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Image quality diagnose/troubleshooting SOS
(Not sure where to post this)
I just got 4 tapes from abroad for a doc I’m editing, 4x1hr ITV’s at 4 different people’s places. The guy was supposed to shoot with a Z1 (like 5 others ITV’s I shot here), and I assume he did. Right after he rushed the tapes to me, I had them captured and delivered into a FCP project.
Problem is that about a third of the material is bearly usable, with something like artefacts initially looking (to my uneducated eyes) like noise; I thought the guy may have used wrong gain settings or something; talked to him and he assured me that it was properly (in this case) set to 0db.
So it just basically looks like low quality/resolution video, although the SONY HDV deck says it’s 1080/50 HDV). Problem is that now I have the tapes, and what I see is difficult to describe over the phone (or here), and I’m not even really able to do a precise diagnose… except that the material is bearly usable (especially mixed with the 5 other clean Z1 shootings I already have)…I then thought it may have been caused by wrong capture settings, but it looks the same played within FCP’s capture window, or in canevas as a clip.
Lower quality is less obvious when the camera/subject stands still, less obvious too whith more light (like outside/day vs. inside). The artefact is almost unperceptible at the size of the deck’s monitor.
Also, part of the material (2/3) is ok… (ie regular Z1 HDV quality), and as far as I can tell, the switch (between lower and normal quality) does not occur within one clip, only between two.
Could that “description” possibly ring a bell to someone? Anything I can check to get a more precise diagnosis?
I think I’ll be able to manoeuver and deliver something acceptable (with the rest of the material I have), but I’m having 2 extra ITV’s shot by that same guy this week-end, so I better find something to tell him (given I can’t replace him).
Uh.
Thanks.
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5 Replies
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It could have been recored on a camera with dirty heads
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Doesn’t HDV and DV have “data code” that tells what the fstop, gain, etc. was? Sounds to me like he had the gain up. My DSR-11 data code will tell the F stop, gain, shutter speed, time and date that it was shot. I’ll bet you’ll find the gain was up.
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Ignatius,
The Z1 comes from the factory with the auto gain switched to the on position. Many who buy the camera don’t realize this and their first shoot is almost always ruined. Chalk one up for the engineer at Sony who made that decision… Could be that your cameraman, even if he’s experienced, made this fatal error.
DRW
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David is absolutely correct, and unfortunately your shooter may also be. If he had the silver gain position switch set to L(ow), but had either the “auto lock” slider set to lock or hold, OR had the plastic “Gain” button in the auto position, he did not have control of the gain setting.
With the Z1 you should be able to see all of the settings in the viewfinder when display is set to on. (focus, gain, white balance and shutter speed). If you don’t, then that setting is in auto and will compensate for your other settings. ie. you could be stopping down the iris and the camera might start pumping in gain to compensate….. and does so without letting you know. If he saw “0” as the gain setting in the viewfinder, than he was indeed in manual and had 0 gain.
The Z1 has one of the quietist electronic gain circuits I’ve ever seen. It would have to be really really high to get pictures that are “barely usable” and unless he was changing the lighting or exposure settings there doesn’t seem to be a good reason why it should change between clips.
Maybe you could post some still frames of his “good” and “barely usable” footage. If we could see the artifacts you’re talking about it might help someone figure out what’s going on.
Regards,
David -
Thanks to all.
I checked the data code on the deck, and as mentioned here, it definitely looks like the auto gain was switched on… (like gain bumping back and forth from 0 to 3, 6, up to 18db within a couple of seconds…).
I talked to the guy, and I think I can manage from here, especially if two more ITV’s are shot with proper settings over the next few days (I’ll be mainly using sound from the first set, + whatever image can be).
Thanks again, it helped.
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