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Question about aperture and ISO.

H

harmonica44

What should I turn up first to let in more light, aperture, or ISO? I tries shooting the the same shot at the same angle. Once with the aperture at 2.0, and the ISO at 400. Then with the aperture at 2.2. and the ISO at 800. Both shots looked exactly the same so how do I know which one to turn up first, or which is more appropriate for what type of shot I want to convey?
 
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When you are adjusting your shots, you should take more than just the aperture into account. Factors that effect brightness/light include aperture, ISO, shutter speed, and filters.

Aperture: determines that amount of light allowed to hit the sensor
What it allows you to do: adjust brightness and depth of field

ISO: determines how sensitive the sensor is to the light that hits it
What it allows you to do: adjust brightness at the cost of noise

Shutter Speed: determines the amount of time light hits the sensor
What it allows you to do: adjust brightness and sharpness

Filter: determines the nature of the light that hits the sensor
What it allows you to do: adjust brightness or color of light (e.g. you can use an ND filter to reduce the brightness without changing sharpness or depth of field)

You will want to use a combination of the four to get the perfect image for your shot. However, ISO should be the last thing you change (increase in this case) as it adds noise. Only use it when you NEED to because you cannot get a bright enough image otherwise.
 
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It depends, but generally open the aperture first. The more open, the more shallow DOF. If you need less DOF, close the aperture and boost the ISO.

If you don't care about DOF, then keep the ISO as low as you can.

Also, most lenses (especially cheap lenses) get a little soft all over wide open. When I can I try to run a notch or two under open, 1.8 on a 1.4 lens, 3.0 on a 2.8, etc.
 
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Okay thanks. That helps a lot. I do take shutter into account as well but try to keep it at 50 or 60 from previous threads. Since I'm still learning, I will keep the ISO as low as I can for now, and adjust that last. If brighter aperture creates DOF, then I'll do that first.
 
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harmonica44 said:
Okay thanks. That helps a lot. I do take shutter into account as well but try to keep it at 50 or 60 from previous threads. Since I'm still learning, I will keep the ISO as low as I can for now, and adjust that last. If brighter aperture creates DOF, then I'll do that first.
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Most people tend to keep the shutter at about 2x the fps so on a DSLR this is usally 50 or 60 rather than 48 like films use. It is the closest to a film look that you will get though.

If you are getting looking for shallow DOF, then there will often be too much light and your best bet to maintain the film look is to use an ND filter rather than change the shutter speed.

If you want a deep DOF then you may not have enough light. If you do not want to change the shutter speed (which would give it a much different look), then you will want to use ISO.

You may sometimes find yourself using a different shutter speed though because it will give you a jittery look. A lot of action films do this, and it started with (by started with I mean got big after) Saving Private Ryan.
 
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Okay thanks. So the higher the shutter, the more jittery right? I don't want the Saving Private Ryan look. I want to practice some low budget action scenes, but not that kind of action. So in order to avoid jittery-ness should I not go over 60? It's hard to tell on my computer cause if I shoot action scenes over 80, the video stalls. Not a little but in long pauses, then repixilates. Is fast movement at 80 shutter, just too much for my computer to compute or what... If I shoot at 50 or 60 though, the footage will play without pausing so much.
 
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harmonica44 said:
Okay thanks. So the higher the shutter, the more jittery right? I don't want the Saving Private Ryan look. I want to practice some low budget action scenes, but not that kind of action. So in order to avoid jittery-ness should I not go over 60? It's hard to tell on my computer cause if I shoot action scenes over 80, the video stalls. Not a little but in long pauses, then repixilates. Is fast movement at 80 shutter, just too much for my computer to compute or what... If I shoot at 50 or 60 though, the footage will play without pausing so much.
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I have never heard of an issue with editing at higher shutter speeds since it should still be the same amount of data being accessed (e.g. 38Mb/s on a Canon DSLR).
As to your not going over 60 rule, go try some stuff out. The longer the shutter is open, the more motion blur you will see. The shorter it is open, the sharper the image will be. A sharp image on a shakey camera (a la Saving Private Ryan) produces a "jittery image" as we can see detail where we expect to see a blur. There is no rule about these kinds of things, but only what the majority of things are shot in. That is to say most films are shot at a shutter speed of 1/48 (double the fps) so when people say the "film look" they are usually talking about a 24fps shot with the shutter at 1/48. For you, 1/60 would be a similar effect (if you can do 1/50, it would be even closer).
Again though, I implore you to try it out and see what looks best in your situation. Film someone in motion for 30sec at a bunch of different shutter speeds (30sec each). Bring them into your NLE, drop them on the timeline and export (dont worry about your playback issue for now since the export will be clean). Look at the exported footage and see which shutter speed gives you the look you want.
 
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I know it's strange since it's the same amount of data being processed but there is something about those videos over 80 that are just acting screwy for some reason. I tried that quite a few times, now, filming my brother or friends doing things like running. I can see the Saving Private Ryan look more so if I play it through a TV instead. Although it is a good look, it's not what I want for any kind of film I want to make right now. I do kind of like the style if it though, so not sure if I'll use it in the current short I'm shooting.

What about slow motion? I have to up the shutter to 125, and rather than light the scene a lot brighter, and having to put an ND filter on the camera, it's a lot easier to put on a 1.4 lens and adjust the aperture, and ISO. Therefore the scene does not have to be so overlit, when going from slow to fast motion. So when it comes to slow motion, after I turn the shutter to 125, should I increase the ISO or aperture first? I've tried some shots, and I don't have to increase the ISO at all, so long as it's lit enough for the aperture to go up a few numbers.
 
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harmonica44 said:
What about slow motion? I have to up the shutter to 125, and rather than light the scene a lot brighter, and having to put an ND filter on the camera, it's a lot easier to put on a 1.4 lens and adjust the aperture, and ISO. Therefore the scene does not have to be so overlit, when going from slow to fast motion. So when it comes to slow motion, after I turn the shutter to 125, should I increase the ISO or aperture first? I've tried some shots, and I don't have to increase the ISO at all, so long as it's lit enough for the aperture to go up a few numbers.
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First, for the film look, you are spot on at 125 (60fps X 2 = 120 which is very close to 125) and will achieve the film like blur I talked about earlier. As to ISO versus aperture, it depends on what look you want (mainly DOF). If you want a shallow DOF, then adjust your ISO first and keep your aperture open (low f-stop). If you want a deep DOF then open your aperture up and keep your ISO lower.

Think about it this way. Aperture and Shutter Speed do not just affect brightness. They effect depth of field and sharpness (of movement) respectively. Use these two tools to establish the look you want for your film. After you have the look you want, adjust the brightness with the ISO or an ND filter to increase brightness or decrease brightness respectively.
 
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harmonica44 said:
What should I turn up first to let in more light, aperture, or ISO? I tries shooting the the same shot at the same angle. Once with the aperture at 2.0, and the ISO at 400. Then with the aperture at 2.2. and the ISO at 800. Both shots looked exactly the same so how do I know which one to turn up first, or which is more appropriate for what type of shot I want to convey?
Click to expand...

Maybe I'm just being a pedant, but they can't have looked exactly the same… the difference between ISO 400 and ISO 800 is one stop; the difference between f/2 and f/2.2 is a third of a stop.
 
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The missing element is, as John Johnson mentioned, ND filters. These are used a lot in film production because most film cameras don't allow (easy) access to the shutter - it's 1/48 sec (at 24fps) and that's it. The tools for adjusting exposure were: ISO (getting a different stock), aperture and ND filters. Oh, and lights.

In order to maintain a look or feel for a scene I'd do as was suggested above - get the DOF using aperture; and if you want a funky look, shutter speed. Changing the ISO (which is really changing the gain of a digital camera) can also affect the look, perhaps in ways you won't like - extreme 'grain' or clipped highlights, for instance. The best solution is to have a handful of NDs available and know how to use them. For our Red cameras we run with .3, .6 and .9, and have an ND1.2 with a "hot mirror" to help deal with potential infrared pollution. Better yet is to have a few ND grads, to help deal with hot skies.
 
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Well the ND I used before I borrowed and I don't have it anymore. I kind of splurged the last of my current budget, on T-stands for blankets, a new hypercardioid mic and the newer 1.4 lens. It seems I can get the exact same light look if I increase the aperture, after turning the shutter to 125 though. Not sure if I want to grainy of a look with ISO, so I keep it under 1600. Maybe for the outdoor night scenes, the grain will look cool, in a stylistic way though.
 
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You are not seeing grain. Grain is film only and can look beautiful. Digital is noise and looks like garbage.

I NEVER go above 1250 and that's on a 5D which is cleaner at high ISO.

The triangulation of shutter speed/aperture/ISO to get good exposure in different ways (that all have a different look to them) is where the "art" of this whole process comes in.
 
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5D is cleaner? No one told me that, if I knew I would have heavily considered a 5D or something different. Well I'm shooting in a bit and use do what I can in and use both lenses. Probably end up choosing a noisy look over a blurry DOF look. I disagree that noise is uglier than film grain, they both look beautiful in there own ways.
 
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harmonica44 said:
5D is cleaner? No one told me that, if I knew I would have heavily considered a 5D or something different. Well I'm shooting in a bit and use do what I can in and use both lenses. Probably end up choosing a noisy look over a blurry DOF look. I disagree that noise is uglier than film grain, they both look beautiful in there own ways.
Click to expand...

But if you'd gone with the 5D, you'd be dealing with even more shallow DOF and more blurriness issues.
 
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harmonica44 said:
... so how do I know which one to turn up first, or which is more appropriate for what type of shot I want to convey?
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Is this an INT. or EXT. shot?

What are the general lighting conditions?

Since you're trying to avoid that (annoyingly trendy) SAVING RYAN'S PRIVATES look (and I applaud you for that), "yeah" you're going to want to keep that shutter speed down under 100.

Unless I missed it you never really did describe what was goin on in the particular scene and the effect you were hoping to maintain.

I'm guessing there's some activity going on which only a high shutter speed makes choppy loooking.
And since the shutter is getting high I'm also guessing there's plenty of light, which also mean likely outside on a sunny or thin overcast day.

Could be two dudes walking down the road for all I know.

So then I gotta wonder how far away they are from the camera, in meters and how much tele-zoom you're using which is where a wide open aperture both pours light in and narrows your DoF - or - if you got that aperture tight as a beaver's bunghole and a near infinite DoF + no d@mn light coming in... but then your shutter speed shouldn't be an issue, and it is, so I'm guessing former rather than latter.

Now, if you're tinkering with f2 and f2.2 then bugger with the ISO until you can cough up for the ND filter set - OR - wait for a more cloudy day - OR - forget about your DoF and lock your aperture at f4 to f5.6.

See what happens.

It all depends upon what you wanna do with the conditions you have.




Oh, and I get the same playback problems on my PoS computer if I try to record in too high a resolution.
It's just too much information for my PaperWeight2000 to handle.

Since this is for testing purposes try testing in a lower resolution that your machine can handle no matter the frame rate or shutter speed, (I'm kinda surprised shutter speed would bugger with the memory, but... okay).
 
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"Since you're trying to avoid that (annoyingly trendy) SAVING RYAN'S PRIVATES look "

I literally walked out of a film that somehow got into a festival I was in because of this. EXT shots where it was strobing like crazy because they had upped the shutter speed to get exposure rather than putting an ND filter on the camera. My thinking being if you are THAT incompetent as a cinematographer then you aren't going to have anything in this movie I want to seee. I'll go smoke a cig instead.
 
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