I was thinking this, too - and it makes me wonder if the Siemens star (or the chart you linked to) with contrasty edges radiating in all directions, might actually make the FB adjustment less accurate. In any case, I doubt that the multi-angular image is helpful at all, except to us humans. Might be worth trying some vertical black tape lines on the wall.

It would be great to see the exact technique that Sony recommends (will there ever be a service manual published for this camera?), though if it's the same technique their service department has been using on our cameras, perhaps it's not all that effective...

I'm pretty sure they use something not unlike the zeiss digiprime back focus tube. It was once described by a sony tech that they need a jig to make the adjustment, and this would be the easiest and most consistent way to do it.

-Sean

For me, Gerald's method improved my backfocus with ND1 filter on dramatically. So I'll take the chance in this thread to say: thank you Gerald (and others who have contributed!)
I have an important shoot, and I would not be able to send my camera back to Sony now.

The backfocus adjustement was really easy, and I'm a real noob at these things, but it worked. I have an even older firmware: 1.02.

Just to update you that I decided to go on with the adjustment (using the plasma displaying the Siemens star chart), and it worked.

Not saing it's perfectly sharp in all ND positions, but it's close.

Will have to do until the firmware update (whenever it happens).

Thanks Gerald for making us less scared off by the procedure involved!

After very careful examination (using my new 50" plasma - the 24" LCD I used before was simply too small!), I must admit that my adjustment has NOT been quite successful, after all :(

Before, the ND2 setting was the softest. Now, it's almost fine; the ND1 is tad sharp, but unfortunately ND off got worse. Much worse, I am afraid.

Before another attempt, I'd like to ask those who fully succeded to tell me:

- did you engage the ND filters in any special sequence?
- did you leave the back focus menu for changing ND?
- after engaging a given ND setting, did you zoom in fully and focussed to your chart before executing the adjustment procedure?
- do you think I should repeat it for all 3 ND settings, or just the one that I really need to improve (ND off)?
- any other consideration that I didn't mention?

Thanks in advance!

I´m sorry to hear that!

I started with ND2 and worked down to ND OFF
No I didn´t

Yes I did!

Yes I would do that.

Thanks Gerald,

I don't quite get your last response - is it that you would repeat the procedure for all three, or just the one offending ND setting?

I wouldn't like to spoil the other two!

Piotr,i did the same as Gerald did in the above post.
Nd off the ND1 then ND 2 though.

Paul.

Ups, sorry!
I would do it for all three once again.
I did it a couple of times as well.

Hope it works for you.

regards,
Gerald

Thanks Gerald!

One more question to all dealing with the back focus problem/adjustment:

The usual way of checking the back focus is of course zooming in-focussing-zooming out and checking the focus. As I said, after my first adjustment it's now OK with ND 1 or 2 on, but not with ND off.

However, I am observing another thing which I am not sure about: when I am in focus having say ND2 on, and switch to ND1, I'm loosing the focus slightly, and have to re-focus (the same can happen when going e.g. from ND off to ND1/ND2, etc.) Now: is this normal, or is it another way of back focus manifesting itself?

I haven't tested it thoroughly enough to unambiguously tell wheter this is due to the DOF change due to the aperture change at ND filter switching, but I guess it is possible... Any opinions?

If you are making the stop compensation Piotr, you should gain more depth when going from ND 2 to ND1. It could easily be that the camera is now compensating for each filter independently, but not matching to each other. If you put the camera on a tripod pointing at something like a siemens star at a specific distance (doesn't really matter what) and measure the distance from the witness mark on the side of the body, do the focus marks in full manual mode match that? If they are significantly off, that is a good indication of a back focus problem.

-Sean

Sean,

Roughly speaking, the distances do match. However, this is not a conclusive indicator, as every tenth of a millimeter matters, and my measurements are really just approximations!

Also, I'm aware that opening up the iris to compensate for ND decreases, and closing down - increases DOF. The examples I have given of changing ND's and loosing focus are not based on "scientific" observations; I just want to know if everybody else can sometimes observe loosing focus when in Auto Iris mode and changing ND filters...

The thing is that while this could be explained without necessarily blaming back focus, I didn't experience it with my previous camera (the V1E) - but than agian, it had much deeper DOF being 1/4".

Taping out the lens doesn't have to be accurate to the millimeter, since the marks on the lens aren't that precise anyway. As long as the lens doesn't say 15 feet instead of 3, there isn't a big problem. I've never noticed losing focus while switching from a heavier ND to a lighter one, only the other way around as the DOF shrinks. It could easily be a software problem that is solved by the new firmware. In theory, the ND filters should be the same thickness, in which case they wouldn't affect the back focus, but perhaps the calibration is off for one of them, or the filters are slightly different. At this point I'd believe either one.

-Sean

Unfortunately, I am loosing some (long distance) focus when in full wide, the ND is switched from 1 to off - which of course denies the DOF change explanation.

Whether this is a software problem, I really don't know - I will be repeating the back focus adjustment procedure. I am not optimisticc however, as there is no apparent logic behind this behaviour.

SONY, please give us some white paper explanation about it - what is adjustable by the procedure in the menu, and what needs the firmware update!

One thing that obviously cannot be fixed by a fw update is this stupid ND switch,, which either stick half-way, or goes by the middle (ND1) postion to easily...

Who has read the procedure for backfocus adjustment for the Z7U? (Hint)

George/