8mm Forum: Bright spot in center of screen

This is topic Bright spot in center of screen in forum 8mm Forum at 8mm Forum.

To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=011093

Posted by Ronald J Wildhaber (Member # 5649) on November 07, 2016, 10:36 AM:

I am using a transfer box to record 16mm film footage with a Sony Mini DV camcorder and Keystone Belmont K-161 projector. The screen has a bright spot in the center. Moving the projector's position does not seem to help this. I have another one of these boxes. Maybe it will not be as apparent with it. Is there a way around this? Thanks...Ron

Posted by Janice Glesser (Member # 2758) on November 07, 2016, 12:59 PM:

Hi Ronald...Changing to another telecine box will probably not solve the center hotspot problem. This is a common issue with this projector. It's how the very bright light is dispersed thru the lens.

When I first started transferring 16mm film I found that a ground glass and mirror system worked better than the telecine box or even projecting to a piece of paper on the wall. You can place the projector further back which reduces the light in the center. There still will be a hotspot, but not as prominent. I was able to use a VirtualDub filter to even out the exposure after capturing. It made it better, but very time consuming. I haven't done this but, you could try DIYing a diffuser between the lamp and the gate. This would have to be glass...the lamp gets extremely hot.

This was my early telecine setup.

I later ended up replacing the lamp in the projector...removing the projector lens... and shooting directly off the film gate with a macro lens on my camcorder. I removed the old lamp and holder and replaced it with a 120v 20w bulb and holder with a separate power cord. I also replaced the 45 degree mirror behind the gate with a piece of white paper. The light bounces of the whit paper and acts as a diffuser.

Here is a video my current setup...
https://www.youtube.com/watch?v=emm1B96pSfw

Posted by Ronald J Wildhaber (Member # 5649) on November 07, 2016, 05:11 PM:

Wow, that looks like it would definitely do the trick. I did not try it yet but would shooting off a movie screen eliminate most of the brightness.
On another note, looking through the Keystone 109D posts you mentioned, I ran across a post where someone needed a power cord. My 16mm Keystone projector did not have a power cord when I bought it at a farm auction. I got 2 - 16 gauge electrical wiring spades and soldered them to a lamp cord and slid some heat shrink tubing over the soldered ends and this worked perfectly. Thanks for your help on this. I have a lot of 16mm film to transfer.

Posted by Ronald J Wildhaber (Member # 5649) on November 07, 2016, 05:12 PM:

Wow, that looks like it would definitely do the trick. I did not try it yet but would shooting off a movie screen eliminate most of the brightness.
On another note, looking through the Keystone 109D posts you mentioned, I ran across a post where someone needed a power cord. My 16mm Keystone projector did not have a power cord when I bought it at a farm auction. I got 2 - 16 gauge electrical wiring spades and soldered them to a lamp cord and slid some heat shrink tubing over the soldered ends and this worked perfectly. Thanks for your help on this. I have a lot of 16mm film to transfer.

Posted by Janice Glesser (Member # 2758) on November 07, 2016, 05:48 PM:

Donald...Do not use a projection screen. Just place a piece of white paper on the wall and project to that.

Here is video example of the setup using white paper. This is an 8mm projector...but it would be the same for 16mm. You will probably need to move the projector back further.

https://www.youtube.com/watch?v=W_qYHymUJys

UBB.classic^TM 6.3.1.2