Weird brown lines
 

This is copied from an earlier thread of mine - but no-one answered, so I'm posting again - I'd really like to know what you guys think is the cause...

"I was trying out a V1 in store, and something weird happened when I played around with the shutter speed. Inside a room with flourescent lights, thick, brownish lines appeared across the screen when the shutter speed was over 60. The lines became more obvious the higher the shutter speed. When I took the camera outside into natural light, the lines disappeared. Does anyone know what could have caused these lines?"

Thanks

I'm guessing the flicker of the flourescent lights are interacting with higher shutter speeds & this is quite normal. As far as them being brown? Umm, I dunno... maybe it was autowhite mode on? :)

On another note, it's always best to just *bump* your original post than to start another one just because someone didn't reply. Bumping simply moves it to the top where it may have been missed before.

Bill

Thanks for your reply, Bill. It's just that I've never seen lines like that before, so I didn't think it was normal... I was also trying out another camera (the A1) under the same conditions, and it didn't exhibit any brown lines. Maybe it's just one of the V1's quirks?

I can't answer about the brown stuff :) but point any video camera at a computer CRT (not an LCD) & you'll more than likely see bars moving vertically bue to scan rate differences. Many cameras have a shutter function, some call it Clear Scan... or something similar, that lets you dial in a shutter speed in smaller increments until the bars are gone. It's hardly a problem anymore since the majority of CRT's ar long gone & most use LCD monitors now.

Bill

V1 has a "rolling shutter" and it will cause some issues at higher shutter speeds in certain conditions.

Lizi, I'm sorry I didn't follow up with your post. I haven't been operating at 100% the past two weeks due to illness. I actually went and checked my camera with fluorescent lights and there is only some rolling shutter effect at extremely fast shutter speeds. At that point, you wouldn't be able to get enough light with flourescents to be getting any useable footage. At shutter speeds faster than 1/1000th I could see some sort of dark area moving slowly through the image. Also, at over 1/350th I can see warping of objects moving quickly. I pointed my camera at my ceiling fan running it's maximum speed and the blades would freeze in place with fast shutter but would look curved. Honestly, I can't ever imaging shooting at anything faster than 1/250th.

I would think you must have been pointing the camera at a CRT to get the effect you describe, but CRT monitors are becoming scarce. Perhaps you were in a room with older fluorescents with magnetic ballasts which operate at the frequency of the power system. Even these are becoming rare, so I have doubts about this being the problem. Could you describe your situation in greater detail? Were you seeing the brown lines on video monitors or the entire room? Did the effect vary as you moved through the room?

I should mention that I am using the V1U. I am assuming you are also using a U.S. version as you mention 1/60th shutter.

That alone could explain this whole thing & never thought of that. It must be some power mains frequency mismatch issue? I dunno.

Bill

I have gotten the same thing in rinks shooting hockey games under (I believe) sodium lights.

The large rolling lines start to appear at 1/250th ... below that it is fine.

Kevin Burton

Thank you for all your posts, and I'm sorry for not replying earlier. To answer some of the questions raised... I wasn't pointing the camera at a CRT screen (which are still quite widespread this side of the world, so I'm used to their flicker) - the lines I saw appeared across the picture, which included the whole room. And the lines didn't change as I moved around the room - however, they did disappear when I went out of the room into natural sunlight. The camera was a V1C, which is PAL.

As no-one else is having the problem I noticed (which appeared at much lower shutter speeds than everyone else has mentioned), I'm assuming there was either something wrong with the unit I tried, or the lights were as Marcus said, old-style flourescents. Would there be any way of getting rid of such lines, apart from changing the lighting source and/or shooting at very low shutter speeds?

Could I ask two more newbie questions? Stephen, what does "rolling shutter" mean, and how does it differ from other cameras? And Marcus, why do you like to shoot at shutter speeds below 250?

Thanks again.

Hi Liz. I was only making reference to a CRT as an example.

At this point, I'd suggest try shooting something in another location/s that has flourescent lighting & see if there's a difference. It could possibly be something to do with their particular flourescent lights, like someone else mentioned here.

Good luck.
Bill

Rolling Shutter vs Frame Shutter
 

Lizi,

The rolling shutter in a CMOS image sensor works differently than the frame shutter in a CCD image sensor, in that the pixels do not collect light at the same time. All pixels in one row of the imager collect light during exactly the same period of time, but the time of the light collection to start and end is slightly different for each row, thus the term rolling shutter.

roller/frame shutters
 

then this means the z1 shutter is better?

"then this means the z1 shutter is better?"

Not necessarily. My tests with the V1 show it to have no significant shutter artifact at normal speeds. Unless you are photographing supersonic objects at extremely fast shutter speeds, you probably would never notice the rolling shutter. The V1 shutter seems fine at least as fast as 1/250 second exposure which will freeze motion quite effectively.

shutter times...
 

Marcus: are there times you would need faster than 250 of a sec?

I don't think I even need 1/250 shutter, but I do know of one use of fast shutter. Ben Winter sometimes uses a fast shutter speed to reduce motion blurring. I believe he does this to reduce motion artifacts from interpolative slow-motion software. Goodervideo.com has slow-motion software and Ben has mentioned using the fast shutter speed when he is planning to use that software. I think 1/250 shutter would be just fine to eliminate motion blur for this software. My test was done simply by pointing my V1 at a ceiling fan set to high. To my eyes, the blades are a complete blur. The V1 is able to eliminate motion blur from the blades without noticeable distortion. Only a very fast-moving object in your scene could generate any warping and then only at a very fast shutter speed. I really can't imagine any real-world reason the rolling shutter of the V1 could ever be a problem.