EX1 with letus extreme ISO/ASA
- Thread starter EzE
- Start date
Barry_Green
Moderator
There is no such thing. You're talking about a video camera, not a film camera, and how you rate the ISO depends a whole lot on what gamma curve you select, and on an EX1 it also depends on what mode you're shooting in (different sensitivities for 720p, 1080p, and 1080i).
Then it'll also depend on the speed of the lens you're using. And then, to really irritate you, lens adapters don't typically transmit light according to a linear progression; if you stop down the 35mm lens by a stop, you won't necessarily be cutting the light hitting the sensor in half.
It's an extraordinarily frustrating thing to deal with. So don't. Forget completely the concept of ISO when working with a video camera overall, and doubly forget it when using a lens adapter.
Now, if you just want to know a vague ballpark idea (as in, is it ISO 50 or ISO 800?) then the answer is: eh, somewhere around 200-300 (assuming 1080p, an f/2 lens, and STD3 gamma; change any of those variables and you'll change the perceived ISO!)
Then it'll also depend on the speed of the lens you're using. And then, to really irritate you, lens adapters don't typically transmit light according to a linear progression; if you stop down the 35mm lens by a stop, you won't necessarily be cutting the light hitting the sensor in half.
It's an extraordinarily frustrating thing to deal with. So don't. Forget completely the concept of ISO when working with a video camera overall, and doubly forget it when using a lens adapter.
Now, if you just want to know a vague ballpark idea (as in, is it ISO 50 or ISO 800?) then the answer is: eh, somewhere around 200-300 (assuming 1080p, an f/2 lens, and STD3 gamma; change any of those variables and you'll change the perceived ISO!)
Lenilenapi
Carbonite Member
Amen Barry!
Lenny Levy
Lenny Levy
Barry_Green
Moderator
You can use a light meter if you want, to judge lighting ratios, contrast levels, etc. You just won't be able to use it to accurately set exposure on a video camera, especially when using an adapter. Trying to do so is going to guarantee that you fail. So, yeah, don't do it. Use the right tools for the job -- a calibrated production monitor, a waveform monitor, or (at the bare minimum) zebras.
Lenilenapi
Carbonite Member
Barry is 100% right on both counts.
A meter is very helpful when lighting a set in video. It can help you get your lighting even, set ratios, and get you reasonably close to the ballpark for exposure, but in the end you have to look at the picture in a decent monitor and trust your zebra's and waveform.
Lenny
A meter is very helpful when lighting a set in video. It can help you get your lighting even, set ratios, and get you reasonably close to the ballpark for exposure, but in the end you have to look at the picture in a decent monitor and trust your zebra's and waveform.
Lenny
Lenilenapi
Carbonite Member
I'm sure there is stuff on the web, but do you even have a waveform available to you. There is a histogram in the Ex which isn't nearly as valuable as a waveform but its better than nothing. Just search the web for both, or get ambitious and buy a book on video.
Tim Naylor
Veteran
I don't use a meter much in video if at all. My gaffer will use it for things like green screen work or pre-lighting a set while I have the camera / waveform elsewhere. He needs an ASA number to work with. For instance, with an F900 to get the waveform line on a green screen to 35 IRE, we set our light meter to something like 400 ASA and worked the green screen lights until they read 2.8. We came up with 400 ASA at -3db after our engineer measured and set a chip chart to the proper exposure. Working backwards from the cameras stop we deduced the ASA until we got the same stop on our meter. I need to get my key to a 4.0 - and he'll have an idea what size of heads we need. Otherwise, his guess is as good as mine. Granted digital cameras don't behave like a film curve but in the middle of the curve ASA is a useful reference.
With my LEX/HVX combo I'd say between 150-200 is about right. But here's the real slap. Not all HVX's have the same sensitivity. Recently did a show with Timurs camera and mine and at identical settings his was 1/2 a stop more sensitive than mine. To get 50 IRE mine was at a 2.8 1/2 and his at 4.0. That's prosumer consistency for you.
Either way, I still think in ASA and on many occasions said to a gaffer that the HVX is app. 320 ASA (with my settings). Now he can now scout, make judgements about the available light and begin to compile a lighting list.
But at the end of the day, your monitor / waveform / vectorscope is the truth. Make sure you know how to calibrate it. Read up on how to use a waveform and vectorscope.
Tim
With my LEX/HVX combo I'd say between 150-200 is about right. But here's the real slap. Not all HVX's have the same sensitivity. Recently did a show with Timurs camera and mine and at identical settings his was 1/2 a stop more sensitive than mine. To get 50 IRE mine was at a 2.8 1/2 and his at 4.0. That's prosumer consistency for you.
Either way, I still think in ASA and on many occasions said to a gaffer that the HVX is app. 320 ASA (with my settings). Now he can now scout, make judgements about the available light and begin to compile a lighting list.
But at the end of the day, your monitor / waveform / vectorscope is the truth. Make sure you know how to calibrate it. Read up on how to use a waveform and vectorscope.
Tim
Barry_Green
Moderator
Keep in mind that the iris is calibrated in 1/6 stop increments. So 2.8 and a half would read out as 3.4. But his saying 3.4, and yours saying 4.0, might have been a real-world difference of only 1/6 of a stop.
As you stop down the iris you can see visible changes in brightness while the dial doesn't change. So you can have 2.0, 2.0 + 1/6, and 2.0 + 1/3, and it'll all read 2.0. Then the next tick you stop down it'll update the readout to now say 2.4.
Lenilenapi
Carbonite Member
When I was doing tests comparing Brevis, SGPro & Letus with 2 HVX's we found about 1/4 - 1/3 stop difference in sensitivity between 2 identically set-up HVX's purchased within a week of each other when they first came out. That was wide open as well - not a difference in reading the iris we really checked it out.
"Either way, I still think in ASA and on many occasions said to a gaffer that the HVX is app. 320 ASA (with my settings). Now he can now scout, make judgements about the available light and begin to compile a lighting list."
- I do agree with that so general ASA's are useful. You could also light a set to that ASA and know you are in the ballpark as long as you look at the waveform at the end.
Lenny Levy
"Either way, I still think in ASA and on many occasions said to a gaffer that the HVX is app. 320 ASA (with my settings). Now he can now scout, make judgements about the available light and begin to compile a lighting list."
- I do agree with that so general ASA's are useful. You could also light a set to that ASA and know you are in the ballpark as long as you look at the waveform at the end.
Lenny Levy
Barry_Green
Moderator
A light meter can be used for setting lighting ratios and as a rough guide for establishing the lighting, but for a video camera it should never be used to set exposure. The waveform monitor, or even the zebras, will be more accurate for setting exposure.
And I measured my EX1 with Letus extreme set up yesterday and found it to be ASA 60 with gamma Cine1 and ASA 125 with Cine4. Can that be?
I'm thinking the fact I measured it with an incident meter could have thrown things too off. The EX1 on it's own is ASA 400. The front lens was on T4 and the EX1 lens was on f2.8.
Barry_Green
Moderator
Can it be that you're getting a different ASA with different gammas? Yes, which is why it makes no sense to try to set exposure on a video camera using a light meter. Unless you've done extensive testing under all possible scenarios. A video camera isn't the same as a film stock, you have to take into account all the processing that's going on with the signal. So why bother trying to chase all that, when you could just plug in a waveform monitor and see exactly what's going on? I know not everyone has a waveform monitor, and especially with an EX1 where you can't stream the high-quality video out the firewire port it makes tools like OnLocation less useful, but still -- you should be setting exposure based on the digital tools available to you, the zebras and the histogram and things like that, rather than trying to guess based on a light meter reading.
The EX1 on its own is ASA400 ONLY WHEN USING STD3 GAMMA. And, again, not really, but that's how a meter would interpret it. But it's also 400 ISO only when shooting 1080P. If you change to 720p mode, or you change to 1080i mode, you'll change the effective ASA.
It's a fool's errand to try to establish or chase a "real" ASA on a video camera with so many settings.
No. I know different gammas will affect ASA. I was asking if it is possible that the ASA would be so low. The Letus is supposed to lose only ½ stops. Then the lens used etc.
Yes, I know. But having a at least close ASA to give you a ball park is great to when pre lighting a set without the camera actually there yet etc. Also, I have developed two picture profiles, one using Cine1 and other using Cine4 and that is all I’m shooting with for the current project we are working on. So I won’t have to account for many different settings etc. I need to establish an approx. ASA for both picture profiles.
Exactly. I don’t have a WF monitor. I also thought measuring out of the firewire to Onlocation or DVrack would be useless. Is that the case? We shoot only HQ.
I would use a WF monitor if I had one, but I don’t. Besides sometimes on location is not practical to carry one. But a light meter can go anywhere you go.
I have found the zebras in the EX1 to be quite weird actually. I have one of them set for 70% and sometimes I’m shining a 1K light from 3 feet away from an actor and it looks great in the monitor and all and incredibly “overexposed” to the eye and the EX1 will refuse to give any zebras at all (yes zebra ON). In any case I heard since the histogram is not a RGB one it is not really that useful to set exposure. Do you agree?
Really, I didn’t know that. I thought it was with picture profile OFF.
Have you rated it in Cine1 and Cine4?
Why would resolution change the ASA?
As I said, if I had a WF monitor I would use. But I don’t and I feel extremely uncomfortable in setting exposure only looking at the preview monitor.
Lenilenapi
Carbonite Member
The cine gammas drop the sensitivity enormously, so its possible I guess that you might get a 60 ASA in Cine. haven't tried it yet.
Well, I have been using ASA 120 with great success for the last week. I pre light the set for ASA 120 and et the key to 2.8 and it works every time. When the actor comes, he has the good zebras. I guess I have found a good working ASA for my picture profile. Now if I could only get usable data from the firewire connect to DVrack or a similar virtual waveform, that would be the icing in the cake for exposure, since the built in histogram is quite weird. It reads different from the Vegas histogram every time.