I can fully vouch for what Matt said about the crash zoom focus issue, I have experienced it while shooting some 300-like action takes. I have a long render queue right now, but I will upload an example ASAP.

Regarding my "funny focus" issue, I'm kind of afraid to touch anything serious, I don't have Sony next door to go knock in case something goes wrong... but do you believe doing a BF should fix my problem?

The focus on the EX camera is completely electronic. There is no mechanical connection between the focus ring and the lens elements.

Traditional manual zoom ENG lenses, like the one supplied with the JVC HD100 use very complex combinations of lens elements that are mechanically connected together and move by different amounts relative to each other through the zoom range. This is done so that the focus remains constant through the zoom range. It's very difficult to get right and wear and tear of the cams and guides can lead to poor performance and collimation errors, it also requires a lot of lens elements some of which may need to be made from some very exotic types of glass. Focus itself is done by moving the front lens element forwards and backwards. The forwards and backwards movement by several mm of the front element is what introduces breathing as this slightly changes the focal length of the lens.

The lenses on most home video cameras and the majority of semi-pro cameras are of a much simpler and thus cheaper design with fewer elements that does not maintain the same focus distance throughout the zoom range (varifocal zoom). To make these usable for video an electronic look-up table is used that compensates for changes in focus by electronically adjusting the rear lens element as you zoom. On the EX cameras (and many other small camcorders) the lens is also focussed by adjusting the rear element electronically according to the look-up table. Because the rear element only moves by a tiny amount there is almost no breathing. Fewer elements means lower cost and reduces the need for expensive exotic glass. There is no breathing and the lens can be setup and calibrated electronically.

This technology is creeping in to high end lenses as well as low cost lenses as any mechanical wear can be programmed out of the lens and it makes larger zoom ratios possible. It may be that in the future all zoom lenses will adopt this technology as it makes the optical design of the lens much simpler which should lead to better image quality at lower cost.

I have had to re back focus my EX1 and EX3 from time to time. Rough handling by airline baggage handlers has upset my EX1 on a couple of occasions. I always use a flat wall with the camera perpendicular to it about 8ft away. Any type of patterned wall paper, textured wall covering or brickwork seems to work just fine.

Great insight, thanks Alister!

That's very reassuring - in that it's not a sign of i) impending doom or ii) the feeling of Camera Hypochondria. Just maintenance.

Alister,

Just wanted to make sure: is it enough to do it once, or is it necessary to repeat the procedure for each position of the ND filter switch?

Hi, Alister . . .

Sounds like great info. to know about. I have two EX1's which seem to be focusing fine. In the event I need to shoot a textured wall, etc. to help regain proper back focus, what is the procedure? Since there are no user adjustable controls for back-focus on the fixed lens EX1 how does one make back focus improvements the camera will store and remember?

Many thanks . . .

Ian

Ian

Take a look at


by Paul Kellett, a DVInfo member. To access the maintenance menu, press Menu while holding down Sel/Set and Cancel.

Well in that case that just Sucks :-)

Does anyone know how to get the EX1R to display the maintenance menu?

Does the EX1's computer have a separate BFocus setting for each ND position? Why is this necessary, technically speaking?

My EX1 files via ClipBrowser show ND1 even when ND is not used, is this normal? Will this affect Auto FB?

Hey, Nick . . .

Thanks for sending the link of Paul Kellett's video demo of how to do a back flange adjustment with the EX1. I didn't even think it was possible to get into a maintenance menu system to perform this adjustment yourself. Very cool indeed. Should my cameras need to be "touched up" I'd rather do this procedure myself then pay Sony big $$$ to do likely the same thing to fix a focus problem.

Thanks once again for posting your video!

Ian

Hi, Ivan . . .

I don't know how the EX1's back flange adjustment really works. But when Sony, for instance, does work to correct a focus problem with a camera having a a removable lens they usually need to "touch up" / set up the focus for each of the ND settings. This is because a good camera has true (non electronic) glass filters. Each filter (the EX1 has two) has a different thickness. Also, each ND filter may have (like each glass element in a lens) slight imperfections that back focus adjustments attempt to correct as best as it can. This is why often doing focus adjustments for each of the ND's is useful. But whether you need to do a back focus set-up for each of the ND settings with the way the EX1 records back flange adjustment data is a very good question. I don't know if the camera has the capability to store and retain back focus data for each filter setting.

Ian

Hi Ian, thanks for your answer. Tomorrow I will run some tests regarding Auto FB and different ND filters and report here.

From the early information almost 2 years ago, I remember it was recommended to run the back flange adjustment procedure separately for all three ND settings (off, 1, and 2) - and yes, some people mentioned there's something like a look-up table for the lens to remember the setting for each. Whether this was conclusive and 100% certain - well, I'd like to know myself..

Alister?

Alister, so have you run the procedure just once, or separately for each ND switch position?

Thanks.

Hi Piotr, hi everybody and sorry for returning to this thread later than expected.

I run my backfocus adjustment with no ND filters at about 6 feet with a Siemens Star, and it didn't work, it was way off. Running the adjustment at 12 feet did it for me.

I tested my camera's backfocus with targets at 6, 12 and 18 feet away and with each ND position (OFF, 1 and 2). Everything seems to be OK. Remember I haven't run any backfocus adjustment with ND filters.

Of course, this is my case, it might not be yours. Maybe this thread bump caughts Alister's attention and he can clear this up.

I'm still afraid though, so I have sticked the Siemens Star to the back of my clapperboard. Under controlled situations I will always use it in conjunction with the peaking function, with this method I guess it's impossible to fail under simple circunstances. On the other hand, this won't easily save me if I have some zoom-in/out shots, but at least it will let me know if everything is working properly or not. I wonder how the backfocus problem affects the shot transition function's focus, any insight?

Cheers and good luck!

May the Focus be with you.

Ivan.