Good lamp for 1000fps recordings.

Discussion about 120fps HFR as well as future Ultra HFR (240fps, 480fps and 1000fps) playing back in real time on high refresh rate displays. See Ultra HFR HOWTO for bleeding edge experimentation.
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dervu
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Good lamp for 1000fps recordings.

Post by dervu » 10 Jul 2022, 07:45

Hi.
I am using Sony RX100VI for 1000fps recordings of my monitor screen and I am wondering what would be good lamp for light source that would make my recordings look better?
Is it necessary to have this light source when whole area of recording is monitor? Would it make much difference?
I am aware of some effects of some kind of lamps that can cause weird effects, because they run from AC. What is best bet for limited budget, lets say up to 200-300EUR?

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Re: Good lamp for 1000fps recordings.

Post by Chief Blur Buster » 15 Jul 2022, 02:22

dervu wrote:
10 Jul 2022, 07:45
Hi.
I am using Sony RX100VI for 1000fps recordings of my monitor screen and I am wondering what would be good lamp for light source that would make my recordings look better?
Is it necessary to have this light source when whole area of recording is monitor? Would it make much difference?
I am aware of some effects of some kind of lamps that can cause weird effects, because they run from AC. What is best bet for limited budget, lets say up to 200-300EUR?
The obvious answer is: No.

You don't need a lamp when using high speed video camera analysis of screen behaviors. The screen itself is the light source.

If you are very familiar with manual photography, but unfamiliar with high speed video, the easiest way to understand is that video is simply a series of photographs, and you want to adjust the video as if it was a still photograph -- especially when it comes to analyzing monitors.

I'm curious why you ask since the answer is (usually) obvious -- but perhaps, to forum members who is new to photography concepts (or never learned specific concepts such as video is simply a series of photographs); perhaps this require some ELI5 parlance (Explain Like I Am Five).

The purpose of a lamp is to light-up an object to be photographed.

By "lamp", replace word "lamp" with "light source".

When reading high speed camera HOWTOs elsewhere on the Internet, replace "lamp" with "light source".

The number of photons hitting a camera sensor's pixel is what makes a digital photograph work.

Total darkness means a totally black photograph.

But the screen is its own lamp (light source).

A monitor is not totally dark. It will expose a camera frame.

Video is simply a series of photographs in rapid succession.

A camera is like a human eye (in a metaphoric manner).

The only reason you might need a lamp is to illuminate the exterior of a monitor (the monitor stand etc).
A lamp does nothing to brightness of the monitor's screen.

You already notice with your eyes, that a lamp doesn't make a screen brighter.
Pointing a lamp at a screen makes the screen harder to see.
If the lamp is sunlight-bright, the screen can become impossible to see.

Likewise, the issue is the same with a camera.
A lamp doesn't help make a screen look brighter.
A screen's light source is its backlight / LED / OLEDs, and that's the "lamp" from the screen's point of view (POV).
You can't replace a screen's "lamp" unless you open up the monitor.

A 1000fps camera means 1000 frames per second, which is 1000 photographs per second.

Many advanced video cameras allow you to adjust per-frame settings just like a SLR camera (ISO, shutter speed (or exposure setting), focus, aperture (F-stop), etc). While not all video cameras support such flexibility, most high speed cameras capable of

This is especially important to learn with high speed cameras because the faster frame rates enforce faster shutter speeds (because the shutter speed can't be any slower than 1/framerate).

A high speed camera can't have a shutter speed slower than its framerate. So 1000fps high speed camera means exposure per frame is 1/1000sec, which can make a frame very dark. Requiring a brighter light source (e.g. brighter lamp for unilluminated objects, or brighter brightness setting for a monitor).

"Light source" can be the sun, or a lamp, or a screen backlight, or whatever. Most high speed video HOWTOs just generically parrot "lamp" or "sun" when it is actually just "light source" in general -- just exactly as it is for your human eyes (to see) or for stationary photographs. The thing with high speed video is that shutter speed is fast by necessity (you can't hold a shutter open longer than the time between two frames in video), but if you already know SLR/manual photographs, faster shutter speeds creates darker photographs, due to limited exposure time.

Things that helps a high speed camera:

(A) If adjustable, widest aperture (smallest F-stop number) and focus the camera to screen plane;
makes photo brighter without brighter lamp or brighter brightness setting

(B) If adjustable, highest noise-free ISO setting.
Experiment as needed, bigger ISO numbers are brighter but can become more noisy if too big;
If no ISO setting is available, you can kind of adjust it in postproduction by adjusting video brightness/contrast/gamma/etc in a video editor.

(C) If adjustable, slowest shutter setting permissible for maximum brightness per frame
For 1000fps high speed camera, your slowest shutter setting is 1/1000sec for 1000fps

(D) If necessary, adjust display brightness setting
If the monitor becomes too bright, lower ISO setting or smaller iris is another option to compensate.

Some high speed cameras has none of these settings and simply lock to 360-degree shutter, so if that is the case, the shutter speed is essentially the frame duration. Older cameras didn't give you as many SLR-like adjustments per video frame, so you have to experiment with settings you have access to (e.g. monitor brightness setting) if you're unable to adjust the camera to suit the current monitor brightness you've pre-calibrated to.

Either way, watch for color gamut clipping of any kind (pastel colors becoming oversaturated, dark colors becoming black, bright colors becoming white), ideally you want to adjust your high speed camera to the points where the monitor's color spectrum is accurately captured as much as possible. Where the camera permits you to do so, treat freezeframes like individual photographs, and play with your existing SLR photographer skillz. Adjust camera settings accordingly, treating the video as if it was a series of very fast burstshoots, and video-settings-adjust like you would SLR-settings-adjust.

If you're used to an auto-everything camera, watch at least a few youtubes to understand the basics (ISO / exposure / shutter speeds / aperture).

If you have no ability to manually configure camera during high speed mode, find out what flexibility you have in automatic-overrides (e.g. focus-lock, exposure-lock). If you do, then use a test pattern (e.g. Lagom) to precalibrate your camera settings. A dark test pattern / bright test pattern can cause the shutter speed and/or iris to automatically change, so you may want to hit a medium-brightness test pattern to force a camera's auto-everything to squeeze the monitor's color gamut into a subset of the photograph's color gamut. Once you lock exposure, switch to your monitor material you need to high-speed film. Learning how to override certain auto-behaviors (e.g. auto exposure).
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