8mm Forum: Lens Hot Spot?

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Posted by John Cook (Member # 203) on November 04, 2004, 10:32 PM:

Hi all,

I've been down in the pit lately copying old family S8 reels to D8. I've noticed a hot spot on the center of the screen, it's as though the bulb itself is projecting a faint outline of itself in the middle of the screen. It only shows up in brighter scenes, darker more colorful scenes appear to wash the faint whiter circle image out. Is this normal for an elmo F1.1 lens? Zooming the lens in and out/refocusing doesn't help, the image is always there. Any suggestions or is this the nature of the beast.

Also, I've noticed dirt/dust spots inside the lens, cleaning both exposed ends of the lens doesn't help, must be inside between the lenses. How hard is it to tear down an F1.1 lens clean and reassemble?

And finally would an upgrade to an F1.0 improve things at all, if so, what specifically?

Regards, John

Posted by Tony Milman (Member # 7) on November 05, 2004, 12:29 AM:

John,

I am not experienced enough to comment on the hot spot but dust dirt and a "milky" coating on the inside surfaces of the lens seems common.

I have not taken a 1.1 lens to bits but I have had a couple of 1.0's in pieces with every element removed and cleaned. The product I have used in the UK is Opticlean. In case you don't recognose it, Opticlean is a liquid polymer that is "painted" onto the lens surface and once cured (2 mins) is removed by applying a sticky label and puling sharply.

The results are superb. The product is designed for optical glass and mirrors but not plastic and removed 95% of the milkiness and all of the dust and debris.

Opening the lens can be a bit tricky- some of them have a dab of glue on the threads and the key issue is to ensure that all of the little elements go back into place correctly.

Tony

Posted by Rob Young. (Member # 131) on November 05, 2004, 05:26 AM:

Tony, my Elmo 1.1 has exactly the same symptoms. Fortunately, it doesn't obviously degrade the projected image, but there must be some loss of quality.

Assuming the 1.1 is similar to the 1.0, is it possible to briefly describe how I might start taking it to bits for cleaning?

I did this once with a broken schneider xenovaron 1.1 and it isn't an experience I like to remember!

Posted by John Clancy (Member # 49) on November 05, 2004, 06:47 AM:

A hammer?

Posted by Tony Milman (Member # 7) on November 05, 2004, 08:20 AM:

John

They did make good HORROR movies!x

Rob, email me and I will give you aphone number if you wan't to call me

Posted by Rob Young. (Member # 131) on November 05, 2004, 09:13 AM:

Tony, thank you, very generous.

I'm away for the next week now, but I will email when I get back.

John, you see that's where I went wrong with the xenovaron [Wink]

Posted by John Cook (Member # 203) on November 05, 2004, 04:40 PM:

Would the bulb be the problem, an aging ESC? Would an EJL produce a different beam pattern?

John

Posted by Brad Miller (Member # 2) on November 05, 2004, 06:59 PM:

For video transfers (which is what you appear to be doing...pointing the camera at the screen...right?) you need to use a _________ (sorry, I can't for the life of me remember what it is called). Basically it's a tiny stick that at the top has a bubble. The stick is thin enough as to not make a difference, and the bubble is just big enough to "eat" some of the excess light. You place it in between your bulb and film gate. That way the corners have the same amount of brightness as the center, or slightly more.

I've never tried putting it in front of the lens, but if it's small enough and it's close enough to the lens, that may work.

Posted by John Cook (Member # 203) on November 05, 2004, 09:54 PM:

Brad,

Thanks, that does make sense, too bad you can't readily identify what it is. [Big Grin]

I have noticed the hot spot when projected full height during normal viewing but never gave it much thought. Compressing the image down to about 12-14" diagonal a capturing with a digital camcorder makes it a bit more noticable.

Regards, John

Posted by Michael De Angelis (Member # 91) on November 05, 2004, 10:28 PM:

John,

I do not know how to construct and apply this item, but I understand it is known as a diffuser or Milk Glass to break down the hot spots.

Michael

Posted by Kevin Faulkner (Member # 6) on November 06, 2004, 09:23 AM:

That all makes sense. I also tried this with one of those small protable daylight screens with a mirror etc ang got exactly the same problem. The hot spot was very noticeable when viewed through the camera viewfinder and in the end I gave up.
Anything you put between the lamp and the gate has got to be metal as its going to get extremely hot but it makes total sense for eliminating the hot spot effect.

Now how about an equivalnet 16mm lamp in a super 8 machine. For instance how about using an EJL lamp instead of an ESC in the GS1200. The EJL was designed for the larger 16mm gate and should give more even coverage of the super 8 gate.

Food for thought.

Kev.

Posted by John Cook (Member # 203) on November 08, 2004, 09:47 PM:

Kevin,

Thanks, I'll take that advice to the bank, I've been wanting to experiment with an EJL anyway. Capturing frames off of a sheet of white posterboard works pretty darned good, except for the hot spot. There's enough detail in the transfer to see plenty of film grain in the captured video.

John

Posted by John Cook (Member # 203) on November 15, 2004, 09:45 PM:

As luck would have it my ESC burnt out over the weekend. I now have two EJLs and a quart of Filmrenew enroute from Larry over at Urbanski's. He doesn't stock the ESC but has plenty of EJLs at $18 american.

I'll post any changes in hot spot obeservations once the EJL is installed.

John

Posted by John Cook (Member # 203) on November 18, 2004, 11:19 PM:

Unfortunately the EJL doesn't appear to have an affect on the hot spot but I am back in business transferring the remaining films.
Getting all the footage copied over to PC, edited, and spun out on multiple DVDs is a chore.

John

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