Z7 push to auto-focus

Laurence wrote on 4/4/2008, 10:07 AM
The "push to auto-focus" function took me a bit of head-scratching to figure out. The good news is that it works just fine once you know how it works. Once you realize what is going on, it makes sense that Sony did it the way that they did.

Here's what is going on with the focus wheel:

There are two positions on the focus wheel: A and B. You get to these by sliding the focus ring forward and back, just like on an EX1. In the slid back (or A) position, the focus ring has start and end points and feels very much like a pro camera focus ring with exact positions for various amounts of focus. In the forward (or B) position, the wheel spins continuously and is more like what you would expect on a DV or HDV camera.

The way the camera comes configured, the A position is manual focus and the slid forward B position is auto-focus. Well the A position is always manual focus, but the B position is actually programmable and does not necessarily have to be set for auto-focus.

The "push to auto-focus" function cannot be set up in the A position and if you think about it, it makes sense. To do this they would have had to add a servo motor or something to actually move the wheel to the correct position. Adding a servo motor would have also added resistance. It is just something that can't realisticly be done.

You can set up a "push to auto-focus" function in the B position however. The way you do it is to assign the B position to manual focus, then assign one of the programmable buttons to "push to auto-focus". The most practical way to do this is to assign two buttons, one to turn autofocus in the B position on or off, and another to "push to autofocus".

If you set up the "push to auto-focus" this way, it acts exactly as it should. You have the focus wheel in the forward B position and assigned to continuous turn manual focus. You zoom in to what you want to focus on, press the "push to auto-focus" assigned button until it focuses, let go of the button, zoom out and start shooting.

Comments

craftech wrote on 4/4/2008, 10:24 AM
Ah, I get it. I have been really puzzled as to why they would omit that invaluable feature on a $6000 camera.

The other question I had about the camera was why you chose it over the EX1 which has three 1/2 inch imagers instead of three 1/3 inch imagers as on the Z7U.

Wish I could find that head to head comparison that indicated that the perceived brightness on the EX1 was better die to the higher resolution despite the better technical light gathering ability of the Z7U.

It seems that just like with the PD-170, in stage lit situations you will end up with incandescent blobs for heads instead of facial features when zoomed out.

John
Laurence wrote on 4/4/2008, 10:42 AM
Why the Z7 instead of the EX1?

I do documentary stuff. On the last interview I did, I shot about 90 minutes of interview. That's thirty minutes more than I could do with the two 8 gig cards that come with the EX1.

Also, a good interview is hard to get. I am scared to trust backing up something so valuable to anything other than tape. Hard discs can crash, optical discs can get errors that make the whole thing unreadable, but tape always seems to work.

I just had a mishap where I accidentally deleted an interview I had been working on off my hard drive. No big deal, I just went back and got it off the tape. With an EX1 that would have been a major catastrophe.

Then there's the price of media. I am currently using 16GB and 32GB Transcend CF cards. They cost $79 and $150 respectively. Try pricing 48GB of Sony SxS media! It costs a whole lot more than $230!

I do a whole lot of hand-held shooting. The Z7 feels a whole lot better balanced in your hand. Then there is the battery drain issue on the EX1...

Picture me getting off a bus in the Amazon somewhere with an EX1. I would have to put the battery in the camera and mount the camera in the shoulder mount that makes working hand-held practical before I could even start shooting. All the while I would be wondering where I was going to do my next footage transfer on my laptop and where the safest place to store it would be in the mean time... all that verses grabbing the Z7 out of the camera bag and feeling for the extra tape in my pocket...

I just couldn't go with the EX1, at least not yet.
Serena wrote on 4/5/2008, 5:33 PM
>>>>Picture me getting off a bus in the Amazon somewhere with an EX1<<<

Your reasons for choosing the Z7 were well thought out and it is a fine camera. However your example scenario does go "overboard", so just to set the record straight: there is a technique for hand holding the EX and the battery doesn't drain away at the rate you believe. After fully charging a battery I leave it in the EX overnight (unless I've got a heavy day's shooting) to discharge it a little (proper care of LIH batteries) and it takes about 18 hours to drain to the recommended storage level. So in your scenario you would have, if being very cautious, have taken the battery from your pocket and popped it into the EX and been ready to shoot. Two 16GB cards provide you with 140 minutes of recording at 25 Mb/s (HDV data rate used by the Z7) and my practice is to capture cards to a portable HDD with a backup copy on the laptop HDD. The issue you might well have raised is the current cost of SxS cards versus the cost of tape, but since the cards are used continuously the argument is "up front cost" versus "running cost".
However you probably see this a nit-picking, and anyway I'm not intending to suggest any fault in your analysis of "which-is-the-right-camera-for-me".
Laurence wrote on 4/5/2008, 7:04 PM
Points well taken Serena. There is no question that the EX1 is a fine camera and it is difficult to argue with full 1920 x 1080 x 35mbps resolution. None the less, I am quite happy with the choice that I made and the picture I got on todays shoot (an outdoor triathlon event which I shot a 30p) was just stunning. :-)
craftech wrote on 4/6/2008, 8:20 AM
Serena,
Have you shot a stage production with the EX1? That is the camera I am probably going to buy in a few months. For me, low light shooting is paramount and while the Z7U seems a good HD follow up to the excellent VX2000 I now shoot with it doesn't seem like it will get me any more resolution zoomed from a stage show than my vx2000. It seems that I will still end up with incandescent blobs for heads due to the three 1/3 image sensors like my VX2000 has instead of the three 1/2 sensors of the EX1.

What do you think?

John
Serena wrote on 4/7/2008, 2:47 AM
John,
No, I haven't done that. I've shot in remarkably poorly lit places (sucessfully, for the pupose) so I've been very impressed with "speed" and latitude of the EX (using the cine gammas) which would help cope with low key stage lighting. Obviously you can expose for the faces, but not a lot of help if in the image they're floating in blackness. The EX has nice capabilities for controlling low light chroma without increasing luma, which might help also. The SDI HD output at 10 bits might also assist latitude. As always there is the question of how much noise is acceptable. I wonder if Bob has had a stage shoot; we could always set up a test scene or attend a lighting rehearsal for some test shooting. I might look into that if important.

Serena
farss wrote on 4/7/2008, 4:01 AM
Well not exactly a stage show, probably something worse. A show in a dimly lit night club. I had to kneel on the bar while taking care not to burn my ear on a downlight in the pelmet. I must have looked quite a sight and I think after two weeks my knees have recovered.

Of all the horrors, for much of the show the only lighting was deep blue, focussing was very difficult. Much of the lighting had some odd frequency flicker that interacted in 'interesting' ways with the rolling shutter as well.

All things considered though the camera performed remarkably well!
Around halfway through the show I dropped the gain back to 6dB and that really showed. I didn't really need that much gain but I wanted enough DOF as I knew accurate focussing would be my undoing and given my shooting 'position' even reaching the focussing ring without falling off my perch was difficult.
I had the camera set to Cine4 and a tiny amount of Black Stretch, shooting 1080i SP. I've got to shoot the same show in the same venue is a few months and I'll be better prepared with a custom camera mount so I can sit on the edge of the bar, phew.

So, the EX1 should be very good for stage shows. Max record time could be an issue though if it's a long show with no breaks. However, you do need a certain amount of skill, the camera really needs to be in full manual to perform well and you need time to get to know it. I think that shoot really showed me just how good it can be but you do have to work at it.

One other thing that did impress me. I recorded the audio for the show from the desk into my R-4 and over 1 hour sync held better between the R-4 and the EX1 than any other camera. That might have just been good luck that my R-4 and my EX1 are both at the same end of the tolerance.

General recommendations. Don't use more than 6dB gain unless you really, really must and that could mean getting good at focussing. Record in HQ if at all possible or even shoot 720p. Lots of gain + blue light = noise = stressed SP codec. Improve any of those and the image looks a lot better.

Bob.
craftech wrote on 4/7/2008, 5:36 AM
Thanks Bob and Serena,

That night club shoot is giving me aches and pains just thinking about it. My neck kills me when I have to sit in an auditorium seat and operate a camera on a tripod mounted on the seat next to me.

In terms of "full manual", that is how I shoot nearly all of the shows anyway so that won't be an issue. The recording time might. Usually I can change tapes after an hour to an hour and ten minutes, but there have been times where I had to shoot EP for two hours. Sometimes.

Still, it doesn't seem like a Z7U is really a step up for what I shoot. Except for the format the VX2000 and that camera will probably produce similar images. The EX1 however, seems like it will give me better resolution at a distance in the dark with funky stage lighting. Of course, on the other hand, the wide screen format of either camera would seem more conducive to the shape of a stage than a 4:3 format without having to resort to a wide angle adapter.

John
Serena wrote on 4/7/2008, 5:50 AM
Bob, that sounds like a real mean ordeal! Were you hand holding as well? These sort of jobs need an assistant, but I guess there wasn't one on this occasion. The EX enables continuous shooting if you have enough cards SxS cards or an assistant to capture cards on the fly.
craftech wrote on 4/7/2008, 6:23 AM
The EX enables continuous shooting if you have enough cards SxS cards or an assistant to capture cards on the fly.
===========
Ah yes, I forgot, the EX1 has two slots and switches seamlessly between them so you can stick a card in one while the other is being recorded to and alternate endlessly (if you have enough cards).

John
Laurence wrote on 4/7/2008, 6:36 AM
I think the Z7 would be more of a step up than you realize. If you shoot at 24p or 30p, you are getting a real resolution of 1440 x 1080. Your real resolution with the VX2000 at 60i is only 720 x 240. That is twice the resolution accross and four and a half times the resolution up and down. The EX1 is even better at two and two thirds the resolution accross and four and a half times the resolution up and down. The colorspace on both cameras is superior as well meaning that you will have much more detail in the colors, especially in lower light.

The progressive modes of both the EX1 and the Z7 are perfect for this type of application. 24p in particular is going to let you use a slower shutter and collect more light in each frame.

For that kind of shooting the EX1 is probably the better choice. You aren't hand-holding, and by capturing the first card while you're shooting the second, you could have the show transferred almost immediately after it was shot. The Z7 is very good in low light but the EX1 is even better.

To be honest, either camera is going to look a whole lot better than what you think.
craftech wrote on 4/7/2008, 6:38 AM
Thanks Laurence,

Points well taken. It would be interesting to read a review of the cameras by a stage event shooter. I couldn't find any - not yet anyway.

John
farss wrote on 4/7/2008, 6:44 AM
Not hand held. I had a Solo as short as it would go. The feet were about an inch from the edge of the bar all around and I had maybe 6 inches where there was a step in the bar for my knees. If the camera did take a tumble it would have been into someones diner.

Bob.
Edit: The venue is called Slide. Should give you some idea of the lighting conditions.
craftech wrote on 4/7/2008, 6:46 AM
The other thing with stage shooting is not just the low light. It's the uneven lighting as well. A few performers with too much light on them and others with not enough. Then they move from one area of lighting to another and suddenly not just one but TWO spots are on someone or two or more. Zoomed out it's even worse trying to get details in all that. When the lights are really low or almost gone, it is sometimes easier to deal with than under the conditions I just described.
It is more for those types of scenes (the more common for me) that I am trying to find something better.

John
farss wrote on 4/7/2008, 7:04 AM
What you need is more dynamic range. I've mostly edited (but not shot) footage from a 570, 1/2" DVCAM camera. It does very well under those conditions. However the client who drives it has a simple trick. He sets exposure for the brightest thing under the full stage lighting and doesn't chase the lighting and the results are very good. He also uses a PDX10 as a B camera for these shows. Now that's got tiny CCDs and yet using the same way of setting exposure it doesn't look too shabby at all when in tight.

The EX1 seems to come very close to the performance of the 570 under extreme lighting. Given that the photosites are relaitvely minute compared to those on the 570 and it's 1/3 the price of what the 570 cost without lens that is fairly remarkable and it doesn't give up any image tweaks to the 570 either, it's probably got more. Plus the 570 is strictly 50i. The EX1 gives you a large choice of shooting formats and that can be a big plus. 24/25p with shutter off gives you another stop.

Bob.
craftech wrote on 4/7/2008, 7:19 AM
However the client who drives it has a simple trick. He sets exposure for the brightest thing under the full stage lighting and doesn't chase the lighting and the results are very good.
===============
I do the same thing normally, but if I am zoomed in the results are good. Zoomed out and covering the whole stage, the details on the performer's faces in the brightest lit areas are practically gone especially post compression in the ifnal product. Incandescent blobs much of the time. The VX2000 just can't pull the resolution lit that way from a distance and retain what little there is after compression delivered in SD especially which is what I will still be doing for any time in the near future.

John