Very strange question (exposing analog film to iPhone screen)

Hi folks,

This is going to sound very odd, so bear with me.

I'm looking to do some experimental "photography", as follows:

I'm going to create some digital art in Blender (CGI program).

I'm then going to display it on an iPhone screen that i'll lay flat against a piece of 120 film in a darkroom environment, to see what happens.

Which leads me to my question, how do i work out what my "exposure" should be?

Because this is fairly uncharted territory (or at least that's the impression i get from google), i'm just going to do some experiments where i flash up small shapes on the screen for varying numbers of frames and brightness, and see what happens.

I curious if anyone has more scientific ideas about working out the exposure or any other thoughts on this hair-brained scheme?! For example, predictions on what's going to happen?

Just in case anyone is wondering about my motivation: i've been messing around with CGI art for a few years, and i'm looking for a way to make it more analog, unique, imperfect & special!

I'd try examining my screen with a spotmeter. That might give some ideas on exposure.

juan said:

I'd try examining my screen with a spotmeter. That might give some ideas on exposure.

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Thanks, i thought about doing that, but couldn't get much further in the thought experiment. I guess i could flash up the brightest white and measure that. But then how do i extrapolate my middle grey value from that?

And what is my F stop?

You would need a film plane meter, if one were to use a meter.

I worked with an artist about 1996 or so who made artwork with a computer. His images were a blend of computer-generated images and scanned photos. He needed some photos of the art that he viewed on his screen. I photographed the screen with a Mamiya RZ67 and 140 mm macro lens on Fujichrome Velvia 50 transparency film.

I set up the camera on a tripod with the screen carefully focused and framed as wanted. The room was in total darkness. The camera was equipped with the metered prism finder. I made the exposures in “A” automatic exposure mode. This worked well. The resulting transparencies looked just like the screen image, with one glaring exception. The monitor was a CRT (essentially obsolete now). The individual pixels of the screen were clearly defined as thousands of individual bright dots and quite evident in the transparency. The exposures were about 1/15 second.

There was nothing wrong with my equipment or the film. It faithfully depicted what it saw. The individual pixels of the screen pulse as they receive the signal. Then they fade until reilluminated by the next pulse. What we see is the average intensity. But the pixels are actually “over-lit” momentarily. Our vision does the time averaging, and we perceive a uniform brightness, not the peak brightness that occurs with each pulse.

I think your project would be much more easily done in the manner I described above with a camera, macro lens, and tripod in a darkened room. Depending on how the screen is illuminated, you might encounter pixels visible in the result. That would likely be that case if you tried to “contact-expose” the film. I don’t know how you’d control the exposure unless you did it with a camera and lens.

Whether the results will satisfy you or not can only be determined by you. I don’t know how defined the individual pixels of an I-phone will appear on film. The artist I worked with eventually got what he wanted by taking the computer file to an agency that used it to produce 4” x 5” color negatives on Kodak VPS which he had printed at 16” x 20” for mounting and display. There were no pixels involved, so none appeared on the final images. I don’t know what sort of equipment was used to convert the file to color negatives.

Using a camera, as indicated above is a great solution. You can also put the i-device in you enlarger. You could use any baseboard meter, but you still would need to calibrate the meter by trial and error.

Dazzer123 said:

Thanks, i thought about doing that, but couldn't get much further in the thought experiment. I guess i could flash up the brightest white and measure that. But then how do i extrapolate my middle grey value from that?

And what is my F stop?

Click to expand...

You're not using a lens how can there be f/stop? Use a lux meter facing flat against the phone screen. If you use ISO 100 then 0.1 lux will expose for 1 sec. But the phone is very bright and thus the exposure time is very short and I doubt that you can time it correctly. If you reduce the brightness of the screen I think you will have poor quality.

Thanks guys!

@ic-racer: regarding the Horseman meter: No idea what that is or how it works, I’ll look into it, thanks for the tip.
About using an enlarger: i don't understand what you mean, why would i need the enlarger?

@Ian C: great story! I'm aware that there might be pixels visible. But i guess i could reduce this by placing some layers of
acetate in between to increase the bleed. It's actually the contact "exposure" nature of this idea that appeals to me.
I think pointing a camera and lens at the screen would get a quite different, albeit more predictable, result.

@Chan Tran: ok, this is interesting! I only mentioned the F stop because i thought a light meter would only tell me my shutter time for a
particular F stop.

So if i'm using ISO 400, a solid screen of 0.1 lux will need a quarter second? Is that how it works?
And at 1 lux i will need an exposure of one fortieth of a second (ISO400)?

So in your example, if half my screen is 0.1 lux, and the other half is middle grey, if i meter off the 0.1 lux and expose for 1 second, the middle grey will expose as middle grey?

You said:
"But the phone is very bright and thus the exposure time is very short and I doubt that you can time it correctly. If you reduce the brightness of the screen I think you will have poor quality".

I can time it accurately depending on the frame rate of the iPhone! I don't follow your logic that the iPhone will be too bright, but if i reduce brightness it'll have poor quality. Why can't i just reduce brightness until i get the exposure i want?

Contact copying your phone screen will prove to be virtually impossible. How will you get the film to the phone screen with the phone off and then turn the screen on for a set amount of time to expose the film?

The best solution is to photograph the phone screen (I've done it dozens of times) using 35mm film. You will get individual pixels on the film visible when you scan the film but not noticeable, even in an 8x10 enlargement.

Don_ih said:

Contact copying your phone screen will prove to be virtually impossible. How will you get the film to the phone screen with the phone off and then turn the screen on for a set amount of time to expose the film?

The best solution is to photograph the phone screen (I've done it dozens of times) using 35mm film. You will get individual pixels on the film visible when you scan the film but not noticeable, even in an 8x10 enlargement.

Click to expand...

Not impossible at all. I'll hook up the iphone to my computer as a second monitor. Then i can just flash up images in a very controlled manner from Blender. And it's easy to get the film against the screen. I just take a phone case, block the camera holes, flip the phone 180 degrees from normal and place it in the case with the 120 film (cut to size) in between. that will be light tight.

Like i said, i'm not interested in photographing a screen, that won't yield anything interesting or unpredictable!

Dazzer123 said:

I can time it accurately depending on the frame rate of the iPhone!

Click to expand...

I doubt you'll be fast enough. You're probably looking at exposures of a few milliseconds if you're lucky - less than a millisecond if you're unlucky.

Dazzer123 said:

I'm then going to display it on an iPhone screen that i'll lay flat against a piece of 120 film in a darkroom environment, to see what happens.

Click to expand...

You'll get an extremely blurry image (if you manage to nail the exposure). The pixels in your iPhone are not at the surface of your phone, evidently. There's protective glass and some film between the actual pixel sites and the phone's surface. As a result, you won't have good contact between the image and the film, and everything will end up a big blur. It'll be recognizable, but a blur, still.

ic-racer said:

You can also put the i-device in you enlarger.

Click to expand...

That's a far more sensible approach. And if an enlarger is involved, I'd also suggest not using film, but exposing RA4 color paper instead. Overall it's a lot quicker and easier to test with, and far cheaper than film, too. Try to reach out to this guy: https://www.instagram.com/andrey.pil.art/?hl=en He's done some work exposing color paper using a phone or ipad using an enlarger. I've got one of his test prints and it's actually quite decent.

Ian C said:

The monitor was a CRT (essentially obsolete now). The individual pixels of the screen were clearly defined as thousands of individual bright dots and quite evident in the transparency.

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I never looked into it, except that coincidentally I did around the same time (1998) photograph the image on a CRT. My guess is I ran the CRT at a refresh rate of 85-100Hz, but that's not too far off the 60Hz you were likely shooting at - although you probably did get some banding (?) Here's part of a scan of one of those negatives - it was shot on consumer-grade 400 ISO Fuji film (whatever that was back in '98) and probably also around 1/10-ish exposure:

This is a 100% crop of a 3200dpi scan. Apart from the film grain, there's nothing that resembles what you describe.
Here's a different area of the same negative:

This bit is actually in focus; what you can see here is:
1: Film grain
2: The R, G and B pixels on the computer screen
3: The shadow mask that constitutes the pixel sites within the CRT

A few years later, I must have been mucking about along similar lines with a Tamron macro lens, some slide film and a CRT monitor:

Again 100% crop of a 3200dpi scan, this time on Fuji Sensia 20 slide film. Note that in this case, the CRT was a slightly more modern aperture grill (like the Sony Trinitron of those days) instead of the older-fashioned shadow-mask shown above.

Not sure what kind of effect you ran into; it's something I have never thought of, and have never noticed. I must confess I never spent much thought about how CRT's made different brightness levels; I always assumed it was just analog modulation of the electron beam. The phosphors then excite to a certain level and have some afterglow for a bit. As you said, on average (so with a sufficiently slow shutter speed), it should all average out quite nice, as it does in the examples above.

In the LCD time, I never bothered repeating these experiments. At least not on film. I must have sat with a digital camera pressed against a computer monitor at some point, but fortunately, my memory is hazy on some of the things I've done when I was younger.

Simply turn on your iPhone in a dark room with a "fully black" screen and see what you have.

Illumination from the backlight will appear rather strongly, as the "black" of the screen is only relative to the rest of the image.

You might be able to strip the LCD out of a phone, remove the backlight and use that as a contact element under an enlarger, using the LCD screen as the "Negative", but it's going to take a lot of experimentation and, as Koraks points out, the pixels will be quite prominent.

That's a good point, @Kino. The backlight alone will probably overexpose film in a contact printing scenario. Unless...it's an OLED screen, which I suppose a modern iPhone would of course have. With OLED, black will really be pretty much black.

OP's approach is overtly pollyannish but perhaps some pretty pictures will result. Photos from the 'analog loophole' i.e. screens can produce interesting results.

Along with prior recommendations (like using an enlarger in lieu of contact printing) I'd start with a slower medium like photo paper.

That's ok, maybe it's very blurry, but that's also something i can use when composited with other images (could be a nice way to create a glow or halo effect).

This is just about pure, arty experimentation, i'm not expecting to put any Hollywood FX houses out of business! But i don't want to pi$s away money on film, that's why i'm trying to get a handle on working out the exposure.

On my iPhone, black is the same as the screen being off.

Pollyanna, haha, sure, nothing wrong with that, worst thing that can happen is i burn a few euros and hours for nothing!

Anyway, thanks for now, gotta go do some work!

Well, then it appears you need to start exposing some film and report back...

Dazzer123 said:

Not impossible at all. I'll hook up the iphone to my computer as a second monitor. Then i can just flash up images in a very controlled manner from Blender. And it's easy to get the film against the screen. I just take a phone case, block the camera holes, flip the phone 180 degrees from normal and place it in the case with the 120 film (cut to size) in between. that will be light tight.

Click to expand...

So, that will all happen in the dark and then you hook the phone up to the computer? Or you can cover the computer with a blanket or something while all that happens.

It's definitely easier to test your theory with b&w paper. You can see how fuzzy the output is.

I've used a phone and a tablet in an enlarger. It works fairly well. I never tried it with colour paper, though.

I just tested it with paper. Brightness turned all the way down. On and off as fast as I could with the side button.

Don_ih said:

So, that will all happen in the dark and then you hook the phone up to the computer? Or you can cover the computer with a blanket or something while all that happens.

It's definitely easier to test your theory with b&w paper. You can see how fuzzy the output is.

I've used a phone and a tablet in an enlarger. It works fairly well. I never tried it with colour paper, though.

Click to expand...

A computer screen would be low resolution. The Iphone screen is more than 400 ppi but most computer monitor even 4K one only a bit over 100 ppi.

Chan Tran said:

A computer screen would be low resolution. The Iphone screen is more than 400 ppi but most computer monitor even 4K one only a bit over 100 ppi.

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PPI's don't really matter here. A high-end iPhone is around 1280x2800 pixels. 4k is 3840x2160. So the 4K computer monitor (or TV) has higher resolution. It'll also be easier to photograph the bigger monitor because you don't need a macro lens. Especially relevant for medium format.

koraks said:

PPI's don't really matter here. A high-end iPhone is around 1280x2800 pixels. 4k is 3840x2160. So the 4K computer monitor (or TV) has higher resolution. It'll also be easier to photograph the bigger monitor because you don't need a macro lens. Especially relevant for medium format.

Click to expand...

But if you do contact printing you only get the pixels that fit in your film so the smaller phone is an advantage.

Chan Tran said:

But if you do contact printing you only get the pixels that fit in your film so the smaller phone is an advantage.

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True, but the whole contact printing thing is pretty much out of the question if resolution is relevant. Regardless if the screen is 72ppi or 400ppi, it'll be a bug blur.

Here's a bit a of date imprinting tech than might be relevant to the conversation and the curious.