EX-3 losing infinity focus
 

So this week during a shoot, my EX-3 suddenly lost infinity focus. I vaguely remembered older EX-1 threads that said a re-boot after taking the battery off generally fixed the issue. We tried that, and after two tries, it cleared up.

Then I was reading Alister's comment in the PMW200 thread about not using a star chart for the EX-3's auto flange adjustment. I had just run the auto flange a few days before with a star chart, so I did the "12 feet from a brick wall" flange adjustment.

Was looking good until I tested the infinity, and when I kicked in the #2 ND filter on the camera...instant lack of infinity focus. (put the camera at about f5.6 or so.) Popped the focus ring from MF to AF and back sharply...infinity focus restored, regardless of ND filter position.

Kind of seems like this lens is all over the place. Any ideas? Locking lens ring to camera is tight. Front element is tight. Lens security lock is tight.

Re: EX-3 losing infinity focus
 

Was the iris completely open during the Auto FB adjust? When doing a Auto FB adjust, you also need to make sure there is proper lighting on the target and the iris is completely open.

Print out a Siemens star just in case to do a proper adjust. The proper distance for a FB adjust is also 3 meters or 10 feet.

Re: EX-3 losing infinity focus
 

But does an inferior flange adjustment result in an intermittent loss of infinity focus? If it's off, wouldn't it stay out of focus?

Re: EX-3 losing infinity focus
 

I repeated your scenario, (ND2 and infinity focus) on my EX1R, and the only thing I could see happening was that the very end of the focus ring on Full MF is not infinity. Infinity is slightly before the end of the ring. Remember that the EX1 and EX3 (with stock lens) use a rear-based focusing system that is servo driven. (Even when Full MF is engaged) Traditional manual lenses use front focusing systems, but the side effect is breathing. This method means there is very minimal to no breathing when focusing.

I experienced a complete backfocus failure at least once in my EX1R's lifetime but it hasn't happened since, I did a reboot and everything was fine afterwards.

Does this happen as you're switching ND filters?

Re: EX-3 losing infinity focus
 

Jack: in the outdoor example, yes, it was when the ND2 engaged that distance focus when away.

Following your advice, I re-flanged the lens inside with dimmer lighting so that the iris would be wide open...and at exactly 9 feet from lens to star chart.

Looks good at the moment. Shooting with the camera in the morning, so we'll see if the problem repeats itself!

Re: EX-3 losing infinity focus
 

Doing a Siemens Star backfocus adjust in outdoor daylight is too bright. Indoor controlled lighting is very important to a proper FB adjust. It's also important not to have complex details surrounding the Siemens Star so that the 2nd step of adjusting the backfocus on wide does not get confused.

For a Siemens Star, position the very center of the chart in the center of the frame at full zoom.

Re: EX-3 losing infinity focus
 

yep, I did that yesterday. All looked good.

Today, outside, no infinity focus, regardless of power down and booting back up. May be time for a call to Sony service.

Re: EX-3 losing infinity focus
 

I find that a star chart is too small and 3m is too close. I normally use a flat wall with a texture or pattern. A brick wall or wall with wall paper work well and I place the camera at least 3m from the wall, typically between 3 and 5m.

One last thing check that the contacts between the lens and the camera body are clean.

However if the back focus routine is completing correctly and your still having issues it does sound like it may need a service.

Re: EX-3 losing infinity focus
 

Quick follow up: the lads at Sony Service say the infinity focus issue was caused by a "floating" front element in the lens. Only a $300 fix. At least it wasn't the lens contacts or an interior board issue!

Re: EX-3 losing infinity focus
 

Good News!

Re: EX-3 losing infinity focus
 

Hmm, must be the steadyshot. Then the problem is the lens.

IMHO, fully manual Fujinons would not have this problem as there is no Steadyshot and the backfocus is even manual.

Re: EX-3 losing infinity focus
 

I've seen the front lens element become loose on a few cameras. It's normally obvious as when you clean the lens you can feel it moving. The cure is normally just to very gently tighten the large ring that holds it in place.

Re: EX-3 losing infinity focus
 

Alister: that's the thing that worries me a bit. I had remembered you mentioning that in another post, and itwas one of the first things I checked when this issue presented itself.

To my explorations, the front element was tight and there was no adjustment possible in the front ring--everything seemed locked down.

But maybe I wasn't pushing and twisting on quite the right spot...