C100: When to use ISOs below 850

Eric Coughlin

Eric Coughlin

Veteran
When would you use ISOs below 850?

It's my understanding that below 850 you don't lose dynamic range, it merely shifts from being more balanced between the highlights and shadows (at ISO 850 and onward), to favoring the shadows more at ISOs below 850.

Thus, if one was filming a night/dark scene, or just felt for whatever reason that the shadows were more important than highlight retention, then shouldn't one film below 850?

For example, during a wedding speech I often light up the speaker well enough with three point lighting such that I can shoot at ISO 320 at f/2.0-2.8, but since my background is often large (unlike an interview), I don't have a background light and thus the background is considerably darker. Since I don't have to worry about the highlights since I'm in a mostly controlled lighting situation, but I do have dark shadows I'm dealing with, wouldn't ISO 320 be ideal to keep noise out of those shadows?

Here is an example of what I mean...

This is a frame grab from the video of a wedding speech, shot on the 5D Mark III, Canon 135mm @ f/2.0, ISO 320, shutter 1/50 (or possibly 1/30).

Full-size image: http://imageshack.us/a/img62/2971/adelaideajsequencespeec.png

adelaideajsequencespeec.png



Also, aside from dynamic range, do ISOs below 850 have more or less noise than 850? Since 850 is native, then digitally pulling back to 320 would actually introduce more noise; is that correct?
 
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I was actually told by a Canon rep that 850 is the native only when using Canon Log. The native ISO when NOT using canon log is 640. At 850 you've got the most even dynamic range of over and under. There is certainly noise present at 850 though. You are correct, lowering the ISO will push the noise floor down, but you will loose range inthe highlights.

What I've starting doing on shoots where I know the blacks will NOT be crushed such as a staged lowlight or night time scenes for narrative work. I'll raise the ambient light in the room by bouncing a light into the ceiling and lowering the ISO in camera to clean up the image, then in Log push around the mids/highlights where I want them. In situations where I know the blacks will be crushed in a night scene, I'll push it up to 3200 if I have to.

Lowering the ISO will clean up the noise you find in the shadows, but it can't effect the actual contrast of your light
 
Native ISO is 640 for canon-log - look for Table1 on page 3 in Canon White Paper "Canon-log Transfer Characteristic" (update June 20, 2012)
http://downloads.canon.com/CDLC/Canon-Log_Transfer_Characteristic_6-20-2012.pdf
or http://learn.usa.canon.com/resources/articles/2012/cinemaeos_white_papers.shtml
text below a table 1:"The nominal sensitivity of the EOS C300 and C500 cameras – with Master gain set to 0 dB – is
ISO 640."

ISO850 (gain +2.5dB) is about 800pct of the Exposure Latitude.

If you try the ISO850 with Canon-log gamma (set exposure to be "just without overexposure") and ISO320 with Canon-log (the same exposure) you will see that exactly the same result at highlights ("just without overexposure" in both case - try changing lens aperture and look to the WF monitor for an overexposure), but the modulation drops from 100pct to 80pct in the second case, look to WF monitor again. But signal differ in tonal gradation and when you will push up this signal level at postproduction you will see some noise in black. You can compare a color correction for canon-log for ISO850-640-320 and them noise, but level of noise also depends on the way of your color correction.

Even if you change ISO to 320 and gamma to cine1 you will see the same result (with the same exposure) at highlights (result "just without overexposure"; but signal differ at overall tonal gradation). The modulation will bee about 107pct on WF monitor but just without overexposure .-) .

Look to these WF monitors screenshot (canon-log gamma):
01 ISO320 - http://www.videoproduce.cz/images/03b_320ISO_minus6dB_gain_gamma_log_minimum_sumu.jpg
02 ISO640 - http://www.videoproduce.cz/images/01b_640ISO_0dB_gain_gamma_log.jpg
03 ISO850 - http://www.videoproduce.cz/images/0...amma_log_maximalni_dynamicky_rozsah800pct.jpg

Look to these WF monitors screenshot (canon-log gamma):
01 ISO320 without overexposure - http://www.videoproduce.cz/images/03b_320ISO_minus6dB_gain_gamma_log_minimum_sumu.jpg
02 ISO320 with overexposure at highlights - http://www.videoproduce.cz/images/04b_320ISO_minus6dB_gain_gamma_log_prepal_odclonenim.jpg
 
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Eric Coughlin said:
For example, during a wedding speech I often light up the speaker well enough with three point lighting such that I can shoot at ISO 320 at f/2.0-2.8, but since my background is often large (unlike an interview), I don't have a background light and thus the background is considerably darker. Since I don't have to worry about the highlights since I'm in a mostly controlled lighting situation, but I do have dark shadows I'm dealing with, wouldn't ISO 320 be ideal to keep noise out of those shadows?
Click to expand...

I suggest to compare canon-log with ISO800 (850) to canon-log with ISO640 (which has less noise but a little different gradation) after color correction (it's really important to finish the color correction before comparison). I personally think that canon-log with ISO640 can be better.
 
I might sound like kinda an A**hole here.... How do any of you get anything shot if you worry about ISO's so much? Is it noise you're all concerned about. I really don't worry about noise with a camera that I can comfortably shoot at 5000ISO. "But you'll lose that 1/4 of a stop at that ISO". There is a reason that ISO 850 has brackets around it. But there is also a reason that the camera can adjust ISO. There is also a menu that one can spend a month playing around in. Try some of Cowpunks profiles. The dude knows whats up.

I saw this today. Images look great.

Back when I was in photo school I had a friend that had ZERO idea about what she was doing. I'd ask her about technique and she would look at me like I was speaking Martian. ZERO clue about film, process, lenses, anything. But yet everything she produced was gorgeous. I asked her once, "How are you going to work in advertising if you can't control what you are doing technically?" She said to me, "I'll let my ideas do the talking". Today she is a top celebrity and fashion shooter and still has no idea of technical crap. She got a full ride to the Art Center of Pasadena and even though that program beats into you not just art but technical process, she could care less. My point? Find what works for you and your artistic abilities and shoot shoot shoot. You will find balance and settings along the way. But before you know it in this day and age, you will have a whole new camera at the rate they come out these days.
 
Talent aside, the OP was technical question about ISO, which does matter depending on what you're shooting. Green screen work with the C300 for instance it's extremely beneficial to shoot at lower ISO's. I've worked with CowPunk several times, he's talented and knows his tech extremely well, it's a good combination.
 
The ISO setting with canon-log gamma is important for the exposure latitude (800pct vs 300pct), it is very clear and I think that nothing wrong with talking about this at this forum.

But if you spend small amount of the time for some short test you will see that you get really the same highlights with ISO850 and log gamma and with ISO320 a cine1 gamma, with the same exposure (but tonal scale and colors differ). It is really good to know this detail.

Noise with C100 camera is a problem more at day scenes than at night scenes. The day scenes with high contrast and canon-log gamma can be really bad (after color correction), I saw some these clips. So in this case is also good to know how to set ISO (gain) and talk about this here may be fine help for somebody.

(tiff) http://www.videoproduce.cz/images/43_ND3_F11_ISO850_WDR.tif (a day noise on C100 with wrong ISO setting)
 
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Spartacus said:
What "wrong" settings were used...?
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WDR gamma with ISO850 was wrong setting because I don't know the detail about the right exposure this gamma, the noise was higher than it must be.
Today for such high-contrast scene I set ISO400 with WDR gamma (or ISO320 with cine or ISO640-800 with canon-log).

But I don't know these details before, I must did some test (it was difficult for me to clarify these relationships between ISO setting and exposure latitude of the C100's different gamma curves).
 
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dustylense said:
Back when I was in photo school I had a friend that had ZERO idea about what she was doing. I'd ask her about technique and she would look at me like I was speaking Martian. ZERO clue about film, process, lenses, anything. But yet everything she produced was gorgeous. I asked her once, "How are you going to work in advertising if you can't control what you are doing technically?" She said to me, "I'll let my ideas do the talking". Today she is a top celebrity and fashion shooter and still has no idea of technical crap. She got a full ride to the Art Center of Pasadena and even though that program beats into you not just art but technical process, she could care less. My point? Find what works for you and your artistic abilities and shoot shoot shoot. You will find balance and settings along the way. But before you know it in this day and age, you will have a whole new camera at the rate they come out these days.
Click to expand...

Perhaps this post was a little off topic but damn if it isn't one of the best things I've read on dvxuser.
 
dustylense said:
I might sound like kinda an A**hole here.... How do any of you get anything shot if you worry about ISO's so much? Is it noise you're all concerned about. I really don't worry about noise with a camera that I can comfortably shoot at 5000ISO. "But you'll lose that 1/4 of a stop at that ISO". There is a reason that ISO 850 has brackets around it. But there is also a reason that the camera can adjust ISO. There is also a menu that one can spend a month playing around in. Try some of Cowpunks profiles. The dude knows whats up.

I saw this today. Images look great.

Back when I was in photo school I had a friend that had ZERO idea about what she was doing. I'd ask her about technique and she would look at me like I was speaking Martian. ZERO clue about film, process, lenses, anything. But yet everything she produced was gorgeous. I asked her once, "How are you going to work in advertising if you can't control what you are doing technically?" She said to me, "I'll let my ideas do the talking". Today she is a top celebrity and fashion shooter and still has no idea of technical crap. She got a full ride to the Art Center of Pasadena and even though that program beats into you not just art but technical process, she could care less. My point? Find what works for you and your artistic abilities and shoot shoot shoot. You will find balance and settings along the way. But before you know it in this day and age, you will have a whole new camera at the rate they come out these days.
Click to expand...

Years ago when I was still working as a photo-assistant I worked for this sort of famous lady photographer who would yell at us during a shoot to give her the film with the "funny colors" asap. We were not really sure what she was talking about, but after a hectic debate between the several photo-assistants we concluded she was talking about cross processing and loaded the right film...We as arrogant pricks had to laugh about it and made fun of it; not realizing she was shooting for huge international magazines and doing large campaigns and we were carrying sand bags back and forth to the truck and holding the shinning boards in the blasting sun...
 
Some people do great work without vast technical knowledge, and others do a terrible job without technical knowledge. I suspect the majority of people who do great work are well versed technically, and bringing up specific people that aren't tech savvy but do great work only shows that it is possible, but doesn't show that it is the norm. I don't think it wise to dismiss the value of learning the tech side of things.

The basic argument here seems to be book smart vs street smart. Neither can be dismissed. I suspect it depends heavily on the person. Some can figure out things on their own quickly and intuitively merely through experience, without the need to be directly shown, told, or to do any research on the matter. Others learn best by being taught, and if left to experience alone, would merely continue making the same mistakes over and over again (such as continually shooting at the wrong ISOs (I just tied this back to the topic ;)). I see plenty of videographers who have been working in the business for over 20 years and make tons of basic mistakes, and people like that could probably gain a lot by researching the technical side of things since apparently they haven't learned from their mistakes merely by experience.
 
I still see a lot of people, who set "basic" ISO 850 for WDR or cine1 gamma in sunny exteriors (over ND filters). I can't still understand why. If you make a short test with C100, you will see that it gives only more noise to your pictures, nothing more. It is all about misunderstanding how the C100 works.

I like my C100, it is cheap and a pretty nice camera, but with 8bit canon-log it is like a child's toy car racing, I can't make the "cine" grading because there is a lot of noise. When I look for F3 footages (every day in my broadcast work) I see a very good s-log where you can make a lot of color correction and where the black is without noise.

I knew this all before my purchasing of C100. I like this camera, the lowlight footages are very nice and it is my persdonal camera for fun with a good ergonomy. But it is "what it is", really a cheap and nice camera, no "cine miracle".
 
Im going to attempt to answer the OP's question simply.

Heres how it works. The lower the ISO (under 850 in Canon Log), the more DR that is allocated to the shadows. This also means you lose out at the top end. If I was shooting very moody lighting in a night scene whereby I had control over the light I may very well opt to drop the ISO to the lowest setting and get more shadow detail. This would enable me to create nicer and more visible subtleties in the lighting on the shadow end of the spectrum.
 
What ISO would you use for shooting an interview where you have full lighting control?

Below is a frame grab from a C100 interview I shot a few days ago. I used Wide DR at ISO 320. I figured since there were dark areas in the interview background, as well as the lower noise levels of lower ISOs, that ISO 320 would be best. Is that right?


Full size image: http://imageshack.us/a/img14/6915/gpv.png

r7o.png
 
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It looks ok.

If you try to shot the same scene with different setting, you get your answer in the easiest way .-) .
 
Matt Turner said:
This image looks interlaced to me. If so, regardless of what your ISO setting is it will look crap(er)... ???
Click to expand...

I don't understand you. It is interlaced, yes, what is wrong with this .-) ?
There is no talk about an interlaced versus a progressive.
 
Its really how you like to work more then differences in the final image, You can shoot 850 and make sure your darks have fill light, or shoot 320 and raise your general exposure and watch your high end. I think the image you posted looks fine exposure wise. Personally I would rather shoot at 320 if there are a lot of dark colored objects in the scene.
 
So if I understand right, when shooting very bright day scenes you don't want to drop the iso? I had thought this would be good to drop down the overall exposure instead of relying only on ND filters. It sounds like you keep more highlight information by keeping the iso at 850 and using the ND's...?
 
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