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Old February 9th, 2006, 08:36 AM   #1
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XL2 footage + loud hum. Advice?

Hello all. I've recently completed my adapter for the XL2, but have run into a snag. There's a heavy flicker in the image, so I merely switched in two new AAA's to speed things up a bit. Well that certainly gets rid of the flicker, but now the adapter generates a loud whirr once it gets up to speed.

Any advice?

I've tried craft foam, but that isn't dense enough. The only options I can see are to slow the cd down with a potentiometer (resulting in flicker) or putting something like car noise insulation inside (thick, dense, and heavy) - but I don't think my set-up would be able to handle it. I've put rubber washers on all connections, but the project box seems to reverberate all the noise. The cd motor is directly glued to a particle board riding on 4 long bolts. Any advice? Thanks for any and all help!

You can see a test here of the rig here, note the flicker: http://oak.cats.ohiou.edu/~dd208802/new_mini35_test.wmv approx. 19mb, right click save as.
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Old February 9th, 2006, 04:56 PM   #2
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DNTEL... nice music choice ;) hehe.

Didn't notice the flicker too much until 3/4 into the video on a certain spot. is it because of uneven diffusion on the disk?

are you overdriving the motor? 2 AAA's is 3v.

the potentionmeter should help in finding the optimal motor speed
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Old February 9th, 2006, 06:53 PM   #3
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if you are actually trying to shoot something more professionally and not guerilla run and gun style, you should be using an external microphone closer to your subject... not the on camera mic. 35mm film cameras dont have a mic on the camera unit itself or it would pick up the sound of the motor turning the film... so what i do is always treat my shoots using a 35mm adapter (the M2 adapter in my case), as a professional shoot. but if i want to shoot little timmies birthday party, thats a different situation.

just some things to think about. foam will dampen the sound, but it will not get rid of it. microphones are sensitive, especially on camera mics.

good luck though on whatever you discover that works for you.
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Old February 10th, 2006, 12:01 PM   #4
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Thanks for your responses guys.

Cody - We always use an external mic on productions, but as we all know: silence is golden. In a quiet environment I fear that you'd still hear the box at several feet away. We'll see this weekend (entering a 48 hour film competition).

Solomon - It could very well be that diffusion is uneven on the disc. I'm using glad press n' seal on a clear cd. I've gotten it as flat as possible, but maybe I ought to try again. I may try driving the motor with a single AAA and see what happens.

Thanks again for your adivce gentleman!
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Old February 10th, 2006, 07:10 PM   #5
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flicker can be caused by a few things.

1) shooting with a high shutter speed.
2) motor isnt spinning fast enough.
3) uneven finish on ground glass.

you can try running your motor faster by using 2 or 3 AA batteries (if your motor can handle that) and decreasing your shutter speed to see how that works.
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Old February 10th, 2006, 10:28 PM   #6
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Devin.

Two more things :-

Set your camcorder gain to a manual setting. I have found a tendency for some cams to hunt for the best level and a flickering disk causes them to overshoot and undershoot as the best condition continuously eludes the camera automatic systems. It is most aggravated in conditions of strong backlight.

Doubling the battery voltage may not solve the problem of variable density around the disk. The density patches may remain just out of phase with the frame rate, if the higher motor speed is simply a double. You may have to select an intermediate voltage and some sort of variable resister is probably the best solution.

My personal preference was to keep the motor speed as slow as I could to de-resolve grain at a shutter of 1/50 sec. The solution for me ended up being use of single batteries already used in other appliance and were half flat.

I eventually gave up on plastic and now use glass. Rotation speed with these disks on a CD player motor is about 400rpm to 1500rpm depending on battery condition.
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Old February 14th, 2006, 03:49 PM   #7
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Both good suggestions guys, I appreciate it. Over this past weekend we participated in our University's 48 hour film contest and utilized the adapter. Here are a couple things I noticed:
  1. The noise seemed to come and go with no explanation. I did a lot of hand-held along with some stuff on sticks. For the most part the box was quiet with a few exceptions in both situations. Thankfully it wasn't that big of a deal as we were given mockumentary as our genre.
  2. I utilized manual settings as per usual: 1/48th shutter at 24pa, sometimes I pushed 3 or 6db of gain with some low NR, but the one time I had to use synchro-scan the batteries were dying on the device. The result? The highlights coming off the monitor have the frosted grain visible due to the higher shutter speed. Unfortunately this is something I noticed in post and not in the viewfinder. Wish we had a monitor present on set. At any rate, I don't think the layman will notice. I wish I could accept shooting at 1/24th to avoid further problems with visible grain, but I can't accept the slower movement pattern. 1/48th creates that film-look that I've come to love.

At any rate, I was very pleased with the adapter and am going to try making a more level press n' seal cd to rid of the flicker apparent at lower battery levels. In the meanwhile switching out the batteries for fresh, fast ones seems to get rid of the problem. Thanks for your suggestions!
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Old February 14th, 2006, 09:28 PM   #8
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Given you have a CD disk for a groundglass, that it happened during hand-held work and the intermittent nature of the noise, my guess is you may be getting end-float on the disk motor.

A quick check is mount the camera on a trpidod, to aim the camera in a slight downward tilt (about 5 - 10 degrees) with the disk motor not running. Focus sharp on a high contrast highly textured object, tablecloth pattern, grass or something like that, or a test pattern if it is handy.

Roll the camera, then turn on the disk motor. If the end float is excessive, you will see a shift in focus as the magetic field of the motor pulls the armature into a centred position or movements in the focus as the armature floats between end stop points.

One attempted solution is to put a small washer and then an "E" clip on the shaft between the spindle hub and the motor front bearing. After the spindle has been refitted, apply traction to the spindle hub whilst you slide the "E" clip up against the washer.

This washer may have to be trimmed or filed down so that it faces up against the motor bearing bush and not the motor case. The highly polished shaft may not offer enough friction to keep the "E" clip in place.

A alternative is to strip a piece of insulation from electical wire, trim it down to a short length and substitute this for the "E" clip.

If there is space within the adaptor case and it can be conveniently done, it may be best to use the matching capping piece which is normally found in the CD player and clamps the disk onto the spindle.

There is a small protrusion on back of this capping piece which bears against a piece of flat metal in the CD player to prevent end-float. Spring pressure normally applies the take-up. Too much take-up pressure will overload or stall the disk motor.
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Old February 15th, 2006, 10:13 AM   #9
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Bob - Thank you for taking the time to write such a detailed response. I'll def. check the end float on the motor and see where it takes me. From my experience with the box I can already agree with you that there's where most of the problem lies. I'll give her a spin.
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