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Shooting exterior with Alexa


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#1 F Bulgarelli

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Posted 08 January 2014 - 01:14 AM

Hello everyone,

I 'm getting ready to shoot a project with the Alexa, all exteriors; mountains, forests, open shade, strong backlights from the sun, flares, etc. It would be mostly available light, except for some bounce to fill in the shadows when possible.
I was curious about other DP's approach in terms of finding a balance between the highlight and the shadow, while protecting for well exposed faces. do people rate at 800, for the most part? Do you use the false color feature, histogram, light meter, polarizer to get a nice, blue sky. Basically, whats your approach when shooting exteriors with the Alexa.

Any advice will be greatly appreciate it,

Thanks

Francisco
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#2 David Mullen ASC

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Posted 08 January 2014 - 01:32 AM

Same approach as when using film.  You can see the exposure on the monitor and see any clipping, etc.  Shoot Log-C, obviously, but it's up to you if you want to monitor in Rec.709 -- it will look a bit clippier than Log-C but that might help you keep the contrast within a more adjustable range because viewing Log-C can make you a bit overconfident, especially regarding shadow detail because the lack of black in the image makes you think you have more shadow detail than you'll have once you correct the blacks.  Plus with Log-C, your whites and highlights are a bit dim if you expose correctly, so if you view in Log-C, you will tend to overexpose just to get your highlights to look less murky.

 

One thing to keep in mind - a monitor, even in a tent, will look darker to your eyes when you are surrounded by daylight, so you have to force yourself to expose so that the image looks a bit dim even in Rec.709 because your eyes are being fooled by all the ambience and if you expose so that the image looks correct on the monitor, you'll actually be overexposing.  Either that or really create a blacked-out tented viewing environment, but that's a bit annoying to deal with.  I usually use a semi-tented area with black behind the monitors and behind my back, but usually one side is open.

 

A waveform doesn't hurt but if the signal is Rec.709 from the camera to the monitor, then you'd be reading the Rec.709 levels, not the Log-C levels being recorded (unless you keep switching the camera back and forth to Log-C output or get a monitor that can generate its own Rec.709 LUT and let the monitor out signal be Log-C.  But if the exposure looks correct on a waveform reading Rec.709, you know that you'll have even more information in Log-C later.

 

The main thing to remember is to avoid clipping except for tiny highlights like sun glints off of car window.

 

Yes, 800 ISO is good though I sometimes go down to 500 ISO just for a cleaner image, either way you'll need some heavy ND filters.


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#3 F Bulgarelli

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Posted 08 January 2014 - 02:29 AM

Thanks David, your advice is always appreciate it

Besides the ND's, do you work with a polarizer as well? I was thinking about using the built-in ND and then adding front filtration, such as 1/4 black promist and polarizer. Does the internal ND eliminate any danger of IR contamination?
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#4 David Mullen ASC

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Posted 08 January 2014 - 03:44 PM

What internal ND in the Alexa?  Do you mean you are getting those internal filters that you can attach to the front of the sensor? There is no ND filter wheel in the Alexa.


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#5 Dom Jaeger

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Posted 08 January 2014 - 09:21 PM

Does the internal ND eliminate any danger of IR contamination?

 

The Alexa Studio has a built-in retractable ND filter with a density of 1.3, not full spectrum so some IR pollution may be visible in certain conditions, correctable with a T1 or IRNDs stacked in front. Not always a noticeable issue but you need to test. See http://cinematograph...s/ir-grabs.html

 

The Arri IFM (In-camera Filter Module) is an optional extra available to use with the Alexa XT range (except XT Studio) which allows custom IRND filters from 0.3 to 2.4 to be fitted behind the lens without altering the colour balance.  I haven't had the opportunity to test it personally, not sure how many rental houses invested in it actually, seems a little fiddly.


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#6 Ben Rowsell

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Posted 09 January 2014 - 03:01 AM

 

 

The Arri IFM (In-camera Filter Module) is an optional extra available to use with the Alexa XT range (except XT Studio) which allows custom IRND filters from 0.3 to 2.4 to be fitted behind the lens without altering the colour balance.  I haven't had the opportunity to test it personally, not sure how many rental houses invested in it actually, seems a little fiddly.

 

I am currently using these on a feature and they are a very good system when supplemented with a handful of regular NDs. We have the base kit, which is a ND6, ND1.2, ND1.8. One of these (or the clear) goes behind the lens depending on the lighting conditions and the DOP rates his meter accordingly, i.e., 800ASA, 200ASA, 50ASA, 12ASA. Then we have a regular ND3, ND6, ND9 that go in the matte box to buffer light changes. This means you are not constantly changing the internal filters and you are not carrying a lot of regular ND filters. We often only change the internals once or twice a day. Also the internal filters are very neutral compared to most IRNDs so we have no issues with colour shifts.

Rating the meter at different ASAs according to the internal filters is a nice way of separating the internal and external filters, and makes it faster & easier to calculate shooting stops from the base. We refer to it as "changing film stock" and it does bring it back to a similar filtering system that you would have used on film.

For drama situations I would recommend it. The filters are fragile compared to regular ones so you need to take care with them, I use a bulb blower to take any dust off, but apart from that have not needed to clean them. They are certainly a lot easier than dealing with gelatine filters.

 

Ben R

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#7 F Bulgarelli

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Posted 09 January 2014 - 12:54 PM

What internal ND in the Alexa?  Do you mean you are getting those internal filters that you can attach to the front of the sensor? There is no ND filter wheel in the Alexa.


Yeah, that s what I meant David, thanks
I guess that system is not as popular as I imaged.
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#8 David Mullen ASC

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Posted 09 January 2014 - 01:10 PM

I haven't used those yet, I guess I'm worried about the time it takes to pull off the lens outdoors and change those filters, plus getting dust on the sensor doing it, etc.  A filter wheel is fast to change, and filters in a matte box are semi-fast to swap out, but this behind the lens system seems only good when you are going to leave an ND1.2 or something on for most of the day.


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#9 F Bulgarelli

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Posted 09 January 2014 - 02:06 PM

I found some interesting tests here, particularly in regards to day exteriors with the Alexa

http://www.hurlbutvi...a-vs-canon-c500
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