I was watching the HBO movie All the Way (which was excellent, BTW), and when they showed the Democratic convention, I was struck by the ginormous photos of LBJ behind the stage–thirty feet high, easy, with no visible seams. It might be interesting to know how such a thing would be made even today, but it seems like there would be options available now that would have been impossible then (like laying the blank canvas out flat and having a Roomba-style printing robot travel around putting different colored ink where it needs to go). I absolutely cannot imagine how it was done with 1964 technology.
Are you asking how photographic enlargements are made, how offset lithography printing works, or something else?
I have no idea what the second thing is, so I guess the first? But I don’t mean normal-sized enlargements. I mean, in 1964, how could they make a photo as tall as my house?
The practical / science of large black and white photographic printing isn’t actually that challenging.
First you need a light tight room. Any factory will do. Black out any windows or light leaks.
Conventional black and white printing materials are blue sensitive which means you can work with red (more recently yellow / brown) safe lighting. In other words you can see quite clearly what you are doing. For large printing the safe lighting would be turned down to a minimum level since the exposure times will be long. Although during exposure it would simply be turned off.
The photographic enlarger can be turned on it’s side - think of a cinema projector on a single frame. The reality is you would typically use a specially built horizontal copy camera set up. All you need is a light source, negative holder and lens holder with a precision method of moving and then locking the lens plus ‘bellows’ between the negative and the lens. The negative will be in a glass carrier (held between two sheets of glass) to stop it falling out or ‘popping’ out of focus as it heats up.
Ideally the enlarger is mounted through a wall so the light source side is isolated completely from the light sensitive material side - other than the actual light making the exposure.
The print material can be mounted on the wall. Conventional print material is available in long rolls - think wall paper. Or you can ‘paint’ (commerially available) light sensitive emulsion on any suitable base including solid panels.
Alternatively, if the room is tall enough, the enlarger can project downwards and the print material can be laid out on the floor. My understanding is the horizontal set up is more usual.
Although these days rolls of paper can be machine developed it was previously just as easy to develop in big trays on the ground. Vital if the image is being made on solid panels.
The developer solution could be slopped around with mops. This actually allowed the technician to slop more, fresher developer on those parts of the image which were too light - underexposed due to fall off from the enlarger lens. Or indeed simply allowed the tones in the image to be balanced.
There is actually one problem. The exposure times can get very long. There is a thing called reciprocity failure. Basically at long (or incidentally very short) exposures the rule of ‘half the brightness needs twice the exposure time’ breaks down and a calculated 10 minute exposure will probably require more like 30 minutes or an hour.
For a really big print an exposure of several hours is possible.
There is a limit to how bright the enlarger light source can be before it will be so hot it damages the negative. However it makes sense to work with a copy negative which is as thin as possible.
On the plus side large prints are intended to be viewed from a distance so (relatively) minor problems with sharpness can be ignored.
Plus there is also the option of exposing a significant fraction (halves, quarters) of the image and assembling the final result from these.
TCMF-2L
What TCMF-2L said - basically just like you would print a photo, only the photo-sensitive paper is much further away from the lens so correspondingly larger, in a nutshell.
However, the kind of poster you’re talking about is more likely to have been made by printing not developing, if many copies of the same poster are desired. The enlarging process outlined already would be used to make printing plates, instead of prints (in 4 colours) and printed on an offset press.
Some detail on how the process works here, under section 2.
The method used by Kodak for their “Colorama” giant color photos in Grand Central Station is explained here. (Unfortunately, slide show with little text/page.)
To get at the nub of the OP’s question, these processes are not theoretically limited in the size of their output, correct? To produce an image as large as the one cited, one just needs a press large enough to accommodate paper that size?
They aren’t all a single sheet of paper. At large enough sizes the seams become invisible at the intended viewing distance.
And is no different from how normal paper billboards are mounted today - a jigsaw puzzle of individual sheets pasted together.
The size of large format outdoor advertising hoardings still use the terminology associated with pasting up lots of sheets to make a complete picture, even if the output now is often a digital screen.
So, a standard billboard is called a ‘48 sheet’, a wide screen billboard a ‘96 sheet’, a poster that sits on the end of a bus shelter is a ‘6 sheet’ on so on.
Just because you can’t see the seams doesn’t mean the poster was printed on one giant football field sized sheet of paper.
It was printed on rolls, and the rolls were pasted on the wall, and the seams don’t show because they’re paper-thin.
I think there might be a limit as to how big they can get where the ink on the cylinder would dry before it made it onto the paper, but like has been said, in practice they’re one size and larger images are pieced together.
FWIW, pantographs are also widely used to create large detailed images, especially one-offs. I’ve made many incredibly detailed drawings from photographs using a pantograph. Very easy to scale up and as said, building sized images would be done in sections. Drawing/painting with “photographic realism” isn’t as difficult as you might imagine.
I recall a huge poster in an airport that you could see close up from an escalator. People were amazed that it was a photo-realistic drawing and not an actual photograph. Large strokes of color were used to create shading on areas that from a distance couldn’t be discerned. The rough edges to shapes were apparent close up but just added to the realism at a distance. I’d think photo billboards would look similar close-up with much less clarity in the details than they appear to have.
Very interesting! Makes sense, thanks.
By the way, until pretty recently, outdoor billboards and other large-format ads were simply painted:
I’m not sure when the switch was made to printed materials, but it wasn’t that long ago (Wikipedia doesn’t say either, but I think the 1990s or so).
They could look just like photos, but they weren’t. I don’t know about the photo of LBJ, but it was possibly simply a photo repainted onto a large surface.
Could be!
It’s hard to be sure, but I’m guessing these were photo reproductions not paintings. It’s not like the tech to do blowups didn’t exist at the time.
Nice find. Is there a discontinuity between the top and bottom half of the LBJ images there, or is that just a shadow?
IIRC, the technology of the time involved giant drums. For one-off giant pictures… Very similar to how old-fashioned scans and faxes were done - Get a giant drum, say 3 feet in diameter gives over 9 feet of width, by however long the drum is. wrap paper around it. The original is put on a correspondingly smaller drum (say, holds an 8x10). as the drums turn in sync, and electric eye (photosensitive cell) translates the value on the original into a command to spray the large drum with the appropriate amount of ink. (For full colour, repeat process with Black Cyan Magenta Yellow ink and sensor filters). For much bigger photos, this process would also produce strips to be pasted together on a more robust backing. Obviously, if you are populating billboards all over America and need 1000 copies of more, offset press is the way to go. For one-off, this drum printing is a lot less labour.
This sort of tech is nothing new. In the film “Citizen Kane”, IIRC there is a giant photo behind him at his political rally too.