Chasing Focus...

[Ryan Gallagher]

This is gonna sound like a dumb newbie question because it is, and 3 years in I still have plenty of newbie questions.

For Cinemascope lenses that have their own focal ring. What is the relationship between it and the projector knob methods. Is the ring generally best thought of as a "course" adjustment, and the knob a "fine" adjustment.

What would a normal install entail. Setting the ACTUAL throw distance on the focus ring.... and only using the knob forever after?

We had our first scope screening tonight of the summer series, where we kinda made our own bed by thinking we were being clever, but in the end we probably set ourselves up for a struggle. One projector has a turret and it's not the problem because it has a dedicated scope focus (we never pull the scope lens), print to print might require tweaking but not much.

Our single lens unit gets swapped all the time, our depth rings have not been set to make going between formats easy without doing a bigger than desired focus correction. With that in mind having just come out of a 1.37 film, we thought hey, let's use the scope focus ring instead so that the knob is barely needed when switching to scope next time. (in reality we should probably start from a flat lens and not 1.37). We ran a couple test reels and fought with focus on that unit, by the time the reel ended we still weren't quite happy and figured we'd have to do a little live focusing during the screening to nail it. But oh boy, nail it we did not, it felt like it would go from out in one direction to out in the other without ever passing through sharp, or we were running into some limit of focal travel. We abandoned the ring method but even the knob wasn't behaving. It doesn't help that the focus knob on this unit has some slop before it engages in either direction.

Is it possible to have a focal distance set on the lens ring that will make it impossible for the knob to bring it into focus? If yes I feel like that is where we might have gone wrong.

Even before we stepped in it by playing with the ring, we have always struggled a bit to find focus. It looked great with 35PA before any of the reels, but it seems like once we are into actual prints there is always a focus correction. What is the story there? Is 35PA thicker? or printed on a different side due to it being measured film? From 120ft away it's a bit challenging to have confidence, even with binoculars. I really need a spotting scope that can mount to an arm next to the port glass (and younger eyes).

Obviously what is probably warranted is an afternoon in the different formats re-setting the lens depth stops to approximate "focus" against a known common print or loop, but it is pretty hard to set those stops up and "nail" a perfect focus without relying on the knob also it seems.

It also didn't help us any that the reference line for the ring on this scope lens when mounted is pointed away from the operator, perhaps that could be sorted too. Even if I had wanted to make a huge move the audience would see and set it back to our throw, I couldn't see that side of the lens easily (christie in the way).

We only got 1 focus complaint at the top of reel 2, and it did improve quite a bit as we worked through it, but we were never satisfied it was actually in focus. There arrived a place where we called it "good enough", rather than continue to poke at it, but we ended the film on that projector and credits, although legible, revealed we definitely weren't there yet.

[Ryan Gallagher]

If one was to undertake resetting lens collars/mounts for better focus uniformity between format changes... what order should one go in?

1. Set focus knob to center of travel.
2. Set up FLAT, adjust collar to approximate focus.
3. Set up SCOPE (with ring set to actual throw distance), adjust collar to approximate focus.
4. Set up 1.37, adjust collar to approximate focus.

Should one do this with 35PA? (Considering 35PA seems to fail us as a starting point more often than not).

Is there a way to get better than "approximate" matching considering the big moves that shoving the lens around in it's mount causes?

[Randy Stankey]

The focus ring on an anamorphic lens only affects alignment of its internal lens elements. It doesn't really affect overall focus.

Anamorphic lenses generally have two components. There is a main lens assembly which brings the image into focus on the screen and an anamorphic prism assembly which "unsqueezes" the image. Those two components work independently of each other. It doesn't matter whether you use an anamorphic adapter on a standard lens or whether you use an "all-in-one" anamorphic lens. They all have those two, basic, components even if they are all in one housing.

When you turn the focus knob on the projector, you are bringing the focal plane of the lens into alignment with the film. When you turn the focus ring on the anamorphic lens, you are bringing the anamorphic prism assembly into alignment with the main lens assembly. The nodal points of those two assemblies have to be in precise alignment.

If internal parts of the lens are not aligned, you won't get a clear picture, no matter how well you adjust the focus knob on the projector.

[Ryan Gallagher]

The focus ring on an anamorphic lens only affects alignment of its internal lens elements. It doesn't really affect overall focus.

Anamorphic lenses generally have two components. There is a main lens assembly which brings the image into focus on the screen and an anamorphic prism assembly which "unsqueezes" the image. Those two components work independently of each other. It doesn't matter whether you use an anamorphic adapter on a standard lens or whether you use an "all-in-one" anamorphic lens. They all have those two, basic, components even if they are all in one housing.

When you turn the focus knob on the projector, you are bringing the focal plane of the lens into alignment with the film. When you turn the focus ring on the anamorphic lens, you are bringing the anamorphic prism assembly into alignment with the main lens assembly. The nodal points of those two assemblies have to be in precise alignment.

If internal parts of the lens are not aligned, you won't get a clear picture, no matter how well you adjust the focus knob on the projector.

So I guess the question is what position to set the "alignment ring" on the anamorphic assembly before doing all the other adjustments. Our other projector has it set near 120, which does correspond to 118ft of our throw measured from the front of the lens. Or is it something that has to be done by eye on screen?

And so yes, once set, no touchy... which explains why most of those rings have a lock feature! That was where we went wrong for sure. So if both knob and ring are now "out"... how does one get back to both alignment and focus?

[Randy Stankey]

We have, here, at Film-Tech, a page in the archives that describes how to focus an anamorphic adapter:
https://www.film-tech.com/warehouse/...amorphics.html

Basically, you turn the anamorphic adapter down to its lowest setting then run a piece of test film. (In a pinch you can use something with a high contrast image like the credits from an old trailer.)
Focus the horizontal as well as you can and lock it in. Focus the anamorphic adapter for the vertical parts. Go back and forth, checking the horizontal focus, then the vertical focus, couple of times until you get the best picture. Lock the anamorphic ring down and keep it that way.

If you have some Kapton tape that you can seal the whole ring in place with, more's the better. Don't use regular, black tape. It will leave all kinds of black stickum all over the place. Use Kapton. It's aerospace grade stuff. It's strong, flexible, heat resistant, fire resistant, chemical resistant and it won't leave so much stickum.

[Ryan Gallagher]

We have, here, at Film-Tech, a page in the archives that describes how to focus an anamorphic adapter:
https://www.film-tech.com/warehouse/...amorphics.html

Basically, you turn the anamorphic adapter down to its lowest setting then run a piece of test film. (In a pinch you can use something with a high contrast image like the credits from an old trailer.)
Focus the horizontal as well as you can and lock it in. Focus the anamorphic adapter for the vertical parts. Go back and forth, checking the horizontal focus, then the vertical focus, couple of times until you get the best picture. Lock the anamorphic ring down and keep it that way.

If you have some Kapton tape that you can seal the whole ring in place with, more's the better. Don't use regular, black tape. It will leave all kinds of black stickum all over the place. Use Kapton. It's aerospace grade stuff. It's strong, flexible, heat resistant, fire resistant, chemical resistant and it won't leave so much stickum.

Perfect. Hah. Knowing now that it is not a focus ring at all makes our evening's follies make total sense. File that one into the pile of "if it's not broken don't fix it, especially right before a screening". We'll take a moment before we swap back to flat on Wednesday to get these lens elements re-aligned. I can save all my mounting/depth improvements for a rainy day as long as we can reliably get a focus.

In hind-site I bet this particular scope lens has been just slightly out of alignment for a while, and explains some of our focus headaches with it. I even have a vague recollection of when I first started in the booth doing some lens cleaning and investigating how the locking ring worked. It was probably me that messed it up 3 years ago! There is a difference between being out of focus and out of focus HORIZONTALLY, the later of which I had no idea was possible until now. Thanks for the quick lesson.

Though it does seem true you learn a lot more a lot faster by making mistakes!

[Randy Stankey]

Wait until the end credit roll, after a movie, when everybody's already left the theater. Focus your anamorphic on that. First the horizontal, then the vertical.

It won't be perfect but it'll be close enough to work until you can get some time to put in a piece of test film and do it proper-like.

[Ryan Gallagher]

Wait until the end credit roll, after a movie, when everybody's already left the theater. Focus your anamorphic on that. First the horizontal, then the vertical.

It won't be perfect but it'll be close enough to work until you can get some time to put in a piece of test film and do it proper-like.

We are fortunate that we only show 1-3 films a day starting no earlier than 3pm, and not all prints. We'll just come in early one day. Next scope print isn't until the 19th.

[Randy Stankey]

Don't forget. Most people probably just set the the distance measurement on the adjustment ring and call it a day. They might tweak it during the credits of the next film but it's only the people who try to do their jobs right that actually break out the test film and do it properly.

Bottom line: Do what you can with what you've got until you have time to do it better.

[Vern Dias]

This is gonna sound like a dumb newbie question because it is, and 3 years in I still have plenty of newbie questions.

For Cinemascope lenses that have their own focal ring. What is the relationship between it and the projector knob methods. Is the ring generally best thought of as a "course" adjustment, and the knob a "fine" adjustment.

What would a normal install entail. Setting the ACTUAL throw distance on the focus ring.... and only using the knob forever after?

We had our first scope screening tonight of the summer series, where we kinda made our own bed by thinking we were being clever, but in the end we probably set ourselves up for a struggle. One projector has a turret and it's not the problem because it has a dedicated scope focus (we never pull the scope lens), print to print might require tweaking but not much.

Our single lens unit gets swapped all the time, our depth rings have not been set to make going between formats easy without doing a bigger than desired focus correction. With that in mind having just come out of a 1.37 film, we thought hey, let's use the scope focus ring instead so that the knob is barely needed when switching to scope next time. (in reality we should probably start from a flat lens and not 1.37). We ran a couple test reels and fought with focus on that unit, by the time the reel ended we still weren't quite happy and figured we'd have to do a little live focusing during the screening to nail it. But oh boy, nail it we did not, it felt like it would go from out in one direction to out in the other without ever passing through sharp, or we were running into some limit of focal travel. We abandoned the ring method but even the knob wasn't behaving. It doesn't help that the focus knob on this unit has some slop before it engages in either direction.

Is it possible to have a focal distance set on the lens ring that will make it impossible for the knob to bring it into focus? If yes I feel like that is where we might have gone wrong.

Even before we stepped in it by playing with the ring, we have always struggled a bit to find focus. It looked great with 35PA before any of the reels, but it seems like once we are into actual prints there is always a focus correction. What is the story there? Is 35PA thicker? or printed on a different side due to it being measured film? From 120ft away it's a bit challenging to have confidence, even with binoculars. I really need a spotting scope that can mount to an arm next to the port glass (and younger eyes).

Obviously what is probably warranted is an afternoon in the different formats re-setting the lens depth stops to approximate "focus" against a known common print or loop, but it is pretty hard to set those stops up and "nail" a perfect focus without relying on the knob also it seems.

It also didn't help us any that the reference line for the ring on this scope lens when mounted is pointed away from the operator, perhaps that could be sorted too. Even if I had wanted to make a huge move the audience would see and set it back to our throw, I couldn't see that side of the lens easily (christie in the way).

We only got 1 focus complaint at the top of reel 2, and it did improve quite a bit as we worked through it, but we were never satisfied it was actually in focus. There arrived a place where we called it "good enough", rather than continue to poke at it, but we ended the film on that projector and credits, although legible, revealed we definitely weren't there yet.

If people referred to this ring using it's proper name (Astigmatism adjustment) then there would be much less confusion on the subject.

The best way to do this is with a test loop with a cross hatch pattern or some form of both vertical and horizontal lines in it.

The procedure is simple:

1: "rock" the projector focus adjustment back and forth observing the sharpness of the vertical and horizontal lines on the screen.
2: observe - do the vertical and horizontal lines come into sharp focus at the same time?

2.1: Yes: the astigmatism adjustment is correct.

2.2: No:
2.2.1 Turn the anamorphic's "focus" (astigmatism) ring slightly in one direction

3: "rock" the projector focus adjustment back and forth observing both the vertical and horizontal lines on the screen.
4: observe - does it take more or less change in projector focus to make the vertical and horizontal lines de-focus at the same rate?

5.1: if less, continue to turn the anamorphic's "focus" (astigmatism) ring slightly in the same direction
5.2: if more, turn the anamorphic's "focus" (astigmatism) ring slightly in the opposite direction

6: Rinse and Repeat - continue adjusting the anamorphic's "focus" (astigmatism) ring until both vertical and horizontal lines on the screen are equally sharp.

The goal is to find the position of the anamorphic's "focus" (astigmatism) ring where both the vertical and horizontal lines are equally sharp at the same position of the projector's focus adjustment knob.

If you cannot achieve this goal, you have a bad anamorphic lens.

[Gordon McLeod]

Some of the integrated anamorphic use a retro focus design and they can be a bit more difficult to setup initially. with certain one set the anamorphic at infinity and use the focus knob to adjust focus to the best and then adjust the anamorphic.

[Ryan Gallagher]

Did anyone have input on why 35PA will seem completely in focus, but then you run a print and it looks like you have a slight adjustment to make still?
I suppose we should make some text heavy scope loops and use those to get a more reliable focus ahead of screenings.

Where there any prudent tips for what format order to go in if we are trying to get our lens collars set better for focus across all formats?

Thanks all on the procedural tips for astigmatism adjustment. 35PA Loops hang next to both projectors, and are used before every film if there are format changes (except double features). The procedure in the link sounds the most intuitive to me, and we have MPAA loops and other loops with text available to check our work, as well as a house print if we want to be doubly sure before running anything else. Plenty of trailers to chop up if we need more scope specific loops. I also have a laster disto and can just shoot the screen and set it from the measurement if I wanted to try the lazy route first.

Our house print is not scope but I suppose if we ran the last reel of it with full crawl it would afford tons of time to feel confident in our astigmatism adjustment without putting more mileage on a distribution reel, it would just be wider than usual.

If your curious our anamorphics according to my inventory notes are:
IscoOptic Ultra MC 5.91in/155mm with Ultra-star Cinemascope Attachment * HD
IscoOptic Ultra MC 5.91in/155mm with Ultra Anamorphic MC 2x

While not identical they are close enough that I could probably just set the ring based on the No. 2 projector's ring position to get back to where we were. But checking if where we were is the best we can do seems prudent.

I like the idea of kapton tape, I have some thin stuff at home but need to pick up some wider stuff. Locking the mating seam between the attachment and the anamorphic, as well as a backstop against pulling out the locking ring seems useful once set.

How we went south this time was, although we moved the ring a little (falsely thinking it was an alternative way to focus) and had good horizontal and vertical focus on 35PA, during the print test reel it seemed we needed more focus adjustment, and I went down to the end of the balcony and tried to call it with my counterpart on radio, but our mistake was we continued to move the astigmatism ring here rather than switching back to the knob. So we landed with the ring not where it was during 35PA, and focus not on screen yet. Once rolling the print we were unaware we had put the ring into a position where focus wasn't going to be possible, and the interplay of the two mechanisms was very difficult to get right on less than ideal focus footage of a very very dark film (There Will Be Blood), especially without the knowledge of exactly what the lens ring was actually for (vertical astigmatism/focus, rather than overall focus).

Venue is film-dark for two days right now, my first chance to correct will be Wednesday ahead of two flat prints, but not absolutely needed until the 19th for next scope print. I'm not worried now that I know what everything does and how to fix it.

[Frank Cox]

Did anyone have input on why 35PA will seem completely in focus, but then you run a print and it looks like you have a slight adjustment to make still?

Not all film is the same thickness.

[Ryan Gallagher]

Not all film is the same thickness.

Thanks Frank. I suspected that was the answer. In handling 35PA the stock feels thicker/stiffer than most prints. I suppose on the bright side if we are "noticing" focus differences between print stocks we are paying appropriate level of attention to focus. So some minor focus tweak is expected for reel 1 and 2 of untested prints, we just need to improve our ability to sight that difference reliably from 120ft away. Experience will probably get us there eventually, but for now we do a lot of looking through binos hoping for some text or looking for grain patterns.

[Phil Ranucci]

Isn't 35PA original camera positive film, not printed at absurd speed?