A near miss disaster EX3

[Vincent Oliver]

Some regular readers on this forum may remember one of my early posts, http://www.dvinfo.net/forum/sony-xdc...3-useless.html. Luckily I managed to claim for a new lens on my insurance.

Last week I was on a job in Switzerland and could not work out why my lens was not focusing correctly. Fortunately I did discover and managed resolved the problem at an early stage.

I didn't want to put my video gear on the luggage in the aircraft hold so I packed the camera in a smaller Kata bag, this bag can be brought on as hand luggage. But because the bag was so tight when placing the camera in it the lens locking lever was knocked to the half way point, even though the lens lock was in position. this meant the lens was not focusing correctly, especially when used at the wide setting. This has the effect of placing a very thin extension tube between the lens and body. Focusing at a telephoto setting was OK but slightly soft.

As I said, I did discover the problem at an early stage, but had the lens locking lever moved another half inch then the lens would have met the concrete floor in a spectacular manner.

If you are using a tight fitting case or have packed your bag with accessories then make a point of checking your lens locking lever, better still use a larger case whenever possible.

[Derek Reich]

Yikes. Interesting about the effect on focus, though. I have traveled extensively for 3 years with my EX, and always carry it on the plane, and don't even put it in a case. I just put it in the overhead (usually with a coat or blanket underneath if possible) and go. I have never had a problem with the lens mount, however I find the 'lock' button pretty much useless. I can't see that it really does anything, because any time I take the lens off, it comes off by rotating the locking lever no matter what position the lock button is in. That said, I have a rather compulsive habit of always pushing the lever down to make sure it's tight any time I pick the camera up.... maybe that's why I've been lucky. I have heard lots of stories about the lens detaching on unsuspecting folks though.

[Vincent Oliver]

The locking switch is just a friction pad that pushes against the lens mount lever, so nothing too complicated or secure for that matter.

I will be checking the lever each time from here on in. I did lose one sequence due to poor focus, I just couldn't work out why the lens wouldn't snap in focus, I thought it was my viewfinder playing up. On the next shot the same problem showed itself and at that point I thought I would remove the lens and re-mount it. This is when I discovered the lever was in the half way position - Oooops.

We all learn by our mistakes, and fortunately this time it was discovered before an inevitable disaster.

A good tip to carry the camera on as hand luggage, another camera crew did just that on the same flight with their Alexa camera.

[Alastair Traill]

Quote: -“This has the effect of placing a very thin extension tube between the lens and the body”.

There is a useful formula that relates lens displacement to changes in focus. If the lens is further than it should be from the sensor the lens will not focus on infinity but on some point closer to the camera. For example if the very thin extension tube is 1/20 mm long, setting the lens at infinity with a focal length of 5.8 mm will focus on a subject ~2/3 metre away. On the other hand the effect at the EX3’s full focal length of 81 mm, setting the lens on infinity will focus on a subject ~ 130 meters away.

In other words the effect could be disastrous at wide angle but negligible at the telephoto end of the range.

[Vincent Oliver]

Thanks for that Alastair, I can confirm the result was unusable at the wide angle setting, although the sound track was OK, so not all was lost. I will overlay the sound on top of some factory shots.

On the subject of extension tubes. I have a Nikon lens adapter for the EX3 and a set of Nikon extension tubes, I have used a couple of the tubes together with a 105mm Nikkor lens to produce some interesting close up work. I also have a set of bellows which I must experiment with too.