Scarlet - base sensitivity

[Laco Gaal]

Hey all,

so I read somewhere that the base sensitivity of Epic/Scarlet is ISO 800.
Sorry for my dumb question, but is it possible, to lower the sensitivity when recording?

I'v seen some MX night footage shot at 800, transferred to 35mm, projected on a screen, and it is a-w-e-s-o-m-e, but I can imagine shooting at iso 800 in daylight could be tricky.


thanks

 

[Graeme Nattress]

Yes, you can go down to 320, but you're going to loose a stop (or so) of highlight protection. You've got to balance that with the need for ND. Scarlet has built-in ND which will help you though.

Graeme

 

[Franck De Togni]

Wow I had missed that one ! I didn't know that. Thanks for the info Graeme !

 

[Mick Doll]

Excuse me but what is the ND ?? and why that begin directly with 800iso ?? we must use obligatorily the filters if i understand, no ??

 

[Erik Bien]

ND = Neutral Density filter. It's my understanding Scarlet will have internal user-selectable NDs — 0.9 (3 stops) and 1.2 (4 stops), IIRC.

 

[Mick Doll]

ND = Neutral Density filter. It's my understanding Scarlet will have internal user-selectable NDs — 0.9 (3 stops) and 1.2 (4 stops), IIRC.

Wow, if it's true it's excel man !!

Thank U Erik

 

[David Mullen ASC]

ND's are unavoidable when filming in direct sunlight, so you need to accept that. There is an old rule of photography called the "Sunny 16" rule, which says that if the ASA number is the same as the shutter speed in fractions, then the exposure in direct sunlight on a clear day is f/16.

Since most filmmaking at 24 fps is done with a 180 degree shutter, i.e. 1/48th of a second, you can round up to 1/50th... therefore at 1/50th and 50 ASA, your f-stop is f/16.

800 ASA is four-stops faster than 50 ASA and most lenses shouldn't be stopped down past f/16, if not f/11, and you're already at f/16 at 50 ASA... so ND filters are unavoidable in direct sunlight on a clear day.

An internal ND filter wheel will be inside the fixed-lens 2/3" Scarlet, but I don't know about any other Red cameras, maybe the non-fixed-lens 2/3" Scarlet as well, but not the 35mm sensor cameras (that would be a rather big filter wheel for one thing.)

 

[Laco Gaal]

ND = Neutral Density filter. It's my understanding Scarlet will have internal user-selectable NDs — 0.9 (3 stops) and 1.2 (4 stops), IIRC.

Actually it's OFF/0.9/1.8
http://www.reduser.net/forum/showpost.php?p=518086&postcount=664

Yes, you can go down to 320, but you're going to loose a stop (or so) of highlight protection.

Thanks Graeme for the fast answer!

An internal ND filter wheel will be inside the fixed-lens 2/3" Scarlet,

Yep, that's true, and according to my experience, ND 1.8 is enough for shooting wide open at ASA 100. But to calculate it with the sunny rule:
with 1/50, and at 800ASA, we would need 4 stops more, than f16.
If I want to shoot almost wide open - let's say at 2.8 - than I'd have to compensate the 9-stop 'difference'. The built-in ND on the fixed solves 6 stops at the 1.8 setting, but - and here comes the thing -:
Even with the built-in ND's on the fixed, I'd need more ND, if:
- it's really a sunny day..
- if I don't lower the sensitivity to 320ASA
- if I want to shoot around f2.4, f2.8.
Is this correct?
Oh, and also, for the screw-in ND I'd need a screw-in hot-mirror?

Anyway, tomorrow I'll test with my still camera, and my ND's, how much can I open the aperture at ASA800.

Thanks!

 

[Sean Finnegan]

800 ASA is four-stops faster than 50 ASA and most lenses shouldn't be stopped down past f/16, if not f/11...

I've read this before but I haven't been able to find a clear answer as to why that is. Mind clarifying David?

 

[David Mullen ASC]

Diffraction from having a tiny aperture causes some loss of sharpness.
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

I seem to recall that ND filter wheels in video cameras tend to be in 2-stop jumps, i.e. ND.60, ND1.2, ND1.8 -- that should be plenty for most situations, 6-stop ND makes 800 ASA into 12 ASA, that should be low enough for most applications. You don't "have" to shoot at f/2.8 in full sunlight, but if you occasionally had to, just add another ND in front. Often adding a Pola (usually a 1.5-stop loss) will also help. And you could, if there isn't a lot of fast motion, close the shutter down from 180 degrees to 90 degrees and lose another stop. And you could rate the camera at 400 ASA if you had to, losing another stop.

 

[Fabricio Morato]

you can also increase the shutter speed and add motion blur in post if you don't have the NDs and don't want to close the aperture...

 

[Eki Halkka]

...and you can also shoot HDR to protect the highlights, if you wanna go ISO 800 / T2.8 or similar without additional ND.

 

[Laco Gaal]

Often adding a Pola (usually a 1.5-stop loss) will also help.

Thanks for this tip David! This is a good thing to know, I'll keep it in my mind!

you can also increase the shutter speed and add motion blur in post if you don't have the NDs and don't want to close the aperture...

I don't want to be rude, but this isn't a solution...Try to imagine a still camera, and a few cars passing by. You can't add nice motion blur to those cars. Or think of a fast camera pan with a wide angle lens, you can't emulate that kind of motion blur.

...and you can also shoot HDR to protect the highlights, if you wanna go ISO 800 / T2.8 or similar without additional ND.

Sorry, but this is the same case, as the other advice. HDRx changes the shutter speed, and higher shutter speed means less motion blur.
The big challenge here is to shoot with 1/48 shutter, at f2.8, at base sensitivity, on a sunny day, outdoor
Think of it, with these settings (without ND), everything should be categorized as "highlights", but rather blown-outs, there's nothing to protect with HDRx.

 

[Eki Halkka]

Thanks for this tip David! This is a good thing to know, I'll keep it in my mind!

You can also use two stacked polarizing filters to get a variable ND filter, from that roughly 1,5 stops when they're aligned to almost full black when they're 90 degrees apart...

I don't want to be rude, but this isn't a solution...Try to imagine a still camera, and a few cars passing by. You can't add nice motion blur to those cars. Or think of a fast camera pan with a wide angle lens, you can't emulate that kind of motion blur.

This actually works pretty well in most cases (there are artifacts sometimes though):

http://www.revisionfx.com/products/rsmb/

Think of it, with these settings (without ND), everything should be categorized as "highlights", but rather blown-outs, there's nothing to protect with HDRx™™™™.

I was thinking of a situation when using the internal 6 -stop ND (but no additional screw-on ND), which should keep most of the content within the base exposure range, leaving just the highs for HDRx™™™ protection... thus one would have blended motion blur, not just the fast shutter blur.

 

[Laco Gaal]

You can also use two stacked polarizing filters to get a variable ND filter, from that roughly 1,5 stops when they're aligned to almost full black when they're 90 degrees apart...

I'm a bit afraid of color shifts

This actually works pretty well in most cases (there are artifacts sometimes though):
http://www.revisionfx.com/products/rsmb/

I see, but just imagine, spending hours to recreate motion blur, that would have been much easier to solve at the recording. It's like, don't use a tripod, hold the camera in your hands, and we'll stabilize it afterwards. (trust me, I do a lot of stabilization, and I don't like it that much

I was thinking of a situation when using the internal 6 -stop ND (but no additional screw-on ND), which should keep most of the content within the base exposure range, leaving just the highs for HDRx™™™™ protection... thus one would have blended motion blur, not just the fast shutter blur.

Oh I see. Well, yes it depends on the actual picture. If only the sky blows out, I would trust in HDRx.
If there are highlights, and blown-out areas on the face/hair of the actor/actress, I wouldn't trust in HDR, I would rather stop it down.

 

[Eki Halkka]

I'm a bit afraid of color shifts

The mileage varies i guess. I've used this trick successfully, but i've also heard of others who have had big issues - i suppose it depends a lot on the quality of the polas.

I use this setup to get better exposure control with my home video camera, HV20, and for that purpose it works fine. Color shifts are minimal in practice, unless going to near 90 degree angles which never happens in real life. Of course, the quality requirements for color accuracy etc. aren't exactly the top priority for the stuff i use that camera for - i haven't tried to measure it or anything like that ;-)

I see, but just imagine, spending hours to recreate motion blur, that would have been much easier to solve at the recording.

I didn't try to say it's the best choice most of the time, just that it's possible.

There are some cases where this kind of MB option is handy though - one can i.e. shoot with high shutter speed for easier tracking, roto etc., or shoot high frame rates for post-production speed ramps while still aiming for natural looking motion blur in the final image.

If there are highlights, and blown-out areas on the face/hair of the actor/actress, I wouldn't trust in HDR, I would rather stop it down.

Me too, likely - or add more ND. But the option is there.

 

[Fabricio Morato]

hi,

it actually depends on the job you are doing and your budget, but adding mb is post is quite easy this days and do a very good job. It also helps vfx guys on tracking...
And hdrx is basically doing this on the x track...so if you use it you will spend a good amount of time in post dealing with this and the tonemaping...

So I wouldn't use this on a documentary with longs interviews on the street or wildlife but on a commercial with lots of vfx it can be helpful...

it's just an alternative..everything have its cons and pros...

 

[Laco Gaal]

i suppose it depends a lot on the quality of the polas.

I see. What kind of polas are you using? Thanks!

everything have its cons and pros...

that's certainly true But if I upgrade to a RED I'd like to find out, what is the way to get the best quality. I don't mind if it takes a lot of time for setup.

 

[Peter Moretti]

Yes, you can go down to 320, but you're going to loose a stop (or so) of highlight protection. You've got to balance that with the need for ND. Scarlet has built-in ND which will help you though.

Graeme

Are the ND's going to have IR blocking built into them or will they need external IR blocking filters? Thanks.

 

[Benoît-Joan Clariana-Roig]

Built-in ND filter ? YEAH ! *dances*