Rolling Shutter

[Ryan Lester]

To Chad and Bob................

Just a question.

The flash problem seems to be highly visable when the setting is darker, such as your reception footage.

I'm just wondering............... did you have the camera in 'Auto' mode during this time?

Is it at all possible that it becomes worse due to the shutter speed that the auto focus will change due to the darker settings?

[Brian Rhodes]

Originally Posted by Robert Bec

What is a rolling shutter problem i shoot weddings is this going to effect me i heard the picture will warp from the photographers flash.
Has anyone experienced any problems with the Z7

regards

Robert

I think this is a none issue for weddings I shot over 50 weddings with my V1U
take a look at the wedding demo shot manual 30p shutter 30 there are photographers flashes when the bride comes down the isle in slow motion. I got almost the same affect with the FX1 and Z1. I did a red carpet event recently with the Z7 no big deal.

http://www.dvdaction.net/dvdaction_002.htm

[Marco Dias]

Here's a link to an article explaining the difference between Global shutter (CCD) and Rolling shutter (CMOS).

Useful information to those who want to buy the Z7.

http://www.bhphotovideo.com/bnh/cont...O=RootPage.jsp

[K.C. Luke]

Originally Posted by Marco Dias

Here's a link to an article explaining the difference between Global shutter (CCD) and Rolling shutter (CMOS).

Useful information to those who want to buy the Z7.

http://www.bhphotovideo.com/bnh/cont...O=RootPage.jsp

Thanks for this info. If you don't like flash on your camera get 3CCD non cmos chip. If you don't have flash taking part, get cmos. 2 cam may be needed for what events to due with.

[Steve Gerhart]

First let me say that the specs of the HVR-Z7 are impressive but all wedding videographers must contend with Pro and amatuer photographers.

Most Pros (including myself) use E-TTL (Evaluative-Through The Lens) flash exposure system that uses a brief pre-flash before the main flash in order to obtain a more correct exposure. So when I shoot the cake cutting for instance I will shoot 7-14 shots depending on action (which are doubled due to pre-flash) and guests maybe 20-40 flashes in 7-14 seconds of important footage. Alot of flashes! and yes I did count them from my last wedding.

I called Sony tech and they said that they have not set up and tested different situations.

So how does pre-flash before the main flash effect shutter?

Flash Duration is very short but why does some test footage "roll" more than one frame?

And has someone tested all shutter speed variations and settings?

I would love to set-up and test but at this point will not Buy a camera just for testing.

[Chad Dyle]

The camera was set to manual, but I did use auto-focus. Another problem I'm running into is that its hard to switch from auto to manual without shaking the camera. I'd much rather have a button to switch. Still, I'm sure I'll learn how to do it smoother in the future.
I'm lagging behind on getting that clip up. I'll have it up today <crosses fingers>.

[Steve Gerhart]

hello chad, was iris set to manual, the reason i ask is if auto exposure adjustment lengthens the roll, also what shutter speed

[Dave Blackhurst]

Had a bit of experience with rolling shutter in the consumer Sony CMOS cams - here's the tricky part...

The flash, if it coincides with the partial frame exposure will show the split frame effect. BUT it can also coincide with the full frame, or with no frame at all (probably not the perfect choice of terms, but hopefully you get the idea).

I ran some tests where I found a series of flashes (like redeye reduction + regular flash) yielded various partial frame flash exposures (i.e. top 1/4, top 1/2, bottom 1/2 bottom 1/4), and some frames with full flash, others with none.

SO, what you run into is a problem of co-incidence of the "flash event" with the camera exposure. It's more noticeable because of the split frame effect, but I also went back and looked at some stuff shot SD with CCD, and flash wasn't a picnic there either - typically 2-3 frames of massive pixellated blotchy yuck...

I hope this helps clarify the challenge that the technology faces when dealing with these short duration events (flashes going off). While in theory global shutter would improve by giving individual frames with full flash overexposure, it may not be as simple as it seems...

[Giroud Francois]

quotes:"typically 2-3 frames of massive pixellated blotchy yuck..."
this is a mpeg compression problem and not related to the shutter.
if by chance the flash duration covers all the rolling shutter scan, you probably will get the same blotchy yuck, because the changes between 2 frames is to heavy for the mpeg compression.

[Steve Gerhart]

thanks dave, why does the flash duration seem to last longer than 1 frame, i own many pro 3 chip ccd cameras and flash duration is never more than 1 frame

so do you think it is <when the flash occurs> during the nonuniform shutter that makes it last longer?

one test i would like to do is capture random ettl flash and examine frame by frame to see how long duration is in Manual Iris( i believe that exposue may be changing and that causes longer flash roll?)

[Chad Dyle]

These clips were shot monday night at a church I shoot at all the time. The camera was set to manual, but focus was set to auto. The Iris was on manual as well. The blurring seemed to be at the same distance each time a bridesmaid /groomsman would walk towards me.

http://www.chaddyleproductions.com/2...t/Blurring.wmv

[Steve Gerhart]

Hi Chad, I never use auto focus and the "real" lens is what i like about the camera.

I think once you get used to manual focus you will like it better, like driving stick shift. if you have time check flash duration <frame by frame> to see if flash is ever more than 1 frame

also what shutter and other settings are you using

[Kevin Walsh]

Chad that looks pretty awful. Do you think the flashes were messing up the autofocus or was the camera just having a hard time tracking moving subjects?

[Steve Gerhart]

Hi Kevin and Chad, focusing is difficult in low light conditions. this lens may need more light coming through the lens for accurate auto focus. Most pro lenses do not have auto focus.

Remove any add-on filters like UV, etc if you are using auto focus.

Flash is not the issue here

Flash issues with rolling shutter do not look bad here, do you have footage of intro or cake cutting, something with alot of flashes

[Dave Blackhurst]

OK, looking at the focus problems in that video, and that's just not right...

It did not appear to be related to the flashes, in fact there was some serious hunting that simply doesn't make any sense at all - nothing else that autofocus could be trying to lock onto, at least in some of the cases, which was my first guess. Sometimes it appeared that the camera was attempting to lock onto the background rather than the couple, but other times it was just all over with nothing in focus!

I think you may have a early production flaw or something. I've never seen any cam I've used hunt like that in anything other than horrid low light... obviously not the case here.

One other question, does the Z7 have an assisted focus option like the FX7? I use that to let the camera do it's thing, but I can adjust the focus ring as needed to fine tune as well as a bit of creative defocusing from time to time allowing the cam to ease into focus.

I did note that if you scroll through you can see the exact phenomenon I spoke of, several times I see a flash that is clearly "synchronized" to a complete frame, while others seem to be "half frame", or split between 2 frames (never seen a flash take more than 2 "half frames").

The more I see of these latest cameras the better my FX7 looks... and I was close to selling it!