Screen Left light bleed or shutter smear?

[Ryan Gallagher]

Quick Q. In testing our 70mm 2001 print on Century JJs, at least one projector, depending on the scene, has a dim light streak screen left. It vanishes on other scenes.

Could framing lights do that? Or maybe we just need to try a shutter timing adjustment? If it is slightly out would it appear on one side before the other like that? Single shutter unit.

we haven’t had prints this wide run in years, so would not shock me if there is a slight timing or shutter slop issue.

Certainly not a show stopper, but I noticed.

it did not exhibit it in the narrower 1.85 70mm screening.

[Ryan Gallagher]

I just checked the shutter timing (2 35mm tooth advancement) and at least that all checks out.

[Brad Miller]

There are several things that could cause that. The most common...

You may have a 35mm Century shutter installed in that JJ by mistake. (They are very similar in size.)

Your working distance from your reflector to your aperture may be incorrect (almost certainly being too far apart).

Your lamphouse may not be horizontally aligned to the center of the film.

You could have some "holes" in your shutter causing light leak during the pulldown process.

[Ryan Gallagher]

There are several things that could cause that. The most common...

You may have a 35mm Century shutter installed in that JJ by mistake. (They are very similar in size.)

Your working distance from your reflector to your aperture may be incorrect (almost certainly being too far apart).

Your lamphouse may not be horizontally aligned to the center of the film.

You could have some "holes" in your shutter causing light leak during the pulldown process.

Thanks for some leads Brad. I have not been around to see what that unit looked like with a 70mm print before we improved the lamphouse alignment (was way out). But perhaps we landed less horizontally aligned than previous perhaps. We did not get all the way there because this is the unit that needs the the hacked brenkert soundhead hanger replaced with the proper brenkert to simplex patterned one. As it is now lamphouse is high relative to the shutter hole with no more travel to lower it, and no adjustments on hanger because of the hack.

Getting into the shutter surround for dust removal is on my maintenance todo list, so will check the shutter type and look for holes then.

It did match it's partner on the reflector distance, but it's partner is a dual shutter unit right now.

Our last 70mm is 1.85:1 blowup with the defect beyond the masking, so we'll finish out the season before I chase this one.

Upon closer watching of it during the screening, it's definitely a shutter ghosting artifact, but only in the left most 1.5ft of image. Visible in the appropriate context with bright objects above dark areas. Did not try chasing it with the timing knob out of fear of not getting back to where we were mid screening.

[Brad Miller]

The 4th possibility is definitely the most far fetched one, as usually if the projector is turned off and the shutter lands in the closed position with the lamp still on the center of the shutter would be burned into a hole(s), not the edge, but you never know. I've seen some weird stuff over the years.

The most likely issue is that your working distance and alignment is simply not correct. The adjustment on a JJ is VERY critical to prevent exactly what you are seeing. I have to assume the JJ has proper sized shutters in there, as in theory this venue has ran 2.20 films before without the left edge smear. I could measure one if you need, but really you just need to compare this one to the other projector's shutter (that doesn't smear) and remember the diameter's difference from a 35mm SA shutter isn't too much smaller than the JJ shutter, so take measurements very carefully.

When you get back to this, you might want to try moving the lamphouse (or reflector) half or one inch closer to the projector to see if that's just enough to clear the smear as a stop-gap measure until such time you can get the proper mounts to do it spot-on. I do agree though it's silly to mess with it immediately though since your only remaining film is 1.85 within 2.20 and all looks good for that format at the moment.

[Ryan Gallagher]

The 4th possibility is definitely the most far fetched one, as usually if the projector is turned off and the shutter lands in the closed position with the lamp still on the center of the shutter would be burned into a hole(s), not the edge, but you never know. I've seen some weird stuff over the years.

We are pretty diligent being a manual house and using the actual lamphouse dowser whenever that projector is not on screen, so I doubt theory 4, but perhaps previous operators behaved different.

The most likely issue is that your working distance and alignment is simply not correct. The adjustment on a JJ is VERY critical to prevent exactly what you are seeing. I have to assume the JJ has proper sized shutters in there, as in theory this venue has ran 2.20 films before without the left edge smear. I could measure one if you need, but really you just need to compare this one to the other projector's shutter (that doesn't smear) and remember the diameter's difference from a 35mm SA shutter isn't too much smaller than the JJ shutter, so take measurements very carefully.

We should have time to check this again before the next summer series for sure, perhaps concurrent with upgrading the hanger.

TWhen you get back to this, you might want to try moving the lamphouse (or reflector) half or one inch closer to the projector to see if that's just enough to clear the smear as a stop-gap measure until such time you can get the proper mounts to do it spot-on. I do agree though it's silly to mess with it immediately though since your only remaining film is 1.85 within 2.20 and all looks good for that format at the moment.

I hesitate here just cause that would mean trimming our snoods down accordingly. Though I did find two spare snoods recently. And two new condition accessory holders too, though TBD if correct size, might have been for a smaller Strong lamphouse.

One day i'd like to try the lamphouse distance adjust rather than the spreader lenses for 70mm, at that time we'll need shorter snoods anyway if I am recalling the direction it has to move correctly.

Which raises a question, could a spreader lens that is clocked out of intended rotation contribute to a left edge smear? That is easy to check/compare.

[Brad Miller]

Which raises a question, could a spreader lens that is clocked out of intended rotation contribute to a left edge smear? That is easy to check/compare.

I don't think I've ever encountered that scenario, but most likely not as it would be spreading the light diagonally or vertically and your issue is related to light making it around the outer edge of the shutter. Maybe one of the other techs on here has ran across that scenario and could chime in.

Email me directly off-site. I should have a loop that you can use to test that left edge smearing.

[Marcel Birgelen]

Maybe a stupid question: Is the "smear" still visible if the shutter is closed?

An easy way to check this without dedicated equipment: if you have a phone with a fairly high-end camera and make a high-speed (e.g. 240 fps) recording of the screen and said smear.
If you fail to adequately capture the smear because it's too dim, you could try to film it close-up and see if it flashes or not.

[Ryan Gallagher]

Maybe a stupid question: Is the "smear" still visible if the shutter is closed?

An easy way to check this without dedicated equipment: if you have a phone with a fairly high-end camera and make a high-speed (e.g. 240 fps) recording of the screen and said smear.
If you fail to adequately capture the smear because it's too dim, you could try to film it close-up and see if it flashes or not.

That's a thought, we haven't tried throwing any light with the douser open and the shutter stopped in it's closed position. Probably would not be a smear, but just a light leak somewhere if visible. Along those lines in 2001 I was noticing that the mostly black frames (space & stars etc) had a tendency to be a bit washed/brighter on the left and right, but wasn't sure if that was us or the print.

[Ryan Gallagher]

Finally had a maintenance window with no 35/70 on the horizon. Started investigating our 70mm 2.20:1 light-bleed left edge smear, either a shutter sizing or alignment issue has been the prior advice to pursue.

Used the opportunity evict the dust from the shutter assembly and make some observations. We have mismatched setups, one Century JJ is a dual shutter unit, the other rocks a single two blade shutter on an shaft that does not appear to support two shutter operation. (So is it even a JJ then I guess is a valid question).

The single 2 blade shutter is the unit with the left edge shutter smear.

Generally they also seem a bit worse for wear, a bit of warping and burned off coating, the front one on the dual unit even has quite a bit of rust present, but no holes detected.

The shutter radii as measured (perhaps not 100% accurate due to not having removed them for measuring).
Dual Shutter Unit: 6 3/16ths in (about 158mm)
Single Shutter Unit: 5 7/8ths in (about 150mm)

They indeed appear to have a non-trivial diameter difference, the problem one being the smaller diameter, so perhaps this unit has had a shutter not really designed for 70mm installed?

All installed appear to be the "butterfly" style, although I'm a bit unclear on terminology here. There is a spare in the booth that is more resembling the bat symbol and appears to be unused, that also happens to be the larger diameter.

I feel like I'd be tempted to try that spare before confirming the lamp-house alignment and distances again. I went as far as fitting it above the existing to verify clearances and take a diameter comparison photo.

Spare:
thumbnail_IMG_5910.jpg

Spare Diameter compared to Installed:
thumbnail_IMG_5916.jpg

Spare Clearance.
thumbnail_IMG_5917.jpg

Currently Installed Single Dual Blade shutter (the one with the screen left edge smear/bleed):
thumbnail_IMG_5914.jpgIMG_5911.jpgthumbnail_IMG_5912.jpg

The Dual Shutter Unit:
thumbnail_IMG_5915.jpg

As always any input appreciated.

My next steps are going to be to reproduce the problem with some black 70mm leader intentionally out of framing to expose the smear.
Then try swapping shutters unless someone says that spare definitely won't work.
If no change, return to confirming the horizontal alignment with the align-o-tron, or try to "live tune" it out with an image on screen.
If no real improvement, investigate our reflector distance again.

If that spare is wrong but there is a correct 70mm shutter I can seek would love to hear it.
Ryan

[Ryan Gallagher]

Also it goes without saying I would love to make these two units alike, so probably single dual blade shutters on both. I know converting from dual to single is trivial if you have the right shutters.

Considering the condition of existing, which style should I be seeking for 35/70mm operation?

[Brad Miller]

Your problem is absolutely that 150mm shutter. You need the 158mm shutters. That extra 4mm is enough to let light leak around the edge and smear the left of your projected image if the working distance from the reflector isn't spot on.

Switch both to a single shutter, but note you cannot use the dual shutter type that has the "V" notch in it for single shutter operation.

[Ryan Gallagher]

Your problem is absolutely that 150mm shutter. You need the 158mm shutters. That extra 4mm is enough to let light leak around the edge and smear the left of your projected image if the working distance from the reflector isn't spot on.

Switch both to a single shutter, but note you cannot use the dual shutter type that has the "V" notch in it for single shutter operation.

Thanks for the confirmation Brad. That really clears up that mystery.

When you say "with the notch" are you referring to the indexing notch at the rim, or the V notch in the bat-wing style that we have loose in the booth.

If that is a dual shutter loner, it's not much use to us it seems. Maybe I can trade it with someone.

Another thought. Are the two installed on the dual shutter unit actual both compatible as single shutters? Could we just move one over to the undersized unit?

[Brad Miller]

Yes, just move the larger dual set across both machines and call it a day.

[Ryan Gallagher]

Yes, just move the larger dual set across both machines and call it a day.

Thanks we'll do that.

From what I can tell those installed on the dual are both relatively close to being intended as single shutters anyway, certainly not the ratio of open to closed I would expect for counter rotating JJ shutters. Which might explain why in my head I have always been like "That SHOULD be the brighter projector", but in reality it was in fact always reading a hair dimmer than the single shutter unit to my eye.

Makes me wonder what the next weirdness I'll discover with these two is!