up to Crater Lake tomorrow. Will see what happens then, and report back.