problem with letus motor/ batteries at DVinfo.net

Phil Bloom · October 26th, 2006, 03:46 PM

Has anyone experienced the same problem as me...?

when I fick my letus flip enhanced on sometimes the motor starts and sometimes it doesn't. Could there be a problem with my motor or it's battery supply...anything I can do with limited technical skills?

Also how long continuous running on a good set of non rechargable AA do people get before they need to change. It's hard to know when to change them, am so paranoid about grain I think I am throwing mine out way too soon!

Thanks

Phil

Bob Hart · October 26th, 2006, 05:43 PM

Phil

Battery life and starting torque. It is a very small motor. In relation to the diameter of the motor itself, the eccentric weight has a lot of leverage. While the motor will turn the weight, initially getting it to lift over against gravity seems to be a difficulty once the batteries have drawn down a little.

In use, if the motor fails to start, point the lens directly towards the ground to remove gravity as a factor and it should start. This should be regarded as the time for battery change. It doesn't take much resistance to stall the motor.

There seems to be some lenses which aggravate the "film of grain" or the "flicker" which occurs on my own non-Letus device. A Tokina f2.8 wide-angle zoom lens I have used seems to provoke it earlier than the f1.8 lenses.

It seems also that regardless of the stated aperture of the lens, the actual size of the exit at the back of the lens has influence. There are some film camera lenses which are described as "optimised" for DSLR which seem to do better.

These have been designed to cast the image on the film plane with reduced angles of incidence.

If you want to study the motion of the GG, it helps to operate it very near a TV screen. This provides a strobe light source and the apparent motion of the GG is slowed enough for the shaped of the "circle" of motion to be observed.

In an attempt to incease the excursion of the GG, I added some extra mass to the eccentric weight by making a tiny concertina of wire solder and glueing this with yellow contact adhesive to the outer surface of the the weight.

The output shaft on the motor is quite narrow so you do not want to overdo the extra weight or exert any force against the motor shaft. The stalling of the motor is aggravated by this extra weight.

I have also added some countermass to the groundglass holder by laying a 30mm strip of wire solder along the inside of the outer edge of the holder next to the motor. This adds a little extra kick to the motion of the GG opposite where the motor is mounted.

I have yet to test this arrangement to see if the occurance of the "film of grain" is pushed up to smaller aperture settings.

Unless you have good miniature engineering skills, please do not attempt these experiments.

Phil Bloom · October 27th, 2006, 02:04 AM

Bob,

As always your information is terrific. I think for the benifit of the environment I need to invest in some very good rechargable AA batts. Probably about half of dozen of them so I can always have my motor ticking along at full whack!

So do you think I should avoid an slr lens made for a digital camera then?

Thanks

phil

Bob Hart · October 27th, 2006, 09:18 AM

Phil.

A lot of the lens issues are really a try it and see proposition but you can get caught out. The 12-24mm f4, I tested in the shop on the Agus/camcorder combination. It worked fine under flourescent lights. It was only in the bright outdoors did truths become known.

Also, because it is set up for the smaller DSLR frame, when you back off on the camcorder zoom to get as much wide-angle as you can, then corner distortion from this lens becomes apparent. For the 24mm x 18m movie frame or smaller, the image area is not so painful an issue.

It is quite a surreal effect. But if you can hide those defects in dark areas of the shot through careful composition, then it becomes a very useful wide-angle, gives a little more than the FX1's own.

Needs lots of light though and the image looks sort of weak compared to the other lenses although it remains a sharp lens if carefully focussed and backfocus is carefully set up.

October 26th, 2006, 03:46 PM	#1
Phil Bloom Trustee Join Date: Aug 2006 Location: London UK Posts: 1,939	problem with letus motor/ batteries Has anyone experienced the same problem as me...? when I fick my letus flip enhanced on sometimes the motor starts and sometimes it doesn't. Could there be a problem with my motor or it's battery supply...anything I can do with limited technical skills? Also how long continuous running on a good set of non rechargable AA do people get before they need to change. It's hard to know when to change them, am so paranoid about grain I think I am throwing mine out way too soon! Thanks Phil __________________ Philip Bloom Cinematographer, Director, Filmmaker www.philipbloom.net

October 27th, 2006, 02:04 AM	#3
Phil Bloom Trustee Join Date: Aug 2006 Location: London UK Posts: 1,939	Bob, As always your information is terrific. I think for the benifit of the environment I need to invest in some very good rechargable AA batts. Probably about half of dozen of them so I can always have my motor ticking along at full whack! So do you think I should avoid an slr lens made for a digital camera then? Thanks phil __________________ Philip Bloom Cinematographer, Director, Filmmaker www.philipbloom.net

October 26th, 2006, 05:43 PM	#2
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Phil Battery life and starting torque. It is a very small motor. In relation to the diameter of the motor itself, the eccentric weight has a lot of leverage. While the motor will turn the weight, initially getting it to lift over against gravity seems to be a difficulty once the batteries have drawn down a little. In use, if the motor fails to start, point the lens directly towards the ground to remove gravity as a factor and it should start. This should be regarded as the time for battery change. It doesn't take much resistance to stall the motor. There seems to be some lenses which aggravate the "film of grain" or the "flicker" which occurs on my own non-Letus device. A Tokina f2.8 wide-angle zoom lens I have used seems to provoke it earlier than the f1.8 lenses. It seems also that regardless of the stated aperture of the lens, the actual size of the exit at the back of the lens has influence. There are some film camera lenses which are described as "optimised" for DSLR which seem to do better. These have been designed to cast the image on the film plane with reduced angles of incidence. If you want to study the motion of the GG, it helps to operate it very near a TV screen. This provides a strobe light source and the apparent motion of the GG is slowed enough for the shaped of the "circle" of motion to be observed. In an attempt to incease the excursion of the GG, I added some extra mass to the eccentric weight by making a tiny concertina of wire solder and glueing this with yellow contact adhesive to the outer surface of the the weight. The output shaft on the motor is quite narrow so you do not want to overdo the extra weight or exert any force against the motor shaft. The stalling of the motor is aggravated by this extra weight. I have also added some countermass to the groundglass holder by laying a 30mm strip of wire solder along the inside of the outer edge of the holder next to the motor. This adds a little extra kick to the motion of the GG opposite where the motor is mounted. I have yet to test this arrangement to see if the occurance of the "film of grain" is pushed up to smaller aperture settings. Unless you have good miniature engineering skills, please do not attempt these experiments.

October 27th, 2006, 09:18 AM	#4
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Phil. A lot of the lens issues are really a try it and see proposition but you can get caught out. The 12-24mm f4, I tested in the shop on the Agus/camcorder combination. It worked fine under flourescent lights. It was only in the bright outdoors did truths become known. Also, because it is set up for the smaller DSLR frame, when you back off on the camcorder zoom to get as much wide-angle as you can, then corner distortion from this lens becomes apparent. For the 24mm x 18m movie frame or smaller, the image area is not so painful an issue. It is quite a surreal effect. But if you can hide those defects in dark areas of the shot through careful composition, then it becomes a very useful wide-angle, gives a little more than the FX1's own. Needs lots of light though and the image looks sort of weak compared to the other lenses although it remains a sharp lens if carefully focussed and backfocus is carefully set up.