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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old March 19th, 2010, 06:33 AM   #1
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Newbie Questions Exposure

Firstly I am trying absorb everything I can. I am new to Video and DSLR's in general. I have just bought a T2i. I have thread through a tonne of information and bought Phillip Blooms DVDs.

My understanding is this so far. On any given lense the greater the size aperture the shorter the depth of field blurring out the foreground and background which isn't in focus. Which is basically one of the main reasons were all using these cameras.

My shutter should be set to double the frame rate are as close as possible. So 25fps shutter set to 50.

Does this mean I should only be adjusting my ISO to get the correct exposure? I also shouldnt go over ISO 1600. So if I can't achieve the right exposure even approaching those levels I need to decrease the size of the aperture by increasing the f-stop setting.

Have I got this principle correct?

I am also aware if shooting outdoors with the sun etc I should be using filters on my lenses.

Thanks,
Jason
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Old March 19th, 2010, 06:58 AM   #2
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Judging by how your question is worded I'm going to assume you are shooting in bright light and want to keep a shallow DOF. The best and really only way to achieve this is to add ND filters or a variable ND filter like the Fader ND (the one I use and really like). There are several brands out there and the Fader ND seems the best to me on cost vs. function.
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Old March 19th, 2010, 07:02 AM   #3
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I see Jerry has written in a good response and saved me from saying what I was going to say. So I'll say this:

The ISO is selected FIRST. Then the lens, then the settings on the lens are changed to get a correct exposure.

ND filters are a necessity. And this is why a Mattebox becomes important outdoors for filming. Especially as you begin to use high quality lenses that allow in a lot of light.
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Last edited by Perrone Ford; March 19th, 2010 at 08:32 AM.
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Old March 19th, 2010, 07:19 AM   #4
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Thanks guys. Indoors where I cannot control the lighting and can only rely on the lighting available and wanting to keep a shallow depth of field I would only adjust the ISO correct?

This is assuming I only have one lense available.
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Old March 19th, 2010, 09:50 AM   #5
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Yes, if want shallow your f needs to be as low as it will go (or as low as you need to accomplish the look you want) Your shutter speed is fixed at double the frame rate and your frame rate should have already been decided 30, 24, 60 (I live in NTSC land) So that leaves the ISO for adjustments for exposure. Or for bright settings ND filters.
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Old March 19th, 2010, 10:27 AM   #6
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Jason,

Set your shutter speed first and work from there. (I'm assuming you are shooting video) This should be twice your frame rate. Next set your aperture. Your aperture controls the amount of light that reaches your sensor, the more open it is (smaller number) will create the most shallow depth of field. Increasing the number makes for more depth of field.

Then starting with a low ISO, start increasing that until you get correct exposure. ISO as it increases adds noise to your image so you want to keep that as low as possible.

Not sure what your one lens is but it may not be able to correctly expose poorly lit indoor scenes. (ie kit lens which is a very good outdoor lens)

Hope this helps.

Dave
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Old March 19th, 2010, 10:43 AM   #7
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Originally Posted by David Chilson View Post
Jason,

Set your shutter speed first and work from there. (I'm assuming you are shooting video) This should be twice your frame rate. Next set your aperture. Your aperture controls the amount of light that reaches your sensor, the more open it is (smaller number) will create the most shallow depth of field. Increasing the number makes for more depth of field.

Then starting with a low ISO, start increasing that until you get correct exposure. ISO as it increases adds noise to your image so you want to keep that as low as possible.
This is the exact opposite of how every photographer and cinematographer I know works. Would you mind explaining the logic behind working this way?

And I fully admit, I grew up and leaned in the era of real film. ISO is set by the film, though we could push or pull it. The decision was made often before the camera was chosen, what ISO we'd be using. Today, in film work (celluloid) the most powerful choice one can make about the look of the project is the chosen film stock. Will it be grainy or clean. Will I need to use open lenses or stop down. Will the colors be highly saturated or soft, will I have sharp contrast of soft. All that is decided merely by the film stock. While this is somewhat different to choosing an ISO in a digital camera, the idea of the basic look is going to come from the chosen ISO.

To me, you choose the ISO last only if you lack the tools to do what you need to do. If I want to shoot outdoors and I want deep DOF, I am going to choose an ISO 200 film, which will let me stop the lens down. If I want shallow DOF outdoors and I want it SUPER clean, I will shoot on ISO 50 speed film, or choose ISO 100 on the digital camera, and use ND to get my aperture open. I will not shoot ISO 1600 just because I lack a $50 ND filter. That's ruining the vision of my film because I lack the tools to do it the right way.

The problem is worse indoors. If you want shallow DOF but you need a wide shot, most shooters are stuck. Of course the answer is the correct lens, but since no one wants to buy decent primes, they are stuck with F3.5 zooms that can't open wide enough to get the correct DOF. Or you've chosen a grainless look, perhaps for a comedy short, and you want things bright indoors but shallow DOF. Well now you actually need to light, and you need the lens at F2. Uh oh... kit lens falls down again.

These new digital cameras are great. But they are no substitute for a basic understanding of photographic principles, and you still need good lenses and other supporting gear if you want to stay true to your vision. Leaving the ISO setting for last is a surefire way to ruin a consistent and cohesive look in your work.
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Old March 19th, 2010, 11:50 AM   #8
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Perrone,

I used to shoot film (photos), so I understand your point about choosing ISO first. (You'd choose indoor or daylight, slide or negative film too.)

But I think David's process makes sense with today's cameras for video. Assuming that your WB is set... Start with the shutter speed, which is usually 180 degrees. Next, decide on your desired DOF and choose the appropriate aperture. That sets your artistic look. The next step is to set a correct exposure, which is largely a technical exercise.

Personally, I choose 100, 160, 320, 640, or 1250. Though I prefer the ISO to be at the lower end, all of these are acceptable to me.

If at 100 ISO, the image is still overexposed, I grab a polarizer or ND filter. If I don't have time for that, I stop down the aperture. I might accept more stutter and increase the shutter speed. I might just let some parts of the image blow out. The solution depends on my situation at the time.

On the other hand, if the image is underexposed at 1250 ISO, I might add artificial lights, move the subject into an area with more natural light, or open the aperture wider. I might choose a faster lens. In a stretch, I'll push the ISO further or decrease the shutter speed, but those are last resorts when I have no time and when capturing the image is more important than the quality of the image.

Of course, experience speeds up the process. I know not to shoot at f/22 under streetlights, or f/1.4 at noon with a naked lens. I'm probably at 1250 ISO at night and 100 ISO at noon, unless I'm doing something unique. And a 180 degree shutter is usually (but not always) a given. (Use 1/60 under US lights and 1/50 under European lights.)

The real challenge in all of this is when you walk in with an idea of the look you want, you set the shutter and aperture as desired, push the ISO to your personal limit, and the exposure still isn't right. That's when creative solutions come into play. Different shooters will go for different results.
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Old March 19th, 2010, 01:16 PM   #9
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Ah, I think I understand.

When I am preparing to shoot, I have an ISO in mind (and generally only 2 per movie), I have an F-Stop in mind, and my frame rate and shutter speed is already in my mind. All these are constants before I set up the camera to shoot. Then it's just a matter of lighting for what I've decided on. If I cannot control the light to my satisfaction, then I will filter or do what I need to do, but I do NOT change my camera settings to get it.

I think that is the difference I am seeing here. My camera settings are fixed entities, and not variables like you guys are using them.

Just a difference in philosophy. Thanks for taking the time to explain. I understand better now.
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Old March 19th, 2010, 01:24 PM   #10
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Quote:
Originally Posted by Jon Fairhurst View Post
That's when creative solutions come into play. Different shooters will go for different results.
Exactly. Play with the camera. Test it out on all the various settings in different environments. Have fun with it and see what works best for YOU.

Enjoy!!
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Old March 19th, 2010, 03:11 PM   #11
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Great discussion - I too "grew up" on film, but I'd agree with the low ISO suggestion.

Depending on exactly how much post you need to do (something with sfx may need lots of passes), grain is going to be added. Sometimes quite a bit of grain. B/c of that, I always try to start as clean as I can, then add in grain if I need to...

It is strange going from film to video (it's taken years for me to wrap my head around it), but the bottom line is this - the camera is your "film stock," both in look/grain structure, and depth of field.

Just as film will have a certain grain structure/ISO rating etc, each camera has it's own foibles; it's own strengths and weaknesses - it's own unique "look". The cameras (and their chip sets) are also the "millimeter" size of the film - 1/3" chip sets will have greater DOF then 2/3" chip sets and so on.

I'm generalizing here, but brands tend to look the same with basic model lines - Sonys are very sharp, Panny's a bit grainier but warmer, JVC somewhere in between. Sort of like Kodak vs Fuji film - they're basically the same, but there are differences.

That's why I bought the T2i - a wee bit grainy, but it just nails the look I want. Some of the stuff I've seen - right out of the box - has been unbelievable.

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Old March 19th, 2010, 05:17 PM   #12
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Perrone,

That's a great way to approach the craft. Start with the vision, set the camera to deliver, and control the light to make it work.

Documentary filmmakers need to approach it from the other side. You are given a situation; now you have to bend the camera to get the shot.

Low budget narrative shooters are somewhere in between. We'd like to control the light, but might not have the equipment, crew, and time to achieve what we want. And then we bend the camera far enough to get what we need, given the constraints.

I guess that's the reality: we either bend the environment, bend the camera, or bend our expectations to get our images. If all three items are rigid, disappointment looms. ;)
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Old March 19th, 2010, 07:31 PM   #13
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One of the great things about this new technology is that we arenít constrained by a set ISO and we should try to use it to our best advantage. Unfortunately for those just entering the fray it can be confusing and a backwards way of working to others.

Perrone obviously knows his workflow and with the set ISO of film stock makes that decision ahead of time and knows from experience what he has to do. I tend to work in a much less controlled environment and shoot for a certain look, knowing I can with the roll of a wheel change from ISO 100 to 6400.

Letís try and remember that for each of us there was a time when we owned one camera and one lens. Helping people learn what that combination can do well is much more constructive then pointing out their equipments shortcomings. If they are serious the shortcomings will become self-evident and those on here can then help point them to a solution. Thanks.
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Old March 19th, 2010, 08:12 PM   #14
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Good post David,

I am still coming to grips with this I guess, but I suppose I don't find it all THAT different from working with film.

When shooting film, I worked with everything from Pan-X at ISO 32, to Fuji's 800 speed color films when all the sports pro's made that jump. At the time (late 80s) it was the best 800 speed I'd ever seen, and shamed some 400s I had used.

I liken documentary filmmaking to photojournalism. You are presented with a scenario, and you have to do what is required to bring home the shot. When I did that kind of work, I often had a zoom lens on, semi-fast film (usually tri-x), and a body on full manual. Shutter was usually at 1/125. I could get a clean shot of nearly anything with that setup as long as I was willing to either push the film, shoot wide open, or stop way down.

In narrative, I think we all would mostly like to keep the images clean. So that pushes us down the ISO range toward 100 or so. I think what gets most people in trouble, is having slow lenses and poor light. That is a KILLER combination that can only be fought with ISO. I spend a lot of time trying to convince people to not buy the slow kit lenses that come on these cameras or sell them and buy something that will help you down the road. Personally, I try not to buy anything slower than a 2.8.

Honestly, I think anyone getting into photography or cinematography should have either a set of 1.4 or 1.8 lenses at 35mm, 50mm, and 85mm (assuming a 1.6 crop). Maybe an F2 down at 24-28mm. Add a 2.8 zoom at the very wide end and the long end, and you've got 5 lenses that will get you out of nearly any crack in shooting a narrative piece. No one should have to be looking at shooting above ISO 320 in a controlled scenario.

As a cinematographer on a collaborative set, the power of working to a set ISO (say 320 indoors and 100 or 200 outdoors) is that it allows me to work with a common set of lighting, and the grips know about how much light it's going to take on set every time. If I shoot scene 3 at ISO 800, scene 3b at ISO 100, and scene 3c at ISO 320 they are going to be moving lights in and out of set like mad men! I'm going to type of a real world example of this, and provide a supporting photo.
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Old March 19th, 2010, 08:47 PM   #15
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Hey guys,

Thanks for all your responses. I only have a 50mm 1.8 lense at the moment and didn't opt for a kit lense when I bought my camera. I am still learning and now know the importance of having the fast primes over the zoom lenses that are slower in low lighting conditions.

Thanks again for this forum its been great.

Jason
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