Photographer's Flashes

[Vaughan Wood]

Has anyone else noticed the weird effect that the rolling shutter produces on photographers flashes.

I have been using my FX 7 at weddings for almost 3 months now, and was noticing that each flash seemed to produce 2 flashes in the viewfinder instead of one! Very Disconcerting!

It is the rolling shutter doing this of course, and seems to be a permanent "benefit" of this technology.

I have attached stills of two adjacent fields to show you what I mean.

When at the wedding or reception it doesn't matter much, as you can put it down to a pre-flash, or even two cameras, but when you at the bride's house and there is only one photographer in the room, it is annoying that you see two flashes virtually every time the photographer takes a picture.
I'm sure it will only be a matter of time before a bride picks it up.

Anyone else noticed this?


Cheers Vaughan

[Vaughan Wood]

Here's a very small clip of slo mo to show you what I mean.

One flash shows as two distinct flashes (50% slo mo)!

[Jim Michael]

Maybe it's the red eye prevention feature that's supposed to constrict the target's pupils.

[Vaughan Wood]

That's what I was calling a "pre-flash".

No, it's a professional photographer in the bride's room with a pro DSLR and only one flash.

I've seen it in every wedding I do, and at first thought it was a camera fault, until I slowed the footage down and realised it was the caused by the rolling shutter.

It's alright unless you slow the footage down in editing, ....as you do for a wedding video.

The next flash that went off in the room was effected even worse than the first one.!!!! (This is the last sample, I promise)

[Marshall Levy]

Wow, that's really bad. I haven't noticed this myself, though, interestingly enough. I'll check some stuff and see....not good by any means.

[Dave Blackhurst]

Hi Vaughn -

I noticed this same effect the other night while editing some footage shot with a Sony HC1 - single CMOS... strange that this phenomenon hasn't gotten more attention...

It's very odd seeing a flash that happens in s fraction of a second bounce from the top half of the frame to the bottom half of the frame... I had to look at it a few times to convice myself I wasn't halucinating... that and I noticed on frame by frame scrolling that when a flash goes off, it often "frags" parts of the subsequent frames - patches of pixels almost as though it overloads the compression algorithm - looks blotchy, like an overcompressed .jpeg...

This video was shot in an afternoon wedding, adequate but not great light. The only way I noticed it was on a 24" computer monitor, full size... I'm guessing that it might become less of an issue once I render it.

Probably wouldn't be an issue MOST of the time, but it sure presents an issue when shooting a wedding... and flashes are going off every which way! Another reason to ask for no/limited flash photography!

This rolling shutter thing is apparently a CMOS issue, and it sure presents a few challenges when shooting - got to really keep the cam stable while shooting - anyone know if the Canon HV10 single CMOS has this same peculiar problem?

DB>)

[Vaughan Wood]

Hi Dave,

Interesting to hear the HC-1 has the same "feature".

This footage has really shocked me today.

I guess I've got away with it before now because a lot of my weddings in the last couple of months have been "no edits" or "limited edit" jobs where I rarely use slow motion in my editing, and this is the first one where the photgrapher was there right through the bride getting ready, shooting everything that was going on, so I couldn't avoid getting some flashes in slow motion.

I was about to go and buy a V1 as we need two cameras for many jobs, but as most of our work is weddings, I'll have to re-assess it as this is just unacceptable to me.

Cheers Vaughan

[Bob Grant]

Flash and strobe lights can be a big problem with video.
Even with conventional cameras I found that you can get one field that is totally different to the other one, get a lot of them and it seems to freak a mpeg encoder right out.

[Steve Mullen]

Originally Posted by Bob Grant

... and it seems to freak a mpeg encoder right out.

Correct -- watch any HDTV program with bright flashes and watch programs pixelate.

Had to laugh that the shower of conffetti at the end of the Oscars would have killed the picture if it had been broadcast in 1080i on either CBS or NBC.

However, I saw no artifacting on motion with the Super Bowl -- so CBS must be really pushing quality. First 1080i sports I've ever seen not filled with artifacts.

Actually, CBS has gone public about not wanting stations to multicast which is a big step forward in that they admit pix quality is compromised by anything but a full 19.4Mbps path.

Bottom line -- even pro big $$$ has issues.

[Dave Blackhurst]

Thanks for the observations guys! I feel a bit better now.

It's so easy to find flaws with technology while missing the "plusses" - the majority of the footage I mixed down looks awesome, and to quibble over a few frames is proably not really "fair" compared to the majority that look great...

Vaughn - I've in the past used the approach of "micro-editing" an offending couple frames out of a sequence if something is really obvious - not sure the implications in HDV/long GOP, but it may offer a way to "cover" if you've got any spots that are too "bad". FWIW, I ONLY noticed the effect when the timing of the flash was "perfect" so that it would be right on the "line" between frames (lousy description, but it's early). It was strange watching the flash on the top and then the bottom of the screen, but it wasn't a "big" issue, just more of an observation!

I think people are used to seeing a bit of pixellization now and again, and won't take offense - for those of us who want our stuff to look "the best", sure it's frustrating, but someimes we miss that the key is the CONTENT, and ultimately that content looks better overall when shot in HD vs. SD... that's what gets us ALL excited about it, and keeps us on the bleeding edge!

I wonder if it will be possible to eliminate the rolling shutter issue (which is what this actually is now that I've seen it and understand it a bit better) by addressing the chip differently? Like all things electronic, it should be a matter of speed and or programming... all in due time, meanwhile pick the tool that gets the job done, I guess!

DB>)

[Stu Holmes]

Originally Posted by Dave Blackhurst

Vaughn - I've in the past used the approach of "micro-editing" an offending couple frames out of a sequence if something is really obvious

Yes this was going to be my suggestion - zap those frames where it looks really bad. Don't know how may frames that would be. But try it and see if it produces a better result.

I have heard that rolling shutter is worse/mpore noticeable at high shutter speeds. So, perhaps, in these situations, try slowing shutter speed down to 1/25th (when there's lots of flash photography going on) and see if that helps reduce the effect. You could do some simple tests to see if changing shutter speed helps at all.

[Vaughan Wood]

On some of the flashes that were affected severely in slow motion, I have put a quick "flash' over the top, to make it look like the original flash.

A Vitascene flash transition seemed to have the best effect and it looks much more natural.

I am convinced wedding editors should be made aware of this limitation of the rolling shutter camera, as I have decided to limit this camera to 'deck' and non wedding use and and probably go to the heavier Z1 for my weddings.

I see mistakes on TV every day which I can't fix and accept like everyone else, (I spent 10 years in the industry), but when I can fix a perceived fault in my own productions by changing directions, then I will.

Wedding videographers like myself, coming from years with VX2000s and PD equivalents, have been looking forward to their replacement with a similar weighted and styled camera to take us into HD.

I know most videographers aren't stuck with taking shots they will probably have to slow down in post with a photographer standing beside them shooting the same thing, but wedding videographers are in that bunch of people that do, and I feel an obligation to let guys considering this camera know of what I perceive to be a serious limitation in that situation.

Interesting on the news last night I noticed the same effect during a press conference, so someone in Canberra is using a V1 for news gathering now.

Cheers Vaughan

[Curtis Heyne]

I've been using the V1U for a lot of event coverage’s, shooting both in 30p and 24pA. I've come across a problem with blowing the bit rate and having strange issues with photographer’s flashes. I've uploaded some footage and would love to know if this is just an issue with my two cameras. I have a hard time believing that though.

http://www.livingcinema.net/upload/lc_v1u_24pa.mov

Its seems that flashes are broken up over several frames and I thought it had something to do with the reverse telecine but no luck fixing it using different settings. I've also noticed, not seen in the above clip, is that as well with the flashes it causes the camera to blow the bit rate. It looks like really bad digital break-up all over a single frame, sometime two frames.


I would love any input.

[Curtis Heyne]

I wish I would have known. This was going to be our HD anytime anywhere camera and I feel very let down.

Here's some footage

http://www.livingcinema.net/upload/lc_v1u_24pa.mov

[Chris Medico]

This is a real torture test for any codec. What you are seeing is the codec hitting the wall regarding available bandwidth to the recording media. Any HDV based device will do the same thing.