Pinhole Aperture Plates

[Ryan Gallagher]

What are the range of intended uses for these factory pinhole aperture plates?

I did manage to score some of these rarities for our booth. I'm only aware of one original intended use, for strong lamphouse alignment along with the factory string kit.
I could see also using them with align-o-tron to get the laser in the ballpark of center.

But are there other uses?

They don't seem too useful for lamp alignment because the lamp shadow would be larger than the projected pinhole. Though if you were way out you could tell.

Maybe to align two projectors on screen (if you lack any more useful tools like SMPTE or RP-40 loops?)

Or were they just another form of blank you could get with a starter hole?

EDIT: I suppose with RP40 you could use them to frame up to dead center. But just as easily doable with RP40 and your masking references.

[Tony Bandiera Jr]

The main purpose is to give a completely blank slate with a rough center reference to custom cut plates to correct for keystone or to create plates for oddball aspect ratios. The alignment kit use was not an "original intended use" as pinhole plates pre-dated the Strong kit by many decades.

They are the best starting point for most severe keystone cuts, as even the standard "undersized" ratio plates were often too open for extreme cases of keystone.

Fun fact: The late Charlie Ajar used to brag that he had "micrometer eye" and could machine anything (or cut plates) without having to measure until the very end. I lost a very expensive bet to him when a studio requested custom plates. He had to start with a pinhole plate, and get either the horizontal or vertical dimensions within three thousandths of an inch of what the guy wanted. With ONLY his eye, he got one dead on and the other off by 2 thousandths. It cost me almost two weeks pay. ($600+ lunch at a swanky Beverly Hills restaurant.)

[John Eickhof]

what Tony said is correct, in fact a typical pin hole plate of the day was a blank plate with a 1/4" hole dead center to provide a starting point for custom filing or cutting, they were often used in studios for custom process shots and matte shots for rear screen projection. there also were plates with a tiny pin hole that were used to project the lamp arc image on the screen minus lens to check arc alignment just like a pin hole in a card is used to view the sun during an eclipse. I still have some in stock for simplex standards, supes, E7s and XLs plus plates for Century C and A series plus Brenkert and Motiograph. Also note that the plate supplied with the strong kit is not a plate at all, it is slotted to insert the string to center and it has clips to snap it into the aperture of the trap thus it can be used with most models of equipment, In the day most lamp manufacturers had alignment kits that were very simple rods and lens barrel adaptors that would line up the aperture with the arc lamp (strong made them, and Ashcraft) the peerless kit was unique in that it had a set of rods of various trims to align with the aperture and lens by a set of parallel discs that you would physically align with each other by moving lamp or projector. I have a nice kit made in the 1930s by Ben Drosty of Western Theatrical Equipment that is usable for several model lamps and trims. As well as an original Peerless alignment kit.

[Ryan Gallagher]

Cheers for the info. The ones I landed are the true pinhole, not the 1/4in starters. I suppose I'll give them a burl when we next adjust our lamp alignment for 35mm coming out of 70mm, I wasn't thinking about the pinhole projection aspect being useful for alignment. (I didn't score any 70mm pinhole ones, just 35mm, You got any of 70mm pinholes for Century JJ John?).

We lack a strong alignment kit, so I have never seen the "plate" that came with it. Only an align-o-tron available here.

I don't believe our keystone is severe enough to have to start from something other than an undersized plate, so these will remain pinhole tools for now.

[Jim Cassedy]

I always thought they were for projecting pictures taken with a pinhole camera...

[Harold Hallikainen]

I always thought they were for projecting pictures taken with a pinhole camera...

In the 1970s and 80s, I had a shop in a metal building that was held together with sheet metal screws. One of screws had fallen out. The remaining hole made a perfect pin hole projector. On the side of a shelf, we could see a bright color image (upside down) of the courtyard outside the building.

[Paul H. Rayton]

That phenomena is known as "camera obscura". It's been observed for centuries, but it's always interesting to see it occurring "in real life"!

[Carsten Kurz]

Back in they days (never thought I'd use that phrase someday), our father took us boys to school with the large Mercedes T1/TN van he was allowed to use from work. We often sat in the back cabin, simply sitting on the wheel arches (no one thought about safety then), as there was not enough space in the front for all of us.
The back compartment had no windows. But at the top of the two back dors, there was a very small opening that let in some light. That made a moving camera obscura, we could see the houses we'd pass sliding away upside down on the side walls of the van. At the time, I didn't know what a camera obscura was, the effect just looked natural to us.

[John Eickhof]

Ryan, I have never seen a 70mm plate for Simplex pr Centuy with a pin hole but have seen solid blanks for custom ratios you had to drill a starter hole in them plus there were some plates of narrow width for keystone correction as well as some with height reduction for deep curved screens like D-150 but that was many years ago, the beautiful feature of the Simplex or Century 70mm is the plate is a flat piece of brass thus very easy to shear out and make...not like a 35mm Century C, or Simplex where they are pressed out and embossed. So if you want one...make one.

[Steve Guttag]

I have definitely seen Century Pinholes. Simplex "Pinholes" are for very large pins (something like ⅛" or maybe larger. The Simplex XL plate pinholes are not even centered to the image.

[Mark Gulbrandsen]

Actually, who made the aperture plates also determines if the pin hole is in the center or not. Wolk plates were all over the place as mush of his tooling was worn out. Some Simplex plates were off, and the Strong made plates were nothing to write home about and were touch and go depending on if you were installing turret or single lens mount machines. The older the plate, the more accurate they generally were.

[Ryan Gallagher]

Actually, who made the aperture plates also determines if the pin hole is in the center or not. Wolk plates were all over the place as mush of his tooling was worn out. Some Simplex plates were off, and the Strong made plates were nothing to write home about and were touch and go depending on if you were installing turret or single lens mount machines. The older the plate, the more accurate they generally were.

One of mine has the black petina on it, probably period or "used", 2 look brand new, and 1 looks "handled" a bit. Will compare them all in a projector and see how well they match.

I guess there was not really a need for 70mm pinhole plates on Century JJ, cause if alignment is good for 35, it is "supposed" to be fine for 70 too. Just focus/eccentric to adjust if you are using the spreader lens, or focus/eccentric plus distance if not. Though I do imagine something equivalent was manufactured as starter custom plates PE-719-04 was in theory a 70mm plate with a .040 pinhole. Someone previously posted this 70mm plate catalog sheet:

Century 70mm Aperture Plate Options.png

[Mark Gulbrandsen]

Some plates had a black oxide coating, and on some, the brass simply turned black from age.

[Ryan Gallagher]

I threw in the two pinhole plates yesterday when we had the theatre to screen test a very pink and beat up print of Fabulous Stains.

I can see it's benefit for lamp alignment. Although dim, it is a much sharper image of the reflector shadow. I didn't poke our focus/alignment to see if I could better make out the hotspot or anode shadow, but certainly will next time we need to touch that.

They also seem handy if you were gonna file new plates, could use it with the lens in to frame RP40 on dead center (the center diamond is all that the pinhole exposes), then set your masking to the RP40 target, then file to your masking. (Assuming of course the pinhole plates you have are reliably on center).

[Mark Gulbrandsen]

Yep, I filed lots of plates from pinhole. Some theater would twin or triplex, and there'd be one or two strange aspect ratios. First I use a nibbling tool, then an aperature file to clean it out to where it needs to be.