Plates and Lenses (thoughts for changes?)

[Ryan Gallagher]

So a couple things: Just looking for ways to improve our situation. The joys of a long throw steep angle house.

My predecessors filed our primary flat plates to what to my eye appears to be slightly over-filed vertically, something closer to 178. My best guess for their logic is that for a matted print this allows you to use the matt line without introducing any of the plate shadlow/roll-off on the top and bottom. But for a un-matted print I feel like unless we close our masking and tilt some more (past the plate lines) we are showing a bit more than 185 worth of content.

Here is what one of them looks like in our as set 185 situation without tweaking masking and tilt. Obviously just burying full-bright image in masking is not ideal either. For a matted print we will adjust per print, but for open this is our starting point generally, somewhat based on how the plate was filed.

90mm lenses for our flat setup. Century JJs. Manual side mask, motorized top. It should be stated that masking references and presets have been redone multiple times since these plates were filed, so perhaps their original masking intent was different.


185_plate_fullsize.jpg
Ignore the intensity shadow, my co-projectionist did not hold the loop out of the way of the lens when he took this photo.
Also our side legs can be "dressed" to better follow the plate line, as shown the bottoms could be teased offstage a hair.
Yes that is a big base scratch on our loop, product of people letting it rest on various parts of chassis over the years.




Separately on Lensing.

Our 185 setup uses most of our available screen height. We recently screened Clockwork Orange (166) and it became apparent in the run up that my predecessors have always used the same 90mm flat lenses and just have 166 plates that are filed to the max vertical limit for our screen/masking, somewhere closer to 178 (not too different from these 185 plates shown). Audience didn't care but we were certainly missing a sliver of intended aspect ratio on the top and bottom due to not having a set of 166 lenses. Enough that I notice when looking at the blu-ray backup.

Thoughts to improve our setup/selection? I'm tempted to relabel these 185 plates as 178/185-matted, and strike some new plates for 185 un-matted? Or would you just adjust the masking spikes and hide some more image that way?

In a perfect world our Flat lenses WOULD work for 166 too, but either approach appears to require sourcing some more lenses. Would you maximize screen usage for 185 and get other 166 lenses? Or would you look for a set that can do both and sacrifice some image size for 185?

We do have separate lenses for 133/137 fortunately, which would be well off the screen if we used our flat lenses.

Thanks for your seasoned advice!

[Mark Gulbrandsen]

The answer is simple... Do you want to present all the films you show correctly or not...?

If you do, then you'll have a lens and plate for each format.

End of story.

[Ryan Gallagher]

The answer is simple... Do you want to present all the films you show correctly or not...?

If you do, then you'll have a lens and plate for each format.

End of story.

Thanks Mark. That validation certainly helps my campaign to convince management to source or borrow 166 lenses next time. With a throw of 118ft and a target image height of 14.7ft it appears a 100mm lens would be adequate (15ft image height on 166, compared to 90mm resulting in 16.7ft being oversized for our screen), we have at least that much wiggle room in height.

On the 185 filing topic, would you agree that photo represents a slightly overfiled flat plate, especially when dealing with open-matt prints?

[Mark Gulbrandsen]

If you don't have a big budget, check around with various dealers to see what they have available in used lenses. Check with Film-Tech and Independent Theater Supply in San Antonio, if Cliff hasn't retired.

[Randy Stankey]

...you'll have a lens and plate for each format.

While it is possible to use different lens and plate combinations and get a reasonable picture, I have always considered lenses and aperture plates to be matched sets. Every theater has its own projector(s). Every projector has its own lens(es). Every lens has its own plate. Never are they to be mixed up or swapped around.

I never even breach the subject of swapping things around. I have always told people that every projector must have its own set of lenses for each format and every lens must have its own plate. In fact, whenever I had a theater that didn't have projectors with turrets and aperture changers, I marked lenses and plates so that they'd always be kept together. For instance, projector No. 1 would have a lens and plate that was marked "1F" and "1S." Projector No. 2 would have lenses marked "2F" and "2S"...and so on.

In commercial theaters where I worked, they were rarely set up for anything other than standard flat and Cinemascope formats so "F" and "S" would suffice. If I had machines that were set up for other formats I'd mark lenses and plates with their aspect ratios. e.g. "1-1.78"

There have been some cases where I have had to pound the proverbial fist or stomp the proverbial foot. Except for emergencies (a damaged lens, for instance) I have been adamant: Projectors, lenses and aperture plates are always kept in matched sets!

If you even hint at the idea that lenses and plates can be used separately, they probably will be. You'll go to a theater and you'll find random lenses in random projectors with random plates and everybody will be walking around scratching their heads, wondering why things look messed up. Then it will be up to you to go around to every projector in the building, checking to be sure the right lenses and plates are installed in the machines that they are supposed to be in.

Hint: When you set up a theater, make a list of projectors, lenses and their serial numbers so that, in case things get mixed up (See "Murphy's Law.") you'll know how to put things back the way they belong.

[Mark Gulbrandsen]

While it is possible to use different lens and plate combinations and get a reasonable picture, I have always considered lenses and aperture plates to be matched sets. Every theater has its own projector(s). Every projector has its own lens(es). Every lens has its own plate. Never are they to be mixed up or swapped around.

I never even breach the subject of swapping things around. I have always told people that every projector must have its own set of lenses for each format and every lens must have its own plate. In fact, whenever I had a theater that didn't have projectors with turrets and aperture changers, I marked lenses and plates so that they'd always be kept together. For instance, projector No. 1 would have a lens and plate that was marked "1F" and "1S." Projector No. 2 would have lenses marked "2F" and "2S"...and so on.

In commercial theaters where I worked, they were rarely set up for anything other than standard flat and Cinemascope formats so "F" and "S" would suffice. If I had machines that were set up for other formats I'd mark lenses and plates with their aspect ratios. e.g. "1-1.78"

There have been some cases where I have had to pound the proverbial fist or stomp the proverbial foot. Except for emergencies (a damaged lens, for instance) I have been adamant: Projectors, lenses and aperture plates are always kept in matched sets!

If you even hint at the idea that lenses and plates can be used separately, they probably will be. You'll go to a theater and you'll find random lenses in random projectors with random plates and everybody will be walking around scratching their heads, wondering why things look messed up. Then it will be up to you to go around to every projector in the building, checking to be sure the right lenses and plates are installed in the machines that they are supposed to be in.

Hint: When you set up a theater, make a list of projectors, lenses and their serial numbers so that, in case things get mixed up (See "Murphy's Law.") you'll know how to put things back the way they belong.

That's pretty much what I did. I filed the room number as tiny notches along one outer edge. In 98% of the installs I did with manual projectors, that's all that was needed. It was pretty obvious which was scope and flat. On Auto turret projectors, I still filed tiny notches in to specify theater number.
On manual change multi format systems, I engraved the projector number, and format at the tab end of the plate.
Never had any confusion doing it this way.

[Ryan Gallagher]

Thanks all. Yeah no doubt plates go with lenses/formats/room/projectors. This is true for us as well except for our outliers that lack a dedicated lens pair. There is however a pile of old plates I have not fully investigated yet, but alternative plates won't solve our 166 being oversized issue. 1.66 lenses seem to be the "next" to acquire, or perhaps a 70/1.85 appropriate lens (we have 70mm blowup Streets of Fire coming at the end of the summer).

But I think our current lenses for 70mm will work cause a blowup in theory is still full frame height, unless the lab did something weird with matting.

[Randy Stankey]

Do you know how to calculate for lens focal length?

Everything in front of the lens (throw ÷ image dimension) is an exact proportion to everything behind the lens. (focal length ÷ aperture plate opening) It doesn't matter what units you use; inches, millimeters or cubits. Just keep everything consistent.

If you are calculating an anamorphic lens, don't forget to multiply for the anamorphic factor. (Usually 2 x the horizontal dimension.)

Your calculations probably will not come out to match a lens's focal length, exactly. Just round off to the nearest.

Find a likely lens. Try it in the projector with test film but no plate. See if the image fits the screen the way you want it to. I prefer to make the image just a hair bit bigger. (Shorter focal length.) Cutting off a few inches of picture is preferable to having sprocket holes and frame lines showing.

Once you have your lens installed and aligned cut an aperture plate to match your screen. There's no magic, there. Just work slowly and carefully. It's not hard to do but it can be tedious.

I've known people who do a lot of cussing and throw things when they cut plates!

[Ryan Gallagher]

Do you know how to calculate for lens focal length?

Everything in front of the lens (throw ÷ image dimension) is an exact proportion to everything behind the lens. (focal length ÷ aperture plate opening) It doesn't matter what units you use; inches, millimeters or cubits. Just keep everything consistent.

If you are calculating an anamorphic lens, don't forget to multiply for the anamorphic factor. (Usually 2 x the horizontal dimension.)

Your calculations probably will not come out to match a lens's focal length, exactly. Just round off to the nearest.

Find a likely lens. Try it in the projector with test film but no plate. See if the image fits the screen the way you want it to. I prefer to make the image just a hair bit bigger. (Shorter focal length.) Cutting off a few inches of picture is preferable to having sprocket holes and frame lines showing.

Once you have your lens installed and aligned cut an aperture plate to match your screen. There's no magic, there. Just work slowly and carefully. It's not hard to do but it can be tedious.

I've known people who do a lot of cussing and throw things when they cut plates!

I cheated with one of the Magna-Tech slide rule lens calculators. Used the height value it gave for our throw+1.85+90mm, and then adjusted to read mm lens target for a 1.66 picture at a similar on paper height. (real world height is stretched by our angle), but this method should be apples to apples. 100-105mm was what I came up with for a 1.66 picture to fill a similar height to our flat setup, which is about as big as we can go vertically.

But in a perfect world we would try before we buy. Have some local resources we can reach out to and borrow if they have what we are after.

[Randy Stankey]

Calculators are fine. I often do it the other way because the only thing you need is a pencil and a piece of paper.

You can never find a calculator when you really need one!
If I can't find a pencil, I can still use a sharp stick and a smooth patch of dirt.

[Martin Brooks]

Do you know how to calculate for lens focal length?

Everything in front of the lens (throw ÷ image dimension) is an exact proportion to everything behind the lens. (focal length ÷ aperture plate opening) It doesn't matter what units you use; inches, millimeters or cubits. Just keep everything consistent.

If you are calculating an anamorphic lens, don't forget to multiply for the anamorphic factor. (Usually 2 x the horizontal dimension.)

Your calculations probably will not come out to match a lens's focal length, exactly. Just round off to the nearest.

Find a likely lens. Try it in the projector with test film but no plate. See if the image fits the screen the way you want it to. I prefer to make the image just a hair bit bigger. (Shorter focal length.) Cutting off a few inches of picture is preferable to having sprocket holes and frame lines showing.

Once you have your lens installed and aligned cut an aperture plate to match your screen. There's no magic, there. Just work slowly and carefully. It's not hard to do but it can be tedious.

I've known people who do a lot of cussing and throw things when they cut plates!

The formula is FW=DA (so F=DA/W, W=DA/F, D=FW/A and A=FW/D) where: F=focal length of the lens in inches
W= width of the image in feet
D=Distance from the screen in feet
A=Aperture of the image in inches.