Thread: Noise and sensor crop on Helium

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  1. #1 Noise and sensor crop on Helium 
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    Folks, what's the relationship between sensor crop and noise on the Helium? Will the amount of noise be the same regardless of whether I shoot the Helium at 8K vs 5K? I get the field of view changes, just concerned if the noise levels are different too?

    If you were zooming in on a 8K frame vs 5K frame in post, what would be the differences then, again from a noise perspective?

    Really looking for any insights on how to think about noise as you shoot anything less than 8K on a Helium. Thanks.
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  2. #2  
    Senior Member Bob Gundu's Avatar
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    Down sampling will always look better. Zooming into an 8k for 5k will have similar noise pattern as shooting at 5k.
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  3. #3  
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    Helium is generally noisy, just don’t underexpose it especially if cropping in
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  4. #4  
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    Part of the reason for this question is whether I "upgrade" my EPIC-W to Gemini. I hate being at 5K (wish it had been 6K) atleast, but I do like that the Gemini will work well for Anamorphic.

    But if Helium is generally noise, it may make sense to switch to Gemini, period, regardless of any other factors. I hate having to make this decision! Red really put me in a spot. ha.
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  5. #5  
    Noise is often a symptom of other failings. Without posting R3D clips, none can say for sure what's what.
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  6. #6  
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    RED's sensor crop 101 article mentions trade-offs with cropping including image quality.
    https://www.red.com/red-101/sensor-crop-factors

    The big thing I see is people want to punch into 4K HD which is a big leap on 8K HELIUM sensor versus doing it on 5K GEMINI sensor.

    Looking at the frame dimensions alone you can see a big difference.



    My advice, use your sensor, reap the benefits of supersampling.

    However Michael is right as well. Most the time the bigger issue is exposure.
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  7. #7  
    Quote Originally Posted by Alex.E View Post
    [...]

    However Michael is right as well. Most the time the bigger issue is exposure.
    It's not always exposure (though usually it is). It can also be composition. It can be lighting choices. It can even be punching into a shot just a little bit too far.

    There will always be noise. Always. What makes noise distracting enough to become a problem is the devil in the details. To cast out the devil, you must understand all the details, and not just blame the sensor or the cropping of the sensor. It's everything from concept to execution that determines whether an image stands or falls on quality.
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  8. #8  
    Moderator Phil Holland's Avatar
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    We talk a lot about oversampling and it's benefit to general image detail, but equally useful is the lessening of image noise on a perceptual and measurable basis.

    Considering that noise in digital manifests usually as a single pixel, I'd recommend mainly to shoot something like 5K for a 4K finish. The higher source acquisition resolution the better when it comes down to it. i.e 6K or 8K for a 4K finish.

    Noise character is equally important too look at. RED generally has a pretty decent level of activity and not looking super digital. But even still some standard workflows for all cameras is to bring them through and even add film grain potentially with NR ahead of that, sometimes not too. Just all depends. When I had Helium I rocked ISO 400 and 800 mainly for my work. Pretty much since moving to Epic ages ago I have not really filmed under 5K resolution with RED cameras. I did a fashion film where I dipped into 120 fps 4K last year, but prior to that mostly at 5K and higher resolution.
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  9. #9  
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    Quote Originally Posted by Phil Holland View Post
    Considering that noise in digital manifests usually as a single pixel, I'd recommend mainly to shoot something like 5K for a 4K finish.
    Thanks Phil. That's concise and helpful.

    Alex, thanks for that tool. That massive reduction in sensor area when you crop to 5/4K on Helium is what was of concern to me. Given the indie nature of my projects, just feels like Gemini might be a better fit. Thanks all.
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  10. #10  
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    Hey Nikhil,

    I would agree that exposure is a huge factor here. In addition I would advise, based on my own experience, that it is prudent to use the sensor that you have in a way where you get the most from what it does best. In the case of the Helium@8K its all about creating exceptionally detailed images that retain the best cinematic qualities down though the final version (which is most likely downsampled) and taking advantage of reducing noise by exposing to the right and then managing ISO and exposure down a bit from there. I feel like if your goal is a commercial workhorse, the Gemeni@5K is more reasonable due to memory, workflow, and getting to use the full sensor all the the time without blowing up your storage. Maybe your clients will appreciate not having to consider the workflow and memory considerations of 8K as well. I have definitely experienced the increase in noise when the sensor is not being largely used. A rule of thumb for me is not to drop below 6K or the noise and field of view disadvantages become to severe for my tastes. Fortunately for my camera (epic-w) 6K is where I need to go to get 60fps so that's as low as I commonly need to go. Hope that adds to the discussion.
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