Emulsion build-up on Simplex tension bands

[Mark Gulbrandsen]

Mark, the DP75 uses metal just for the straight section around the aperture. Delrin is used above and below. However, below the aperture, after the film leaves the metal skates, there is nothing pushing/holding the film in the guide/trap area other than the intermittent sprocket.

I'm reasonably certain that the DP70 runners had the three radiuses but I don't have a runner handy to verify. A lot of the DP70 skites I dealt with had grooves worn in by the mag tracks. There is a TSI about sanding down the runner to get a fresh surface and, of course, keeping the thickness uniform/symmetrical. They don't list the radius just that the height measure above the aperture has to be the same as the height below the aperture.

Gotcha Steve! Never serviced any DP-75, and the ones I have seen were projecting at the time... I've only seen pictures of the runner. As for the DP-70 runner, there are resurfacing instructions in some of the older manuals. I've done that as they did get grooved from the outer mag tracks. The older manuals have service bulletin's of which one of them is how to resurface it, and it gives the specs to check. And yes, the 70mm does appear to have a compound curve, but it may just be an illusion because the aperture is not in the exact center of the runner...

[Jesse Crooks]

To my great relief, this was not a substantial issue during the marathon we ran this weekend. We ran a total of 15 features (14 of which had a preshow reel) and it was not a consistent issue. I was the primary projectionist on six of the features and only had a serious issue with the first print. The following print was archival and there was no break between them, so I ended up spending probably 10min scraping the emulsion build-up off of the tension bands to get them as pristine as possible (and was a few frames late on that changeover) but the following print barely left any residue. However, the fact that the grime builds up in the same locations on the bands every time does lead me to believe there is wear on the bands. I think I'll replace them the next time I have an opportunity to.

[Jesse Crooks]

Since Mark mentioned that he thought this amount of build-up is normal for X-Ls and Centurys, I should note that X-Ls were my daily drivers for six years before we went digital, and I have never had this issue before. And we ran a ton of older prints from the 50s and 60s. That's why I thought this amount of build-up was alarming.

[Ryan Gallagher]

175mm lenses for 70mm format? Pray tell, who made them? Schneider and ISCO stopped at 150mm for their 70mm format lenses, on the late model ones. I tried some Kiptars in that range and they would vignette.

As for depth of field/focus and EF. If you have some lenses handy for an SLR...look at the f-stop ring and note how close focus ranges are on longer lenses versus shorter ones (EFs). Teles have much shallower depth of fields. In fact, one of the issues with filming in 65mm is that you have almost no depth of field. It completely changes how you film a shot to get the look you want. That and 65mm needs a lot more light (bigger aperture to light up and you are going to want to stop down the lens to get your depth of field back).

Ahh yeah I wasn't thinking about the f-stop factoring into the depth of field variation. Was just thinking about being closer to the screen and having the distances from the center to the extremes vary more (especially with steep angles involved).

My notes from my lens inventory are thus:

Isco-Gottingen

Kiptar

6.88in/175mm

1:3.0

SN 9138527

Isco-Gottingen

Kiptar

6.88in/175mm

1:3.0

SN 9138248

They may vignette a bit as I haven't had much to compare them to nor metered my corners. If there is something better to try out there I'd love to, just working with what the booth has.

Here are some crappy phone pictures from the 1.85 Searchers run on 70mm. I really need to find a phone that doesn't struggle to focus on the screen from the booth, or just use a real damn camera.

IMG_5678.jpgIMG_5681.jpgIMG_5684.jpg

This was the only shot I snagged during last 2001, not the best example shot, but perhaps some more vignette definitely visible in true 2.20 full frame. This scene did not capture the left edge shutter bleed/smear issue we uncovered (or created when we "improved" the lamp-house alignments). Or we were not on that projector when I took the photo.

IMG_5689.jpg

[Vern Dias]

Since Mark mentioned that he thought this amount of build-up is normal for X-Ls and Centurys, I should note that X-Ls were my daily drivers for six years before we went digital, and I have never had this issue before. And we ran a ton of older prints from the 50s and 60s. That's why I thought this amount of build-up was alarming.

In my experience (many many years ago) the amount of build up on the bands was heavily dependent on the print. Some (usually newer) prints were problematical and required cleaning the gate after every reel. Others maybe once per show. However I would be suspicious of the amount of tension on the bands and the amount of heat in the gate area. Almost all of the XL's I had experience with had liquid cooled gates.

[Mark Gulbrandsen]

In my experience (many many years ago) the amount of build up on the bands was heavily dependent on the print. Some (usually newer) prints were problematical and required cleaning the gate after every reel. Others maybe once per show. However I would be suspicious of the amount of tension on the bands and the amount of heat in the gate area. Almost all of the XL's I had experience with had liquid cooled gates.

And XL's had really poor water cooling at that. All it did was cool the aperture plate. Every one else's water cooling cooled the entire aperture and gate casting itself. Century was the best as far as American made projectors. I've seen quite a few XL's with warped shutter guards, and even a few with slightly warped main castings.

[Steve Guttag]

Um, no. Simplex only needed to cool that area because that is where your spot of light (and heat) should be. Century's trap area was a big heat sink so it soaked up the heat and distributed it everywhere. Simplex didn't do that. Century also had a thicker trap design which had the spot of light larger when it entered, which again heated up more of the trap.

[Mark Gulbrandsen]

That's simply not my experience Steve. The spot sight box on X-L's was warped metal central! You have the plates, P3312 and P-3314 in the XL before and after the shutter itself. Those were often badly warped.or loosened up when large lamp houses were used. Then there was the cheap casting on the XL known as the P-4146 Spot Sight Box. I probably replaced at least a dozen of those over the years that were so warped from heat that they couldn't safely use them.

The good aspect of the Century is that the water block actually acted as a heat sink for the aperture and gate, and to some extent, the entire projector. Even heating of metal is actually beneficial because it. I never ran into any warped castings in a Century. Were they as light efficient... No... But that's really the only negative thing about them (other than some batches of Wolk Gears!

[Steve Guttag]

Let's see. Simplex used two light shields...Century...none...so yeah, Century's didn't warp. They weren't there. If your shields are warping, you are hitting them hard. The heat shield thing was a bit more questionable in their size/mounting. They were there to keep the heat off of the gate area above/below the aperture. The 35/70 was dubious for the 35mm trap, for sure. As for the spot sight box. Simplex's metal was a bit thin and their castings were a bit porous.

Century...it's thicker, for sure. Then again, Century shutter blades warp 100:1 more than Simplex. Again, different metals (thickness and, in some cases, material itself. The benefit you give Century on the size of their cooling block is giving them credit for creating a problem and then coming up with a way to minimize its impact. Simplex doesn't create the problem in the first place.

There are things you can ding Simplex for, even in the trap area (e.g. the lateral guide roller was too think and would warp when it was heat treated) but being too hot versus Century isn't one of them.

[Mark Gulbrandsen]

Let's see. Simplex used two light shields...Century...none...so yeah, Century's didn't warp. They weren't there. If your shields are warping, you are hitting them hard. The heat shield thing was a bit more questionable in their size/mounting. They were there to keep the heat off of the gate area above/below the aperture. The 35/70 was dubious for the 35mm trap, for sure. As for the spot sight box. Simplex's metal was a bit thin and their castings were a bit porous.

-Simplex shutters generally didn't warp much, but I've had a few with a hole blasted through both the shutter and the C\O blade too. Obviously someone forgot to close the dowser and kill the lamp. The light shields in the spot sight box were not heavy enough over the long haul, as they warped too, not to mention the light box itself, which apprered to be a die cast part. The chrome plating on those light shields was also gone from them in no time flat, often replaced by rust, especially in Drive Ins.

Century...it's thicker, for sure. Then again, Century shutter blades warp 100:1 more than Simplex. Again, different metals (thickness and, in some cases, material itself. The benefit you give Century on the size of their cooling block is giving them credit for creating a problem and then coming up with a way to minimize its impact. Simplex doesn't create the problem in the first place.

- The poor Simplex design causes a multitude of other problems Steve. I already mentioned them, but I did leave out the porous main castings. Easily rectified by powder coating. Well we're here discussing wax on the bands. That was a not as big an issue with Century as long as you used their gate alignment tool. Buildup happened, but a lot slower. I can't ever lay claim on very many warped shutter blades in Century's. None in the ones I acquired from up North, nor the ones from the West Coast. But I always put Wolk steel shutter blades on my rebuilds anyway. The Century's I rebuilt in the Midwest mostly got Kelmar lens changers so the Century trap and gate went away. My dailies stuff was all straight gate stuff.

There are things you can ding Simplex for, even in the trap area (e.g. the lateral guide roller was too think and would warp when it was heat treated) but being too hot versus Century isn't one of them.

-Well, there is also supposed to be a final grind on something critical like the lateral guide roller after heat treatment, pretty much SOP in most machine shops. Just enough extra metal is left for that reason... Like the final grind on the Star Wheels at Lavezzi was the slot. It was done on an air bearing grinder in a sound proof booth. However, my biggest ding for Simplex was the extremely porous main castings, not the Spot Sight Box. Leaking was also aggravated by a hot running projector, Hence the name Simplex Valdez.
The Strong castings were a lot better, plus they also powder coated them.

[Steve Guttag]

I never found that Simplex had more shedding than Century. There was a generation of Simplex runners made by one of the manufacturers where it was evident that they were ground on a CNC but not polished smooth so the stair-steps, fine as they were, acted in an abrasive manner. Those runners would have the film powder up. Century may have had a similar issue but I don't recall any. It was just one era where I came across those runners.

[Mark Gulbrandsen]

I never found that Simplex had more shedding than Century. There was a generation of Simplex runners made by one of the manufacturers where it was evident that they were ground on a CNC but not polished smooth so the stair-steps, fine as they were, acted in an abrasive manner. Those runners would have the film powder up. Century may have had a similar issue but I don't recall any. It was just one era where I came across those runners.

Geez, those must have made a mess. I never had runners like that show up. Sounds like a case where they missed doing the final grind on them, or possibly, a final lapping...

[Randy Stankey]

There was a generation of Simplex runners made by one of the manufacturers where it was evident that they were ground on a CNC but not polished smooth so the stair-steps, fine as they were, acted in an abrasive manner.

My god! You might as well run the film over a saw blade!