T2i "Native ISO" and other rumors

M. Gilden

M. Gilden

Canon DSLR Moderator
I recently came across some threads here that described using specific ISOs in video mode to reduce film grain.
More specifically, the theory was that only certain specific ISOs were native, starting with 160 and doubling along the way (160, 320, 640, 1280, etc), and that all others were actually pulling/pushing exposure, which would result in extra noise in the image.

Folks with Magic Lantern have been saying that setting those "magic" ISOs manually will yield a cleaner looking image.

This was news to me, so I did some testing on my own just now.
And I'm convinced this is total and complete hogwash.

I zoomed using the camera's live view zoom button so I could see the grain clearly on a dark area, and cycled though all ISOs on Magic Lantern's menu. No surprisingly, the higher I went, the worse the noise, and it was TOTALLY CONSISTENT. That is, 320 looked worse than 300, yet better than 400.

There appears to be absolutely no merit to this claim, at least not that I could detect using a t2i/550D.

Just figured I should throw this out there.
 
The idea of the 160, 320, etc. ISOs is that the camera overexposes the image, then pulls it down digitally (all before you see it), so you get a "cleaner" image. I personally, like you, have not found a drastic difference in the images and, if you like shooting at those ISOs, you need to make sure you watch for highlight clipping as it is much easier to do with that process.

That is my understanding of the plus sides and the minus sides of the use of these ISOs.
 
Film has grain........ I DO NOT like super clean footage and always add a grain filter to my material. Stop worrying about simple things people.
 
dishe said:
I recently came across some threads here that described using specific ISOs in video mode to reduce film grain.
More specifically, the theory was that only certain specific ISOs were native, starting with 160 and doubling along the way (160, 320, 640, 1280, etc), and that all others were actually pulling/pushing exposure, which would result in extra noise in the image.

Folks with Magic Lantern have been saying that setting those "magic" ISOs manually will yield a cleaner looking image.

This was news to me, so I did some testing on my own just now.
And I'm convinced this is total and complete hogwash.

I zoomed using the camera's live view zoom button so I could see the grain clearly on a dark area, and cycled though all ISOs on Magic Lantern's menu. No surprisingly, the higher I went, the worse the noise, and it was TOTALLY CONSISTENT. That is, 320 looked worse than 300, yet better than 400.

There appears to be absolutely no merit to this claim, at least not that I could detect using a t2i/550D.

Just figured I should throw this out there.
Click to expand...

There are images out there that show that 320 looks better than 300 and 400 as far as noise goes... it's all over these boards.

Do you have images that dispel that?
 
I also ran my own tests (on a 550D), and found no improvement with "native" ISO

sure, 320 has less noise than 400, but that's only if you compensate by giving more light to the sensor; if you keep your lights, filtering and aperture the same, and equalize the images in post, the noise I see is basically the same (or maybe a bit more on the more-tweaked-in-post version, be it an enlighted 320 or the darkened 400)
 
soren said:
Live view zoom should not be trusted, as it may be imparting noise that would never show on a recording.

That's the problem with tests sometimes---the testing method itself can alter the results.


:)
Click to expand...

True, fair enough.
My test was hardly scientific. I was skeptical of the whole concept, and when it didn't work right away, I assumed it to be false. I suppose it would require further testing to be fair.
 
NormanBates said:
I also ran my own tests (on a 550D), and found no improvement with "native" ISO

sure, 320 has less noise than 400, but that's only if you compensate by giving more light to the sensor; if you keep your lights, filtering and aperture the same, and equalize the images in post, the noise I see is basically the same (or maybe a bit more on the more-tweaked-in-post version, be it an enlighted 320 or the darkened 400)
Click to expand...

As posted prior, there are images--with lens caps on and no change in light--that show that 320 is cleaner than 300, 240, etc. It may not be the BEST ISO to use, but it's been illustrated that it's cleaner.

I personally shoot at 500~640 on Canons if I can, even in broad daylight.

On GH-1 I think 320~400 is about right for all scenarios if possible, including no light.
 
Wow huge difference, so moral of the video is only use multiples of 160? Any idea for why it degrades in between the multiples so much. Gotta be some weird software issue.
 
There are other sources that say the actual ISO's are 200, 400, etc, and the 160's are software enhanced.

I haven't read anything that's definitive on the matter, I can say that I wouldn't shoot 160 ISO for any situation, nor would I roll above 800.

I think no matter the situation, for the Canon's that range is good. If at all possible, 500 ~ 640 ISO has always been my ideal setting.

video: http://www.vimeo.com/12209296


All high iso in broad daylight.
 
ok, so I run this test, what do you see here?
http://www.vimeo.com/20486388

each pair of ISO settings (320+400, 640+800, 1250+1600) are recorded with the same amount of light (same lighting, same ND filter), then the gamma of the "native ISO" is changed to match (more or less) the lighting of its "regular ISO" pair (maybe I should have moved saturation also, but some people might complain in that case)

550D + magic lantern
leitz elmarit-R 35mm f/2.8
tiffen screw-in ND filters (0.3, 0.6, 0.9)
 
Kholi,

Why do you prefer to stay in the ISO 400-800 range, even outdoors? This seems so counter intuitive that I suspect you have a good reason for saying this. Wouldn't you want to always stay as close to ISO 100 as you could get away with to reduce noise? Or maybe you like the noise?

Your footage looks great by the way.
 
robotsound said:
Kholi,

Why do you prefer to stay in the ISO 400-800 range, even outdoors? This seems so counter intuitive that I suspect you have a good reason for saying this. Wouldn't you want to always stay as close to ISO 100 as you could get away with to reduce noise? Or maybe you like the noise?

Your footage looks great by the way.
Click to expand...

I think when I first began to test the 7D, before I owned a 5D, I took it down to the beach a lot and shot random footage. Outdoors, I began to notice that blue skies got really blocky at 100-240ish ISO, and began to sort of clear up at 320. Always owned two sets of ND filters so stopping power wasn't an issue, decided to stay away from those ISO's altogether no matter the scenario and just shoot high.

It may very well be the noise that I find pleasant and it never registered consciously, I wouldn't rule out that possibility.

And, thanks much.
 
I've also read complaints about banding in the sky at low iso settings, but I haven't seen the problem myself (yet), maybe my eyes are not as sensitive to banding as they are to other IQ problems
 
NormanBates said:
I've also read complaints about banding in the sky at low iso settings, but I haven't seen the problem myself (yet), maybe my eyes are not as sensitive to banding as they are to other IQ problems
Click to expand...

Pretty easy to replicate: walk outside, point camera to blue patch of sky (not blown out/white) and record for a number of seconds.

You'll see it. Starts to vanish at 320ish.
 
maybe it's because, unlike most people, I don't shoot flat; or, as I said, maybe my eyes are not as sensitive to banding as they are to other IQ problems
 
Excellent works Bw and Norman. My question is how effective a denoiser, like Neat video, is in cleaning up the non-native ISOs?
 
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