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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Ask David Mullen ANYTHING

F stop/T stop

F stop/T stop

Hi David,

Thanks for sharing so much valuable information.

Coming from a TV/Broadcasting background and recently being 1st AC on a feature shoot with the RED One, and more specifically using cine-lenses I'm slightly confused at the term T-stop which I came across. Can you explain the difference between that and F-stop?

Cheers, Kirk
 
This is the Wikipedia definition of f-stop:
In optics, the f-number (sometimes called focal ratio, f-ratio, or relative aperture[1]) of an optical system expresses the diameter of the entrance pupil in terms of the focal length of the lens; in simpler terms, the f-number is the focal length divided by the "effective" aperture diameter. It is a dimensionless number that is a quantitative measure of lens speed, an important concept in photography.
Click to expand...

See:
http://en.wikipedia.org/wiki/F-stop#T-stops

Since the f-stop is basically determined by physical measurements, even though it describes the size of the aperture which controls exposure, it doesn't factor in any light loss within the lens due to internal reflections, etc.

So basically someone measures the actual light transmission through the lens and adjusts the f-stop mark to become more accurate in terms of actual exposure -- in other words, the T-stop mark is a "corrected" f-stop mark, adjusted for light loss in the lens. Hence why an f/2.8 lens is also sometimes called a T/3.1 lens... it's not really f/2.8 in terms of exposure. So you measure the light and get an f-stop reading and set your lens to the same T-stop -- in practical terms, you treat the T-stop on the lens as if it were an f-stop.

However, since depth of field is determined by the physical dimensions of the aperture, in theory, you're supposed to use f-stops in determining depth of field, not T-stops.
 
I just want to give an update to my issue:
Reinstalling software (B17) gave me two identical cameras! I am a happy DITpuppy...

Fredrik Harreschou said:
Dear David Mullen,

I have a question for you regarding something you experienced on Manure:



Did you find any solution or answer to this? We are in the middle of a two camera production and just discovered that one of the cameras are yellower/warmer than the other. We have tried to black shade twice, but the results are consistent.

Thank you in advance,
Fredrik
Click to expand...
 
Balancing Color

Balancing Color

David,

Firstly, thank you for taking the time to provide this community with such a valuable resource of information.

My question is about an upcoming short project, which will be shot on the Red One. Due to budgetary reasons, we won't have an opportunity to shoot tests. A majority of the film takes place in an office, at night, and I am having trouble planning how to control color.

To reflect the sterile, imposing nature of the office setting, we are hoping to utilize hard, back cross light and render the setting in cool colors, similar to some of Jordan Cronenworth's work in Blade Runner. Ideally, we would have access to HMI's, but we can only get our hands on Tungsten fixtures. This presents questions in the following lighting scenarios:

1. Scenes lit ONLY with Tungsten fixtures: In this case, would it be safe to leave the lights clean, white balance to 3200K, and let the director / editor tweak the color to their liking in post? I know the old adage is to get your neg. / file as close as possible to the image you want in camera, but if I gel all of the lights 3/4 blue or full blue I'll be losing some valuable stops which I can't really afford to use based on wattage concerns.

2. Scenes with existing Fluorescents AND Tungsten fixtures:
 I will be gelling the Tungsten lights to match the color temp of existing Flo's. Once that is accomplished, should I just white balance to 3200K and let the editor "time out" the green AND shift color towards the aforementioned blue hue in post?

3. Scenes lit with Tungsten sources AND warm Incandescents: For scenes involving a desk lamp which is supposed to be much warmer than the cool hues, i.e. 2700K (lamp)/ 5000K(tung. sources), with white balance at 3200K, would it be smart to gel the Tung. lights to 5000K and let the incandescent maintain its native color temp (albeit dimmed) and hope that the cooler hues match the hue of the scenes mentioned in the above sections?

Sorry for the long winded question!
 
It would be a bad idea to light at 3200K balance and then try to blue-up the image in post -- you're already pushing the blue channel to get to 3200K on the RED, it would be very noisy to push it further to make 3200K look blue-ish.

You need bigger tungstens with blue gels or HMI's, etc.

Any deliberate color temp difference or mismatch between sources should be done in lighting, you can't really make different lights of the same color now look like they have different colors compared to each other, in post.

Besides the color temp metadata, you can also play with the tint in metadata to correct out the green, or use a magenta camera filter.
 
David,
thanks for your valuable advice, time and pacience.
Here´s my question. I´m shooting a feature and want to have as a start point reference and main key back light, soft controlled light. I know that the way of achieving it is by having a big source, let´s say a 6k hmi, putting it far away, with a difussion, and let´s say bring it through a window. Inside the room it will be a very soft light but directional. If you shoot it against it it gives a glow which I´m looking for. Soft controlled light. It also comes through a window from an overcast sky, you can cut it and direct it, give it direction. Now the thing is that I´m shooting mainly night, and don´t have the all you need budget. So I´m seeking advice on an alternative, that is simpler than a 6k hmi at 30 feet. Also seeking ways of justifying this kind of light at night, since this kind of light is mostly motivated by overcast light coming through the window. At night I don´t like it all the time for the window to glow and be too obvious. I´m also considering breaking the rules a bit and play with it. I guess the main thing is being constant and not flashy, subtle, lots of shadows.
Hope wasn´t too confusing.

thanks,
francisco
 
You could use a soft backlight that is closer to the actors, like a row of 4' 4-bank daylight Kinos just above the top of frame.

You could also backlight the window as well with a 1200w HMI.

I'm just saying that you should not plan on lighting with ungelled tungstens and then timing it bluer. You already have to push the blue channel very heavily to get 3200K to look white.
 
Best Vintage Lenses

Best Vintage Lenses

David,

This might seem like a broad novice question, which it is, but... What are the "best" lenses for the budget/student filmmaker? I'm looking for something affordable with a "soft" look; interested in vintage cinema lenses.

I've heard a lot about Zeiss, Cooke, and Angeneiux. How would you rate them and are there any other brands or individual lenses that make the mark? Specifically looking for primes but at my budget a really good all-round zoom might make sense. Oh, these should be lightweight lenses for handheld work.

Thanks,
Mike
 
Are you talking about 35mm PL-mount cine primes and zooms?

Yes, today you have the top tier of primes, which are: Panavision Primos (rental only, PV-mount), Cooke S4's, Zeiss Master Primes, and Zeiss Ultra Primes.

Next level below that would be Zeiss Super-Speeds and Standard-Speeds, which are actually quite sharp, just not wide-open. Some people swear by the Elites, which are Russian-made lenses -- I haven't tried them.

In this range and below are all sorts of different lenses, many adapted from still camera glass. Canon, for example, made cine lenses in the 1970's.

Then below this are probably the much older lenses from the 1960's and earlier, like Cooke Panchros and B&L Baltars, many of which used older lens mounts, pre PL-mount. A lot of people have mentioned Panchros here; they are popular with some to get a softer look with more flare.

I usually rent everything, and usually from Panavision, so I'm not as knowledgeable about what's out there to buy, and I usually don't have to deal with old optics or non-standard manufacturers.

35mm cine zooms tend to be large and heavy, very hard to handhold. The two biggest players in cine zooms are Cooke and Angenieux -- they both make some shorter, lightweight zooms now for handholding but they are not cheap. Some people have adapted still camera zooms for handheld work -- "Bourne Ultimatum" adapted some Nikon zooms for that.

Most 35mm handheld shooting involves using primes.

The 1970's era Cooke 20-100mm T/3.1 zoom is a good classic 35mm cine zoom, though not light enough for handholding.

You'd get more useful advice from the people out there actually trying to buy lenses right now for the RED.

The RED lenses seem like a good bargain, and the new RED 18-85mm zoom gets a lot of praise. The upcoming primes look interesting too.
 
Hi David, Thanks for all you do here!

I think I am correct on this, please double check me: I am shooting here in LA a spot for Europe, so we will shoot at 25fps. I can set my shutter in the Red at 1/60th for flicker-free practical fluorescent lights. It should work because it's the 1/60th shutter time that matters.

I am divorcing my mental marriage to the 180 shutter! It would not be so easy on film, It would be a shutter angle thing.... but it is that easy on the Red....... right?

Cheers,
Rich Schaefer
 
http://www.panavision.com.au/Information/Flickerfree60Hz.htm

At 25 fps, a 150 degree shutter angle gives you a shutter speed of 1/60th, which is an optimal shutter speed for 60 Hz lighting. So at 25P on the RED, set your shutter angle to 150 degrees or your shutter speed to 1/60th, it's the same thing.
 
richcam1 said:
Hi David, Thanks for all you do here!

I think I am correct on this, please double check me: I am shooting here in LA a spot for Europe, so we will shoot at 25fps. I can set my shutter in the Red at 1/60th for flicker-free practical fluorescent lights. It should work because it's the 1/60th shutter time that matters.

I am divorcing my mental marriage to the 180 shutter! It would not be so easy on film, It would be a shutter angle thing.... but it is that easy on the Red....... right?

Cheers,
Rich Schaefer
Click to expand...

Why would you set your shutter for 1/60?
Surely if you want to avoid frequency related issues, you should set it to 1/50 as that is the frequency of AC in most (all???) of Europe.
And that would simply be a 180 degree shutter.

Take a look at
http://en.wikipedia.org/wiki/List_of_countries_with_mains_power_plugs,_voltages_and_frequencies
 
Because he's shooting in the US (under 60Hz lighting) for European (50Hz/25fps) output.

Your point would be correct were he shooting in Europe, for either output...

Cheers,
Dom.
 
Dominic Jones said:
Because he's shooting in the US (under 60Hz lighting) for European (50Hz/25fps) output.

Your point would be correct were he shooting in Europe, for either output...

Cheers,
Dom.
Click to expand...

Ahhh. I didn't pick up that LA meant Los Angeles at the time. I just read "for Europe" and assumed he was shooting in Europe. My bad!

Edit: I keep forgetting that some of the users here are based in the US :sarcasm:
 
Hi David

What are some of your favorite black-and-white films from the '40s and '50s that used filtration for what's commonly called "soft focus"? And what filters would you use to achieve that today, to retain as much contrast as possible?
 
newbie question about shutter speed and ISO/ASA

newbie question about shutter speed and ISO/ASA

hi David,

Thank for so many great posts. I've been lurking for over a year now on this thread and I've learned so much. I'm a newbie to cinematography.

So I have a question regarding the shutter speed and it's effect on cinematography. I have a some basic knowledge in still photography. In traditional still photography shutter speed changes exposure and motion blur. In cinematography does changing shutter speed equal to the same effect in still photography? In red camera, how would changing from 1/48 sec to 1/2000 sec effect the look on footage?

I was reading AC magazine about shooting "Gladiator" opening battle scene. John Mathieson used a 45 degree shutter(1/200 sec shutter, correct?)to achieve that sharp and rigid action look. I also learned that by shooting at higher shutter speed, you have an option doing slow motion by double or triple printing each frame. If you did this with a "normal" shutter speed picture (1/50th) the result would be blurry.


My other question is about ISO/ASA in Red One. ISO/ASA also controls exposure in still photography. But in film if I want to bring down the ISO/ASA from 320 to 100 in Red to get shallower DOF, how would that effect the look of the footage? Is this a recommended way to use ISO or I need to stack up NDs instead?

Thanks!

Shaun
 
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