Rolling Shutter
 

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

Hi Robert....
 

Go to Google, and type in:

"cmos rolling shutter".

If that doesn't answer your question, I don't know what will.

BTW. A good many of the links lead straight back to DVinfo.


CS

No your picture won't "warp" from a photographer's flash. What you'll see with flashes is that they won't always illuminate the whole frame. This effect will happen top to bottom. In other words, you might see the flash just on the top of the frame or just on the bottom. Whether or not this will bother you or not is something I can't tell you. To me it doesn't look that different from the shadows you get from a flash anyway. It may drive you nuts, but I doubt your customers would even notice.

The "warping' effect comes during very fast pans or jerky hand-held movement. To my eyes, this problem only happens during motion that is too extreme to use anyway.

As far as I'm concerned, the concern with CMOS's rolling shutter is quite overblown.

Disguising the CMOS Rolling Shutter (Flash) Effect
 

Yep, I agree!

However, someone posted a good solution on here a while back as well (sorry to that person - but I can't easily find the specific post right now.) Basically, if I remember correctly, what he did was select the instant that the flash appears in the NLE (and as Laurence states, only part of the frame will be flashed/overexposed) and then he overlayed a blank white frame for that brief instant.

I can't remember if he did it as a solid or partly transparent frame - but the result was stated as being a more "natural looking" flash effect. Personally, it does n't bother me so I've not experimented with this idea - but just mentioning it for anyone who needs a potential solution!

Hope this helps!! And if anyone knows the specific post please add the link in here. Thanks!

http://www.spike.com/group/filmfest?...wOption=images

Go to about 30 seconds in and there is a quick snippet of an interview on the red carpet. So many flashes are going off that at one point they look like they are rippling up and down the frame. Some parts of the interview weren't so bad, others were worse. This was shot w/a V1U.

If a big part of your job is shooting events w/flash photography I'd stay away from cameras w/CMOS chips and rolling shutters as long as possible.


-A

The Demi Moore interview is the only place where it is really noticable.

It seems to me like there might be some shutter speeds where the effect is worse than others. Has anybody experimented with this? It might be a simple matter of locking the shutter-speed at slower rate when you know you are going to be fighting with flashes.

There is a really good article about rolling shutter here:

http://dvxuser.com/jason/CMOS-CCD/

Not a Z7 owner myself, but I thought a link to a post on the Syntheyes forums might be appropriate here: http://www.ssontech.com/phpBB2/viewtopic.php?t=478

Scroll down to the eighth post for sample footage taken from a helicopter to see the worst of it, and go through the rest of the thread for details. Seems rolling shutters (whether modern CMOS sensors or the old tube cameras) cause problems when doing effects work involving a matchmove.

Rolling UGH
 

I have been new to the Rolling Shutter. and find that it is very annoying,
THE BIGGEST issue I find is when we use slow motion. You CANNOT use these clips as the half frame of flash is terrible.

It looks ok when you roll through in real time.

I think for this time i would rather buy a Z1 or go JVC and then wait until they introduce global shutters to the cmos cameras

Thumbs down Sony

For somebody like myself doing documentaries, it is pretty much a non issue. I see a bit of rolling shutter once in a blue moon. On the other hand, I can see where it would be a real issue for somebody shooting weddings or paparazzi style stuff.

I like the idea of overlaying a single white frame over camera flashes. I use Sony Vegas and I'll bet the whole thing could be automated with a little script.

I have only shot a couple of weddings with my Z7's so far, but I did notice the rolling shutter last night. This totally sucks for anyone that shoots anything with flashes (obviously). Does this problem rear its head under any other conditions?

http://www.chaddyleproductions.com/2...lling_Test.wmv

This wedding highlights clip shot with the Z7U is filled with examples of the rolling shutter in slo-mo. Doesn't concern me one bit, as I don't think my clients care how a flash manifests itself in video - it still looks like a flash.

http://www.indyvisual.com/blog.htm ("Joanna & Louis")

When I see this wmv clip is like watching old film stock adding effects. some parts the rolling just roll from top to bottom. is that so bad on this Z7 rolling shutter !!!!!!!!!

It's the same ClearVid sensor so if you move it too much, It could be just as bad. That's why the Z1U is still a commodity to matchmovers.

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?

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

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.

more testing needs to be done
 

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.

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>.

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

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...

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.

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?)

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

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

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?

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

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!

Chad...............

Did you do a back focus on the camera when you first got it?

Ryan,

I was told that I didn't have to adjust the back focus unless I had problems. This was the first problem that I have had with the camera. I did read a little about setting it up and its going to be the next thing that I try.

Chad, checking backfocus is easy, on all my pro lenses you simply setup a test image

http://www.dsclabs.com/

http://www.bealecorner.org/red/test-patterns/\

zoom in and focus...zoom wide and if out of focus (manual focus)

loosen the backfocus screw and adjust

p.s. shoot wide open and Don't over tighten( I onced cracked my back focus ring on a jvc-3)

also a long time ago on a old tube camera my backfocus screw loosened up on me and didn't realize untill 10 minutes later, so it is good to know where that adjustment is and check occasionaly

any chance of uploading footage with multiple flashes going off
thnx steve

Yeah...... the lens comes attatched so i would have assumed that you didn't have too............ but it's worth trying anyway.

Edit:-
Oh........ and i'm pretty sure that a test pattern comes with the camera..... did yours?

Both of them came with the test pattern. A previous post suggested that I should remove the UV filters and see if that helps. We have 5 weddings this weekend, so I'm gonna give that a shot. I'll keep you guys updated on what happens.

That looks like the autofocus went haywire, has nothing to do with back focus.

Hello,
There is no backfocus ring on the Z7 lens to adjust the backfocus.
We have just to focus in tight shot then adjust the focus in wide shot.
It's clearly impossible to adjust a focus on the shorter focal lenght because the focus stands still from 2m to infinity... So the auto mode seems to be the more appropriate.
On my own experience, I 've never achieved a correct back flange on my Z7, using manual or auto mode.