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Sony HVR-V1 / HDR-FX7
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Old May 19th, 2007, 02:27 AM   #1
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sky overexposing: will French flag help?

This is a naive question, so please forgive me. I never was so serious about getting as good video as possible before; the V1 is my first camera I'm considering fixing a French flag to. Not a full matte box (I guess it would be an overkill for my purposes), but something that would help handle light better. Frankly, I'm not even certain it's a French flag that I need, so let me explain.

With fine weather, plenty of sunshine, I have no problems with properly exposing my video. However, when the sky is overcast with light-gray clouds (not those dark, stormy ones), I get them overexposed long before other areas get proper lighting! When I open the iris to properly expose anything else, those clouds are gone and the whole sky detail is blown away. Please take a look at those grabs that roughly illustrate the situation.

Now, my question is: will a french flag help in situations like this, when there is high contrast with the sky above? If not a French flag, what can help?

I know this is a very general question on filming techniques; if I put it in the V1 forum is because I'm seeking advise with this particular camera in mind. Unfortunately, setting knee low and stretching blacks is not enough with scenery like this; I've even been wondering why the knee lacks a really low position, that would allow for 1-2 full stops more in bright areas...
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sky overexposing: will French flag help?-image5.jpg   sky overexposing: will French flag help?-image4.jpg  

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Old May 19th, 2007, 02:39 AM   #2
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no it will not help.
you need a progressive ND filter (dark at top, transparent at bottom).
This is elementary accessory used by photographs , most of time ignored by videographs.
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Old May 19th, 2007, 02:41 AM   #3
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Thanks Giroud; do I need a matte box to mount such a filter, or are there any that I could fix on the lens?
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Old May 19th, 2007, 02:42 AM   #4
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Hi there

Firstly a matte box would not be over kill for your camera, I use one all the time on my Z1... Check out models by TLS and Formatt...

A french flag while it will stop stray light from hitting the lens and flaring, it is a bit like wearing a baseball cap, it will shade the lens thus improving your picture, but won't have a massive effect on exposure.

To get the even exposure you are looking for you'll need to use an ND Grad filter... I've been using that and a polarizer a lot for the scenics I've been shooting recently. I find a 0.9 ND Grad gives me the best results...

regards
Gareth
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Old May 19th, 2007, 03:27 AM   #5
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Originally Posted by Gareth Watkins View Post
A french flag while it will stop stray light from hitting the lens and flaring, it is a bit like wearing a baseball cap, it will shade the lens thus improving your picture, but won't have a massive effect on exposure.
Yep, I guess you're right: a french flag versus an ND grad filter is like wearing a baseball cap versus good sun-glasses.

OK, so an ND grad filter is a way to go, but why is the knee setting so subtle, and unefficient in such circumstancies? Do other cameras use an even lower and stronger settings for knee than the "Low" on the V1?
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Old May 19th, 2007, 05:16 AM   #6
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Piotr, you are running into the biggest problem with electronic cameras. The exposure latitude is much less than the human eye. In big-budget movies, a whole lot of lighting gear is used (and a lot of money spent) fighting difficult lighting situations.

Of your two examples, the best exposure is the first one where you kept the exposure a bit low. It may not look like that, but if you assume color correction is going to be done in post you want to ensure that the whole scene is within exposure limits. A little underexposure to prevent the sky from blowing out is good because there is still enough detail in your highs, mids, and lows to create a good final result. If you overexpose and the sky disappears, the only thing you could do in post is use a luminance key and put in an artificial sky. In some circumstances, this may be preferable. The good thing about the V1 is that it doesn't smear out other details when part of the scene overexposes, so at least only the sky is ruined.
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Old May 19th, 2007, 05:35 AM   #7
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Markus, if the left (underexposed) picture is the right one - what kind of tool do I use in post to lighten the fence, while keeping detail in the sky?
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Old May 19th, 2007, 05:51 AM   #8
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You would use the color correction tools in your NLE. There are all sorts of things that can be done with color correction. I am not an expert in color correction (I'm about to go through Glen Chan's dvd on the subject), but I've seen amazing things done as long as some information is preserved in the original shot. Use the histogram on the V1 and make sure as little as possible is going beyond 110ire or going down to complete black. Keep as much as possible from going off the far right or left. The histogram helps with exposure because it can be hard to remain objective in different lighting conditions as our eyes react to different illumination levels. It's inevitable that there will be some loss in some scenes, but do your best to keep from losing detail.

The exception would be in situations where you can not ensure that color correction will be done in the post production process. If you are shooting live broadcast or have serious time limitations in post, you will need to shoot to make it look as good as possible to your eye. When in shooting situations like that, I always keep people's faces exposed properly and try to change my angles until I get the best lighting possible in the background. Often, this means reducing the amount of sky that appears in the shot.

With color correction, you can brighten or enhance colors, eliminate colors, make the gamma curve more gradual, bring up or crush the blacks, and probably other things I have yet to see.
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Old May 19th, 2007, 08:36 AM   #9
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If your shot is fixed and on a tripod, you might be able to shoot 2 versions and combine them in post - a properly exposed sky shot, and then an identical shot with the fence properly exposed... I'm not sure on the specifics but do some kind of mix in the edit between the two shots and take the best elements from each shot to make one good shot (maybe someone else could advise on the best way to do this)
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Old May 19th, 2007, 09:50 AM   #10
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that is exactly what i was saying about elementary photographics accessories and rules ignored by videographers.
They will tell you to use a computer and programs and electronics tricks and tons of time, where a simple filter will solve all your problems for few dollars in seconds.
These kind of filter can be used with or without matte box, cokin (or chinese copy) offering a filter holder, the adapter ring and the progressive ND for less than 50$.
I use a FX1 and wanted to keep the the original sunshade, so the only solution was to put it in front of the cam. I had to purchase the X-Pro size from cokin. you can find a kit for less than 200$ for the holder and 3 filters (B&H).
with some luck, the V1 has a smaller aperture and you can use the Z-pro size that cost a lot less.
for sure if you need a french flag (nice to prevent flares), go to the full stuff and add a mattebox with 4x4 filters, you can find for cheap on ebay.

Last edited by Giroud Francois; May 19th, 2007 at 12:27 PM.
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Old May 19th, 2007, 08:30 PM   #11
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Set the camera for wide lattitude -- before you buy anything. Knee at LOW and BLK STRETCH ON.

The lattude should be about 10-stops. But, your scene may be even greater. So you'll need to sacrifice a bit of the shadow detail be lowering exposure a stop or two.

If you plan to CC, don't allow the histogram to go very much beyond 100IRE (orange line). Information that is clipped away can't be gotten back.

Use gamma curves in CC to handle the too dark shadows. But, don't count on fully restoring them.
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Old May 19th, 2007, 10:54 PM   #12
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Originally Posted by Steve Mullen View Post
Set the camera for wide lattitude -- before you buy anything. Knee at LOW and BLK STRETCH ON.

The lattude should be about 10-stops. But, your scene may be even greater. So you'll need to sacrifice a bit of the shadow detail be lowering exposure a stop or two.

If you plan to CC, don't allow the histogram to go very much beyond 100IRE (orange line). Information that is clipped away can't be gotten back.

Use gamma curves in CC to handle the too dark shadows. But, don't count on fully restoring them.
Hi Steve,

I have a question about your comment..

I try to keep things below 100IRE but at times I've found that I need to let the sky or other area creep a bit above (below 110 for sure). The camera (V1U) has no problems with levels up to 110IRE and with a single checkbox in my NLE it handles up to 110IRE fine as well. I find that I can bring the levels down to safe limits in the computer. I figured this was in effect expanding the latitude of the setup slightly. My question is.. Is this wrong?

Chris
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Old May 20th, 2007, 01:58 AM   #13
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Originally Posted by Steve Mullen View Post
Set the camera for wide lattitude -- before you buy anything. Knee at LOW and BLK STRETCH ON.
As I stated in my original post, Steve, these were exactly my settings - hence my comment that KNEE is not very effective on the V1; or is it my unit? It makes a difference in highlights, but only a slight one.

Please comment!
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Old May 20th, 2007, 03:22 AM   #14
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Originally Posted by Piotr Wozniacki View Post
As I stated in my original post, Steve, these were exactly my settings - hence my comment that KNEE is not very effective on the V1; or is it my unit? It makes a difference in highlights, but only a slight one.

Please comment!
Sorry -- I missed that. I try to shoot with clear blue skys because "when the sky is overcast with light-gray clouds" the sky is like a white wall catching the sun. A gradient filter will help if you can carefully compose the shot. EZier is to compose to avoid the sky.

On the other hand, since they sky is white -- I suppose the fact it photographs white might acceptable. :)
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Old May 20th, 2007, 06:29 AM   #15
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"They will tell you to use a computer and programs and electronics tricks and tons of time, where a simple filter will solve all your problems for few dollars in seconds."

A graduated ND filter will work for some shots, but these are just test shots. Assuming that a subject might be placed in the real thing, a graduated ND might darken the top half of your subject. Also, graduated filters sometimes can be obvious in their use if they are not perfectly aligned with the bright part of the scene. With video cameras, the shot will often be dynamic so the ND filter would need to be re-oriented during a take which is not practical. I have gradual ND filters, but they are only part of the solution.

The only type of filter that may help without darkening your subject is a Contrast filter. There are Low Contrast, Soft Contrast, and Ultra Contrast filters that either darken the highlights, raise the blacks, or a combination of the two.

Controlling contrast involves many disciplines of photography:

-Observing your environment and selecting the best time to take advantage of natural lighting conditions

-Choosing the right exposure

-Using correct lighting, reflectors, and other lighting controls like scrims

-Using appropriate filters like Contrast and Neutral Density

-Selecting the best angle of your shot for the existing light

-Composing the shot so it will stay within the limits of your medium

These things are all done at the time of the shot irrespective of electronics. There are still more things that can be done now that we have sophisticated cameras and computers:

-Setting your camera for greatest contrast range compression by lowering knee and raising black levels

-Using color correction to bring highlight details down into the range of the display device and to bring underexposed areas back to a more natural appearance

-Using color correction to accentuate colors that may be made dull by exposing for greatest contrast range

-Replacing overexposed areas with substitute information using a luminance key (often "sky replacement")

There may even other things that people with more knowledge can elaborate upon, but these things are a good start. None of them will work alone and some of them take a great deal of effort. Combined, you can get amazing results but it will take time, expertise, and even money unless you are always able to shoot in perfect lighting conditions.
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