A few questions concerning exposure that I'm struggling with

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digifruitella

Active member
I shot this on a whim just for the sake of practicing a few things with the Canon T2i I have.. and you can skim through the video - although the second, or third shots is what my questions will be about.

http://www.youtube.com/watch?v=MpAJSp9gNCM

Nevermind the color-grade, it only made it a bit worse - this is a test video.

BUT.

I must be either doing something wrong, or I'm shooting at the wrong time of day. This video was shot at around 7pm, two days ago...you could say it's the golden hour, but we were in an area with trees so it blocked a bit of the sunlight.

As you can see, in the second, and third shots (i'm just concentrating on these as these type of shots matter the most for me right now)

The sunlight is becoming darker and darker during the time we're shooting - and I exposed for the faces, but that leaves the background (the sky mostly) overexposed.

What I want to understand is next.. is it because the sunlight is darker and it makes it harder to have a "balanced" exposure front-to-back? Because obviously if I expose for the skies, the foreground is extremely dark even at the lowest aperture (on that lens I had a f/4 max) and lighting the scene with lights is what's needed (I'd think so)

As I understand in situations like these one needs to use a Graduated Density filter

but problems arise right away...

hypothetically, if we're to stick with my two given shots I described and I have used a GND filter, the top area MAY have balanced out the exposure for the sky, but then the faces would also be "touched" by the top half of the GND.

So that's out of the question unless one is shooting landscapes without people.

Two...I see in many films, where BOTH the sky and the foreground is balanced in exposure - what is the magic trick here? Are DP's shooting at a certain time of day that allows them this? Or are they lighting the foreground while exposing for the sky? Please help me understand this. I'm eager to know how this is done.

Thank you very much!
 
You pretty much answered your own questions. What comes into play here is dynamic range and the bit depth of your camera. Your camera is trying to read and squeeze as much dynamic range info off the sensor that your dsp/codec will hold. Most video cameras do 5-1/2 to 6 1/2 stops. The dslr's might be more. Anything above or below renders as black or white respectively.

So the problem your having is your environment has more dynamic range then your camera can handle. The only way you can fix this is to alter your environment.

Their are many different ways to do this. You could use a bounce card on your foreground subjects, blast them with HMI's or huge 5k and 10k lights, use a graduated filter (usually for landscapes), aim your camera so the sun is behind you, anything that will lower your environments dynamic range.

In most cases, your going to have to let the sky blow out because their are just too many stops between your subject and the sky, so you end up choosing between silhouette or overexposure of your sky. Not much you can do about it on a small budget.....this is the main reason movies need grip trucks even for simples shots.

Good luck!
 
digifruitella said:
... hypothetically, if we're to stick with my two given shots I described and I have used a GND filter, the top area MAY have balanced out the exposure for the sky, but then the faces would also be "touched" by the top half of the GND. ...
Click to expand...

Its not very difficult to learn to work with ND Grads to either suppress the heaviness of the gradation or bring it out so its fully noticable. The two images below both use an ND Grad. The top image uses suppression techniques and the bottom image the opposite so you can clearly see the gradation.

stace_ponder.jpg





boiling_sky.jpg
 
Understood. Would I be correct if I avoided dynamic range environments when shooting pretty much no budget ?

So it seems the camera just can't handle too much of light blasted that way, and it has a tough job compensating between the two... I think I understand it a bit clearly now.
 
craighbowman, thanks for illustrations!

So what you're saying is that I could have used an ND Grad filter on those two shots in my video to suppress the light a bit and even out the exposure ?

the second image, that's a GND you speak of right? did you make a mistake or did I misunderstood you?



However...I'm not understanding the first illustration - why did you need an ND filter there? Too much light? It seems like that kind of shot would not really need an ND?
 
Forgive me, I misread what you were saying. That first image almost seems like it does not even utilizes it. Which part of the image did you use it on? and how did you suppress the gradation?
 
Focal length of lens, distance of focal plane to subject and even aspect ratio were combined to lessen how noticeable the gradient appears.

The reason its so obvious in the clouds image is a much shorter focal length and the distance of the focal plane to subject is much closer to infinity.
 
craigbowman said:
Focal length of lens, distance of focal plane to subject and even aspect ratio were combined to lessen how noticeable the gradient appears.

The reason its so obvious in the clouds image is a much shorter focal length and the distance of the focal plane to subject is much closer to infinity.
Click to expand...
craig: but why did you use grad nd on the first one? Was the guy's hair getting clipped or something? I don't even notice where you use it maybe you turned the filter tray sideways and the grad part is running vertical on the left side of the screen to cover much of the sky?


digifruitella: this is a question I two struggled with and was trying to learn about a few weeks ago and this is what I discovered:

DSLR's simply don't have the dynamic range of film. they get "overblown" or "clipped" very easily compared to film and as such you will never truly be able to shoot some of the shots you see in hollywood movies because of DSLR's inferior dynamic range. you have to make up for this with tricks such as the aforementioned GRAD ND filters or using bounce boards or lights onto the actor. i.e. you expose for the sky so your actor is darker then you light them up with lights and/or bounces/reflectors etc. many people will just tell you to expose for your subject and just let the sky blow out or blow it out deliberately then fill in a new sky via post production matte painting.
There ARE ways to get around it though you just can't be lazy. I have a GH1 which has arguably even poorer dynamic range than t2i or the same and here's an example for you that I shot.

this next photo is of my exposing for a blue sky and the subject's face being dark (there was actually still some bounce on it, just not focused on it as much so without the bounce the subject's face would have been quite a bit even darker)

ohqn0g.jpg


and here the next picture is with the bounce more focused on subject's face. In fact you can see the cheap foamcore $2.00 bounce board on the left side of the screen that I bought at Target

2ahir1x.jpg


so as long as you take your time and setup each scene properly you can still do it. Keep in mind craigbowman's shots above are from a Red One camera and your t2i doesn't have the dynamic range even close to Red, but then again Red doesn't have the dynamic range of Film either
 
Homunculus, thanks a lot for explaining this even further - I thought I was doing something extremely wrong, but since you mention that digital is just much inferior with capturing dynamic range than film - it makes all the more sense.

So if I was shooting the same scene with film, in an environment with big dynamic range, the cameras would balance out the exposure more evenly. However, I'd think that there would be times where bounce cards, or extra lights would still have to be used even in film.
 
Even film has a limited dynamic range. The shots you are talking about, shooting portraiture against a sunset sky, will stretch the limit of film also. In a situation like that, even with a modern color negative film, you really should either lessen the light coming from the sky (Graduated ND filters), increase the amount of light on the subject (Supplemental light), or a combination of both. What film will give is more "Room" to play with when making the adjustments. Now, modern color negative film does handle overexposed highlights and underexposed shadows much better than digital imaging systems so your compromise exposure, say underexposing the subject by a couple of stops or more, may leave enough "Head room" so that there is going to some detail in the overexposed sky and some detail in the underexposed subject. This may hold up when taking the image to a film print. The problem is that sooner or latter this shot is going to be transferred to a digital image, and will more than likely loose most of the highlight and shadow detail that your compromised exposure captured. To me, that was the big lesson of the Zacuto Shootout series, that is, film transferred to digital images just does not hold up, and does not really look that much better than images captured on consumer/pro-sumer DSLRs. (that discussion is for another thread). So it is best to bring the luminance range of the scene you are shooting within the dynamic range of your imaging system and expose the shot correctly.
 
yes digifruitella this guy above is right. film still has poor dynamic range compared to the human eye I believe but it's still much better than lower end DSLR. a t2i/gh1 has maybe 7 to 8 stops of dynamic range on a certain chart I've seen where the Red One camera has like 11 or 12 and film maybe 13 or more? I can't accurately remember but this is just to give you an idea. But yes even in film some of the shots you're talking about or tried to do are impossible. If your subject's back is to a sunset and you're shooting their front with the sunset behind them they will always be a silhouette and there's no way of getting around that even on film for instance. you have to be smart and choose your shots wisely and always supplement with bounces and/or lights when you have them
 
Homunculus said:
craig: but why did you use grad nd on the first one? Was the guy's hair getting clipped or something? I don't even notice where you use it maybe you turned the filter tray sideways and the grad part is running vertical on the left side of the screen to cover much of the sky?

...
Click to expand...

As I mentioned there are techniques you can use the make the use of a Grad less obvious. That's what the first image was an example of. The fact you can't tell for me is a good thing. I still can make out the very subtle gradation in the sky, even though its rezzed down as a JPG.
 
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