Adjusting in post vs adjusting when shooting

P

Paper_bag

Active member
Hi! I'm a student and very new to cameras, so apologies both for the cluelessness of the question, and for the likelihood that it's been asked a billion times before, but... What's the difference between adjusting something when shooting, and adjusting in post?

Exposure, focal length, shutter speed I kind of understand. I'm thinking, in particular, of the following:

1. Speed changes. Is there a visual difference between adjusting frame rate when you're shooting, and applying a speed change in an NLE?

2. White balance. Say you're shooting under fluorescents and everything looks green. What do you lose by colour correcting in post instead of doing a white balance at time of shooting? (I have half an idea about this one, but don't have it clear in my mind.)

3. Coloured lens filters and gels. Is there a difference between using a blue filter, say, when you're shooting, or sticking a gel on a light, and applying a tint in post?

4. Gels vs white balance... Not altogether on topic, but anyway... You're converting tungsten to daylight. Should you slap on a gel, or adjust white balance, or both?

Any help is much appreciated!



Regards,

Paper_Bag
 
Some of your questions need a little bit of a background to answer, but I'll try my best not to be length about it.

1. Adjusting frame-rate while shooting is called ramping, and it is visually different from a speed change in an NLE because the frame-rate is changing for a part of the ramping process, whereas a speed change does not affect the total number of frames shot on the camera - just the time frame in which the frames actually play and at what speed. So in short, yes there is a visual difference.

2. I think the way you're thinking about white balance is a little misguided. Firstly, white balance is a technique that is used to contextualize colors within the frame, namely it makes white appear white or to be technically correct, grays appear gray. It's black counter part is called black balance. So, if one where to properly white balance under fluorescent lights, then the image would not appear green at all - it would look neutral. Fluorescent lights would only cast a green colored light if you had white balanced for something other than the given color temperature for said lights. Fluorescent lights tend to be all over the place as far as color temperature, but they fall anywhere between 4200-4800K.

So, now to your actual question. I'd say the most important part of getting white balance correct is to make skin tones look natural, unless you are making an artistic choice where the film should appear colder or warmer. The reason I say this is because if you screw up white balance by forgetting an 85 filter for a tungsten film stock and you shoot in daylight, in my experience the amount of orange you add into the image will never equal the amount of blue cast by the sun and what you end up with is muddled skin tones, and SUPER oversaturated colors in the frame. Of course, utilizing this knowledge is what makes a cinematographer a good artist. For example, a common technique is to purposely warm the lights with quarter or even half CTO to give the appearance of late afternoon. By using this technique instead of warming the whole image through post production white balance adjustment, skin tones look far more natural contextualized with the background and set.

4. This question is confusing me because applying a gel and changing white balance are two completely different things. So you said, "you're converting tungsten to daylight". To me, that means we only have a tungsten light, but we want the light it casts to be balanced for daylight. Is that correct? If so, you slap a CTB on it. Changing white balance won't help you there, at least, not without screwing up everything else.
 
Every creative shooter wants a look for their work and everything in your post are viable concerns.

I can't imagine a situation where you wouldn't WB before the shoot.
Frame rate changes (overrcrank for sure) are best recorded in cam. That gives you the most information to work with in editing when it is slowed down.
Tints, colors, and masks are different. If you record with a significant effect, you are pretty much stuck with it, so make sure you want the effect before shooting it. It still might be the best way to get the effect, but it is a one way street; no backing out after the fact.

Going a little beyond your post, professional cameras have many built in adjustments to tweek the recorded image. On Panasonic cams, these are called scene files. A scene file remembers all the parameters you set to achieve a certain look. That might range from a very neutral setting which you would adjust in post, to a very saturated filmic look which you might not do much with at all. learning the various parameters and how they effect your image is primal knowledge to getting the look you want.

Welcome to DVXuser.

Grant
 
Sean and Grant, thanks very much for your helpful replies; and, Grant, thank you for your welcome!

About speed changing vs ramping -- I think I conceptually get it, but I can't picture it in my mind's eye. I think the best thing to do is for me to shoot some comparison footage and see for myself.

About gels -- Sean, I think your point about contextualisation is a key one for me. Thank you.

About white balance... Well, Grant writes, "If you record with a significant effect, you are pretty much stuck with it, so make sure you want the effect before shooting it. It still might be the best way to get the effect, but it is a one way street; no backing out after the fact." What I don't yet understand is why it's not always better to "shoot dry" and have the option of backing out, even if you're 99% sure you'll want warmer or colder. What do you lose by giving yourself a two-way street, so to speak? Is the one-way street simply a matter of saving yourself some post-production work?

One more in-cam vs post query -- diffusion and soft-focus filters... Apparently, to achieve a soft, dreamy look for Picnic at Hanging Rock, Russell Boyd used a stocking over the lens. Wim Wenders' DoP used the same technique for Wings of Desire. And I'm told applying vaseline to lenses is a traditional aid when filming ageing film stars. But now that we have access to filters in NLEs, is there any real reason to apply diffusion or soft focus at the time of shooting? Could one really tell the difference between a Russell Boyd-applied stocking, and a Final Cut Pro-applied stocking? Does it matter whether the vaseline is chemical or electronic?
 
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I think you've hit on the great debate of do it in post versus in the camera. With all the bells and whistles available now you can duplicate most anything in post that you can do in the camera...so the real answers for you are time and money to do it in post if in fact the post-effect looks as good as or better than the real effect via camera.

People like to rush to get to post and say they will fix it or do it in post...then they find out they have a trememdous workload in post to get everything correct.

I would run some tests to determine the effects answer then determine how much time you will need for post. Be very conservative on the time required.

Go for it!
 
One thing to remember when shooting under certain kinds of lighting (low-pressure sodium and mercury vapor lamps are chronic offenders) is that the color spectra of these lights is very uneven, with most of the light's output peaking in very narrow spectral bands. In practical terms this means that you cannot post-correct the image's color effectively because your subject is not being lit across a broad spectrum (note the graying corpse-look of your skin under nasty parking lot mercury-vapor lamps, for example).

I'm told applying vaseline to lenses is a traditional aid when filming ageing film stars.
Click to expand...

The standard joke is time to shoot her through linoleum.
 
Overcranking is the best way to achieve slow motion. For example if you shoot 60fps and then view it at 30fps you get 1/2 of realtime. Ramping is an entirely different issue, and most cams won't do this.

Your comment about white balance is is pretty much true. Just shoot it straight and play with it later. Kess hit it right, you can do it later, but it will probably be time intensive and more expensive, though some of the basic software like magic bullet is pretty amazing. But the larger context of the same issue is controlling saturation, contrast for the different ranges (gamma) especially blacks, detail (sharpness) settings which effect noise, amongst others. Once those parameters are recorded, you live with them. I would also say that for me, if I know I want a certain look, and I can get that from the cam, that is the easiest way to avoid a lot of work in post, or having to hire someone to do it.

You haven't mentioned what type of cam you might be using, but Pana cams are well known for having a measure of mojo for the saturated-fimic type look. The parameters you adjust (about a dozen) to get the look you want are captured in scene files which are remembered by the cam or to SDHC card.

The other effects like blur or soft focus IMO should be done in post.

Grant
 
Thanks gentlemen! Max, I wasn't awake to the differences in spectral bands between different sorts of lights, so thank you for teaching me.

Grant, I don't own a camera, but am in the market for a secondhand HVX200 or HMC150, so your comments are on point. I've watched Barry Green's DVDs, and have a beginner's understanding of the scene file settings. Will have to do a lot of experiments to check out the results when particular settings are combined with particular effects in post.

The camera I'm most used to, incidentally, is an older Panasonic one; I think the model was "HDV900E", but I can't find information about it online. Shoulder-mounted, non-P2, records DVCPRO50 to tape. Kind of looks like the HPX500. Used it for a month of 16-hour days shooting a low-budget feature in the course of my course.
 
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The best way to learn is by doing. No one ever got anywhere just by reading books (though reading books is good). If you're into cinematography and getting an all-encompassing book about the art itself, check out Blain Brown's book entitled "Cinematography: Image Making for Cinematographers and Directors". I highly recommend it.
 
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