Cannot Focus or Motion Blurrrr??

[Compo]

Now then......
I'm trying to video commercial (disco) lighting effects using moving light type things. Moonflower etc. The kind oth lights that project various spinning patterns on to walls and floors in Disco's etc.
Simply projecting them on to a wall etc is unnacceptable so I am using a Cini Transfer box.
I set up the light shining directly into the Cini Transfer box which hits the miirror and is reflected on to the small screen of the box.
Now with some drastic lens adjustment I can get the full effect of the light (lots of coloured light shapes circling around) to display on the screen of the Box beutifully and with pinpoint focus!.. Its Lovely!!!

I set up my Canon XF100 next to the box. 0.5m away from the screen as this is the maximum distance I can go in order to be able to zoom so that the screen of the Telecini box fills the frame.

The resultant footage is blurred and looks a bit streaky. I have tried all kinds of Iris, focus, ND, gain settings etc but I just cant seem to get the image to focus properly.
Any Ideas you clever people??

[jagabo]

Under normal lighting condition can the camera focus that closely (with the same lens settings)?

[magillagorilla]

I have a Canon HF100. You likely don't have enough light. Also the AF relies on light coming off of real objects. In this sceanrio the only real object is the surface of the box. In low light all the AF can see is dancing light and likely cannot lock on to the surface of the screen. DO you have any other cameras? A DSLR video capture using manual focus would be perfect. Does the Canon XF100 have manual focus control?

The bluring and streaking is the result of the camera slowing down the shutter speed due to low light. More light = faster shutter = sharper image and focus.

You may need to set the camera to shutter priority, adjust the shutter speed and use manual focus, if you have it. In low light the aperture will be wide open which also adds to the lack of sharpness.

[Compo]

Under normal lighting condition can the camera focus that closely (with the same lens settings)?

Yes. Camera can focus to 0.2m. I'm operating at 0.5.
I'm using manual focus and anything up to F22.

[Compo]

I am usin Manual focus / manual everything and I can close the iris down to F22.

What shutter speed would you suggest?

+ I dont particularly want to focus on the screen, that defeats the object of trying to capture just the light.
It is also quite a bright scene hence the F22 as I Iris up it is even harder to focus.

I will rephrase the above as it sounds a bit silly! I can focus perfectly on the small Telecini box screen however although the moving light images show up pinpoint sharp on this screen when vieved through my camera they are out of focus!

[magillagorilla]

We need to determine of this is an actual focus problem or a problem with mothin blur due to slow shutter speed. I think your shutter speed is the problem, since you have everything else dialed in. Crank your shutter speed all the way up and work down from there.

EDIT: I said frame rate in my statement but I ment shutter speed, I fixed it.

[jagabo]

Is this a direct projection into the camera or onto a piece of white frosted glass/plastic? If onto frosted glass -- is it focused when you look at it with you own eyes?

[Compo]

The light is focused through the Telecini box (ie Reflected from a super flat grade 1 mirror on to a frosted parafin filled sandwich of glass).
Yes the light focuses absolutely pinpoint sharp onto the frosted glass.

I'm already running at 50i but I will check the bit rate and have a meddle with that.

It's begining to look like motion blur, but to my eye it seems out of focus and at the same time I can see some motion blur (which I expected) and they look kike seperate issues???

[jagabo]

It's begining to look like motion blur, but to my eye it seems out of focus and at the same time I can see some motion blur (which I expected) and they look kike seperate issues???

That's easy to test. Shoot a static image. If it's not sharp you have a focus problem. If it is sharp, shoot a moving image. If that's not sharp you have a motion blur problem. Use as fast a shutter speed as you can. One other possibility is the image is way too bright and you're getting internal reflections inside the camera/lens. But I think you'd have diagnosed that already.

+ I dont particularly want to focus on the screen, that defeats the object of trying to capture just the light.

Since you're shooting a frosted screen -- you do want to focus on the screen (the parafin layer, not the front of the glass) because that's what's scattering the light.

[Compo]

I'm liking the idea of the source being too bright causing internal reflections!!!
I had assumed that closing the iris right down would be enough to stop this but maybe not?
OFF to buy a filter or 2 !
Will report back!

[jagabo]

Also, maybe the frosted screen isn't matte enough -- letting too much light pass straight through into the camera. That light would not be focused and would not contain the entire frame, just a portion near the center.