Help Requested: Video recording with a DSLR or Mirrorless camera.

As Clint said, still photography and video are different. With stills, it's a standard procedure to frequently (or automatically) adjust ISO and shutter speed. With video, the frame rate and shutter speed must remain fixed. Likewise, the ISO normally must remain fixed while rolling. Otherwise, it causes a discontinuity on the clip.

So controlling the exposure on video is harder than with stills. You can't generally change the shutter speed. ISO can be changed in between clips, but depending on the camera, that may not help. It is increasingly common that video-centric mirrorless cameras have one or two native ISOs, and the in-between values merely use digital amplification -- no different than if you adjusted the exposure in FCP. I've tested that many times on my Sony FX6 - there's no difference in final image quality if I shoot it underexposed at native ISO 800 and brighten it in post vs increasing the in-camera ISO.

That can leave the video shooter having only aperture, ND, and light as methods of adjusting exposure.

Unfortunately, there are no "compact" DSLR-form factor mirrorless cameras that have built-in ND. This is due to the large sensor size combined with insufficient mechanical space to roll or pivot the ND element out of the light path. One semi-exception is the Blackmagic Design Pocket Cinema Camera 6K Pro, but that's pretty big, and ideally, you'd shoot BRAW, which FCP cannot read. But there is a third-party FCP plugin that can read that.

Thirteen years ago, when I shot video with the Canon 5D Mark III, I used auto ISO and a fixed shutter speed, but that was for less serious material. Since 2015, my doc team hasn't used auto ISO -- we manually control that. Our FX6 cameras have smoothly variable internal auto ND, but we almost never use that because the auto-exposure system isn't sufficiently responsive.

Well any decent modern camera will be able to shoot in shutter priority mode with AF on.  You have a huge choice of cameras that will do that so it is not an issue if you are willing to invest a few quid. 

However, the problem with using autoexposure is that, as the camera decides to change exposure, you can get jumps. I prefer to be in control and to set a manual exposure that is not going to clip highlights and to use keyframes in post to control exposure if there is changing light. This is greatly facilitated by shooting log or even raw where there is far greater flexibility in post. In any case you still need to use ND filters if you want to use wide apertures in bright light.

I would still argue that the jitter is mainly caused by camera movement. You can easily test this by shooting on a tripod at high shutter speed with no camera movement, adding movement in post, and compare with what you get if you pan the camera.

I would guess almost all modern mirrorless cameras allow you to shoot in shutter priority with AF on but that will not solve your issue if shooting outdoors in bright light as you would still have to use a small aperture or you would clip highlights. In fact it is a lot better to use manual exposure mode and just set the shutter and aperture manually but that would not solve the issue. The only way to do that is to use an ND (external or internal) or other filter (e.g. polariser) to reduce the amount of light hitting the sensor. 

However, as far as jitter is concerned, the  jitter you are talking about is caused by non-smooth camera movement and not by using a shutter speed that breaks the 180 rule. So ND filters will not solve that problem anyway. A stabiliser is required.

Finally, you are the man who said you could afford some ridiculously expensive car so what is a few grand to you for a camera and lenses plus accessories that allow you to do what you want while you can? Seriously, you can’t take it with you 🤣. The Nikon cameras I use have excellent subject tracking which makes life a lot easier than manual focusing.

That is a good question. Digital cameras cannot effectively support ISOs more than about two stops below the rated value, and even then, it risks image quality. When you switched from (say) ASA 160 to ASA 20 film, that was like changing to a sensor with three stops lower native sensitivity. But today, we can't change the camera sensor.

We can select a lower ISO, within limits. But the sensor has a single fixed native sensitivity, with the exception of dual-gain sensors, which have two. Some cameras let you go (say) two stops below the lowest rated ISO, but there is always an asterisk or warning. That is because the sensor is really still at the lowest base ISO, say 800. When you select ISO 200, the sensor is still exposed at 800 from the standpoint of "full well capacity." It may show you a darker LCD image and lower waveform or histogram, but you have no more real headroom than before.

The camera may try to hide this by digitally manipulating the sensor data or in some cases using negative analog gain, but this cannot hide the lower dynamic range.

In the film days the closest similarity would be shooting ASA 160 film, setting the camera ASA dial to 20 (which overexposes three stops), then pull-processing that by three stops during chemical film development. This works better than digital because film has better, smoother highlight roll-off characteristics. But that still negatively affects the overall film image quality. With digital, it's worse -- once it's clipped, it's gone.

In broad conceptual terms, pull-processing film was more like shooting a log profile in digital. Both methods capture a wider dynamic range in a lower-contrast format but require reintroducing contrast later in post.

There were no dual-native sensors until the late 2000s. Aptina Imaging Corp developed and patented this around 2006 (US7075049B2). The dual-gain approach was marketed as “DR-Pix” (Dynamic Response Pixel). Their patent was later acquired by Sony. Canon's simultaneous dual-gain approach was separately developed and has different characteristics.

Despite these advances, I'm not aware of any sensor-based tricks that eliminate the need for ND filters. There are apparently fundamental limitations that currently prevent multi-gain sensors from having multiple widely-spaced native sensitivity levels of (say) ISO 50, 800, 5000 and 12,800. Each level would require additional circuitry for *each* pixel photosite and would probably entail other adverse impacts.

The problem with screw-on ND filters is that they must be removed to get back to zero attenuation, and they often mechanically interfere with the lens hood. Even the highest-quality front-mounted variable NDs can introduce artifacts in certain lighting situations. There are variable ND adapters, but they often require even more juggling to remove them for a zero-attenuation shot.

Good morning Ian. (my time)

Have you looked into the magnetic type ND filter holders?

I've used these for years. None of that time consuming screw/unscrewing.

Flip on or off as required. Only proviso is "keep 'em clean".

Al

Motion Blurs can be added to an "adjustment layer" for areas where it is needed. You still need to shoot with a relatively low shutter speed for it to make that much of a difference. Eight samples would probably be the most you would need going from 24/25 to 60 fps — so not a *terrible* processing hit. The "shutter angle" would probably depend on the circumstance, 240 or greater (emphasis on greater). It is also possible to combine Motion Blurs of two (or more) different sets... (Either way, I'm not sure it really entirely makes up for properly shot footage.)

Fastest film? In America, I think that was Kodak 2475 Recording Film. I used to use it for night football games. But it sucked! The grain was horrendous. I got better results from Tri-X (400ASA, shot at 4800ASA) and pushing it in processing...

Have you tried applying your 25fps footage to a 60 fps project and setting the Rate Conform to Frame Blending? I know it's not a "cure-all", but it might mitigate the "staccato motion" somewhat. Another option might be to apply a Motion Blur to the footage (with or without Frame Blending). I do not, however, recommend optical flow!

I'd have to see examples of these clips.

Get a new camera?