F55: HFR mode - getting noise vs adjusting your exposure

Grug said:
Are you noticing the gain up on CineEI mode Dennis? Or just in Custom?

I don't do a huge amount of HFR work, but I can't say I've ever noticed exposure issues when I've shot it (adjusting my meter accordingly). I'm only shooting in CineEI mode though.
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I was in CineEI mode. I tested again today, 180 degree shutter and from 24fps to 60fps there was dip in exposure.
 
I think its down to taste..with film cameras the shutter was part of the mechanism to shift the film through the gate.. video camera you don't need this.. it depends on the speed of what you are shooting.. (I don't think we will be shooting bullets with an FS7 or F55.. :)... the detail you want,the amount of light you have.. and any flicker issues .. if its going to be ramped in post..

Over 60 fps the camera read in 2k mode .. F5/55 has center scan to avoid this issue.. but FS7 doesnt have CC yet I believe..?

Please use the -factory installed- 4K Optical Low P****** Filter “OLPF” when recording 4K, 2K or HD and the Scan mode is set to: [Normal Scan] or [2K Center Scan (any frame rate)]. The camera uses “pixel binning” when operating in [2K Full Scan] or [Normal Scan-HFR (72fps ~240fps)] modes; to avoid moiré in these modes, the optional 2K OLPF should be used. Please note that moiré seldom occurs when shooting natural objects; it’s more likely to occur when the scene contains manmade objects with repetitive fine pitch patterns. The table below indicates the recommended OLPF for Scan/ Rec. modes:

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Note: You may use the 2K OLPF with Normal Scan when shooting scenes in 4K, 2K and HD at sync sound speeds (below 60fps) to achieve a softer, dreamy, filmic look. However, use of the 2K OLPF when 2 K Center Scan mode selected, will result in extremely soft images.
 
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broughtonfilm said:
How can there be no change in exposure if shutter speed changes? Of course exposure changes, all you need to do is look at the waveform and you'll see. The difference is just short of 3 stops when you go from 24fps to 180fps (assuming the shutter angle stays at 180 degree angle), as expected and the same as in any other camera, film camera included. You contradict yourself by saying that "I tend to 'lift' exposure in those circumstances" - it is simply because it is as if you shot at higher EI rating effectively, your neg is thinner which results in increased noise.
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Sorry, I meant in terms of reciprocity - I should have written that post better, it's entirely misleading! Of course, if I change from 25fps to 100fps I change the aperture 2 stops. What I meant was there was no additional change in exposure due to gain. Exposure on my camera in HFR behaves exactly as one would expect. Sorry for the confusion - I shouldn't post after the third bottle of wine....
 
Liam you've made my brain hurt!

SO you are having a change in exposure commensurate with what you'd expect by changing framerate/shutter?
 
Ha ha, sorry Ben, didn't mean to lead anyone on a merry dance.

So for clarity:

My camera behaves in exactly the way I would expect it to when switching frame rates. I see no gain applied. For example; if I shoot at 25fps on a 180 degree shutter at f/4 then switch to 100fps I will lose 2 stops so I either remove 2 stops of ND or shoot at f/2.

The only thing I notice is an increase in shadow noise (again, this is normal)and sharpness.
 
Guys, the Sony cameras (F5/7/55/700) all work on a purely linear scale in terms of exposure levels when adjusting frame rate. They are just like the Phantom high speed cameras in this regard. There is no gain or other compensation applied, although there are some odd quirks where certain settings will prompt a change in shutter angle to "help" you without tell you and then you have to remember to switch it back.

As for shutter angle when shooting high speed, there can be many reasons for adjusting the shutter angle for various effects, but please remember that even though one is capturing at very high frame rates, the playback is at a "normal" one. We may be slowing down time but we are not slowing down relative motion within a frame. If an object is passing through the frame and you wish it to have some motion blur so that the motion does not appear strobe-like from frame to frame, then the same 180 degree shutter rule applies. The fact that the camera may have been running at 180p or 10,000p is not germaine. It is the resulting relative motion within the frame during playback that dictates this, thus the standard shutter rule.

Take it from the guy who use to be Mr. Phantom. There's always room to push and pull on this a bit, but in general the rule holds.
 
I'm not about to make a YouTube video showing the Exposure dim when I go from 24fps to 60fps... so Mitch I hope you are not saying that the actual shutter speed isn't affected when you go from 24fps to 60fps or even higher.

Maybe I just misunderstood your last post.
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starcentral said:
I'm not about to make a YouTube video showing the Exposure dim when I go from 24fps to 60fps... so Mitch I hope you are not saying that the actual shutter speed isn't affected when you go from 24fps to 60fps or even higher.

Maybe I just misunderstood your last post.
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No, he is talking about relative speed of motion of object within a frame. Meaning that if you look at the playback of slow motion footage, then the motion blur must be proportionally smaller, it has to be diminished the same way the motion is slowed down. If for example you shot at 48fps and had a 360 shutter angle, then the motion blur would be that of the footage shot at 24fps (at 180 degree), so the motion blur would be twice the normal blur an object moving at this speed should create. Why? Why would an object moving slower (in playback) have a motion blur that is not proportionally smaller too? It must be diminished proportionally in order to look natural. Understand that motion blur is a "side effect" of things moving within a frame - how much of it there is depends on how fast objects moves across the frame (it is the resulting speed that matters, the speed it moves across in the playback because this is how we view it) so amount of it has to be proportional to that speed.
 
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If you change the sensor framerate from 24p to 60p then of course the image gets darker -- the sensor is seeing light for less time. If you go from 24p to 48p then it will be one stop darker. To 60p means another 1/4 stop. But the camera doesn't add any gain, that is unless you have it set to auto. It just gets darker. You can compensate by opening up the iris or adjusting the shutter angle. Or add light. And this is exactly how the camera works no matter what speed you set it to.

Motion blur is a different topic. Motion blur is not about the frame rate at which you shoot, it is about the frame rate at which you play back the material. Object X moves 1/10th of a screen width across the screen from Frame A to Frame B. In order to make that motion smooth rather than strobe-like, a shutter angle of 180 degrees provides the motion blur appropriate to bridge the two frames. It does not matter what framerate the photography employs. It could be a cat walking through frame at 24p or a bullet whizzing by at 30,000p.
 
Hi Mitch.. But does the camera always have to set to exactly 180 shutter .. for what ever FPS you are using in HFR..

Thanks
 
Sometimes when you shoot slow motion and resulting speed of objects within the frame (during playback at 24fps) is not significant, you can get away with a shutter that is wider because the amount of motion blur is insignificant to begin with. But if you film something in slow motion that despite being slowed down still moves across the frame relatively fast when played back, you'll immediately notice that the resulting motion blur is not proportional to the speed the object moves within the frame.

Motion blur is a result of objects moving within a frame and amount of it proportional to their speed. What is important to understand is that it is the speed the objects move within the frame in playback that dictates how much motion blur it should have (how much viewer's eyes expect it to have).
 
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broughtonfilm said:
Sometimes when you shoot slow motion and resulting speed of objects within the frame (during playback at 24fps) is not significant, you can get away with a shutter that is wider because the amount of motion blur is insignificant to begin with. But if you film something in slow motion that despite being slowed down still moves across the frame relatively fast when played back, you'll immediately notice that the resulting motion blur is not proportional to the speed the object moves within the frame.

Motion blur is a result of objects moving within a frame and amount of it proportional to their speed. What is important to understand is that it is the speed the objects move within the frame in playback that dictates how much motion blur it should have (how much viewer's eyes expect it to have).
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What he said.

No, you do not always have to be at 180 degrees. Just like when shooting at 24p, 30p or any other frame rate you do not have to be at 180p. There are plenty of times when I have opened up to 220 degrees or even went the full 360 and got away with it. And other times when I went to 90, 45 or something else for various reasons. Hey, there's a reason the camera has the adjustment -- it's a tool so use it. Amazing the difference in a water pour when you change the shutter angle.

Just understand that the rules that apply to changing the shutter angle when at 24p are the same rules that apply when shooting at high frame rates. You can often "get away" with it a bit more because the activity in the image appears so different in the first place. I'm looking at obvious slow motion so I'm more forgiving to other aspects of the image. But understand that you are only just "getting away" with it, i.e., know the rules so that you know when you can break them. If I am using slow motion but for a subtle emotional effect and the viewer should never realize that there was a slow motion shot in there when the material is all cut together, then it is your job to make as many aspects of the image match the rest of the footage as possible. That would generally include shutter angle.
 
In summary I THINK we're all agreed that the FS7 behaves entirely as you'd expect in regards to exposure levels and motion blur when changing framerates and shutter speeds.
 
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