New Canon EF 70-200mm f/4 L USM Lens - But what's with the CRAZY flashing from my camera?

[Globespy]

Love the build quality of the lens...bleh bleh.....


I was able to take maybe 2 shots before my camera's flash (REbel T2i) started going crazy...like in a way that would make any subject go into shock or epilepsy! At the same time the lens was unable to focus on any subjects, again continuing to cause the flash to go NUTS!


I have tried searching on google for this, but can't find an answer?

Could the lens be broken, or could it be something wrong with my camera? Battery levels seemed ok etc, so really confused right now.....and a little dissapointed after dropping a lot of quid on this lens (for my first foray into 'proper' digital photogrpahy).


All help appreciated!


Sean

[Rodger]

Sean,


Does the flash fire repeated bursts? If so, what you're describing sounds alot like the built in flash's AF assist. That goes right in line with your lens not being able to focus also.


Was it a dark area you were trying to focus on?


-Rodger

[Sean Setters]

I'd have to agree with Roger on this. It sounds like the Auto Focas assist flash (where the flash illuminates the subject so that the camera can obtain proper focus). I'd suggest trying to repeat your portrait session in a better lit area and see if the focus problem persists (the AF assist flash my still fire, but you should be able to obtain focus thereby shortening the AF assist burst).

[Shea Design]

I don't know if your camera has a DOF preview button, but mine fires a nasty modeling light by default (disabled now) so it may be worth a look.


-S

[jcrowe87]

I don't know if your camera has a DOF preview button, but mine fires a nasty modeling light by default (disabled now) so it may be worth a look.


-S

I was going to say this, if it looks like a flicker thats like 60Hz or something like that then I would say thats its totally DOF preview. Fun to blind people with, otherwise a little overkill.

[neuroanatomist]

So, consensus is that it's probably the AF assist required in low light - which, for the T2i is a 4-5 strobe burst of the pop-up flash. An f/4 lens is not especially fast (wide aperture) so when used indoors, your camera may not have enough light to achieve focus.


I'll add that for your next purchase as part of your "foray into 'proper' digital photogrpahy" you might consider an external Speedlite flash (430EX II or 580EX II). In addition to the ability to bounce a flash off the ceiling and thus avoid both red-eye and the 'deer in headlights' look of subjects, one of the features I like best about the Speedlites is that they provide a different kind of AF assist - a red/infrared pattern of lines that's much less annoying. (Side note: I don't recommend the cheaper 270EX flash - even though that can bounce, it has no AF assist lamp so it's AF assist is still just a series of strobes.)

[Globespy]

ok cool. another purchase for using this lens indoors at night. maybe i will check out these lightds to avoid blinding the next group of 4 year olds at a birthday party, or stick wuth my prime. ok cool

[Steve Combs]

I agree with the others that this sounds like AF assist.... My 40D used to do this to me at times. The 430 EX II and 580 EX II have the (almost) IR focus assist which projects a series of lines on your subject and provides high contrast areas to assist with the AF. Works MUCH better than strobing flashes as it provides a series of lines which will provide good contrast even on a white/neutral wall. AF will work MUCH better (a VERY good reason for my 580!)...