C100: ISO vs Aperture for best low light image

Eric Coughlin

Eric Coughlin

Veteran
As lenses are sharper when stopped down from wide open, but the camera loses sharpness as the ISO increases, I'm wondering where the trade-offs are as far as creating the sharpest (or best) image.

For example, which would be sharper, a 35mm f/1.4 at f/1.4 at ISO 850, or the 35mm at f/2.8 at ISO 3200? The basic question here is, is stopping down the aperture while raising the ISO going to increase or decrease sharpness, and at what point would the raising of ISO decrease the sharpness?

I've always leaned toward opening up the aperture more in low light to avoid higher ISOs, but that's coming from first generation DSLRs which aren't nearly as good at handling higher ISOs, so perhaps it's different with the C-series cameras.
 
I would say do the simple test with your chosen lens at these settings and judge with them peepers you posses and see what looks best to you. All I can say is that I often have shot at 4000 and 5000 ISO's and been pretty darn impressed with the results.

But let me also add this....I say it and I say it often.

Not sure what you're monitoring with when editing. But it's helped me and maybe can help you. We probably sit on average about 20 inches away from our monitors and lets assume 27 inch monitors are the average. What distance do you sit away from your television when watching your favorite programs or on movie night at home? Lets give the home TV and average of 50 inches. DO you and your family sit 50 inches (4 ft.) away from your TV? Most dens or family rooms are 10 or 12 ft, right. I'm gonna assume you sit 8-10 ft from your TV. So, lets equate 2X.

Now, when you want to review your footage on your 27 inch NLE monitor, back up 2x or sit 50 inches away from your computer (4 ft). You'll be amazed at how wonderful your footage looks....Give it a try :happy:
 
I'm a C300 owner and I haven't noticed a decrease in sharpness in upper ISO's. May want to check your noise reduction settings, as that will affect sharpness. You can also boost or decrease sharpness inside the Custom Picture Profile menu.

Most lenses perform best between a 5.6 and an 8. I was recently on a shoot with my C300 and noticed that the Rokinon Cine lenses were remarkably soft wide open. Impossible to get a sharp infinite focus. However, stopping down the lens to a 2.2 or 2.8 solved this.

As for your specific lens question, the lens will certainly perform better at 2.8 for sure, but my experience with the Canon L glass has been pretty great even wide open. These lenses were designed for professional photography at upwards of 24 mega pixels. HD is only 2 mega pixels and 4k video is 8 mega pixels, so the lens has got you covered!
 
I agree that it depends on the quality of the lens. Cheap f1.4 lenses perform better with aperture about F2.8, better lens perform better with ap. F2.2 and the best lens with app. T1.5.

About ISO setting you can try do this easy test - with canon-log gamma and ISO850 set exposure to be just without "overexposure" on the waveform monitor.
And now set WDR gamma and ISO500 and cine1 gamma with ISO320 and normal4 gamma (with knee on 90) with ISO320, all with the exactly the same exposure (don't change apperture or shutter speed or ND filter or amount of the light).

Record these pictures and put them into your sw and look for overexposure in highlights and levels and noise in black. After this make grading of the canon-log and WDR gamma pictures and repeat looking for noise in black parts of all these pictures. Repeat this test with ND1 and ND2 on the high-contrast scene (an interier with window).

This get you good start point for working with higher ISO and choosing the right gamma for them.
 
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I would also recommend doing a black balance before every shoot. It should be in the menu as ABB. That will help with noise control as well.
 
FYI, Im doing F8, ISO 8000

1.2, 1.4 is my last choice, eventhough all of my lens are primes.

BUT !

for example, if you are so far away from subject, when using 85mm L 1.2, I sometimes use 1.2 - 1.8 for that nice bokeh.

but again, apeture should serve your art, not for your low light compromise.
 
jm.gardiner said:
What are you shooting at an F8 /8000iso?
Click to expand...

all night scenes, like streets, where you need that DOF.

C100 noise for me is clean under 12800 (noise reduction at 3), easy tweak and still the same detail.

if its darker, then I stay on ISO 8000 and dial up the aperture until 1.8. that mostly will do everything


my shoot principle for landscape : F8, then iso 850 - 8000, then F8- f1.8 while ISO stay on 8000.

this is ONLY when you need that DOF

that usually does the work, technology is moving forward and we should take advantage of it right? lol, thats why we get c100 for low light.

any suggestions?
 
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Eric Coughlin said:
As lenses are sharper when stopped down from wide open, but the camera loses sharpness as the ISO increases, I'm wondering where the trade-offs are as far as creating the sharpest (or best) image.

For example, which would be sharper, a 35mm f/1.4 at f/1.4 at ISO 850, or the 35mm at f/2.8 at ISO 3200? The basic question here is, is stopping down the aperture while raising the ISO going to increase or decrease sharpness, and at what point would the raising of ISO decrease the sharpness?

I've always leaned toward opening up the aperture more in low light to avoid higher ISOs, but that's coming from first generation DSLRs which aren't nearly as good at handling higher ISOs, so perhaps it's different with the C-series cameras.
Click to expand...

again, 1.2 is incredibly softer than F8, and you start to see that purple fringe like on the Canon 50mm F1.2 L. that sucks!!!!!!!!!!
 
Gotcha! I don't pass ISO 3200 for narrative and I've been as high as 6400 for doc shoots. But I'm rarely stopped down beyond a 5.6 for anything I do. Anything online of this F8 8000iso footage?
 
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